Micromachines

9 pages, 1217 KiB

Open AccessArticle

Absolute Copy Numbers of β-Actin Proteins Collected from 10,000 Single Cells

by Beiyuan Fan, Xiufeng Li, Lixing Liu, Deyong Chen, Shanshan Cao, Dong Men, Junbo Wang and Jian Chen

Micromachines 2018, 9(5), 254; https://doi.org/10.3390/mi9050254 - 22 May 2018

Cited by 6 | Viewed by 4295

Abstract

Semi-quantitative studies have located varied expressions of β-actin proteins at the population level, questioning their roles as internal controls in western blots, while the absolute copy numbers of β-actins at the single-cell level are missing. In this study, a polymeric microfluidic flow cytometry [...] Read more.

Semi-quantitative studies have located varied expressions of β-actin proteins at the population level, questioning their roles as internal controls in western blots, while the absolute copy numbers of β-actins at the single-cell level are missing. In this study, a polymeric microfluidic flow cytometry was used for single-cell analysis, and the absolute copy numbers of single-cell β-actin proteins were quantified as 9.9 ± 4.6 × 10⁵, 6.8 ± 4.0 × 10⁵ and 11.0 ± 5.5 × 10⁵ per cell for A549 (n_cell = 14,754), Hep G2 (n_cell = 36,949), and HeLa (n_cell = 24,383), respectively. High coefficients of variation (~50%) and high quartile coefficients of dispersion (~30%) were located, indicating significant variations of β-actin proteins within the same cell type. Low p values (≪0.01) and high classification rates based on neural network (~70%) were quantified among A549, Hep G2 and HeLa cells, suggesting expression differences of β-actin proteins among three cell types. In summary, the results reported here indicate significant variations of β-actin proteins within the same cell type from cell to cell, and significant expression differences of β-actin proteins among different cell types, strongly questioning the properties of using β-actin proteins as internal controls in western blots. Full article

(This article belongs to the Special Issue Glassy Materials Based Microdevices)

► Show Figures

Figure 1

12 pages, 4373 KiB

Open AccessArticle

Microfluidic Formation of Double-Stacked Planar Bilayer Lipid Membranes by Controlling the Water-Oil Interface

by Kan Shoji and Ryuji Kawano

Micromachines 2018, 9(5), 253; https://doi.org/10.3390/mi9050253 - 22 May 2018

Cited by 9 | Viewed by 6135

Abstract

This study reports double-stacked planar bilayer lipid membranes (pBLMs) formed using a droplet contact method (DCM) for microfluidic formation with five-layered microchannels that have four micro guide pillars. pBLMs are valuable for analyzing membrane proteins and modeling cell membranes. Furthermore, multiple-pBLM systems have [...] Read more.

This study reports double-stacked planar bilayer lipid membranes (pBLMs) formed using a droplet contact method (DCM) for microfluidic formation with five-layered microchannels that have four micro guide pillars. pBLMs are valuable for analyzing membrane proteins and modeling cell membranes. Furthermore, multiple-pBLM systems have broadened the field of application such as electronic components, light-sensors, and batteries because of electrical characteristics of pBLMs and membrane proteins. Although multiple-stacked pBLMs have potential, the formation of multiple-pBLMs on a micrometer scale still faces challenges. In this study, we applied a DCM strategy to pBLM formation using microfluidic techniques and attempted to form double-stacked pBLMs in micro-meter scale. First, microchannels with micro pillars were designed via hydrodynamic simulations to form a five-layered flow with aqueous and lipid/oil solutions. Then, pBLMs were successfully formed by controlling the pumping pressure of the solutions and allowing contact between the two lipid monolayers. Finally, pore-forming proteins were reconstituted in the pBLMs, and ion current signals of nanopores were obtained as confirmed by electrical measurements, indicating that double-stacked pBLMs were successfully formed. The strategy for the double-stacked pBLM formation can be applied to highly integrated nanopore-based systems. Full article

(This article belongs to the Section B：Biology and Biomedicine)

► Show Figures

Graphical abstract

14 pages, 22483 KiB

Open AccessArticle

A Micromachined Coupled-Cantilever for Piezoelectric Energy Harvesters

by Agin Vyas, Henrik Staaf, Cristina Rusu, Thorbjörn Ebefors, Jessica Liljeholm, Anderson D. Smith, Per Lundgren and Peter Enoksson

Micromachines 2018, 9(5), 252; https://doi.org/10.3390/mi9050252 - 21 May 2018

Cited by 13 | Viewed by 5233

Abstract

This paper presents a demonstration of the feasibility of fabricating micro-cantilever harvesters with extended stress distribution and enhanced bandwidth by exploiting an M-shaped two-degrees-of-freedom design. The measured mechanical response of the fabricated device displays the predicted dual resonance peak behavior with the fundamental [...] Read more.

This paper presents a demonstration of the feasibility of fabricating micro-cantilever harvesters with extended stress distribution and enhanced bandwidth by exploiting an M-shaped two-degrees-of-freedom design. The measured mechanical response of the fabricated device displays the predicted dual resonance peak behavior with the fundamental peak at the intended frequency. This design has the features of high energy conversion efficiency in a miniaturized environment where the available vibrational energy varies in frequency. It makes such a design suitable for future large volume production of integrated self powered sensors nodes for the Internet-of-Things. Full article

(This article belongs to the Special Issue Microsystems for Power, Energy, and Actuation)

► Show Figures

Figure 1

13 pages, 3361 KiB

Open AccessArticle

Simultaneous Measurement of Viscosity and Optical Density of Bacterial Growth and Death in a Microdroplet

by Karolina Sklodowska, Pawel R. Debski, Jacek A. Michalski, Piotr M. Korczyk, Miroslaw Dolata, Miroslaw Zajac and Slawomir Jakiela

Micromachines 2018, 9(5), 251; https://doi.org/10.3390/mi9050251 - 21 May 2018

Cited by 13 | Viewed by 6422

Abstract

Herein, we describe a novel method for the assessment of droplet viscosity moving inside microfluidic channels. The method allows for the monitoring of the rate of the continuous growth of bacterial culture. It is based on the analysis of the hydrodynamic resistance of [...] Read more.

