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Thio SK, Park SY. A review of optoelectrowetting (OEW): from fundamentals to lab-on-a-smartphone (LOS) applications to environmental sensors. LAB ON A CHIP 2022; 22:3987-4006. [PMID: 35916120 DOI: 10.1039/d2lc00372d] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Electrowetting-on-dielectric (EWOD) has been extensively explored as an active-type technology for small-scale liquid handling due to its several unique advantages, including no requirement of mechanical components, low power consumption, and rapid response time. However, conventional EWOD devices are often accompanied with complex fabrication processes for patterning and wiring of 2D arrayed electrodes. Furthermore, their sandwich device configuration makes integration with other microfluidic components difficult. More recently, optoelectrowetting (OEW), a light-driven mechanism for effective droplet manipulation, has been proposed as an alternative approach to overcome these issues. By utilizing optical addressing on a photoconductive surface, OEW can dynamically control an electrowetting phenomenon without the need for complex control circuitry on a chip, while providing higher functionality and flexibility. Using commercially available spatial light modulators such as LCD displays and smartphones, millions of optical pixels are readily generated to modulate virtual electrodes for large-scale droplet manipulations in parallel on low-cost OEW devices. The benefits of the OEW mechanism have seen it being variously explored in its potential biological and biochemical applications. This review article presents the fundamentals of OEW, discusses its research progress and limitations, highlights various technological advances and innovations, and finally introduces the emergence of the OEW technology as portable smartphone-integrated environmental sensors.
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Affiliation(s)
- Si Kuan Thio
- Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, 117575, Singapore
| | - Sung-Yong Park
- Department of Mechanical Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA, 92182, USA.
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Thio SK, Park SY. Optical Dielectrophoretic (DEP) Manipulation of Oil-Immersed Aqueous Droplets on a Plasmonic-Enhanced Photoconductive Surface. MICROMACHINES 2022; 13:112. [PMID: 35056277 PMCID: PMC8777958 DOI: 10.3390/mi13010112] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 01/04/2022] [Accepted: 01/09/2022] [Indexed: 02/04/2023]
Abstract
We present a plasmonic-enhanced dielectrophoretic (DEP) phenomenon to improve optical DEP performance of a floating electrode optoelectronic tweezers (FEOET) device, where aqueous droplets can be effectively manipulated on a light-patterned photoconductive surface immersed in an oil medium. To offer device simplicity and cost-effectiveness, recent studies have utilized a polymer-based photoconductive material such as titanium oxide phthalocyanine (TiOPc). However, the TiOPc has much poorer photoconductivity than that of semiconductors like amorphous silicon (a-Si), significantly limiting optical DEP applications. The study herein focuses on the FEOET device for which optical DEP performance can be greatly enhanced by utilizing plasmonic nanoparticles as light scattering elements to improve light absorption of the low-quality TiOPc. Numerical simulation studies of both plasmonic light scattering and electric field enhancement were conducted to verify wide-angle scattering light rays and an approximately twofold increase in electric field gradient with the presence of nanoparticles. Similarly, a spectrophotometric study conducted on the absorption spectrum of the TiOPc has shown light absorption improvement (nearly twofold) of the TiOPc layer. Additionally, droplet dynamics study experimentally demonstrated a light-actuated droplet speed of 1.90 mm/s, a more than 11-fold improvement due to plasmonic light scattering. This plasmonic-enhanced FEOET technology can considerably improve optical DEP capability even with poor-quality photoconductive materials, thus providing low-cost, easy-fabrication solutions for various droplet-based microfluidic applications.
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Affiliation(s)
- Si Kuan Thio
- Department of Mechanical Engineering, National University of Singapore, Singapore 117575, Singapore;
| | - Sung-Yong Park
- Department of Mechanical Engineering, San Diego State University, San Diego, CA 92182-1323, USA
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Abstract
The continuously decreasing size of device features in microelectronics draws growing attention to the structuring of silicon at the molecular level with powerful tools provided by synthetic chemistry. Silicon clusters are of particular importance in this regard not only as potential precursors for silicon deposition but also as well-defined model systems for bulk and surfaces of silicon at the nanoscale as well as possible starting points for future construction of molecularly precise device structures. This review aims to give a comprehensive overview about the state of the art in the synthesis of molecular silicon clusters, which are grouped into (1) electron-precise saturated clusters, (2) soluble polyhedral Zintl anions, and (3) unsaturated silicon clusters, the so-called siliconoids. Particular attention is paid to functionalization as it is generally considered a necessary prerequisite for the design and construction of more extended systems. The interrelations between the three different classes of molecular silicon clusters, e.g., arising from the introduction of negatively charged functional groups, are highlighted on grounds of NMR properties and computed electronic structures.
