Polymer Mass Loading of CMOS/MEMS Microslot Cantilever for Gravimetric Sensing

A post CMOS/MEMS fabrication method using inkjet printing of mass sensitive polymer into slotted microcantilevers is explored with the goal of increasing the polymer to cantilever mass ratio. This method involves wicking the dissolved polymer, poly(butyl methacrylate) (PBMA), into a microslot cantilever via a capillary slot running its length using surface tension forces. This is done by jetting into a target well paced at the base of the cantilever. By this method, inkjet printing is made compatible with device scaling to achieve higher mass sensitivities for gravimetric sensing applications and small electrostatic gaps for low noise capacitive actuation and detection. Also, we are able to achieve repeatable sub-nanogram dosing of material onto suspended devices with only a few microns in dimensional widths. Limits of this wicking method are explored on gravimetric arrays with varying microslot aspect ratios. The vertical resonant mode shows higher mass sensitivity than the lateral resonant mode.