Herein, we describe a novel method for the assessment of droplet viscosity moving inside microfluidic channels. The method allows for the monitoring of the rate of the continuous growth of bacterial culture. It is based on the analysis of the hydrodynamic resistance of a droplet that is present in a microfluidic channel, which affects its motion. As a result, we were able to observe and quantify the change in the viscosity of the dispersed phase that is caused by the increasing population of interacting bacteria inside a size-limited system. The technique allows for finding the correlation between the viscosity of the medium with a bacterial culture and its optical density. These features, together with the high precision of the measurement, make our viscometer a promising tool for various experiments in the field of analytical chemistry and microbiology, where the rigorous control of the conditions of the reaction and the monitoring of the size of bacterial culture are vital. Full article

(This article belongs to the Special Issue Integrated Microfluidics for Chemical Synthesis and Analysis)

► Show Figures

Graphical abstract

2 pages, 161 KiB

Open AccessEditorial

Editorial for the Special Issue on Passive Micromixers

by Arshad Afzal, Mubashshir A. Ansari and Kwang-Yong Kim

Micromachines 2018, 9(5), 250; https://doi.org/10.3390/mi9050250 - 21 May 2018

Cited by 1 | Viewed by 2744

Abstract

Micromixers are important components of microfluidic systems [...] Full article

(This article belongs to the Special Issue Passive Micromixers)

24 pages, 3635 KiB

Open AccessArticle

Motion Constraints and Vanishing Point Aided Land Vehicle Navigation

by Zhenbo Liu, Naser El-Sheimy, Chunyang Yu and Yongyuan Qin

Micromachines 2018, 9(5), 249; https://doi.org/10.3390/mi9050249 - 20 May 2018

Cited by 21 | Viewed by 4675

Abstract

In the typical Inertial Navigation System (INS)/ Global Navigation Satellite System (GNSS) setup for ground vehicle navigation, measures should be taken to maintain the performance when there are GNSS signal outages. Usually, aiding sensors are utilized to reduce the INS drift. A full [...] Read more.

In the typical Inertial Navigation System (INS)/ Global Navigation Satellite System (GNSS) setup for ground vehicle navigation, measures should be taken to maintain the performance when there are GNSS signal outages. Usually, aiding sensors are utilized to reduce the INS drift. A full motion constraint model is developed allowing the online calibration of INS frame with respect to (w.r.t) the motion frame. To obtain better heading and lateral positioning performance, we propose to use of vanishing point (VP) observations of parallel lane markings from a single forward-looking camera to aid the INS. In the VP module, the relative attitude of the camera w.r.t the road frame is derived from the VP coordinates. The state-space model is developed with augmented vertical attitude error state. Finally, the VP module is added to a modified motion constrains module in the Extended Kalman filter (EKF) framework. Simulations and real-world experiments have shown the validity of VP-based method and improved heading and cross-track position accuracy compared with the solution without VP. The proposed method can work jointly with conventional visual odometry to aid INS for better accuracy and robustness. Full article

► Show Figures

Figure 1

12 pages, 2148 KiB

Open AccessArticle

Micro Droplet Formation towards Continuous Nanoparticles Synthesis

by Marek Wojnicki, Magdalena Luty-Błocho, Volker Hessel, Edit Csapó, Ditta Ungor and Krzysztof Fitzner

Micromachines 2018, 9(5), 248; https://doi.org/10.3390/mi9050248 - 18 May 2018

Cited by 16 | Viewed by 7143

Abstract

In this paper, micro droplets are generated in a microfluidic focusing contactor and then they move sequentially in a free-flowing mode (no wall contact). For this purpose, two different micro-flow glass devices (hydrophobic and hydrophilic) were used. During the study, the influence of [...] Read more.

In this paper, micro droplets are generated in a microfluidic focusing contactor and then they move sequentially in a free-flowing mode (no wall contact). For this purpose, two different micro-flow glass devices (hydrophobic and hydrophilic) were used. During the study, the influence of the flow rate of the water phase and the oil phase on the droplet size and size distribution was investigated. Moreover, the influence of the oil phase viscosity on the droplet size was analyzed. It was found that the size and size distribution of the droplets can be controlled simply by the aqueous phase flow rate. Additionally, 2D simulations to determine the droplet size were performed and compared with the experiment. Full article

(This article belongs to the Special Issue Synthesis, Assembly and Functional Application of Nanomaterials in Microsystems)

► Show Figures

Figure 1

13 pages, 968 KiB

Open AccessReview

Fluorescent Nanodiamond Applications for Cellular Process Sensing and Cell Tracking

by Sandra Claveau, Jean-Rémi Bertrand and François Treussart

Micromachines 2018, 9(5), 247; https://doi.org/10.3390/mi9050247 - 18 May 2018

Cited by 52 | Viewed by 7062

Abstract

Diamond nanocrystals smaller than 100 nm (nanodiamonds) are now recognized to be highly biocompatible. They can be made fluorescent with perfect photostability by creating nitrogen-vacancy (NV) color centers in the diamond lattice. The resulting fluorescent nanodiamonds (FND) have been used since the late [...] Read more.

