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Micromachines
Volume 12
Issue 10
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Micromachines, Volume 12, Issue 10 (October 2021) – 136 articles

Cover Story (view full-size image): The heterogeneity of cancer cells plays a key role in chemotherapy resistance and cancer recurrence. Therefore, for effective treatment, cancer cells need to be analyzed at the single-cell level. We propose a microfluidic chip for a single-cell proteomics assay that can analyze complex cellular signaling systems to reveal the heterogeneity of cancer cells. View this paper
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28 pages, 19580 KiB  
Article
Investigation of Integrated Reactive Multilayer Systems for Bonding in Microsystem Technology
by El-Mostafa Bourim, Il-Suk Kang and Hee Yeoun Kim
Micromachines 2021, 12(10), 1272; https://doi.org/10.3390/mi12101272 - 19 Oct 2021
Cited by 12 | Viewed by 3821
Abstract
For the integration of a reactive multilayer system (iRMS) with a high exothermic reaction enthalpy as a heat source on silicon wafers for low-temperature bonding in the 3D integration and packaging of microsystems, two main conflicting issues should be overcome: heat accumulation arising [...] Read more.
For the integration of a reactive multilayer system (iRMS) with a high exothermic reaction enthalpy as a heat source on silicon wafers for low-temperature bonding in the 3D integration and packaging of microsystems, two main conflicting issues should be overcome: heat accumulation arising from the layer interface pre-intermixing, which causes spontaneous self-ignition during the deposition of the system layers, and conductive heat loss through the substrate, which leads to reaction propagation quenching. In this work, using electron beam evaporation, we investigated the growth of a high exothermic metallic Pd/Al reactive multilayer system (RMS) on different Si-wafer substrates with different thermal conduction, specifically a bare Si-wafer, a RuOx or PdOx layer buffering Si-wafer, and a SiO2-coated Si-wafer. With the exception of the bare silicon wafer, the RMS grown on all other coated wafers underwent systematic spontaneous self-ignition surging during the deposition process once it reached a thickness of around 1 μm. This issue was surmounted by investigating a solution based on tuning the output energy by stacking alternating sections of metallic reactive multilayer Pd/Al and Ni/Al systems that have a high and medium enthalpy of exothermic reactions, respectively. This heterostructure with a bilayer thickness of 100 nm was successfully grown on a SiO2-coated Si-wafer to a total thickness of 3 μm without any spontaneous upsurge of self-ignition; it could be electrically ignited at room temperature, enabling a self-sustained propagating exothermic reaction along the reactive patterned track without undergoing quenching. The results of this study will promote the growth of reactive multilayer systems by electron beam evaporation processing and their potential integration as local heat sources on Si-wafer substrates for bonding applications in microelectronics and microsystems technology. Full article
(This article belongs to the Special Issue MEMS Packaging Technologies and 3D Integration)
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16 pages, 4973 KiB  
Article
A 3D-2D Multibranch Feature Fusion and Dense Attention Network for Hyperspectral Image Classification
by Hongmin Gao, Yiyan Zhang, Yunfei Zhang, Zhonghao Chen, Chenming Li and Hui Zhou
Micromachines 2021, 12(10), 1271; https://doi.org/10.3390/mi12101271 - 18 Oct 2021
Cited by 3 | Viewed by 1993
Abstract
In recent years, hyperspectral image classification (HSI) has attracted considerable attention. Various methods based on convolution neural networks have achieved outstanding classification results. However, most of them exited the defects of underutilization of spectral-spatial features, redundant information, and convergence difficulty. To address these [...] Read more.
In recent years, hyperspectral image classification (HSI) has attracted considerable attention. Various methods based on convolution neural networks have achieved outstanding classification results. However, most of them exited the defects of underutilization of spectral-spatial features, redundant information, and convergence difficulty. To address these problems, a novel 3D-2D multibranch feature fusion and dense attention network are proposed for HSI classification. Specifically, the 3D multibranch feature fusion module integrates multiple receptive fields in spatial and spectral dimensions to obtain shallow features. Then, a 2D densely connected attention module consists of densely connected layers and spatial-channel attention block. The former is used to alleviate the gradient vanishing and enhance the feature reuse during the training process. The latter emphasizes meaningful features and suppresses the interfering information along the two principal dimensions: channel and spatial axes. The experimental results on four benchmark hyperspectral images datasets demonstrate that the model can effectively improve the classification performance with great robustness. Full article
(This article belongs to the Special Issue Advanced Machine Learning Techniques for Sensing and Imaging Applications)
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13 pages, 8592 KiB  
Article
Batch Manufacturing of Split-Actuator Micro Air Vehicle Based on Monolithic Processing Technology
by Xiang Lu, Chengxiang Wang, Kun Lu, Xiang Xi, Yulie Wu, Xuezhong Wu and Dingbang Xiao
Micromachines 2021, 12(10), 1270; https://doi.org/10.3390/mi12101270 - 18 Oct 2021
Cited by 1 | Viewed by 1830
Abstract
Microrobots have a wide range of applications. The rigid–flexible composite stereoscopic technology based on ultraviolet laser cutting technology is primarily researched for the design and manufacture of microrobots and has been used to fabricate microscale motion mechanisms and robots. This paper introduces a [...] Read more.
Microrobots have a wide range of applications. The rigid–flexible composite stereoscopic technology based on ultraviolet laser cutting technology is primarily researched for the design and manufacture of microrobots and has been used to fabricate microscale motion mechanisms and robots. This paper introduces a monolithic processing technology based on the rigid–flexible composite stereoscopic process. Based on this process, a split-actuator micro flapping-wing air vehicle with a size of 15 mm × 2.5 mm × 30 mm was designed. We proposed a batch manufacturing method capable of processing multiple micro air vehicles at the same time. The main structure of 22 flapping-wing micro air vehicles can be processed at the same time within the processing range of the composite sheet with an area of 80 mm × 80 mm, and the processing effect is good. Full article
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15 pages, 5761 KiB  
Article
A Hybrid Structure of Piezoelectric Fibers and Soft Materials as a Smart Floatable Open-Water Wave Energy Converter
by Sina Baghbani Kordmahale, Jitae Do, Kuang-An Chang and Jun Kameoka
Micromachines 2021, 12(10), 1269; https://doi.org/10.3390/mi12101269 - 18 Oct 2021
Cited by 11 | Viewed by 2468
Abstract
An open-water wave energy converter (OWEC) made of a new soft platform has been developed by combining piezoelectric macro-fiber composites (MFCs) and a low-cost elastomer. In the past decades, numerous types of water wave energy conversion platform have been developed and investigated, from [...] Read more.
