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Title: A study of dip-coatable, high-capacitance ion gel dielectrics for 3D EWOD device fabrication
Authors: Clement, C.E 
Jiang, D 
Thio, S.K 
Park, S.-Y 
Keywords: Acetone
Dielectric materials
Ionic liquids
Spin coating
Surface defects
Chemical compositions
Dip coating
Electric double layer
Electro-wetting on dielectrics
Ion gels
Liquid prisms
Mechanical moving parts
Threedimensional (3-d)
Dielectric devices
Issue Date: 2017
Publisher: MDPI AG
Citation: Clement, C.E, Jiang, D, Thio, S.K, Park, S.-Y (2017). A study of dip-coatable, high-capacitance ion gel dielectrics for 3D EWOD device fabrication. Materials 10 (1) : 41. ScholarBank@NUS Repository.
Abstract: We present a dip-coatable, high-capacitance ion gel dielectric for scalable fabrication of three-dimensional (3D) electrowetting-on-dielectric (EWOD) devices such as an n × n liquid prism array. Due to the formation of a nanometer-thick electric double layer (EDL) capacitor, an ion gel dielectric offers two to three orders higher specific capacitance (c ? 10 ?F/cm2) than that of conventional dielectrics such as SiO2. However, the previous spin-coating method used for gel layer deposition poses several issues for 3D EWOD device fabrication, particularly when assembling multiple modules. Not only does the spin-coating process require multiple repetitions per module, but the ion gel layer also comes in risks of damage or contamination due to handling errors caused during assembly. In addition, it was observed that the chemical formulation previously used for the spin-coating method causes the surface defects on the dip-coated gel layers and thus leads to poor EWOD performance. In this paper, we alternatively propose a dip-coating method with modified gel solutions to obtain defect-free, functional ion gel layers without the issues arising from the spin-coating method for 3D device fabrication. A dip-coating approach offers a single-step coating solution with the benefits of simplicity, scalability, and high throughput for deposition of high-capacitance gel layers on non-planar EWOD devices. An ion gel solution was prepared by combining the [EMIM][TFSI] ionic liquid and the [P(VDF-HFP)] copolymer at various wt % ratios in acetone solvent. Experimental studies were conducted to fully understand the effects of chemical composition ratios in the gel solution and how varying thicknesses of ion gel and Teflon layers affects EWOD performance. The effectiveness and potentiality of dip-coatable gel layers for 3D EWOD devices have been demonstrated through fabricating 5 1 arrayed liquid prisms using a single-step dip-coating method. Each prism module has been individually controlled to achieve spatial beam steering without the need for bulky mechanical moving parts. © 2017 by the authors.
Source Title: Materials
ISSN: 19961944
DOI: 10.3390/ma10010041
Appears in Collections:Elements
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