Diamond nanocrystals smaller than 100 nm (nanodiamonds) are now recognized to be highly biocompatible. They can be made fluorescent with perfect photostability by creating nitrogen-vacancy (NV) color centers in the diamond lattice. The resulting fluorescent nanodiamonds (FND) have been used since the late 2000s as fluorescent probes for short- or long-term analysis. FND can be used both at the subcellular scale and the single cell scale. Their limited sub-diffraction size allows them to track intracellular processes with high spatio-temporal resolution and high contrast from the surrounding environment. FND can also track the fate of therapeutic compounds or whole cells in the organs of an organism. This review presents examples of FND applications (1) for intra and intercellular molecular processes sensing, also introducing the different potential biosensing applications based on the optically detectable electron spin resonance of NV⁻ centers; and (2) for tracking, firstly, FND themselves to determine their biodistribution, and secondly, using FND as cell tracking probes for diagnosis or follow-up purposes in oncology and regenerative medicine. Full article

(This article belongs to the Special Issue Color Centers in Diamond: Fabrication, Devices and Applications)

► Show Figures

Figure 1

20 pages, 3767 KiB

Open AccessArticle

Improved Morphological Filter Based on Variational Mode Decomposition for MEMS Gyroscope De-Noising

by Yicheng Wu, Chong Shen, Huiliang Cao and Xu Che

Micromachines 2018, 9(5), 246; https://doi.org/10.3390/mi9050246 - 17 May 2018

Cited by 20 | Viewed by 5850

Abstract

An adaptive multi-scale method based on the combination generalized morphological filter (CGMF) is presented for de-noising of the output signal from a MEMS gyroscope. A variational mode decomposition is employed to decompose the original signal into multi-scale modes. After choosing a length selection [...] Read more.

An adaptive multi-scale method based on the combination generalized morphological filter (CGMF) is presented for de-noising of the output signal from a MEMS gyroscope. A variational mode decomposition is employed to decompose the original signal into multi-scale modes. After choosing a length selection for the structure element (SE), the adaptive multi-scale CGMF method reduces the noise corresponding to the different modes, after which a reconstruction of the de-noised signal is obtained. From an analysis of the effect of de-noising, the main advantages of the present method are that it: (i) effectively overcomes deficiencies arising from data deviation compared with conventional morphological filters (MFs); (ii) effectively targets the different components of noise and provides efficacy in de-noising, not only primarily eliminating noise but also smoothing the waveform; and (iii) solves the problem of SE-length selection for a MF and produces feasible formulae of indicators such as the power spectral entropy and root mean square error for mode evaluations. Compared with the other current signal processing methods, the method proposed owns a simpler construction with a reasonable complexity, and it can offer better noise suppression effect. Experiments demonstrate the applicability and feasibility of the de-noising algorithm. Full article

► Show Figures

Figure 1

13 pages, 2725 KiB

Open AccessReview

Manipulation of Biological Cells Using a Robot-Aided Optical Tweezers System

by Mingyang Xie, Adnan Shakoor and Changcheng Wu

Micromachines 2018, 9(5), 245; https://doi.org/10.3390/mi9050245 - 17 May 2018

Cited by 37 | Viewed by 6212

Abstract

This article reviews the autonomous manipulation strategies of biological cells utilizing optical tweezers, mainly including optical direct and indirect manipulation strategies. The typical and latest achievements in the optical manipulation of cells are presented, and the existing challenges for autonomous optical manipulation of [...] Read more.

This article reviews the autonomous manipulation strategies of biological cells utilizing optical tweezers, mainly including optical direct and indirect manipulation strategies. The typical and latest achievements in the optical manipulation of cells are presented, and the existing challenges for autonomous optical manipulation of biological cells are also introduced. Moreover, the integrations of optical tweezers with other manipulation tools are presented, which broadens the applications of optical tweezers in the biomedical manipulation areas and will also foster new developments in cell-based physiology and pathology studies, such as cell migration, single cell surgery, and preimplantation genetic diagnosis (PGD). Full article

► Show Figures

Figure 1

11 pages, 1642 KiB

Open AccessArticle

Energy Harvesting Combat Boot for Satellite Positioning

by Haluk Akay, Ruize Xu, Dexter Chew Xuan Han, T. Hui Teo and Sang-Gook Kim

Micromachines 2018, 9(5), 244; https://doi.org/10.3390/mi9050244 - 17 May 2018

Cited by 11 | Viewed by 6415

Abstract

Most portable electronic devices are power-limited by battery capacity, and recharging these batteries often interrupts the user’s experience with the device. The product presented in this paper provides an alternative to powering portables by converting regular human walking motion to electricity. The device [...] Read more.

Most portable electronic devices are power-limited by battery capacity, and recharging these batteries often interrupts the user’s experience with the device. The product presented in this paper provides an alternative to powering portables by converting regular human walking motion to electricity. The device harvests electric power using air bulbs, distributed in the sole of a shoe to drive a series of micro-turbines connected to small DC motors. The number and position of air bulbs is optimized to harvest the maximum airflow from each foot-strike. The system is designed to continuously drive the micro-turbines by utilizing both outflow and inflow from the air bulbs. A prototype combat boot was fitted on the right foot of a 75 kg test subject, and produced an average continuous power on the order of 10 s of mW over a 22 Ω load during walking at 3.0 mph. This combat boot provides enough electric power to a passive GPS tracker that periodically relays geographical coordinates to a smartphone via satellite without battery replacement. Full article

(This article belongs to the Special Issue Microsystems for Power, Energy, and Actuation)

► Show Figures

Figure 1

29 pages, 1892 KiB

Open AccessFeature PaperReview

Nanostructure-Enabled and Macromolecule-Grafted Surfaces for Biomedical Applications

by Madeline Small, Addison Faglie, Alexandra J. Craig, Martha Pieper, Vivian E. Fernand Narcisse, Pierre F. Neuenschwander and Shih-Feng Chou

Micromachines 2018, 9(5), 243; https://doi.org/10.3390/mi9050243 - 17 May 2018

Cited by 10 | Viewed by 6028

Abstract

Advances in nanotechnology and nanomaterials have enabled the development of functional biomaterials with surface properties that reduce the rate of the device rejection in injectable and implantable biomaterials. In addition, the surface of biomaterials can be functionalized with macromolecules for stimuli-responsive purposes to [...] Read more.

