In this paper, we report the results of the HCL wet etching process to fabricate a PMN-PT single crystal piezoelectric thin membrane. A piezoelectric thin membrane can offer the ability to passively sense vibrations without power requirements. Furthermore the new generation oxide material exhibits extraordinary piezoelectric properties. The material, the single-crystal solid-solutions (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT), has been shown to possess piezoelectric coefficients and electromechanical coupling responses significantly larger than conventional ceramics. A four-fold enhancement in piezoelectric coefficients and much higher efficiencies in electrical to mechanical energy conversions have been found. Use of a PMN-PT sensor to detect, with high sensitivity, minute amounts of waterborne pathogenic bacteria such as E. coli O157:H7 is one promising direct application. Design of a compact and portable PMN-PT sensor device used in produce packaging facilities and grocery stores is a primary focus. In this paper, we present the research results produced from the experimental work for the PMN-PT wet etching in HCL solution.