Abstract
This paper reports the study of both the mechanical strength and interfacial failure of cantilevered SU-8 microposts fabricated on silicon substrates. An ultra-precision instrument was developed to simultaneously measure both the displacement and resultant force of specially designed SU-8 microposts under a static bending load increasing up to an interfacial fracture. Experimental results were presented for two sets of SU-8 microposts with different geometry, one with a circular cross-section and the other with a square cross-section, both having an aspect ratio larger than 1. Shear failure stresses of both circular and square microposts were estimated to be approximately 6.53 MPa ± 4.2% and 6.83 MPa ± 9.7%, respectively. The failure regions were characterized by a scanning electron microscope to determine the failure mechanism. Our experiments showed that the hardness and Young's modulus of SU-8 decreased with increasing penetration depth, and both quantities are sensitive to loading/unloading speeds.