Design, simulation and characterization of hydrogel-based thermal actuators

This paper presents the design, assembly, simulation and testing of hydrogel-based thermal actuators. Actuators utilizing stimuli-responsive hydrogel materials have a number of advantages compared to conventional ones, including relatively simple fabrication and large force generation. The thermal actuator here utilizes a temperature-sensitive hydrogel to provide an adjustable force/pressure with a fast dynamic response. The actuator is used as part of a hydrogel-based pH sensor, where force compensation via this actuator keeps the sensor in its initial state and, hence, avoids relaxation and drift process. A finite element simulation with ANSYS is introduced to assess temperature distribution and maximum allowable actuating pressure in this actuator. Three actuators are assembled and tested. Two crucial factors, including the depth of the hydrogel reservoir and the filling factor of hydrogel, are investigated to improve the response time (1.9 min) and actuating pressure (65 kPa), respectively. The trade-off between actuating pressure and response time should be carefully considered in the further work. (C) 2016 Elsevier B.V. All rights reserved.