Glass Micromachining

A special issue of Micromachines (ISSN 2072-666X).

Deadline for manuscript submissions: closed (31 October 2016) | Viewed by 45838

Special Issue Editor


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Guest Editor
Department of Mechanical and Industrial Engineering, Concordia University, 1455 de Maisonneuve Blvd. West, Montreal, QC H3G 1M8, Canada
Interests: micro- and nano- systems; nano-particle fabrication; micro-machining technologies; green energy converting systems

Special Issue Information

Dear Colleagues

Glass micromachining is becoming an essential material for optical micro-electro-mechanical-systems (MOEMS), miniaturized total analysis systems (µTAS), and microfluidic devices (e.g., for biosensing). In particular, the machining of smooth, high aspect ratio through glass vias (TGVs) in glass is crucial for the fabrication of interposers in the emerging packaging industry for small consumer electronics. However, glass is challenging to machine, in particular, at the micro-scale. Due to its brittleness, mechanical processes often result in undesired micro-cracks, and its relatively high thermal conductivity challenges the thermal process, which faces the issue of thermally affected zones. Additionally, its amorphous structure makes it difficult to etch high aspect-ratio structures. These challenges stimulate research in industry and academia, and, in recent years, this field has seen major advances.

This special issue seeks reviews, regular research papers and short communication on: (i) new approaches to micro machine glass, (ii) innovative use of existing techniques to address current challenges in glass micro-machining and (iii) opinions on future needs in glass micro-machining in emerging markets.

Prof. Dr. Rolf Wuthrich
Guest Editor

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Keywords

  • glass micro-machining
  • glass micro/nano devices

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Published Papers (6 papers)

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Research

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5149 KiB  
Article
Glass Imprint Templates by Spark Assisted Chemical Engraving for Microfabrication by Hot Embossing
by Lucas Abia Hof, Xin Guo, Minseok Seo, Rolf Wüthrich and Jesse Greener
Micromachines 2017, 8(1), 29; https://doi.org/10.3390/mi8010029 - 23 Jan 2017
Cited by 9 | Viewed by 7400
Abstract
As the field of microelectromechanical systems (MEMS) matures, new demands are being placed on the microfabrication of complex architectures in robust materials, such as hard plastics. Iterative design optimization in a timely manner—rapid prototyping—places challenges on template fabrication, for methods such as injection [...] Read more.
As the field of microelectromechanical systems (MEMS) matures, new demands are being placed on the microfabrication of complex architectures in robust materials, such as hard plastics. Iterative design optimization in a timely manner—rapid prototyping—places challenges on template fabrication, for methods such as injection moulding and hot embossing. In this paper, we demonstrate the possibility of using spark assisted chemical engraving (SACE) to produce micro patterned glass templates. The direct, write-based approach enabled the facile fabrication of smooth microfeatures with variations in all three-dimensions, which could be replicated by hot embossing different thermoplastics. As a proof of principle, we demonstrated the technique for a high glass transition temperature polycarbonate. Good fidelity over more than 10 cycles provides evidence that the approach is viable for rapid prototyping and has the potential to satisfy commercial-grade production at medium-level output volumes. Glass imprint templates showed no degradation after use, but care must be taken due to brittleness. The technique has the potential to advance microfabrication needs in academia and could be used by MEMS product developers. Full article
(This article belongs to the Special Issue Glass Micromachining)
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2207 KiB  
Article
Fabrication of Vacuum-Sealed Capacitive Micromachined Ultrasonic Transducer Arrays Using Glass Reflow Process
by Nguyen Van Toan, Shim Hahng, Yunheub Song and Takahito Ono
Micromachines 2016, 7(5), 76; https://doi.org/10.3390/mi7050076 - 25 Apr 2016
Cited by 21 | Viewed by 5780
Abstract
This paper presents a process for the fabrication of vacuum-sealed capacitive micromachined ultrasonic transducer (CMUT) arrays using glass reflow and anodic bonding techniques. Silicon through-wafer interconnects have been investigated by the glass reflow process. Then, the patterned silicon-glass reflow wafer is anodically bonded [...] Read more.
This paper presents a process for the fabrication of vacuum-sealed capacitive micromachined ultrasonic transducer (CMUT) arrays using glass reflow and anodic bonding techniques. Silicon through-wafer interconnects have been investigated by the glass reflow process. Then, the patterned silicon-glass reflow wafer is anodically bonded to an SOI (silicon-on-insulator) wafer for the fabrication of CMUT devices. The CMUT 5 × 5 array has been successfully fabricated. The resonant frequency of the CMUT array with a one-cell radius of 100 µm and sensing gap of 3.2 µm (distance between top and bottom electrodes) is observed at 2.84 MHz. The Q factor is approximately 1300 at pressure of 0.01 Pa. Full article
(This article belongs to the Special Issue Glass Micromachining)
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5837 KiB  
Article
A One-Square-Millimeter Compact Hollow Structure for Microfluidic Pumping on an All-Glass Chip
by Xing Yue (Larry) Peng
Micromachines 2016, 7(4), 63; https://doi.org/10.3390/mi7040063 - 9 Apr 2016
Cited by 8 | Viewed by 4805
Abstract
A micro surface tension pump is a new type of low-cost, built-in, all-glass, microfluidic pump on a glass microchip fabricated by one-step glass etching. However, geometric minimization and optimization for practical use are challenging. Here, we report a one-square-millimeter, built-in, all-glass pump controlled [...] Read more.
A micro surface tension pump is a new type of low-cost, built-in, all-glass, microfluidic pump on a glass microchip fabricated by one-step glass etching. However, geometric minimization and optimization for practical use are challenging. Here, we report a one-square-millimeter, built-in, all-glass pump controlled by two-way digital gas pressure. The pump consists simply of two joint chambers and a piston between two gas control channels. It does not require pre-perfusion for initialization, and can immediately begin to run when a liquid enters its inlet channel. It is also more reliable than conventional micro pumps for practical use due to its ability to restart after the formation of a blocking bubble, which can serve as a valuable troubleshooting procedure. Its volumetric pump output was 0.5–0.7 nL·s−1 under a pump head pressure of 300 Pa. Full article
(This article belongs to the Special Issue Glass Micromachining)
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7367 KiB  
Article
An Investigation of Processes for Glass Micromachining
by Nguyen Van Toan, Masaya Toda and Takahito Ono
Micromachines 2016, 7(3), 51; https://doi.org/10.3390/mi7030051 - 22 Mar 2016
Cited by 33 | Viewed by 8692
Abstract
This paper presents processes for glass micromachining, including sandblast, wet etching, reactive ion etching (RIE), and glass reflow techniques. The advantages as well as disadvantages of each method are presented and discussed in light of the experiments. Sandblast and wet etching techniques are [...] Read more.
This paper presents processes for glass micromachining, including sandblast, wet etching, reactive ion etching (RIE), and glass reflow techniques. The advantages as well as disadvantages of each method are presented and discussed in light of the experiments. Sandblast and wet etching techniques are simple processes but face difficulties in small and high-aspect-ratio structures. A sandblasted 2 cm × 2 cm Tempax glass wafer with an etching depth of approximately 150 µm is demonstrated. The Tempax glass structure with an etching depth and sides of approximately 20 μm was observed via the wet etching process. The most important aspect of this work was to develop RIE and glass reflow techniques. The current challenges of these methods are addressed here. Deep Tempax glass pillars having a smooth surface, vertical shapes, and a high aspect ratio of 10 with 1-μm-diameter glass pillars, a 2-μm pitch, and a 10-μm etched depth were achieved via the RIE technique. Through-silicon wafer interconnects, embedded inside the Tempax glass, are successfully demonstrated via the glass reflow technique. Glass reflow into large cavities (larger than 100 μm), a micro-trench (0.8-μm wide trench), and a micro-capillary (1-μm diameter) are investigated. An additional optimization of process flow was performed for glass penetration into micro-scale patterns. Full article
(This article belongs to the Special Issue Glass Micromachining)
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1774 KiB  
Article
Surface Free Energy Determination of APEX Photosensitive Glass
by William R. Gaillard, Emanuel Waddell and John D. Williams
Micromachines 2016, 7(3), 34; https://doi.org/10.3390/mi7030034 - 23 Feb 2016
Cited by 5 | Viewed by 5185
Abstract
Surface free energy (SFE) plays an important role in microfluidic device operation. Photosensitive glasses such as APEX offer numerous advantages over traditional glasses for microfluidics, yet the SFE for APEX has not been previously reported. We calculate SFE with the Owens/Wendt geometric method [...] Read more.
Surface free energy (SFE) plays an important role in microfluidic device operation. Photosensitive glasses such as APEX offer numerous advantages over traditional glasses for microfluidics, yet the SFE for APEX has not been previously reported. We calculate SFE with the Owens/Wendt geometric method by using contact angles measured with the Sessile drop technique. While the total SFE for APEX is found to be similar to traditional microstructurable glasses, the polar component is lower, which is likely attributable to composition. The SFE was modified at each stage of device fabrication, but the SFE of the stock and fully processed glass was found to be approximately the same at a value of 51 mJ·m−2. APEX exhibited inconsistent wetting behavior attributable to an inhomogeneous surface chemical composition. Means to produce more consistent wetting of photosensitive glass for microfluidic applications are discussed. Full article
(This article belongs to the Special Issue Glass Micromachining)
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Review