An open-water wave energy converter (OWEC) made of a new soft platform has been developed by combining piezoelectric macro-fiber composites (MFCs) and a low-cost elastomer. In the past decades, numerous types of water wave energy conversion platform have been developed and investigated, from buoys to overtopping devices. These harvesters mainly use electromagnetic-based generators, and they have faced challenges such as their enormous size, high deployment and maintenance costs, and negative effects on the environment. These problems hinder their practicality and competitiveness. In this paper, a soft open-water wave energy converter is introduced which integrates piezoelectric MFCs and bubble wrap into an elastomer sheet. The performance of the OWEC was investigated in a wave flume as a floatable structure. The maximum 29.7 µW energy harvested from the small OWEC represents a promising energy conversion performance at low frequencies (<2 Hz). The elastomer was able to protect the MFCs and internal electrical connections without any degradation during the experiment. In addition, the OWEC is a foldable structure, which can reduce the deployment costs in real-world applications. The combination of no maintenance, low fabrication cost, low deployment cost, and moderate energy harvesting capability may advance the OWEC platform to its real-world applications. Full article
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11 pages, 4251 KiB  
Article
Experimental Demonstration of a Stacked Hybrid Optoacoustic-Piezoelectric Transducer for Localized Heating and Enhanced Cavitation
by Pil Gyu Sang, Deblina Biswas, Seung Jin Lee, Sang Min Won, Donghee Son, Jong G. Ok, Hui Joon Park and Hyoung Won Baac
Micromachines 2021, 12(10), 1268; https://doi.org/10.3390/mi12101268 - 18 Oct 2021
Cited by 1 | Viewed by 2087
Abstract
Laser-generated focused ultrasound (LGFU) is an emerging modality for cavitation-based therapy. However, focal pressure amplitudes by LGFU alone to achieve pulsed cavitation are often lacking as a treatment depth increases. This requires a higher pressure from a transmitter surface and more laser energies [...] Read more.
Laser-generated focused ultrasound (LGFU) is an emerging modality for cavitation-based therapy. However, focal pressure amplitudes by LGFU alone to achieve pulsed cavitation are often lacking as a treatment depth increases. This requires a higher pressure from a transmitter surface and more laser energies that even approach to a damage threshold of transmitter. To mitigate the requirement for LGFU-induced cavitation, we propose LGFU configurations with a locally heated focal zone using an additional high-intensity focused ultrasound (HIFU) transmitter. After confirming heat-induced cavitation enhancement using two separate transmitters, we then developed a stacked hybrid optoacoustic-piezoelectric transmitter, which is a unique configuration made by coating an optoacoustic layer directly onto a piezoelectric substrate. This shared curvature design has great practical advantage without requiring the complex alignment of two focal zones. Moreover, this enabled the amplification of cavitation bubble density by 18.5-fold compared to the LGFU operation alone. Finally, the feasibility of tissue fragmentation was confirmed through a tissue-mimicking gel, using the combination of LGFU and HIFU (not via a stacked structure). We expect that the stacked transmitter can be effectively used for stronger and faster tissue fragmentation than the LGFU transmitter alone. Full article
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8 pages, 24245 KiB  
Article
In Situ Sputtering Silver Induction Electrode for Stable and Stretchable Triboelectric Nanogenerators
by Jinyuan Yao, Qi Zhang, Haodong Zhang, Mengqiu Li, Xichi Lu, Yu Xiao, Rujiao Yao and Xuhong Wang
Micromachines 2021, 12(10), 1267; https://doi.org/10.3390/mi12101267 - 18 Oct 2021
Cited by 3 | Viewed by 2103
Abstract
Triboelectric nanogenerators (TENG) can convert mechanical energy into electricity and exhibit unique advantages in the field of low-frequency and discrete energy harvesting. However, the interfacial state and stability between the triboelectric layer and electrode layer influence the output and applications of TENG. Herein, [...] Read more.
Triboelectric nanogenerators (TENG) can convert mechanical energy into electricity and exhibit unique advantages in the field of low-frequency and discrete energy harvesting. However, the interfacial state and stability between the triboelectric layer and electrode layer influence the output and applications of TENG. Herein, an in situ sputtering Ag process for fabricating induction electrodes is proposed to match with TENG. The sputtering Ag process is optimized by a variety of parameters, such as sputtering power, single-cycle time, number of cycles, cycle interval, and vacuum degree. In addition, the chemical state of Ag as a function of air placement is investigated, showing the sputtered Ag has excellent conductivity and stability. Moreover, four kinds of polymers are selected for fabricating TENGs based on the sputtered Ag induction electrodes, i.e., nylon 66, polyimide (PI), fluorinated ethylene propylene (FEP), and polydimethylsiloxane (PDMS), which shows great applicability. Considering the demand of flexible power suppliers, the sputtered Ag is integrated with a PDMS substrate, and shows good adhesion, flexibility, and ductility after severe deformation of the PDMS. Finally, the developed induction electrode processing technology is used in flexible TENG and shows great prospects in self-powered electronics for practical applications. Full article
(This article belongs to the Special Issue Advanced Functional Materials for Energy Harvesting and Storage Devices)
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14 pages, 3209 KiB  
Article
Advancing 3D-Printed Microfluidics: Characterization of a Gas-Permeable, High-Resolution PDMS Resin for Stereolithography
by Elyse Fleck, Alec Sunshine, Emma DeNatale, Charlise Keck, Alexandra McCann and Joseph Potkay
Micromachines 2021, 12(10), 1266; https://doi.org/10.3390/mi12101266 - 18 Oct 2021
Cited by 22 | Viewed by 4458
Abstract
The rapid expansion of microfluidic applications in the last decade has been curtailed by slow, laborious microfabrication techniques. Recently, microfluidics has been explored with additive manufacturing (AM), as it has gained legitimacy for producing end-use products and 3D printers have improved resolution capabilities. [...] Read more.
The rapid expansion of microfluidic applications in the last decade has been curtailed by slow, laborious microfabrication techniques. Recently, microfluidics has been explored with additive manufacturing (AM), as it has gained legitimacy for producing end-use products and 3D printers have improved resolution capabilities. While AM satisfies many shortcomings with current microfabrication techniques, there still lacks a suitable replacement for the most used material in microfluidic devices, poly(dimethylsiloxane) (PDMS). Formulation of a gas-permeable, high-resolution PDMS resin was developed using a methacrylate–PDMS copolymer and the novel combination of a photoabsorber, Sudan I, and photosensitizer, 2-Isopropylthioxanthone. Resin characterization and 3D printing were performed using a commercially available DLP–SLA system. A previously developed math model, mechanical testing, optical transmission, and gas-permeability testing were performed to validate the optimized resin formula. The resulting resin has Young’s modulus of 11.5 MPa, a 12% elongation at break, and optical transmission of >75% for wavelengths between 500 and 800 nm after polymerization, and is capable of creating channels as small as 60 μm in height and membranes as thin as 20 μm. The potential of AM is just being realized as a fabrication technique for microfluidics as developments in material science and 3D printing technologies continue to push the resolution capabilities of these systems. Full article
(This article belongs to the Special Issue Microfluidic Artificial Organs)
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14 pages, 5126 KiB  
Article
Modeling Brownian Microparticle Trajectories in Lab-on-a-Chip Devices with Time Varying Dielectrophoretic or Optical Forces
by Mohammad Asif Zaman, Mo Wu, Punnag Padhy, Michael A. Jensen, Lambertus Hesselink and Ronald W. Davis
Micromachines 2021, 12(10), 1265; https://doi.org/10.3390/mi12101265 - 18 Oct 2021
Cited by 11 | Viewed by 2860
Abstract
Lab-on-a-chip (LOC) devices capable of manipulating micro/nano-sized samples have spurred advances in biotechnology and chemistry. Designing and analyzing new and more advanced LOCs require accurate modeling and simulation of sample/particle dynamics inside such devices. In this work, we present a generalized computational physics [...] Read more.
