Fabrication of thermoresponsive gel blocks using hysteresis towards cell assembly

In this paper, we propose a new method to assemble microstructures made of a thermoresponsive gel using hysteresis character of the thermoresponsive polymer solution. This method can be used for 3 dimensional cell assembly by embedding cells in the thermoresponsive gel structures. Gel blocks can be maintained the gel condition by the hysteresis character and the microstructures can be formed by assembling the gel blocks. The temperature distribution around a microheater was analyzed to generate the thermoresponsive gel and avoid thermal damages to cells. The generation of thermoresponsive gel was conducted using the microheater which was embedded in a probe tip and manipulated by a micromanipulator. The fabrication of a gel block was achieved using the hysteresis character and the fabricated gel block was picked and placed by the probe. Cells were embedded in the gel by controlling the position of microheater to avoid the influence of thermal convection flow. The positioning of the gel blocks can be precisely controlled by the micromanipulator. The results indicate the method we propose has a great possibility to achieve 3D cell assembly without large stress to cells during the assembly and cell culture.