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1207 KiB  
Review
Micro-Hole Drilling on Glass Substrates—A Review
by Lucas A. Hof and Jana Abou Ziki
Micromachines 2017, 8(2), 53; https://doi.org/10.3390/mi8020053 - 13 Feb 2017
Cited by 97 | Viewed by 12880
Abstract
Glass micromachining is currently becoming essential for the fabrication of micro-devices, including micro- optical-electro-mechanical-systems (MOEMS), miniaturized total analysis systems (μTAS) and microfluidic devices for biosensing. Moreover, glass is radio frequency (RF) transparent, making it an excellent material for sensor and energy transmission devices. [...] Read more.
Glass micromachining is currently becoming essential for the fabrication of micro-devices, including micro- optical-electro-mechanical-systems (MOEMS), miniaturized total analysis systems (μTAS) and microfluidic devices for biosensing. Moreover, glass is radio frequency (RF) transparent, making it an excellent material for sensor and energy transmission devices. Advancements are constantly being made in this field, yet machining smooth through-glass vias (TGVs) with high aspect ratio remains challenging due to poor glass machinability. As TGVs are required for several micro-devices, intensive research is being carried out on numerous glass micromachining technologies. This paper reviews established and emerging technologies for glass micro-hole drilling, describing their principles of operation and characteristics, and their advantages and disadvantages. These technologies are sorted into four machining categories: mechanical, thermal, chemical, and hybrid machining (which combines several machining methods). Achieved features by these methods are summarized in a table and presented in two graphs. We believe that this paper will be a valuable resource for researchers working in the field of glass micromachining as it provides a comprehensive review of the different glass micromachining technologies. It will be a useful guide for advancing these techniques and establishing new hybrid ones, especially since this is the first broad review in this field. Full article
(This article belongs to the Special Issue Glass Micromachining)
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