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

GOY, CARLA B; MURGA, JULIAN; VARGAS, MATILDA; KLER, PABLO A.; CHAILE, ROBERTO E.; MADRID, ROSSANA E.

Congreso; III Brazil-Argentine Microfluidics Congress - VI Congreso de Microfluídica Argentina; 2022

Microfluidic technology is always in continuous advance and nowadays its applicability is ubiquitous.Flow control inside the chips has a very important role in order to improve their performance. Inthis context, this work presents the development and evaluation of hydrogel-based thermo andpH responsive valves for flow control inside microfluidic chips. The valves were fabricated withN-isopropylacrylamide copolymerized with Acrilic Acid (p-NIPAAm-co-AAc), in order to obtain athermo and pH-responsive hydrogel with a 42°C Low Critical Solution Temperature. The microfluidicchips were fabricated using a mold-based technique to print channels over a PDMS bulk. To dothis, a 3D-printed ABS pattern of microchannels was located in the bottom of a 30mm-microwellwhere then a PDMS solution (10:1 ratio base/curing agent) was casted, degassed during 1 hour inorder to eliminate bubbles and cured at room temperature during 24hs. Finally, the PDMS bulkwas placed and pressed over a glass slide to seal the chip. To create the valves, NIPAAm-co-AAchydrogel was polymerized via UV irradiation: a) inside the microchannel using a photomask tolimit the area of the valve, and b) in an external microwell, from where it was picked and placedin the desired spot inside the channel. Several valves configurations are studied. The mechanicalresponse of the hydrogel under temperature/pH changes, the ON-OFF behavior of the valves, andthe relationship flow rate vs pressure are evaluated for each configuration by using a hydrostaticfluidic pump replicated from the literature.