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Affiliation(s)
- Yannic Heider
- Chair of General and Inorganic Chemistry, Department of Chemistry, Saarland University, 66123 Saarbrücken, Germany
| | - David Scheschkewitz
- Chair of General and Inorganic Chemistry, Department of Chemistry, Saarland University, 66123 Saarbrücken, Germany
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Lee S, Thio SK, Park SY, Bae S. An automated 3D-printed smartphone platform integrated with optoelectrowetting (OEW) microfluidic chip for on-site monitoring of viable algae in water. HARMFUL ALGAE 2019; 88:101638. [PMID: 31582154 DOI: 10.1016/j.hal.2019.101638] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 06/20/2019] [Accepted: 06/26/2019] [Indexed: 06/10/2023]
Abstract
A sudden increase of algae and their associated toxins in aquatic ecosystems can detrimentally affect the quality of the water, causing serious socio-economic and public health problems. To prevent the spread of harmful algae in aquatic ecosystems, it is essential to track the water's quality through rapid and in-situ monitoring systems. Conventional methods of algae quantification such as microscopy, hemocytometry, and UV-vis spectroscopy, however, are often unsuitable or inconvenient for in-situ assessment as they require skilled labor and expensive equipment. In this study, we developed a three-dimensional (3D)-printed smartphone platform integrated with a light-driven microfluidic chip operated by optoelectrowetting (OEW). This OEW-driven microfluidic chip not only allows multiplexed drop-wise functions such as droplet transportation, merging, mixing, immobilization on a detection zone, for on-chip water sample preparation but also fluorescent detection and counting of target algae cells using a commercially-available smartphone. Two freshwater algae (C. reinhardtii and M. aeruginosa) and two marine water algae (Amphiprora sp and C. closterium) were employed to validate the 3D-printed smartphone platform in this study. The fluorescence images of viable algae and the cell counting from the microfluidic chip were comparable to the results from a hemocytometer (P > 0.05). We have further conducted tests with spiked samples using freshwater and marine water that were directly collected from environmental samples, showing the same order of magnitude of cell numbers in the spiked and control cultures of algae cells (106 cell/mL, P > 0.05). Unlike traditional quantification methods, the 3D-printed smartphone platform integrated with the OEW offers a highly portable, user-friendly, low-cost tool that enables simple on-chip sample preparation and detection of viable algae. Thus, this stand-alone technology has the potential for rapid and in-situ monitoring of water quality, while using the smartphone's wireless communication capabilities to report the quality of the water in real-time.
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Affiliation(s)
- Seunguk Lee
- Department of Civil and Environmental Engineering, National University of Singapore, Singapore
| | - Si Kuan Thio
- Department of Mechanical Engineering, National University of Singapore, Singapore
| | - Sung-Yong Park
- Department of Mechanical Engineering, National University of Singapore, Singapore
| | - Sungwoo Bae
- Department of Civil and Environmental Engineering, National University of Singapore, Singapore.