Lab-on-a-chip (LOC) devices capable of manipulating micro/nano-sized samples have spurred advances in biotechnology and chemistry. Designing and analyzing new and more advanced LOCs require accurate modeling and simulation of sample/particle dynamics inside such devices. In this work, we present a generalized computational physics model to simulate particle/sample trajectories under the influence of dielectrophoretic or optical forces inside LOC devices. The model takes into account time varying applied forces, Brownian motion, fluid flow, collision mechanics, and hindered diffusion caused by hydrodynamic interactions. We develop a numerical solver incorporating the aforementioned physics and use it to simulate two example cases: first, an optical trapping experiment, and second, a dielectrophoretic cell sorter device. In both cases, the numerical results are found to be consistent with experimental observations, thus proving the generality of the model. The numerical solver can simulate time evolution of the positions and velocities of an arbitrarily large number of particles simultaneously. This allows us to characterize and optimize a wide range of LOCs. The developed numerical solver is made freely available through a GitHub repository so that researchers can use it to develop and simulate new designs. Full article
(This article belongs to the Special Issue Micromachines for Dielectrophoresis, Volume II)
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7 pages, 2073 KiB  
Article
Micromagnetic Simulation of L10-FePt-Based Exchange-Coupled-Composite-Bit-Patterned Media with Microwave-Assisted Magnetic Recording at Ultrahigh Areal Density
by Pirat Khunkitti, Naruemon Wannawong, Chavakon Jongjaihan, Apirat Siritaratiwat, Anan Kruesubthaworn and Arkom Kaewrawang
Micromachines 2021, 12(10), 1264; https://doi.org/10.3390/mi12101264 - 17 Oct 2021
Cited by 5 | Viewed by 2067
Abstract
In this work, we propose exchange-coupled-composite-bit-patterned media (ECC-BPM) with microwave-assisted magnetic recording (MAMR) to improve the writability of the magnetic media at a 4 Tb/in2 recording density. The suitable values of the applied microwave field’s frequency and the exchange coupling between magnetic [...] Read more.
In this work, we propose exchange-coupled-composite-bit-patterned media (ECC-BPM) with microwave-assisted magnetic recording (MAMR) to improve the writability of the magnetic media at a 4 Tb/in2 recording density. The suitable values of the applied microwave field’s frequency and the exchange coupling between magnetic dots, Adot, of the proposed media were evaluated. It was found that the magnitude of the switching field, Hsw, of the bilayer ECC-BPM is significantly lower than that of a conventional BPM. Additionally, using the MAMR enables further reduction of Hsw of the ECC-BPM. The suitable frequency of the applied microwave field for the proposed media is 5 GHz. The dependence of Adot on the Hsw was additionally examined, showing that the Adot of 0.14 pJ/m is the most suitable value for the proposed bilayer ECC-BPM. The physical explanation of the Hsw of the media under a variation of MAMR and Adot was given. Hysteresis loops and the magnetic domain of the media were characterized to provide further details on the results. The lowest Hsw found in our proposed media is 12.2 kOe, achieved by the bilayer ECC-BPM with an Adot of 0.14 pJ/m using a 5 GHz MAMR. Full article
(This article belongs to the Special Issue Magnetic and Spin Devices)
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21 pages, 16099 KiB  
Article
Design, Fabrication, Testing and Simulation of a Rotary Double Comb Drives Actuated Microgripper
by Nicola Pio Belfiore, Alvise Bagolini, Andrea Rossi, Gabriele Bocchetta, Federica Vurchio, Rocco Crescenzi, Andrea Scorza, Pierluigi Bellutti and Salvatore Andrea Sciuto
Micromachines 2021, 12(10), 1263; https://doi.org/10.3390/mi12101263 - 17 Oct 2021
Cited by 16 | Viewed by 2596
Abstract
This paper presents the development of a new microgripper actuated by means of rotary-comb drives equipped with two cooperating fingers arrays. The microsystem presents eight CSFH flexures (Conjugate Surface Flexure Hinge) that allow the designer to assign a prescribed motion to the gripping [...] Read more.
This paper presents the development of a new microgripper actuated by means of rotary-comb drives equipped with two cooperating fingers arrays. The microsystem presents eight CSFH flexures (Conjugate Surface Flexure Hinge) that allow the designer to assign a prescribed motion to the gripping tips. In fact, the adoption of multiple CSFHs gives rise to the possibility of embedding quite a complex mechanical structure and, therefore, increasing the number of design parameters. For the case under study, a double four-bar linkage in a mirroring configuration was adopted. The presented microgripper has been fabricated by using a hard metal mask on a Silicon-on-Insulator (SOI) wafer, subject to DRIE (Deep Reactive Ion Etching) process, with a vapor releasing final stage. Some prototypes have been obtained and then tested in a lab. Finally, the experimental results have been used in order to assess simulation tools that can be used to minimize the amount of expensive equipment in operational environments. Full article
(This article belongs to the Special Issue Microgrippers)
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14 pages, 1629 KiB  
Article
Locality-Based Cache Management and Warp Scheduling for Reducing Cache Contention in GPU
by Juan Fang, Zelin Wei and Huijing Yang
Micromachines 2021, 12(10), 1262; https://doi.org/10.3390/mi12101262 - 17 Oct 2021
Cited by 5 | Viewed by 3161
Abstract
GPGPUs has gradually become a mainstream acceleration component in high-performance computing. The long latency of memory operations is the bottleneck of GPU performance. In the GPU, multiple threads are divided into one warp for scheduling and execution. The L1 data caches have little [...] Read more.
