Hydrogel-based thermo and pH responsive valves for flow control inside microfluidics chips

GOY, CARLA B.; MURGA HURTADO, JULIÁN; VARGAS AIGNASSE, MATILDA; KLER, PABLO; CHAILE, ROBERTO E.; MADRID, ROSSANA E.

Buenos Aires

Workshop; II Brazil-Argentine Microfluidics Congress and V Congreso de Microfluídica Argentina; 2022

Microfluídica Argentina

Microfluidic technology is always in continuous advance and nowadays its applicability isubiquitous. Flow control inside the chips has a very important role in order to improve theirperformance. In this context, this work presents the development and evaluation of hydrogelbased thermo and pH responsive valves for flow control inside microfluidic chips. The valves werefabricated with N-isopropylacrylamide copolymerized with Acrilic Acid (p-NIPAAm-co-AAc),in order to obtain a thermo and pH-responsive hydrogel with a 42°C Low Critical SolutionTemperature. The microfluidic chips were fabricated using a mold-based technique to printchannels over a PDMS bulk. To do this, a 3D-printed ABS pattern of microchannels was locatedin the bottom of a 30mm-microwell where then a PDMS solution (10:1 ratio base/curing agent)was casted, degassed during 1 hour in order to eliminate bubbles and cured at room temperatureduring 24hs. Finally, the PDMS bulk was placed and pressed over a glass slide to seal the chip. Tocreate the valves, NIPAAm-co-AAc hydrogel was polymerized via UV irradiation: a) inside themicrochannel using a photomask to limit the area of the valve, and b) in an external microwell,from where it was picked and placed in the desired spot inside the channel. Several valvesconfigurations are studied. The mechanical response of the hydrogel under temperature/pHchanges, the ON-OFF behavior of the valves, and the relationship flow rate vs pressure areevaluated for each configuration by using a hydrostatic fluidic pump replicated from the literature.