Advances in nanotechnology and nanomaterials have enabled the development of functional biomaterials with surface properties that reduce the rate of the device rejection in injectable and implantable biomaterials. In addition, the surface of biomaterials can be functionalized with macromolecules for stimuli-responsive purposes to improve the efficacy and effectiveness in drug release applications. Furthermore, macromolecule-grafted surfaces exhibit a hierarchical nanostructure that mimics nanotextured surfaces for the promotion of cellular responses in tissue engineering. Owing to these unique properties, this review focuses on the grafting of macromolecules on the surfaces of various biomaterials (e.g., films, fibers, hydrogels, and etc.) to create nanostructure-enabled and macromolecule-grafted surfaces for biomedical applications, such as thrombosis prevention and wound healing. The macromolecule-modified surfaces can be treated as a functional device that either passively inhibits adverse effects from injectable and implantable devices or actively delivers biological agents that are locally based on proper stimulation. In this review, several methods are discussed to enable the surface of biomaterials to be used for further grafting of macromolecules. In addition, we review surface-modified films (coatings) and fibers with respect to several biomedical applications. Our review provides a scientific update on the current achievements and future trends of nanostructure-enabled and macromolecule-grafted surfaces in biomedical applications. Full article

(This article belongs to the Special Issue Biomedical Applications of Nanotechnology and Nanomaterials)

► Show Figures

Figure 1

11 pages, 3429 KiB

Open AccessFeature PaperArticle

Micromachined Planar Supercapacitor with Interdigital Buckypaper Electrodes

by Yun-Ting Chen, Cheng-Wen Ma, Chia-Ming Chang and Yao-Joe Yang

Micromachines 2018, 9(5), 242; https://doi.org/10.3390/mi9050242 - 16 May 2018

Cited by 13 | Viewed by 5118

Abstract

In this work, a flexible micro-supercapacitor with interdigital planar buckypaper electrodes is presented. A simple fabrication process involving vacuum filtration method and SU-8 molding techniques is proposed to fabricate in-plane interdigital buckypaper electrodes on a membrane filter substrate. The proposed process exhibits excellent [...] Read more.

In this work, a flexible micro-supercapacitor with interdigital planar buckypaper electrodes is presented. A simple fabrication process involving vacuum filtration method and SU-8 molding techniques is proposed to fabricate in-plane interdigital buckypaper electrodes on a membrane filter substrate. The proposed process exhibits excellent flexibility for future integration of the micro-supercapacitors (micro-SC) with other electronic components. The device’s maximum specific capacitance measured using cyclic voltammetry was 107.27 mF/cm² at a scan rate of 20 mV/s. The electrochemical stability was investigated by measuring the performance of charge-discharge at different discharge rates. Devices with different buckypaper electrode thicknesses were also fabricated and measured. The specific capacitance of the proposed device increased linearly with the buckypaper electrode thickness. The measured leakage current was approximately 9.95 µA after 3600 s. The device exhibited high cycle stability, with 96.59% specific capacitance retention after 1000 cycles. A Nyquist plot of the micro-SC was also obtained by measuring the impedances with frequencies from 1 Hz to 50 kHz; it indicated that the equivalent series resistance value was approximately 18 Ω. Full article

(This article belongs to the Special Issue Atomic Scale Materials for Electronic and Photonic Devices)

► Show Figures

Figure 1

13 pages, 1987 KiB

Open AccessArticle

Hysteresis Compensation and Sliding Mode Control with Perturbation Estimation for Piezoelectric Actuators

by Bingxiao Ding and Yangmin Li

Micromachines 2018, 9(5), 241; https://doi.org/10.3390/mi9050241 - 16 May 2018

Cited by 33 | Viewed by 4602

Abstract

Based on the background of atomic force microscope (AFM) driven by piezoelectric actuators (PEAs), this paper proposes a sliding mode control coupled with an inverse Bouc–Wen (BW) hysteresis compensator to improve the positioning performance of PEAs. The intrinsic hysteresis and creep characteristics degrade [...] Read more.

Based on the background of atomic force microscope (AFM) driven by piezoelectric actuators (PEAs), this paper proposes a sliding mode control coupled with an inverse Bouc–Wen (BW) hysteresis compensator to improve the positioning performance of PEAs. The intrinsic hysteresis and creep characteristics degrade the performance of the PEA and cause accuracy loss. Although creep effect can be eliminated by the closed-loop control approach, hysteresis effects need to be compensated and alleviated by hysteresis compensators. For the purpose of dealing with the estimation errors, unmodeled vibration, and disturbances, a sliding mode control with perturbation estimation (SMCPE) method is adopted to enhance the performance and robustness of the system. In order to validate the feasibility and performance of the proposed method, experimental studies are carried out, and the results show that the proposed controller performs better than a proportional-integral-derivative (PID) controller at 1 and 2 Hz, reducing error to 1.2% and 1.4%, respectively. Full article

(This article belongs to the Section A：Physics)

► Show Figures

Figure 1

11 pages, 935 KiB

Open AccessArticle

How Hydrogen Dielectric Strength Forces the Work Voltage in the Electric Discharge Machining

by José António Almacinha, António Mendes Lopes, Pedro Rosa and José Duarte Marafona

Micromachines 2018, 9(5), 240; https://doi.org/10.3390/mi9050240 - 15 May 2018

Cited by 11 | Viewed by 3813

Abstract

An electro-thermal model based on the Joule heating effect is proposed to simulate a single discharge in an electric discharge machining process. Normally, the dielectric strength of the hydrocarbons oil is approximately 20 MV/m, but it varies with both the thickness of the [...] Read more.

An electro-thermal model based on the Joule heating effect is proposed to simulate a single discharge in an electric discharge machining process. Normally, the dielectric strength of the hydrocarbons oil is approximately 20 MV/m, but it varies with both the thickness of the film and its decomposition. After the breakdown, the hydrocarbon oil has an average dielectric strength value of 2 MV/m. This value is close to the dielectric strength of the hydrogen, which is the main gas that results from the hydrocarbon oil decomposition, at temperatures between 6000 K and 9000 K. Therefore, the electric discharge occurs in a hydrogen atmosphere that imposes both the discharge gap and the work voltage. A 200 V voltage is associated to a 100 μm discharge gap, leading to a 20 V work voltage. Therefore, the 3 V work voltage control corresponds to approximately 15 μm. In other words, the increase of the discharge gap originates other discharge during the discharge pulse. The work voltage control, together with the multiple discharge method, is taken into account. The 100 μm discharge gap corresponds to the higher value of the transitory discharge gap that over evaluates the material removal and the tool wear rates. The results of the numerical simulations are validated with experimental data. Full article

► Show Figures

Figure 1

8 pages, 12076 KiB

Open AccessArticle

An Organic Flexible Artificial Bio-Synapses with Long-Term Plasticity for Neuromorphic Computing

by Tian-Yu Wang, Zhen-Yu He, Lin Chen, Hao Zhu, Qing-Qing Sun, Shi-Jin Ding, Peng Zhou and David Wei Zhang

Micromachines 2018, 9(5), 239; https://doi.org/10.3390/mi9050239 - 15 May 2018

Cited by 30 | Viewed by 5511

Abstract

Artificial synapses, with synaptic plasticity, are the key components of constructing the neuromorphic computing system and mimicking the bio-synaptic function. Traditional synaptic devices are based on silicon and inorganic materials, while organic electronics can open up new opportunities for flexible devices. Here, a [...] Read more.