GPGPUs has gradually become a mainstream acceleration component in high-performance computing. The long latency of memory operations is the bottleneck of GPU performance. In the GPU, multiple threads are divided into one warp for scheduling and execution. The L1 data caches have little capacity, while multiple warps share one small cache. That makes the cache suffer a large amount of cache contention and pipeline stall. We propose Locality-Based Cache Management (LCM), combined with the Locality-Based Warp Scheduling (LWS), to reduce cache contention and improve GPU performance. Each load instruction can be divided into three types according to locality: only used once as streaming data locality, accessed multiple times in the same warp as intra-warp locality, and accessed in different warps as inter-warp data locality. According to the locality of the load instruction, LWS applies cache bypass to the streaming locality request to improve the cache utilization rate, extend inter-warp memory request coalescing to make full use of the inter-warp locality, and combine with the LWS to alleviate cache contention. LCM and LWS can effectively improve cache performance, thereby improving overall GPU performance. Through experimental evaluation, our LCM and LWS can obtain an average performance improvement of 26% over baseline GPU. Full article
(This article belongs to the Special Issue Power-MEMS and Energy Storage Devices for On-Chip Microsystems)
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10 pages, 3623 KiB  
Article
The Improvement of Performance through Minimizing Scallop Size in MEMS Based Micro Wind Turbine
by Young Chan Choi, June Soo Kim, Soon Yeol Kwon and Seong Ho Kong
Micromachines 2021, 12(10), 1261; https://doi.org/10.3390/mi12101261 - 17 Oct 2021
Cited by 1 | Viewed by 2794
Abstract
In this paper we report on the improvement of performance by minimizing scallop size through deep reactive-ion etching (DRIE) of rotors in micro-wind turbines based on micro-electro-mechanical systems (MEMS) technology. The surface profile of an MEMS rotor can be controlled by modifying the [...] Read more.
In this paper we report on the improvement of performance by minimizing scallop size through deep reactive-ion etching (DRIE) of rotors in micro-wind turbines based on micro-electro-mechanical systems (MEMS) technology. The surface profile of an MEMS rotor can be controlled by modifying the scallop size of the DRIE surface through changing the process recipe. The fabrication of a planar disk-type MEMS rotor through the MEMS fabrication process was carried out, and for the comparison of the improvements in the performance of each rotor, RPM testing and open circuit output voltage experiments of stators and permanent magnets were performed. We found that the smooth etching profile with a minimized scallop size formed using DRIE results in improved rotation properties in MEMS-based wind turbine rotors. Full article
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19 pages, 3156 KiB  
Review
Artificial Neural Networks in MPPT Algorithms for Optimization of Photovoltaic Power Systems: A Review
by César G. Villegas-Mier, Juvenal Rodriguez-Resendiz, José M. Álvarez-Alvarado, Hugo Rodriguez-Resendiz, Ana Marcela Herrera-Navarro and Omar Rodríguez-Abreo
Micromachines 2021, 12(10), 1260; https://doi.org/10.3390/mi12101260 - 17 Oct 2021
Cited by 108 | Viewed by 9803
Abstract
The use of photovoltaic systems for clean electrical energy has increased. However, due to their low efficiency, researchers have looked for ways to increase their effectiveness and improve their efficiency. The Maximum Power Point Tracking (MPPT) inverters allow us to maximize the extraction [...] Read more.
The use of photovoltaic systems for clean electrical energy has increased. However, due to their low efficiency, researchers have looked for ways to increase their effectiveness and improve their efficiency. The Maximum Power Point Tracking (MPPT) inverters allow us to maximize the extraction of as much energy as possible from PV panels, and they require algorithms to extract the Maximum Power Point (MPP). Several intelligent algorithms show acceptable performance; however, few consider using Artificial Neural Networks (ANN). These have the advantage of giving a fast and accurate tracking of the MPP. The controller effectiveness depends on the algorithm used in the hidden layer and how well the neural network has been trained. Articles over the last six years were studied. A review of different papers, reports, and other documents using ANN for MPPT control is presented. The algorithms are based on ANN or in a hybrid combination with FL or a metaheuristic algorithm. ANN MPPT algorithms deliver an average performance of 98% in uniform conditions, exhibit a faster convergence speed, and have fewer oscillations around the MPP, according to this research. Full article
(This article belongs to the Special Issue Artificial Intelligence Integration with Micro-Nano Systems)
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12 pages, 2865 KiB  
Article
Chitosan-Based Flexible Memristors with Embedded Carbon Nanotubes for Neuromorphic Electronics
by Jin-Gi Min and Won-Ju Cho
Micromachines 2021, 12(10), 1259; https://doi.org/10.3390/mi12101259 - 17 Oct 2021
Cited by 16 | Viewed by 3452
Abstract
In this study, we propose high-performance chitosan-based flexible memristors with embedded single-walled carbon nanotubes (SWCNTs) for neuromorphic electronics. These flexible transparent memristors were applied to a polyethylene naphthalate (PEN) substrate using low-temperature solution processing. The chitosan-based flexible memristors have a bipolar resistive switching [...] Read more.
In this study, we propose high-performance chitosan-based flexible memristors with embedded single-walled carbon nanotubes (SWCNTs) for neuromorphic electronics. These flexible transparent memristors were applied to a polyethylene naphthalate (PEN) substrate using low-temperature solution processing. The chitosan-based flexible memristors have a bipolar resistive switching (BRS) behavior due to the cation-based electrochemical reaction between a polymeric chitosan electrolyte and mobile ions. The effect of SWCNT addition on the BRS characteristics was analyzed. It was observed that the embedded SWCNTs absorb more metal ions and trigger the conductive filament in the chitosan electrolyte, resulting in a more stable and wider BRS window compared to the device with no SWCNTs. The memory window of the chitosan nanocomposite memristors with SWCNTs was 14.98, which was approximately double that of devices without SWCNTs (6.39). Furthermore, the proposed SWCNT-embedded chitosan-based memristors had memristive properties, such as short-term and long-term plasticity via paired-pulse facilitation and spike-timing-dependent plasticity, respectively. In addition, the conductivity modulation was evaluated with 300 synaptic pulses. These findings suggest that memristors featuring SWCNT-embedded chitosan are a promising building block for future artificial synaptic electronics applications. Full article
(This article belongs to the Special Issue New Advances in Ionic-Drift Resistive Switching Memory and Neuromorphic Applications)
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13 pages, 2395 KiB  
Article
Effect of Concave Stave on Class I Barrel-Stave Flextensional Transducer
by Duo Teng, Xiaoyong Liu and Feng Gao
Micromachines 2021, 12(10), 1258; https://doi.org/10.3390/mi12101258 - 17 Oct 2021
Cited by 7 | Viewed by 2500
Abstract
To meet the requirements of low frequency, high power, small size and light weight, a type of Class I barrel-stave flextensional transducer employing improved concave stave is presented. As the key component of flextensional transducer, concave stave plays an important role in vibrating [...] Read more.