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Jiang D, Lee S, Bae SW, Park SY. Smartphone integrated optoelectrowetting (SiOEW) for on-chip sample processing and microscopic detection of water quality. LAB ON A CHIP 2018; 18:532-539. [PMID: 29334390 DOI: 10.1039/c7lc01095h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
With the increasing capabilities and ubiquity of smartphones and their associated digital cameras, this study presents a smartphone integrated optoelectrowetting (SiOEW) device as a simple, portable tool capable of on-chip water sample preparation and microscopic detection of the target cells in water samples, which significantly reduce the detection time and the labor cost required for water quality monitoring. A commercially available smartphone is used as a low-intensity portable light source to perform optoelectrowetting (OEW)-based microfluidic operations such as droplet transportation, merging, mixing, and immobilization on a hydrophobic detection zone. Furthermore, a built-in smartphone camera allows on-chip microscopic detection of water quality with a 45× magnification. We have experimentally demonstrated that the SiOEW platform is able not only to automate the sample processing of marine water including the target algae cells (Amphiprora sp.) and staining reagents fluorescein diacetate (FDA) and 5-chloromethylfluorescein diacetate (CMFDA), but also detect the fluorescence signals emitted from the target cells in water samples and count their populations. Using the smartphone, the collected information (e.g. the location of the water sample collected and the time it was detected, the number of the target cells, etc.) can be rapidly and wirelessly shared with a central host such as an environmental regulation agency for real-time monitoring and further management of water quality.
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Affiliation(s)
- Dongyue Jiang
- Department of Mechanical Engineering, Biomedical Institute for Global Health Research and Technology (BIGHEART), National University of Singapore (NUS), 117576, Singapore.
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Silicon deposition in nanopores using a liquid precursor. Sci Rep 2016; 6:37689. [PMID: 27874085 PMCID: PMC5118725 DOI: 10.1038/srep37689] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 11/01/2016] [Indexed: 11/08/2022] Open
Abstract
Techniques for depositing silicon into nanosized spaces are vital for the further scaling down of next-generation devices in the semiconductor industry. In this study, we filled silicon into 3.5-nm-diameter nanopores with an aspect ratio of 70 by exploiting thermodynamic behaviour based on the van der Waals energy of vaporized cyclopentasilane (CPS). We originally synthesized CPS as a liquid precursor for semiconducting silicon. Here we used CPS as a gas source in thermal chemical vapour deposition under atmospheric pressure because vaporized CPS can fill nanopores spontaneously. Our estimation of the free energy of CPS based on Lifshitz van der Waals theory clarified the filling mechanism, where CPS vapour in the nanopores readily undergoes capillary condensation because of its large molar volume compared to those of other vapours such as water, toluene, silane, and disilane. Consequently, a liquid-specific feature was observed during the deposition process; specifically, condensed CPS penetrated into the nanopores spontaneously via capillary force. The CPS that filled the nanopores was then transformed into solid silicon by thermal decomposition at 400 °C. The developed method is expected to be used as a nanoscale silicon filling technology, which is critical for the fabrication of future quantum scale silicon devices.
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Cádiz Bedini AP, Muthmann S, Flohre J, Thiele B, Willbold S, Carius R. Sonophotolytically Synthesized Silicon Nanoparticle-Polymer Composite Ink from a Commercially Available Lower Silane. MACROMOL CHEM PHYS 2016. [DOI: 10.1002/macp.201600005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Andrew P. Cádiz Bedini
- IEK-5: Photovoltaics; Forschungszentrum Jülich GmbH; Wilhelm-Johnen-Str. 52425 Jülich Germany
| | - Stefan Muthmann
- IEK-5: Photovoltaics; Forschungszentrum Jülich GmbH; Wilhelm-Johnen-Str. 52425 Jülich Germany
| | - Jan Flohre
- IEK-5: Photovoltaics; Forschungszentrum Jülich GmbH; Wilhelm-Johnen-Str. 52425 Jülich Germany
| | - Björn Thiele
- Forschungszentrum Jülich GmbH; IBG-2: Institute of Plant Sciences/BioSpec; Wilhelm-Johnen-Str. 52425 Jülich Germany
| | - Sabine Willbold
- Forschungszentrum Jülich GmbH; ZEA-3: Central Institute for Engineering; Electronics and Analytics; Wilhelm-Johnen-Str. 52425 Jülich Germany
| | - Reinhard Carius
- IEK-5: Photovoltaics; Forschungszentrum Jülich GmbH; Wilhelm-Johnen-Str. 52425 Jülich Germany
