Special Issue "Glass Micromachining"

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

Deadline for manuscript submissions: closed (31 October 2016)

Special Issue Editor

Guest Editor
Prof. Dr. Rolf Wuthrich

Department of Mechanical and Industrial Engineering, Concordia University, 1455 de Maisonneuve Blvd. West, Montreal, QC H3G 1M8, Canada
Website | E-Mail
Phone: +1 514 848 2424 (ext. 3150)
Fax: +1 514 848 3175
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

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • glass micro-machining
  • glass micro/nano devices

Published Papers (6 papers)

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Research

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Open AccessArticle Glass Imprint Templates by Spark Assisted Chemical Engraving for Microfabrication by Hot Embossing
Micromachines 2017, 8(1), 29; doi:10.3390/mi8010029
Received: 21 December 2016 / Revised: 10 January 2017 / Accepted: 16 January 2017 / Published: 23 January 2017
Cited by 1 | PDF Full-text (5149 KB) | HTML Full-text | XML Full-text
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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Open AccessArticle Fabrication of Vacuum-Sealed Capacitive Micromachined Ultrasonic Transducer Arrays Using Glass Reflow Process
Micromachines 2016, 7(5), 76; doi:10.3390/mi7050076
Received: 26 February 2016 / Revised: 6 April 2016 / Accepted: 19 April 2016 / Published: 25 April 2016
Cited by 6 | PDF Full-text (2207 KB) | HTML Full-text | XML Full-text
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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Open AccessArticle A One-Square-Millimeter Compact Hollow Structure for Microfluidic Pumping on an All-Glass Chip
Micromachines 2016, 7(4), 63; doi:10.3390/mi7040063
Received: 22 February 2016 / Revised: 4 April 2016 / Accepted: 5 April 2016 / Published: 9 April 2016
PDF Full-text (5837 KB) | HTML Full-text | XML Full-text | Supplementary Files
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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Open AccessArticle An Investigation of Processes for Glass Micromachining
Micromachines 2016, 7(3), 51; doi:10.3390/mi7030051
Received: 15 February 2016 / Revised: 11 March 2016 / Accepted: 14 March 2016 / Published: 22 March 2016
Cited by 6 | PDF Full-text (7367 KB) | HTML Full-text | XML Full-text
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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Open AccessArticle Surface Free Energy Determination of APEX Photosensitive Glass
Micromachines 2016, 7(3), 34; doi:10.3390/mi7030034
Received: 7 January 2016 / Revised: 6 February 2016 / Accepted: 14 February 2016 / Published: 23 February 2016
PDF Full-text (1774 KB) | HTML Full-text | XML Full-text
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)

Review

Jump to: Research

Open AccessReview Micro-Hole Drilling on Glass Substrates—A Review
Micromachines 2017, 8(2), 53; doi:10.3390/mi8020053
Received: 14 November 2016 / Revised: 18 January 2017 / Accepted: 3 February 2017 / Published: 13 February 2017
PDF Full-text (1207 KB) | HTML Full-text | XML Full-text
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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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Micro-hole drilling on glass substrates—A review
Authors: Lucas A. Hof and Jana D. Abou Ziki
Abstract: Glass micromachining is nowadays becoming essential for the fabrication of micro-devices including optical micro-electro-mechanical-systems (MOEMS), miniaturized total analysis systems (µTAS) and microfluidic devices for biosensing. Moreover, glass is RF transparent, making it an excellent material for sensor and energy transmission devices. Advancements are constantly being made in this field, yet machining smooth high-aspect-ratio through glass vias (TGVs) remains challenging due to glass poor machinability. As TGVs are demanded for several micro-devices, research is being immensely carried out on numerous number of glass micro-machining 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 under four machining categories: thermal, chemical, mechanical, and hybrid machining which combines several machining methods. Achieved features by these methods are summarized in a table and presented in two graphs.
Keywords: micro-drilling techniques; glass; micro-devices; micro-fluidics

Title: Plasma milled glass as templates for microfluidic applications
Author: Jesse Greener
Abstract: As microfluidics matures, new demands on production volumes and device complexities will put pressures on manufacturers to search for innovations in microfabrication techniques. In this paper, we evaluate the possibility of using templates based on a new plasma milling technique for polymer devices via curing of elastomers and hot embossing of thermoplastics. Target materials are PDMS. We evaluate this new approach in terms of the quality of template tools and imprinted parts, the ease of use and longevity of templates and the ability to generate 3D features.

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