Artificial synapses, with synaptic plasticity, are the key components of constructing the neuromorphic computing system and mimicking the bio-synaptic function. Traditional synaptic devices are based on silicon and inorganic materials, while organic electronics can open up new opportunities for flexible devices. Here, a flexible artificial synaptic device with an organic functional layer was proposed. The organic device showed good switching behaviors such as ON/OFF ratio over 100 at low operation voltages. The set and reset voltages were lower than 0.5 V and −0.25 V, respectively. The long-term plasticity, spike-timing-dependent plasticity learning rules (STDP), and forgetting function were emulated using the device. The retention times of the excitatory and inhibitory post-synaptic currents were both longer than 60 s. The long-term plasticity was repeatable without noticeable degradation after the application of five voltage pulse cycles to the top electrode. These results indicate that our organic flexible device has the potential to be applied in bio-inspired neuromorphic systems. Full article

(This article belongs to the Special Issue Flexible Electronics: Fabrication and Ubiquitous Integration)

► Show Figures

Figure 1

11 pages, 2919 KiB

Open AccessArticle

Fabrication and Characterization of Inhomogeneous Curved Artificial Compound Eye

by Fengli Liu, Xiaolei Diao, Lun Li, Yongping Hao and Zhongyuan Jiao

Micromachines 2018, 9(5), 238; https://doi.org/10.3390/mi9050238 - 15 May 2018

Cited by 7 | Viewed by 3154

Abstract

Compared with the conventional compound eye processing method, a new fabrication method—namely, a mold casting method—was presented. This method is simple, low-cost, easy to implement, and can be reused. A bionic compound eye array model with 61 ommatidia arranged inhomogeneously onto a curved [...] Read more.

Compared with the conventional compound eye processing method, a new fabrication method—namely, a mold casting method—was presented. This method is simple, low-cost, easy to implement, and can be reused. A bionic compound eye array model with 61 ommatidia arranged inhomogeneously onto a curved surface was fabricated. The curved surface had a radius of 9 mm and a thickness of 0.5 mm. The margin imaging quality was improved significantly by the analysis of light beam focus and the optical imaging properties of the fabricated compound eye. The sub-image of each ommatidium had a high resolution. There was 5% error between the collecting spot brightness and simulation analysis results, which proved that the production method is feasible. Full article

► Show Figures

Figure 1

3 pages, 183 KiB

Open AccessEditorial

Editorial for the Special Issue on Piezoelectric MEMS

by Ulrich Schmid and Michael Schneider

Micromachines 2018, 9(5), 237; https://doi.org/10.3390/mi9050237 - 15 May 2018

Cited by 2 | Viewed by 2851

Abstract

Electromechanical transducers that utilize the piezoelectric effect have been increasingly used in micro-electromechanical systems (MEMS) either as substrates or as thin films[...] Full article

(This article belongs to the Special Issue Piezoelectric MEMS)

10 pages, 2431 KiB

Open AccessFeature PaperCommunication

Assembly and Connection of Micropatterned Single Neurons for Neuronal Network Formation

by Shotaro Yoshida, Midori Kato-Negishi and Shoji Takeuchi

Micromachines 2018, 9(5), 235; https://doi.org/10.3390/mi9050235 - 15 May 2018

Cited by 20 | Viewed by 11082

Abstract

Engineering of neuronal network geometry by micropatterning technology is a key future technology for creating artificial brains on a chip. However, engineering of network geometry at the single-cell-level with functional morphology (axon/dendrite) and connectivity (synapses) is still challenging. Here, we describe a method [...] Read more.

Engineering of neuronal network geometry by micropatterning technology is a key future technology for creating artificial brains on a chip. However, engineering of network geometry at the single-cell-level with functional morphology (axon/dendrite) and connectivity (synapses) is still challenging. Here, we describe a method for controlling the axon and dendrite morphology of single primary-cultured neurons and assembling a neural circuit using mobile microplates. The microplates enabled morphological control of neurons by their shapes and bringing their ends into contact caused the formation of physical connections. Functional synapse formation at the connection was indicated by immunostaining of synapse-related proteins and intracellular Ca²⁺ imaging of neural activity. We believe that the method will be useful in engineering neural circuits with selected neurons and defined morphology. Full article

(This article belongs to the Special Issue State-of-the-Art Lab-on-a-Chip Technology in Japan)

► Show Figures

Figure 1

17 pages, 4509 KiB

Open AccessArticle

Decoupling Research of a Novel Three-Dimensional Force Flexible Tactile Sensor Based on an Improved BP Algorithm

by Yang Song, Feilu Wang and Zhenya Zhang

Micromachines 2018, 9(5), 236; https://doi.org/10.3390/mi9050236 - 14 May 2018

Cited by 19 | Viewed by 4105

Abstract

Decoupling research on flexible tactile sensors play a very important role in the intelligent robot skin and tactile-sensing fields. In this paper, an efficient machine learning method based on the improved back-propagation (BP) algorithm is proposed to decouple the mapping relationship between the [...] Read more.

