Evaluation and application of Thermoresponsive Gel handling towards manipulation of single cells

This paper proposes a method to evaluate Thermoresponsive Gel probe (GeT probe) which was newly developed and also a method of manipulating microobjects in liquid. The proposed GeT probe realizes the pick and place of microobjects using adhesion to the thermoresponsive gel. The probe has a microheater, which can generate the thermal gel at the probe tip. The 10 wt% poly(N-isopropylacrylamide) (PNIPAAm) solution, which is gelled over 32 °C, was used as a thermoresponsive polymer. The 3 dimensional structures were assembled by the probe. The temperature at the probe tip was analyzed using Finite Element Method (FEM) analysis in this paper. The fixation force by the thermal gel was also measured using atomic force microscopy (AFM) cantilever. The results of temperature analysis show that the probe temperature was less than 50 °C even if the gel diameter is more than 200 µm. The enough gel was generated to handle cells even if the tip temperature was less than 40 °C. The results indicate that the probe can handle cells in a viable condition. And the measured fixation force was µN order force. The results show that the probe can generate larger force compared to optical tweezers, and the probe can generate enough force to handle large objects such as egg cells. The handling of microobjects in pure water was finally demonstrated by the probe. The results indicate that the environment for the probe application is not restricted in the thermoresponsive polymer solution. The evaluation in this paper shows that the GeT probe can contribute to handling microobjects, especially living cells.