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Jiang D, Park SY. Light-driven 3D droplet manipulation on flexible optoelectrowetting devices fabricated by a simple spin-coating method. LAB ON A CHIP 2016; 16:1831-1839. [PMID: 27094708 DOI: 10.1039/c6lc00293e] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Technical advances in electrowetting-on-dielectric (EWOD) over the past few years have extended our attraction to three-dimensional (3D) devices capable of providing more flexibility and functionality with larger volumetric capacity than conventional 2D planar ones. However, typical 3D EWOD devices require complex and expensive fabrication processes for patterning and wiring of pixelated electrodes that also restrict the minimum droplet size to be manipulated. Here, we present a flexible single-sided continuous optoelectrowetting (SCOEW) device which is not only fabricated by a spin-coating method without the need for patterning and wiring processes, but also enables light-driven 3D droplet manipulations. To provide photoconductive properties, previous optoelectrowetting (OEW) devices have used amorphous silicon (a-Si) typically fabricated through high-temperature processes over 300 °C such as CVD or PECVD. However, most of the commercially-available flexible substrates such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) experience serious thermal deformation under such high-temperature processes. Because of this compatibility issue of conventional OEW devices with flexible substrates, light-driven 3D droplet manipulations have not yet been demonstrated on flexible substrates. Our study overcomes this compatibility issue by using a polymer-based photoconductive material, titanium oxide phthalocyanine (TiOPc) and thus SCOEW devices can be simply fabricated on flexible substrates through a low-cost, spin-coating method. In this paper, analytical studies were conducted to understand the effects of light patterns on static contact angles and EWOD forces. For experimental validations of our study, flexible SCOEW devices were successfully fabricated through the TiOPc-based spin-coating method and light-driven droplet manipulations (e.g. transportation, merging, and splitting) have been demonstrated on various 3D terrains such as inclined, vertical, upside-down, and curved surfaces. Our flexible SCOEW technology offers the benefits of device simplicity, flexibility, and functionality over conventional EWOD and OEW devices by enabling optical droplet manipulations on a 3D featureless surface.
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Affiliation(s)
- Dongyue Jiang
- Department of Mechanical Engineering, National University of Singapore, 117576, Singapore.
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Tillmann J, Moxter M, Bolte M, Lerner HW, Wagner M. Lewis acidity of Si6Cl12 and its role as convenient SiCl2 source. Inorg Chem 2015; 54:9611-8. [PMID: 26378930 DOI: 10.1021/acs.inorgchem.5b01703] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The free cyclohexasilane Si6Cl12 (1) was obtained in 66% yield from the corresponding Cl(-) diadduct [nBu4N]2[1·2Cl] and AlCl3 in C6H6. The substituted cyclohexasilane 1,1-(Cl3Si)2Si6Cl10 (2), however, cannot be liberated from [nBu4N]2[2·2Cl] under comparable reaction conditions. Instead, a mixture of several products was obtained, from which the oligosilane Si19Cl36 (3) crystallized in low yields. X-ray crystallography revealed 3 to consist of two Si5 rings, bridged by one silicon atom. Compound 1 possesses Lewis acidic sites above and below the ring centroid. Competition experiments reveal that their corresponding acid strengths are comparable to that of BCl3. The reaction of 1 with 6 equiv of 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (Idipp) leads to a complete breakdown of the cyclic scaffold and furnishes the dichlorosilylene adduct Idipp-SiCl2.
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Affiliation(s)
- Jan Tillmann
- Institut für Anorganische Chemie, Goethe-Universität Frankfurt am Main , Max-von-Laue-Straße 7, 60438 Frankfurt am Main, Germany
| | - Maximilian Moxter
- Institut für Anorganische Chemie, Goethe-Universität Frankfurt am Main , Max-von-Laue-Straße 7, 60438 Frankfurt am Main, Germany
| | - Michael Bolte
- Institut für Anorganische Chemie, Goethe-Universität Frankfurt am Main , Max-von-Laue-Straße 7, 60438 Frankfurt am Main, Germany
| | - Hans-Wolfram Lerner
- Institut für Anorganische Chemie, Goethe-Universität Frankfurt am Main , Max-von-Laue-Straße 7, 60438 Frankfurt am Main, Germany
| | - Matthias Wagner
- Institut für Anorganische Chemie, Goethe-Universität Frankfurt am Main , Max-von-Laue-Straße 7, 60438 Frankfurt am Main, Germany
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