Rapid hydrogel micropatterning utilizing CNT-induced thermoresponsive effect

In the paper, the new approach towards fabrication of microscale hydrogel patterns is shown. Microchannels of diverse shapes were obtained based on the hydrogel thermoresponsive effect. The stamps manufactured additively in the form of the microchannels, covered with carbon nanotubes (CNT) layers, were used to provide the imprint within the 3D printed hydrogel substrates for the first time. Self-developed hydrogel inks and extrusion technique were applied to obtain planar hydrogel matrices. In order to transfer the pattern thanks to Joule–Lenz law, the CNT-covered stamp powered by the safe voltage was pressed to the hydrogel structure for 30 s. In result, microchannels corresponding faithfully to the designs were obtained, with preserved geometry and pattern continuity along the entire length. The average depths obtained for the 1 mm and 0.5 mm wide channels were measured utilizing optical profilometry and showed promise towards fabrication of fine microscale structures. Moreover, roughness measurements and tensile tests were conducted to confirm that hydrogel stamping does not significantly affect its structure and mechanical properties. Results presented herein are a good base towards development of new microfabrication methods. As demonstrated, our micropatterned hydrogels can be easily applied for microflow experimentation with lab-on-chip platforms.