Decoupling research on flexible tactile sensors play a very important role in the intelligent robot skin and tactile-sensing fields. In this paper, an efficient machine learning method based on the improved back-propagation (BP) algorithm is proposed to decouple the mapping relationship between the resistances of force-sensitive conductive pillars and three-dimensional forces for the 6 × 6 novel flexible tactile sensor array. Tactile-sensing principles and numerical experiments are analyzed. The tactile sensor array model accomplishes the decomposition of the force components by its delicate structure, and avoids direct interference among the electrodes of the sensor array. The force components loaded on the tactile sensor are decoupled with a very high precision from the resistance signal by the improved BP algorithm. The decoupling results show that the k-cross validation (k-CV) algorithm is a highly effective method to improve the decoupling precision of force components for the novel tactile sensor. The large dataset with the k-CV method obtains a better decoupling accuracy of the force components than the small dataset. All of the decoupling results are fairly good, and they indicate that the improved BP model with a strong non-linear approaching ability has an efficient and valid performance in decoupling force components for the tactile sensor. Full article

(This article belongs to the Special Issue Tactile Sensing for Soft Robotics and Wearables)

► Show Figures

Figure 1

8 pages, 2581 KiB

Open AccessArticle

Side-Group Effect on Electron Transport of Single Molecular Junctions

by Miao-Ling Huang, Fan Zhang, Chen Wang, Ju-Fang Zheng, Hui-Ling Mao, Hu-Jun Xie, Yong Shao, Xiao-Shun Zhou, Jin-Xuan Liu and Jin-Liang Zhuang

Micromachines 2018, 9(5), 234; https://doi.org/10.3390/mi9050234 - 13 May 2018

Cited by 8 | Viewed by 4131

Abstract

In this article, we have investigated the influence of the nitro side-group on the single molecular conductance of pyridine-based molecules by scanning tunneling microscopy break junction. Single molecular conductance of 4,4′-bipyridine (BPY), 3-nitro-4-(pyridin-4-yl)pyridine (BPY-N), and 3-nitro-4-(3-nitropyridin-4-yl)pyridine (BPY-2N) were measured by contact with Au [...] Read more.

In this article, we have investigated the influence of the nitro side-group on the single molecular conductance of pyridine-based molecules by scanning tunneling microscopy break junction. Single molecular conductance of 4,4′-bipyridine (BPY), 3-nitro-4-(pyridin-4-yl)pyridine (BPY-N), and 3-nitro-4-(3-nitropyridin-4-yl)pyridine (BPY-2N) were measured by contact with Au electrodes. For the BPY molecular junction, two sets of conductance were found with values around 10^−3.1 G₀ (high G) and 10^−3.7 G₀ (low G). The addition of nitro side-group(s) onto the pyridine ring resulted in lower conductance of 10^−3.8 G₀ for BPY-N and 10^−3.9 G₀ for BPY-2N, respectively, which can be attributed to the twist angle of two pyridine rings. Moreover, the steric hindrance of nitro group(s) also affects the contacting configuration of electrode-molecule-electrode. As a consequence, only one set of conductance value was observed for BPY-N and BPY-2N. Our work clearly shows the important role of side-groups on the electron transport of single-molecule junctions. Full article

(This article belongs to the Special Issue Atomic and Molecular Junction for Molecular Electronic Devices)

► Show Figures

Figure 1

18 pages, 6922 KiB

Open AccessArticle

Acceleration Sensitivity in Bulk-Extensional Mode, Silicon-Based MEMS Oscillators

by Beheshte Khazaeili, Jonathan Gonzales and Reza Abdolvand

Micromachines 2018, 9(5), 233; https://doi.org/10.3390/mi9050233 - 12 May 2018

Cited by 5 | Viewed by 4862

Abstract

Acceleration sensitivity in silicon bulk-extensional mode oscillators is studied in this work, and a correlation between the resonator alignment to different crystalline planes of silicon and the observed acceleration sensitivity is established. It is shown that the oscillator sensitivity to the applied vibration [...] Read more.

Acceleration sensitivity in silicon bulk-extensional mode oscillators is studied in this work, and a correlation between the resonator alignment to different crystalline planes of silicon and the observed acceleration sensitivity is established. It is shown that the oscillator sensitivity to the applied vibration is significantly lower when the silicon-based lateral-extensional mode resonator is aligned to the <110> plane compared to when the same resonator is aligned to <100>. A finite element model is developed that is capable of predicting the resonance frequency variation when a distributed load (i.e., acceleration) is applied to the resonator. Using this model, the orientation-dependent nature of acceleration sensitivity is confirmed, and the effect of material nonlinearity on the acceleration sensitivity is also verified. A thin-film piezoelectric-on-substrate platform is chosen for the implementation of resonators. Approximately, one order of magnitude higher acceleration sensitivity is measured for oscillators built with a resonator aligned to the <100> plane versus those with a resonator aligned to the <110> plane (an average of ~5.66 × 10⁻⁸ (1/g) vs. ~3.66 × 10⁻⁹ (1/g), respectively, for resonators on a degenerately n-type doped silicon layer). Full article

(This article belongs to the Special Issue Micro-Resonators: The Quest for Superior Performance)

► Show Figures

Figure 1

28 pages, 6123 KiB

Open AccessReview

Controlled Mechanical Motions of Microparticles in Optical Tweezers

by Jing Liu and Zhiyuan Li

Micromachines 2018, 9(5), 232; https://doi.org/10.3390/mi9050232 - 12 May 2018

Cited by 42 | Viewed by 9018

Abstract

Optical tweezers, formed by a highly focused laser beam, have intriguing applications in biology and physics. Inspired by molecular rotors, numerous optical beams and artificial particles have been proposed to build optical tweezers trapping microparticles, and extensive experiences have been learned towards constructing [...] Read more.