To meet the requirements of low frequency, high power, small size and light weight, a type of Class I barrel-stave flextensional transducer employing improved concave stave is presented. As the key component of flextensional transducer, concave stave plays an important role in vibrating efficiently to radiate acoustic energy. The structure of concave stave has a great effect on its behavior. In this paper, the main parameters of concave stave are discussed, especially the effect of radius on flextensional transducer. Both concave stave and transducer are analyzed through finite element method, including mechanical transformation behavior of concave stave and performances of flextensional transducer. On the basis of finite element design, five prototypes employing concave staves with different radii are manufactured and measured. The simulations and tests reveal that concave stave can affect performances of flextensional transducer. A larger radius of concave stave will result in a greater amplification of vibration and a lower resonance frequency of transducer. This can be a feasible way to optimize the resonance frequency or source level of flextensional transducer through adjusting the radius of concave stave in a small range. According to the electrical and acoustical tests, our Class I barrel-stave flextensional transducer is capable of being used as underwater low-frequency small-size projector. Full article
(This article belongs to the Special Issue Piezoelectric Transducers: Materials, Devices and Applications, Volume II)
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29 pages, 7653 KiB  
Review
Review of Recent Development of MEMS Speakers
by Haoran Wang, Yifei Ma, Qincheng Zheng, Ke Cao, Yao Lu and Huikai Xie
Micromachines 2021, 12(10), 1257; https://doi.org/10.3390/mi12101257 - 16 Oct 2021
Cited by 44 | Viewed by 13034
Abstract
Facilitated by microelectromechanical systems (MEMS) technology, MEMS speakers or microspeakers have been rapidly developed during the past decade to meet the requirements of the flourishing audio market. With advantages of a small footprint, low cost, and easy assembly, MEMS speakers are drawing extensive [...] Read more.
Facilitated by microelectromechanical systems (MEMS) technology, MEMS speakers or microspeakers have been rapidly developed during the past decade to meet the requirements of the flourishing audio market. With advantages of a small footprint, low cost, and easy assembly, MEMS speakers are drawing extensive attention for potential applications in hearing instruments, portable electronics, and the Internet of Things (IoT). MEMS speakers based on different transduction mechanisms, including piezoelectric, electrodynamic, electrostatic, and thermoacoustic actuation, have been developed and significant progresses have been made in commercialization in the last few years. In this article, the principle and modeling of each MEMS speaker type is briefly introduced first. Then, the development of MEMS speakers is reviewed with key specifications of state-of-the-art MEMS speakers summarized. The advantages and challenges of all four types of MEMS speakers are compared and discussed. New approaches to improve sound pressure levels (SPLs) of MEMS speakers are also proposed. Finally, the remaining challenges and outlook of MEMS speakers are given. Full article
(This article belongs to the Special Issue Micromachined Acoustic Transducers for Audio-Frequency Range)
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13 pages, 2498 KiB  
Article
New Ultrasensitive Sandwich-Type Immunoassay of Dendritic Tri-Fan Blade-like PdAuCu Nanoparticles/Amine-Functionalized Graphene Oxide for Label-Free Detection of Carcinoembryonic Antigen
by Pingping Xu, Wenpo Feng, Mei Wang, Ling Zhang, Gaofeng Liang and Aihua Jing
Micromachines 2021, 12(10), 1256; https://doi.org/10.3390/mi12101256 - 16 Oct 2021
Cited by 5 | Viewed by 2283
Abstract
The early detection of tumor markers has an effective role in the treatment of cancer. Here, a new sandwich-type electrochemical immunosensor for early label-free detection of the cancer biomarker carcinoembryonic antigen (CEA) was developed. Dendritic tri-fan blade-like PdAuCu nanoparticles (PdAuCu NPs)/amine functionalized graphene [...] Read more.
The early detection of tumor markers has an effective role in the treatment of cancer. Here, a new sandwich-type electrochemical immunosensor for early label-free detection of the cancer biomarker carcinoembryonic antigen (CEA) was developed. Dendritic tri-fan blade-like PdAuCu nanoparticles (PdAuCu NPs)/amine functionalized graphene oxide (NH2-GO) were the label of secondary antibodies (Ab2), and Au nanoparticle-decorated polydopamines (Au/PDA) were immobilized on a screen-printed carbon electrode (SPCE) as the substrate materials. Dendritic tri-fan blade-like PdAuCu NPs/NH2-GO was synthesized according to a simple hydrothermal procedure and used to immobilize antibodies (Ab2) with large surfaces areas, increased catalytic properties and good adsorption to amplify the current signals. Subsequently, Ab2/PdAuCu NPs/NH2-GO catalyzed the reduction of H2O2 in the sandwich-type immunoreactions. Under optimal conditions, the immunosensor exhibited a satisfactory response to CEA with a limit detection of 0.07 pg mL−1 and a linear detection range from 0.1 pg mL−1 to 200 ng mL−1. The proposed immunosensor could be suitable enough for a real sample analysis of CEA, and has clinical value in the early diagnosis of cancer. Full article
(This article belongs to the Special Issue Microparticle Fabrication and Its Biomedical Application)
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9 pages, 1667 KiB  
Article
Batch Transfer Printing of Small-Size Silicon Nano-Films with Flat Stamp
by Wenping Cao, Guochang Liu, Jinwei Miao, Guojun Zhang, Jiangong Cui, Yuhua Yang, Changde He, Wendong Zhang and Renxin Wang
Micromachines 2021, 12(10), 1255; https://doi.org/10.3390/mi12101255 - 16 Oct 2021
Cited by 4 | Viewed by 2287
Abstract
Silicon nano-film is essential for the rapidly developing fields of nanoscience and flexible electronics, due to its compatibility with the CMOS process. Viscoelastic PDMS material can adhere to Si, SiO2, and other materials via intermolecular force and play a key role [...] Read more.
Silicon nano-film is essential for the rapidly developing fields of nanoscience and flexible electronics, due to its compatibility with the CMOS process. Viscoelastic PDMS material can adhere to Si, SiO2, and other materials via intermolecular force and play a key role in flexible electronic devices. Researchers have studied many methods of transfer printing silicon nano-films based on PDMS stamps with pyramid microstructures. However, only large-scale transfer printing processes of silicon nano-films with line widths above 20 μm have been reported, mainly because the distribution of pyramid microstructures proposes a request on the size of silicon nano-films. In this paper, The PDMS base to the curing agent ratio affects the adhesion to silicon and enables the transfer, without the need for secondary alignment photolithography, and a flat stamp has been used during the transfer printing, with no requirement for the attaching pressure and detaching speed. Transfer printing of 20 μm wide structures has been realized, while the success rate is 99.3%. The progress is promising in the development of miniature flexible sensors, especially flexible hydrophone. Full article
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15 pages, 3016 KiB  
Article
A Pillar-Free Diffusion Device for Studying Chemotaxis on Supported Lipid Bilayers
by Jia Hao, Winfield Zhao, Jeong Min Oh and Keyue Shen
Micromachines 2021, 12(10), 1254; https://doi.org/10.3390/mi12101254 - 16 Oct 2021
Viewed by 2301
Abstract
Chemotactic cell migration plays a crucial role in physiological and pathophysiological processes. In tissues, cells can migrate not only through extracellular matrix (ECM), but also along stromal cell surfaces via membrane-bound receptor–ligand interactions to fulfill critical functions. However, there remains a lack of [...] Read more.
