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<p>Electrowetting (EW) based devices always demand a top hydrophobic polymer layer coated on a dielectric surface as it enables wide range for contact angle modulation while maintaining minimal contact angle hysteresis. Here, a commercially available silica nanoparticle dispersion (SND) has been investigated as an “off-the shelf” superhydrophobic top coating on dielectric to replace routinely used fluoropolymer layers such as Teflon or Cytop. The SND coating is tested for its wettability, demonstrating a static water contact angle (WCA) of <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\:{\theta\:}_{Y}\sim151\pm\:2^\circ\:\)</EquationSource> </InlineEquation> for air and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\:163\pm\:2^\circ\:\)</EquationSource> </InlineEquation> for oil ambient respectively. The proposed coating is extensively tested for EW in oil ambient using AC and DC voltages on dielectric substrates such as Polymethyl Methacrylate (PMMA) and Parylene-C. The SND coating exhibits nearly hysteresis-free EW response across a range of electrowetting number η, 0.37 ≤ η ≤ 0.76. The contact angle modulation of <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\:\varDelta\:\theta\:\left(U\right)&gt;50^\circ\:\)</EquationSource> </InlineEquation> is successfully achieved without any appreciable degradation of the dielectric layer over large number of voltage ramping cycles. As a proof of concept, droplet actuations are performed on a PCB based digital microfluidic (DMF) chip comprising a Parylene-C dielectric layer coated with a top SND layer. A maximum droplet transport speed of <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\:v\:=\:33.3\:mm/s\)</EquationSource> </InlineEquation> is achieved at an applied AC voltage of <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\:U\sim115.8\:{V}_{rms}\)</EquationSource> </InlineEquation> demonstrating the potential of the SND as a high performance and fluorine free superhydrophobic coating for EW based DMF devices.</p> Graphical Abstract <p></p>

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Superhydrophobic silica nano-particle coating on dielectric for droplet transport on digital microfluidic devices

  • 期刊论文

  • 发表日期：

    2026年7月9日

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  • Swaranjali Shinde,
  • Jayesh Patekari,
  • Mayuresh Kulkarni,
  • Yogesh B. Sawane,
  • Arun Banpurkar

摘要

Electrowetting (EW) based devices always demand a top hydrophobic polymer layer coated on a dielectric surface as it enables wide range for contact angle modulation while maintaining minimal contact angle hysteresis. Here, a commercially available silica nanoparticle dispersion (SND) has been investigated as an “off-the shelf” superhydrophobic top coating on dielectric to replace routinely used fluoropolymer layers such as Teflon or Cytop. The SND coating is tested for its wettability, demonstrating a static water contact angle (WCA) of \(\:{\theta\:}_{Y}\sim151\pm\:2^\circ\:\) for air and \(\:163\pm\:2^\circ\:\) for oil ambient respectively. The proposed coating is extensively tested for EW in oil ambient using AC and DC voltages on dielectric substrates such as Polymethyl Methacrylate (PMMA) and Parylene-C. The SND coating exhibits nearly hysteresis-free EW response across a range of electrowetting number η, 0.37 ≤ η ≤ 0.76. The contact angle modulation of \(\:\varDelta\:\theta\:\left(U\right)>50^\circ\:\) is successfully achieved without any appreciable degradation of the dielectric layer over large number of voltage ramping cycles. As a proof of concept, droplet actuations are performed on a PCB based digital microfluidic (DMF) chip comprising a Parylene-C dielectric layer coated with a top SND layer. A maximum droplet transport speed of \(\:v\:=\:33.3\:mm/s\) is achieved at an applied AC voltage of \(\:U\sim115.8\:{V}_{rms}\) demonstrating the potential of the SND as a high performance and fluorine free superhydrophobic coating for EW based DMF devices.

Graphical Abstract