A powerful and effective design of a polymeric thermal microactuator is presented. The design has SU-8 epoxy layers filled and bonded in a meandering silicon (Si) microstructure. The silicon microstructure reinforces the SU-8 layers by lateral restraint. It also improves the transverse thermal expansion coefficient and heat transfer for the bonded SU-8 layers. A theoretical model shows that the proposed SU-8/Si composite can deliver an actuation stress of 1.30 MPaK, which is approximately 2.7 times higher than the unconstrained SU-8 layer, while delivering an approximately equal thermal strain.