On-chip cell immobilization and monitoring system using thermosensitive gel controlled by suspended polymeric microbridge

In this paper, we describe the fabrication of a temperature-controlled microfluidic chip for cell immobilization using a thermosensitive hydrogel of poly (N-isopropylacrylamide) (PNIPAAm). A mixture of PNIPAAm solution, yeast cells, and Calcein-AM fluorescent dye is flowed in the microchannel, and the indium-tin-oxide (ITO) microheaters that were fabricated by micromachining technology heat a PNIPAAm gel. However, if the gel is very thick, it blocks the observation of the culturing cells and reduces the SNR. To address this problem, we fabricate a suspended microbridge above the microheater that limits the height of the gel, ensuring that it forms a thin and transparent layer above the heater. Microheaters and suspended biocompatible microbridge are integrated on a chip in which yeast-cell immobilization can be performed by gelation of a PNIPAAm solution.