Chemotactic cell migration plays a crucial role in physiological and pathophysiological processes. In tissues, cells can migrate not only through extracellular matrix (ECM), but also along stromal cell surfaces via membrane-bound receptor–ligand interactions to fulfill critical functions. However, there remains a lack of models recapitulating chemotactic migration mediated through membrane-bound interactions. Here, using micro-milling, we engineered a multichannel diffusion device that incorporates a chemoattractant gradient and a supported lipid bilayer (SLB) tethered with membrane-bound factors that mimics stromal cell membranes. The chemoattractant channels are separated by hydrogel barriers from SLB in the cell loading channel, which enable precise control of timing and profile of the chemokine gradients applied on cells interacting with SLB. The hydrogel barriers are formed in pillar-free channels through a liquid pinning process, which eliminates complex cleanroom-based fabrications and distortion of chemoattractant gradient by pillars in typical microfluidic hydrogel barrier designs. As a proof-of-concept, we formed an SLB tethered with ICAM-1, and demonstrated its lateral mobility and different migratory behavior of Jurkat T cells on it from those on immobilized ICAM-1, under a gradient of chemokine CXCL12. Our platform can thus be widely used to investigate membrane-bound chemotaxis such as in cancer, immune, and stem cells. Full article
(This article belongs to the Special Issue Microfluidics Technologies for Cell-Based Assays, Volume II)
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12 pages, 3447 KiB  
Article
Microfluidic Bioreactor Made of Cyclo-Olefin Polymer for Observing On-Chip Platelet Production
by Hiroki Kumon, Shinya Sakuma, Sou Nakamura, Hisataka Maruyama, Koji Eto and Fumihito Arai
Micromachines 2021, 12(10), 1253; https://doi.org/10.3390/mi12101253 - 15 Oct 2021
Cited by 5 | Viewed by 2946
Abstract
We previously proposed a microfluidic bioreactor with glass–Si–glass layers to evaluate the effect of the fluid force on platelet (PLT) production and fabricated a three-dimensional (3D) microchannel by combining grayscale photolithography and deep reactive ion etching. However, a challenge remains in observing the [...] Read more.
We previously proposed a microfluidic bioreactor with glass–Si–glass layers to evaluate the effect of the fluid force on platelet (PLT) production and fabricated a three-dimensional (3D) microchannel by combining grayscale photolithography and deep reactive ion etching. However, a challenge remains in observing the detailed process of PLT production owing to the low visibility of the microfluidic bioreactor. In this paper, we present a transparent microfluidic bioreactor made of cyclo-olefin polymer (COP) with which to observe the process of platelet-like particle (PLP) production under a bright-field, which allows us to obtain image data at a high sampling rate. We succeeded in fabricating the COP microfluidic bioreactor with a 3D microchannel. We investigated the bonding strength of COP-COP layers and confirmed the effectiveness of the microfluidic bioreactor. Results of on-chip PLP production using immortalized megakaryocyte cell lines (imMKCLs) derived from human-induced pluripotent stem cells show that the average total number of produced PLPs per imMKCL was 17.6 PLPs/imMKCL, which is comparable to that of our previous glass–Si–glass microfluidic bioreactor (17.4 PLPs/imMKCL). We succeeded in observing PLP production under a bright-field using the presented microfluidic bioreactor and confirmed that PLP fragmented in a narrow area of proplatelet-like protrusions. Full article
(This article belongs to the Special Issue 3D Biomedical Microdevices)
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11 pages, 3697 KiB  
Article
Design of Broadband Flat Optical Frequency Comb Based on Cascaded Sign-Alternated Dispersion Tellurite Microstructure Fiber
by Guocheng Huang, Meicheng Fu, Junli Qi, Jinghan Pan, Wenjun Yi and Xiujian Li
Micromachines 2021, 12(10), 1252; https://doi.org/10.3390/mi12101252 - 15 Oct 2021
Cited by 2 | Viewed by 1774
Abstract
We designed a tellurite microstructure fiber (TMF) and proposed a broadband optical frequency comb generation scheme that was based on electro-optical modulation and cascaded sign-alternated dispersion TMF (CSAD-TMF). In addition, the influence of different nonlinear effects, the ultrashort pulse evolution in the CSAD-TMF [...] Read more.
We designed a tellurite microstructure fiber (TMF) and proposed a broadband optical frequency comb generation scheme that was based on electro-optical modulation and cascaded sign-alternated dispersion TMF (CSAD-TMF). In addition, the influence of different nonlinear effects, the ultrashort pulse evolution in the CSAD-TMF with the anomalous dispersion (AD) zones and the normal dispersion (ND) zones were analyzed based on the generalized nonlinear Schrodinger equations (GNLSE) modelling. According to the simulations, when the input seed comb had a repetition rate of 20 GHz and had an input pulse peak power of 30 W, the generation scheme could generate optical frequency combs with a 6 dB spectral bandwidth spanning over 170 nm centered at 1550 nm. Furthermore, the generated combs showed good coherence in performance over the whole 6 dB spectral bandwidth. The highly coherent optical frequency combs can be used as high-repetition-rate, multi-wavelength light sources for various integrated microwave photonics and ultrafast optical signal processing applications. Full article
(This article belongs to the Special Issue Photonic Chips for Optical Communications)
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25 pages, 3321 KiB  
Review
Oxygen Generation Using Catalytic Nano/Micromotors
by Sumayyah Naeem, Farah Naeem, Jawayria Mujtaba, Ashish Kumar Shukla, Shirsendu Mitra, Gaoshan Huang, Larisa Gulina, Polina Rudakovskaya, Jizhai Cui, Valeri Tolstoy, Dmitry Gorin, Yongfeng Mei, Alexander A. Solovev and Krishna Kanti Dey
Micromachines 2021, 12(10), 1251; https://doi.org/10.3390/mi12101251 - 15 Oct 2021
Cited by 13 | Viewed by 5800
Abstract
Gaseous oxygen plays a vital role in driving the metabolism of living organisms and has multiple agricultural, medical, and technological applications. Different methods have been discovered to produce oxygen, including plants, oxygen concentrators and catalytic reactions. However, many such approaches are relatively expensive, [...] Read more.
Gaseous oxygen plays a vital role in driving the metabolism of living organisms and has multiple agricultural, medical, and technological applications. Different methods have been discovered to produce oxygen, including plants, oxygen concentrators and catalytic reactions. However, many such approaches are relatively expensive, involve challenges, complexities in post-production processes or generate undesired reaction products. Catalytic oxygen generation using hydrogen peroxide is one of the simplest and cleanest methods to produce oxygen in the required quantities. Chemically powered micro/nanomotors, capable of self-propulsion in liquid media, offer convenient and economic platforms for on-the-fly generation of gaseous oxygen on demand. Micromotors have opened up opportunities for controlled oxygen generation and transport under complex conditions, critical medical diagnostics and therapy. Mobile oxygen micro-carriers help better understand the energy transduction efficiencies of micro/nanoscopic active matter by careful selection of catalytic materials, fuel compositions and concentrations, catalyst surface curvatures and catalytic particle size, which opens avenues for controllable oxygen release on the level of a single catalytic microreactor. This review discusses various micro/nanomotor systems capable of functioning as mobile oxygen generators while highlighting their features, efficiencies and application potentials in different fields. Full article
(This article belongs to the Special Issue Dream Nanomachines: Recent Advances in Nano/Micromotors)
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32 pages, 4842 KiB  
Review
Modelling Human Physiology on-Chip: Historical Perspectives and Future Directions
by Sirjana Pun, Li Cai Haney and Riccardo Barrile
Micromachines 2021, 12(10), 1250; https://doi.org/10.3390/mi12101250 - 15 Oct 2021
Cited by 16 | Viewed by 5487
Abstract
For centuries, animal experiments have contributed much to our understanding of mechanisms of human disease, but their value in predicting the effectiveness of drug treatments in the clinic has remained controversial. Animal models, including genetically modified ones and experimentally induced pathologies, often do [...] Read more.
