Sensing and actuating functionality of hybrid MEMS combining enhanced chemi-mechanical transduction with surface enhanced Raman spectroscopy

The present work extends the concept of microcantilever (MC) based transducers to hybrid MEMS that integrate actuation and multiple sensing modes. Theoretical models predict significant limitations for the mechanical energy produced due to molecular interactions of conventional MCs with the environment. In order to overcome these limitations, we focus on cantilever designs and technologies of nanostructured coatings that are more compatible with fluidic MEMS and provide highly efficient molecular-driven actuation as well as additional modes of selectivity. In particular, co-evaporated Au:Ag films were used to prepare nanostructured interfaces that strongly enhance both chemi-mechanical transduction and Raman scattering. Acquisition of surface enhanced Raman scattering (SERS) signals generated on the cantilevers with nanostructured gold coatings provided highly specific molecular information. Additionally, highly efficient, environmentally-responsive sensor-actuator hybrids were created using MCs made of epoxy based photoresist SU-8 that were modified with hydrogel. Immobilization of colloidal silver particles in the acrylate based hydrogels provides multi-modal functionality for these MCs. Using several alternative technologies, we have created MC transducers that exhibit micrometer scale deflections in response to changes in the molecular microenvironment and provide vibrational signatures of constituents in that environment. It is anticipated that these molecular-actuated MC transducers will constitute a novel platform for future biomedical devices.