Enhanced dimethyl methylphosphonate (DMMP) detection sensitivity by lead magnesium niobate-lead titanate/copper piezoelectric microcantilever sensors via Youngʹs modulus change

We have examined the detection of dimethyl methylphosphonate (DMMP) using lead magnesium niobate-lead titanate (PMN-PT) piezoelectric microcantilever sensor (PEMS) coated with various planar and particulate receptor coatings. We showed that a two-order-of-magnitude enhancement in the flexural-mode resonance frequency shift, Δf, in DMMP detection that was not accountable for by mass loading alone could be achieved by using a planar Cu2+ adsorbed 11-Mercaptoundecanoic Acid (MUA/Cu2+) or planar 3-mercaptopropyltrimethoxysilane (MPS) coated PEMS. We also showed that the enhancement of Δf of PEMS was a result of the Youngʹs modulus change in the PMN-PT layer induced by the surface stress generated by the binding of DMMP on a continuous receptor coating. Furthermore, the Youngʹs modulus-change enhanced Δf in PEMS with a planar receptor coating was shown to be inversely proportional to the product of the average Youngʹs modulus and thickness of the PEMS and independent of the PEMS lateral dimension. We also showed that with an array of three PEMS, one uncoated, one coated with planar MUA/Cu2+ and the other with planar MPS, the detection Δf pattern for DMMP was distinctively different from those of acetone and ammonia.