For centuries, animal experiments have contributed much to our understanding of mechanisms of human disease, but their value in predicting the effectiveness of drug treatments in the clinic has remained controversial. Animal models, including genetically modified ones and experimentally induced pathologies, often do not accurately reflect disease in humans, and therefore do not predict with sufficient certainty what will happen in humans. Organ-on-chip (OOC) technology and bioengineered tissues have emerged as promising alternatives to traditional animal testing for a wide range of applications in biological defence, drug discovery and development, and precision medicine, offering a potential alternative. Recent technological breakthroughs in stem cell and organoid biology, OOC technology, and 3D bioprinting have all contributed to a tremendous progress in our ability to design, assemble and manufacture living organ biomimetic systems that more accurately reflect the structural and functional characteristics of human tissue in vitro, and enable improved predictions of human responses to drugs and environmental stimuli. Here, we provide a historical perspective on the evolution of the field of bioengineering, focusing on the most salient milestones that enabled control of internal and external cell microenvironment. We introduce the concepts of OOCs and Microphysiological systems (MPSs), review various chip designs and microfabrication methods used to construct OOCs, focusing on blood-brain barrier as an example, and discuss existing challenges and limitations. Finally, we provide an overview on emerging strategies for 3D bioprinting of MPSs and comment on the potential role of these devices in precision medicine. Full article
(This article belongs to the Special Issue Unlocking the Next Level in Precision Medicine with Organ-on-Chips and Biosensors)
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25 pages, 10013 KiB  
Review
A Review of Microrobot’s System: Towards System Integration for Autonomous Actuation In Vivo
by Zhongyi Li, Chunyang Li, Lixin Dong and Jing Zhao
Micromachines 2021, 12(10), 1249; https://doi.org/10.3390/mi12101249 - 15 Oct 2021
Cited by 26 | Viewed by 4808
Abstract
Microrobots have received great attention due to their great potential in the biomedical field, and there has been extraordinary progress on them in many respects, making it possible to use them in vivo clinically. However, the most important question is how to get [...] Read more.
Microrobots have received great attention due to their great potential in the biomedical field, and there has been extraordinary progress on them in many respects, making it possible to use them in vivo clinically. However, the most important question is how to get microrobots to a given position accurately. Therefore, autonomous actuation technology based on medical imaging has become the solution receiving the most attention considering its low precision and efficiency of manual control. This paper investigates key components of microrobot’s autonomous actuation systems, including actuation systems, medical imaging systems, and control systems, hoping to help realize system integration of them. The hardware integration has two situations according to sharing the transmitting equipment or not, with the consideration of interference, efficiency, microrobot’s material and structure. Furthermore, system integration of hybrid actuation and multimodal imaging can improve the navigation effect of the microrobot. The software integration needs to consider the characteristics and deficiencies of the existing actuation algorithms, imaging algorithms, and the complex 3D working environment in vivo. Additionally, considering the moving distance in the human body, the autonomous actuation system combined with rapid delivery methods can deliver microrobots to specify position rapidly and precisely. Full article
(This article belongs to the Special Issue Imaging-Guided Intelligent Micromachines)
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7 pages, 2722 KiB  
Article
Growth and Drug Interaction Monitoring of NIH 3T3 Cells by Image Analysis and Capacitive Biosensor
by Gayoung Lee, Jaehun Jeong, Yeeun Kim, Dahyun Kang, Sooyong Shin, Jongwon Lee, Sung Ho Jeon and Moongyu Jang
Micromachines 2021, 12(10), 1248; https://doi.org/10.3390/mi12101248 - 14 Oct 2021
Cited by 6 | Viewed by 2094
Abstract
Capacitive biosensors are manufactured on glass slides using the semiconductor process to monitor cell growth and cell–drug interactions in real time. Capacitance signals are continuously monitored for each 10 min interval during a 48 h period, with the variations of frequency from 1 [...] Read more.
Capacitive biosensors are manufactured on glass slides using the semiconductor process to monitor cell growth and cell–drug interactions in real time. Capacitance signals are continuously monitored for each 10 min interval during a 48 h period, with the variations of frequency from 1 kHz to 1 MHz. The capacitance values showed a gradual increase with the increase in NIH 3T3 cell numbers. After 48 h of growth, 6.67 μg/mL puromycin is injected for the monitoring of the cell–drug interaction. The capacitance values rapidly increased during a period of about 10 h, reflecting the rapid increase in the cell numbers. In this study, we monitored the state of cells and the cell–drug interactions using the developed capacitive biosensor. Additionally, we monitored the state of cell behavior using a JuLiTM Br&FL microscope. The monitoring of cell state by means of a capacitive biosensor is more sensitive than confluence measuring using a JuLiTM Br&FL microscope image. The developed capacitive biosensor could be applied in a wide range of bio-medical areas; for example, non-destructive real-time cell growth and cell–drug interaction monitoring. Full article
(This article belongs to the Special Issue Nano Korea 2021)
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13 pages, 1146 KiB  
Article
Configurable 3D Printed Microfluidic Multiport Valves with Axial Compression
by Juliane Diehm, Verena Hackert and Matthias Franzreb
Micromachines 2021, 12(10), 1247; https://doi.org/10.3390/mi12101247 - 14 Oct 2021
Cited by 5 | Viewed by 3815
Abstract
In the last decade, the fabrication of microfluidic chips was revolutionized by 3D printing. It is not only used for rapid prototyping of molds, but also for manufacturing of complex chips and even integrated active parts like pumps and valves, which are essential [...] Read more.
