Long-term hydrophilization of polydimethylsiloxane (PDMS) for capillary filling microfluidic chips

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Abstract

We present a simple and facile method for long-term preservation of hydrophilicity of oxygen plasma-hydrophilized poly (dimethylsiloxane) (PDMS) by cold storage. We show that storage under temperature of − 80 °C can maintain superhydrophilicity of plasma-exposed PDMS for at least 100 days. Storage at − 15 °C and at 22 °C room temperature (RT) is shown to exhibit, respectively, about half and full recovery of the original hydrophobicity after 100 days in storage. Furthermore, we investigated the implications of the cold storage for microfluidic applications, the capillary filling rate and the ability of the flow to bypass geometrical obstacles in a microfluidic channel. It is shown that the preservation of capillary filling properties of microchannels is in close agreement with the contact angle (CA) measurements and that the colder the storage temperature, the better the capillary filling capability of the channels is preserved. We ascribe the significantly reduced recovery rate to reduced thermally activated relaxation phenomena such as diminished diffusion of low molecular weight species (LMW) in the polymer matrix at colder temperatures. This is supported by ATR-FTIR measurements of the OH vibration band over time for samples stored at different temperatures.

Details

Original languageEnglish
Article number2
JournalMicrofluidics and Nanofluidics
Volume24
Issue number1
Publication statusPublished - 1 Jan 2020
MoE publication typeA1 Journal article-refereed

    Research areas

  • ATR-FTIR analysis, Capillary microfluidics, Cold storage, Geometrical valves, Hydrophobic recovery, Long-term hydrophilicity, PDMS

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