Microfluidic devices using thiol-ene polymers

Here, a new polymeric microfluidic platform using off-stoichiometric thiol-ene (OSTE) polymers was developed. Thiolene polymers were chosen as they afford rapid UV curing, low volume shrinkage and optical transparency for use in microfluidic devices. Three different off-stoichiometric thiol-ene polymers with 30% excess allyl, 50% excess thiol and a 90% excess thiol (OSTE Allyl-30, OSTE-50 and OSTE-90, respectively) were fabricated. Attenuated reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and solid-state cross polarisation-magic angle spinning (CP-MAS) nuclear magnetic resonance (NMR) spectroscopy confirmed which functional groups (thiol or allyl) were present in excess in the OSTE polymers. The polymers were shown to have a more hydrophilic surface (water contact angle of 65°± 3) compared to polydimethylsiloxane (water contact angle of 105° ± 5). Testing of the mechanical properties showed the glass transition temperatures to be 15.09 °C, 43.15°C and, 57.48°C for OSTE-90, OSTE Allyl-30 and, OSTE-50, respectively. The storage modulus was shown to be less than 10 MPa for the OSTE-90 polymer and approximately 1750 MPa for the OSTE Allyl-30 and OSTE-50 polymers. The polymers were then utilised to fabricate microfluidic devices via soft lithography practices and devices sealed using a one-step UV lamination "click" reaction technique. Finally, gold nanoparticles were used to form gold films on the OSTE-90 and OSTE-50 polymers as potential electrodes. Atomic force microscopy and sheet resistances were used to characterise the films.