Optical tweezers, formed by a highly focused laser beam, have intriguing applications in biology and physics. Inspired by molecular rotors, numerous optical beams and artificial particles have been proposed to build optical tweezers trapping microparticles, and extensive experiences have been learned towards constructing precise, stable, flexible and controllable micromachines. The mechanism of interaction between particles and localized light fields is quite different for different types of particles, such as metal particles, dielectric particles and Janus particles. In this article, we present a comprehensive overview of the latest development on the fundamental and application of optical trapping. The emphasis is placed on controllable mechanical motions of particles, including rotation, translation and their mutual coupling under the optical forces and torques created by a wide variety of optical tweezers operating on different particles. Finally, we conclude by proposing promising directions for future research. Full article

(This article belongs to the Special Issue Optical Manipulation of Cells: Strategies and Devices)

► Show Figures

Figure 1

8 pages, 4224 KiB

Open AccessLetter

Hard-Baked Photoresist as a Sacrificial Layer for Sub-180 °C Surface Micromachining Processes

by Hani H. Tawfik, Mohannad Y. Elsayed, Frederic Nabki and Mourad N. El-Gamal

Micromachines 2018, 9(5), 231; https://doi.org/10.3390/mi9050231 - 11 May 2018

Cited by 4 | Viewed by 5090

Abstract

This letter proposes a method for utilizing a positive photoresist, Shipley 1805, as a sacrificial layer for sub-180 °C fabrication process flows. In the proposed process, the sacrificial layer is etched at the end to release the structures using a relatively fast wet-etching [...] Read more.

This letter proposes a method for utilizing a positive photoresist, Shipley 1805, as a sacrificial layer for sub-180 °C fabrication process flows. In the proposed process, the sacrificial layer is etched at the end to release the structures using a relatively fast wet-etching technique employing resist remover and a critical point dryer (CPD). This technique allows high etching selectivity over a large number of materials, including silicon-based structural materials such as silicon-carbide, metals such as titanium and aluminum, and cured polymers. This selectivity, as well as the low processing thermal budget, introduces more flexibility in material selection for monolithic integration above complementary metal oxide semiconductor (CMOS) as well as flexible substrates. Full article

(This article belongs to the Special Issue Carbon Based Materials for MEMS/NEMS)

► Show Figures

Figure 1

13 pages, 6383 KiB

Open AccessFeature PaperArticle

Development of a Fully Flexible Sheet-Type Tactile Display Based on Electrovibration Stimulus

by Hiroki Ishizuka, Ryuhei Hatada, Carlos Cortes and Norihisa Miki

Micromachines 2018, 9(5), 230; https://doi.org/10.3390/mi9050230 - 11 May 2018

Cited by 15 | Viewed by 5272

Abstract

Tactile displays have been extensively studied for several decades. However, owing to their bulkiness and stiffness, it has been difficult to integrate these displays with information devices to enable tactile communication between the devices and their users. This paper proposes a novel sheet-type [...] Read more.

Tactile displays have been extensively studied for several decades. However, owing to their bulkiness and stiffness, it has been difficult to integrate these displays with information devices to enable tactile communication between the devices and their users. This paper proposes a novel sheet-type electrovibration tactile display that consists of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate conductive layers and an insulation layer of polydimethylsiloxane. The tactile display is sufficiently thin and flexible for attaching onto various surfaces. In this study, the tactile display was micro-fabricated and characterized through experiments. The experimental results indicated that the tactile display exhibited good durability under bending and that it could present various tactile sensations depending on the type of voltage waveform. In addition, the effect of using a combination of electrovibration and thermal stimuli was also demonstrated. The sheet-type display was attached onto a Peltier element; the thinness of the structure enabled the display to conform to the element and ensure good heat transfer. In the experiment, subjects were asked to scan the display with their fingertips. The results showed that multiple tactile stimuli were also successfully perceived by the subjects. Full article

► Show Figures

Figure 1

17 pages, 4264 KiB

Open AccessArticle

Electroosmotic Flow in Microchannel with Black Silicon Nanostructures

by An Eng Lim, Chun Yee Lim, Yee Cheong Lam and Rafael Taboryski

Micromachines 2018, 9(5), 229; https://doi.org/10.3390/mi9050229 - 11 May 2018

Cited by 15 | Viewed by 5252

Abstract

Although electroosmotic flow (EOF) has been applied to drive fluid flow in microfluidic chips, some of the phenomena associated with it can adversely affect the performance of certain applications such as electrophoresis and ion preconcentration. To minimize the undesirable effects, EOF can be [...] Read more.

Although electroosmotic flow (EOF) has been applied to drive fluid flow in microfluidic chips, some of the phenomena associated with it can adversely affect the performance of certain applications such as electrophoresis and ion preconcentration. To minimize the undesirable effects, EOF can be suppressed by polymer coatings or introduction of nanostructures. In this work, we presented a novel technique that employs the Dry Etching, Electroplating and Molding (DEEMO) process along with reactive ion etching (RIE), to fabricate microchannel with black silicon nanostructures (prolate hemispheroid-like structures). The effect of black silicon nanostructures on EOF was examined experimentally by current monitoring method, and numerically by finite element simulations. The experimental results showed that the EOF velocity was reduced by 13 ± 7%, which is reasonably close to the simulation results that predict a reduction of approximately 8%. EOF reduction is caused by the distortion of local electric field at the nanostructured surface. Numerical simulations show that the EOF velocity decreases with increasing nanostructure height or decreasing diameter. This reveals the potential of tuning the etching process parameters to generate nanostructures for better EOF suppression. The outcome of this investigation enhances the fundamental understanding of EOF behavior, with implications on the precise EOF control in devices utilizing nanostructured surfaces for chemical and biological analyses. Full article

(This article belongs to the Special Issue Micro/Nano-Chip Electrokinetics, Volume II)

► Show Figures

Figure 1

10 pages, 2083 KiB

Open AccessArticle

A Microfluidic Platform for Investigating Transmembrane Pressure-Induced Glomerular Leakage

by Ting-Hsuan Chen, Jie-Sheng Chen, Yi-Ching Ko, Jyun-Wei Chen, Hsueh-Yao Chu, Chih-Shuan Lu, Chiao-Wen Chu, Hsiang-Hao Hsu and Fan-Gang Tseng

Micromachines 2018, 9(5), 228; https://doi.org/10.3390/mi9050228 - 10 May 2018

Cited by 7 | Viewed by 4378

Abstract

Transmembrane pressure across the glomerular filter barrier may underlie renal failure. However, studies of renal failure have been difficult owing to a lack of in vitro models to capture the transmembrane pressure in a controlled approach. Here we report a microfluidic platform of [...] Read more.

