MICRO/NANO-PRINTING OF METAL AND NANOPARTICLE THIN FILM AND ITS APPLICATION TO MEMS DEVICE

This present paper describes some test results about fabrication of micro/nano-structure for MEMS using printing techniques of metal and nanoparticle thin films. Transfer-printing of a bi-layered film of graphene oxide (GO) and Au is processed on a PET substrate. Nano-particles of GO are cast on a micro-ridged poly-dimethyl-siloxane stamp that is previously coated with Au by solution casting. The layer of GO nanoparticles functions as a reinforcing material to strengthen the layered film while the Au thin-film is a matrix that links the GO nanoparticles. The thickness of GO nanoparticles varies with concentration of GO suspension. In the case of thicker coating of GO with an average thickness of 13 nm, the transfer-printing makes the GO/Au bi-layered film form into 50-mu m-wide two-dimensional line patterns on the PET substrate. Additionally, transfer-printing of another bi-layered film with a 128 nm thickness fabricates a three-dimensional microstructure of a rectangular-corrugated film on the PET substrate because the entire bi-layered film is transferred from the stamp. The modulus of transfer-printed GO/Au bi-layered film is investigated by a simple bending tests using AFM cantilever. FEM analysis of the bending test results indicates that the mechanical modulus of the GO/Au film is not less than 120 GPa, and this significantly exceeds that of the Au film by itself. The present study also fabricated a capacitive MEMS sensor by a combination of transfer-printing and inkjet printing. Inkjet printing makes GO nanoparticles on the 100-.m-wide comb-like microelectrode, which is previously fabricated by transfer-printing of Au thin film. The fabricated MEMS sensor successfully shows its change of capacitance with relative humidity in the range of 40% to 80%. These results demonstrate that the printing of Au and GO nanoparticles is effective for MEMS fabrication.