In the last decade, the fabrication of microfluidic chips was revolutionized by 3D printing. It is not only used for rapid prototyping of molds, but also for manufacturing of complex chips and even integrated active parts like pumps and valves, which are essential for many microfluidic applications. The manufacturing of multiport injection valves is of special interest for analytical microfluidic systems, as they can reduce the injection to detection dead volume and thus enhance the resolution and decrease the detection limit. Designs reported so far use radial compression of rotor and stator. However, commercially available nonprinted valves usually feature axial compression, as this allows for adjustable compression and the possibility to integrate additional sealing elements. In this paper, we transfer the axial approach to 3D-printed valves and compare two different printing techniques, as well as six different sealing configurations. The tightness of the system is evaluated with optical examination, weighing, and flow measurements. The developed system shows similar performance to commercial or other 3D-printed valves with no measurable leakage for the static case and leakages below 0.5% in the dynamic case, can be turned automatically with a stepper motor, is easy to scale up, and is transferable to other printing methods and materials without design changes. Full article
(This article belongs to the Special Issue Rapid Prototyping Methods for Microfluidics and Lab-on-a-Chip)
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11 pages, 2266 KiB  
Article
Transparent and Flexible Vibration Sensor Based on a Wheel-Shaped Hybrid Thin Membrane
by Siyoung Lee, Eun Kwang Lee, Eunho Lee and Geun Yeol Bae
Micromachines 2021, 12(10), 1246; https://doi.org/10.3390/mi12101246 - 14 Oct 2021
Cited by 2 | Viewed by 2942
Abstract
With the advent of human–machine interaction and the Internet of Things, wearable and flexible vibration sensors have been developed to detect human voices and surrounding vibrations transmitted to humans. However, previous wearable vibration sensors have limitations in the sensing performance, such as frequency [...] Read more.
With the advent of human–machine interaction and the Internet of Things, wearable and flexible vibration sensors have been developed to detect human voices and surrounding vibrations transmitted to humans. However, previous wearable vibration sensors have limitations in the sensing performance, such as frequency response, linearity of sensitivity, and esthetics. In this study, a transparent and flexible vibration sensor was developed by incorporating organic/inorganic hybrid materials into ultrathin membranes. The sensor exhibited a linear and high sensitivity (20 mV/g) and a flat frequency response (80–3000 Hz), which are attributed to the wheel-shaped capacitive diaphragm structure fabricated by exploiting the high processability and low stiffness of the organic material SU-8 and the high conductivity of the inorganic material ITO. The sensor also has sufficient esthetics as a wearable device because of the high transparency of SU-8 and ITO. In addition, the temperature of the post-annealing process after ITO sputtering was optimized for the high transparency and conductivity. The fabricated sensor showed significant potential for use in transparent healthcare devices to monitor the vibrations transmitted from hand-held vibration tools and in a skin-attachable vocal sensor. Full article
(This article belongs to the Special Issue Hybrid Organic Electronics: Material, Structure and Application)
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14 pages, 2366 KiB  
Review
Systematic Review: Microfluidics and Plasmodium
by Nicolas Thorne, Luis Flores-Olazo, Rocío Egoávil-Espejo, Emir A. Vela, Julien Noel, Julio Valdivia-Silva and Danny van Noort
Micromachines 2021, 12(10), 1245; https://doi.org/10.3390/mi12101245 - 14 Oct 2021
Cited by 5 | Viewed by 3248
Abstract
Malaria affects 228 million people worldwide each year, causing severe disease and worsening the conditions of already vulnerable populations. In this review, we explore how malaria has been detected in the past and how it can be detected in the future. Our primary [...] Read more.
Malaria affects 228 million people worldwide each year, causing severe disease and worsening the conditions of already vulnerable populations. In this review, we explore how malaria has been detected in the past and how it can be detected in the future. Our primary focus is on finding new directions for low-cost diagnostic methods that unspecialized personnel can apply in situ. Through this review, we show that microfluidic devices can help pre-concentrate samples of blood infected with malaria to facilitate the diagnosis. Importantly, these devices can be made cheaply and be readily deployed in remote locations. Full article
(This article belongs to the Special Issue Microfluidics for Cells and Other Organisms, Volume III)
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11 pages, 5107 KiB  
Article
A Novel Step–Doped Channel AlGaN/GaN HEMTs with Improved Breakdown Performance
by Jianhua Liu, Yufeng Guo, Jun Zhang, Jiafei Yao, Man Li, Maolin Zhang, Jing Chen, Xiaoming Huang and Chenyang Huang
Micromachines 2021, 12(10), 1244; https://doi.org/10.3390/mi12101244 - 14 Oct 2021
Cited by 4 | Viewed by 2444
Abstract
The AlGaN/GaN high electron mobility transistor with a step–doped channel (SDC–HEMT) is first proposed in this paper. The potential distribution and the electric field (E–field) distribution of the device are explored by the numerical approach and analytical approach simultaneously. By introducing extra dopants [...] Read more.
The AlGaN/GaN high electron mobility transistor with a step–doped channel (SDC–HEMT) is first proposed in this paper. The potential distribution and the electric field (E–field) distribution of the device are explored by the numerical approach and analytical approach simultaneously. By introducing extra dopants to the channel layer, the E–field distribution along the AlGaN/GaN heterojunction interface is reshaped, resulting in an improved breakdown characteristic. An optimized doping concentration gradient of channel layer of 2 × 1016 cm−3/step is proposed and verified by simulations. The breakdown voltage (BV) of the optimized SDC–HEMT reaches 1486 V with a 59.8% improvement compared with conventional AlGaN/GaN HEMT. In addition, the average E–field in the region between gate and drain improves from 1.5 to 2.5 MV/cm. Based on the equivalent potential method (EPM), an analytical model of the E–field and potential distribution is presented. The veracity and effectiveness of the proposed methodology is verified by the good agreement between the simulated and modeled results. Full article
(This article belongs to the Special Issue GaN-Based Semiconductor Devices)
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17 pages, 2927 KiB  
Article
Multi-Input Logic-in-Memory for Ultra-Low Power Non-Von Neumann Computing
by Tommaso Zanotti, Paolo Pavan and Francesco Maria Puglisi
Micromachines 2021, 12(10), 1243; https://doi.org/10.3390/mi12101243 - 14 Oct 2021
Cited by 7 | Viewed by 2285
Abstract
Logic-in-memory (LIM) circuits based on the material implication logic (IMPLY) and resistive random access memory (RRAM) technologies are a candidate solution for the development of ultra-low power non-von Neumann computing architectures. Such architectures could enable the energy-efficient implementation of hardware accelerators for novel [...] Read more.
Logic-in-memory (LIM) circuits based on the material implication logic (IMPLY) and resistive random access memory (RRAM) technologies are a candidate solution for the development of ultra-low power non-von Neumann computing architectures. Such architectures could enable the energy-efficient implementation of hardware accelerators for novel edge computing paradigms such as binarized neural networks (BNNs) which rely on the execution of logic operations. In this work, we present the multi-input IMPLY operation implemented on a recently developed smart IMPLY architecture, SIMPLY, which improves the circuit reliability, reduces energy consumption, and breaks the strict design trade-offs of conventional architectures. We show that the generalization of the typical logic schemes used in LIM circuits to multi-input operations strongly reduces the execution time of complex functions needed for BNNs inference tasks (e.g., the 1-bit Full Addition, XNOR, Popcount). The performance of four different RRAM technologies is compared using circuit simulations leveraging a physics-based RRAM compact model. The proposed solution approaches the performance of its CMOS equivalent while bypassing the von Neumann bottleneck, which gives a huge improvement in bit error rate (by a factor of at least 108) and energy-delay product (projected up to a factor of 1010). Full article
(This article belongs to the Special Issue Advances in Emerging Nonvolatile Memory)
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