Transmembrane pressure across the glomerular filter barrier may underlie renal failure. However, studies of renal failure have been difficult owing to a lack of in vitro models to capture the transmembrane pressure in a controlled approach. Here we report a microfluidic platform of podocyte culture to investigate transmembrane pressure induced glomerular leakage. Podocytes, the glomerular epithelial cells essential for filtration function, were cultivated on a porous membrane supplied with transmembrane pressure ΔP. An anodic aluminum oxide membrane with collagen coating was used as the porous membrane, and the filtration function was evaluated using dextrans of different sizes. The results show that dextran in 20 kDa and 70 kDa can penetrate the podocyte membrane, whereas dextran in 500 kDa was blocked until ΔP ≥ 60 mmHg, which resembles the filtration function when ΔP was in the range of a healthy kidney (ΔP < 60 mmHg) as well as the hypertension-induced glomerular leakage (ΔP ≥ 60 mmHg). Additionally, analysis showed that synaptopodin and actin were also downregulated when ΔP > 30 mmHg, indicating that the dysfunction of renal filtration is correlated with the reduction of synaptopodin expression and disorganized actin cytoskeleton. Taking together, our microfluidic platform enables the investigation of transmembrane pressure in glomerular filter membrane, with potential implications for drug development in the future. Full article

(This article belongs to the Special Issue Microfluidic Devices for Healthcare and Environment Monitoring)

► Show Figures

Figure 1

13 pages, 2537 KiB

Open AccessArticle

High-Precision Lens-Less Flow Cytometer on a Chip

by Yuan Fang, Ningmei Yu, Yuquan Jiang and Chaoliang Dang

Micromachines 2018, 9(5), 227; https://doi.org/10.3390/mi9050227 - 10 May 2018

Cited by 21 | Viewed by 4623

Abstract

We present a flow cytometer on a microfluidic chip that integrates an inline lens-free holographic microscope. High-speed cell analysis necessitates that cells flow through the microfluidic channel at a high velocity, but the image sensor of the in-line holographic microscope needs a long [...] Read more.

We present a flow cytometer on a microfluidic chip that integrates an inline lens-free holographic microscope. High-speed cell analysis necessitates that cells flow through the microfluidic channel at a high velocity, but the image sensor of the in-line holographic microscope needs a long exposure time. Therefore, to solve this problem, this paper proposes an S-type micro-channel and a pulse injection method. To increase the speed and accuracy of the hologram reconstruction, we improve the iterative initial constraint method and propose a background removal method. The focus images and cell concentrations can be accurately calculated by the developed method. Using whole blood cells to test the cell counting precision, we find that the cell counting error of the proposed method is less than 2%. This result shows that the on-chip flow cytometer has high precision. Due to its low price and small size, this flow cytometer is suitable for environments far away from laboratories, such as underdeveloped areas and outdoors, and it is especially suitable for point-of-care testing (POCT). Full article

(This article belongs to the Special Issue Micro/Nano Devices for Blood Analysis)

► Show Figures

Figure 1

7 pages, 1833 KiB

Open AccessArticle

Optimization of Pulley-Type Ring Resonator with Waveguide Offset

by Meng-Hua Yen, Pei-Yu Feng, Chu-En Lin, Chii-Chang Chen and Jenq-Yang Chang

Micromachines 2018, 9(5), 226; https://doi.org/10.3390/mi9050226 - 10 May 2018

Cited by 4 | Viewed by 5110

Abstract

In this work, we dealt with the optimization of the pulley-type ring resonator using the offset of the straight input and output waveguide at the junction with the curved waveguide. We adopted the finite-difference time-domain method to simulate the structure. It was found [...] Read more.

In this work, we dealt with the optimization of the pulley-type ring resonator using the offset of the straight input and output waveguide at the junction with the curved waveguide. We adopted the finite-difference time-domain method to simulate the structure. It was found that the coupling loss could be significantly reduced and the critical coupling could be precisely tuned. This results in the possibility of the Q-factor being higher than that of the structure without waveguide offset. In this study, the Q-factor of the ring resonator is increased from 9180 to 11,302. The corresponding enhancement is 23.1%. Full article

► Show Figures

Figure 1

11 pages, 4760 KiB

Open AccessArticle

Theoretical and Experimental Research on Bubble Actuated Micro-Pumps

by Yang Qu, Junjie Zhou and Wei Wu

Micromachines 2018, 9(5), 225; https://doi.org/10.3390/mi9050225 - 9 May 2018

Cited by 12 | Viewed by 3735

Abstract

Bubble actuated micro-pumps have great potential to be integrated into microfluidic systems to allow the independence of peripheral equipment. Previous studies on bubble actuated valveless micro-pumps have been mainly limited to experimental studies and numerical simulations due to the complex behavior of bubbles. [...] Read more.

Bubble actuated micro-pumps have great potential to be integrated into microfluidic systems to allow the independence of peripheral equipment. Previous studies on bubble actuated valveless micro-pumps have been mainly limited to experimental studies and numerical simulations due to the complex behavior of bubbles. In this paper, the construction of a mathematical model for a bubble actuated valveless micro-pump considering fluid dynamics, heat and mass transfer and bubble dynamics is described. A prototype was fabricated and tested to verify this theoretical model. The morphological evolution of the driving bubbles during the heating process was observed by a high-speed charge-coupled device (CCD) camera, the flow rate produced by the micro-pump under different working conditions was recorded and the test results were explained by the heat dissipation model. The model in this study was able to precisely predict the flow of micro-pumps in different drive modes. The principle behind defining the heating frequency and the duty cycle based on the pump chamber volume was determined. The study shows the mechanism of bubble controlling and the good prospects of bubble actuated valveless micro-pumps. Full article

(This article belongs to the Section B：Biology and Biomedicine)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Micromachines, Volume 9, Issue 5 (May 2018) – 58 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI