11. Micro/Nanorobotic Manufacturing of Thin-Film NEMS Force Sensor

This chapter presents the fabrication and characterization of piezoresistive force sensors based on helical nanobelts. The three-dimensional helical nanobelts are self-formed from 27-nm-thick n-type InGaAs/GaAs bilayers using rolled-up techniques and assembled onto electrodes on a micropipette using nanorobotic manipulation. Patterned gold electrodes were fabricated using thermal evaporation or fountain-pen-based gold nanoink deposition. Nanomanipulation inside a scanning electron microscope was conducted to locate small metal pads of helical nanobelts to be connected to the fabricated pipette-type electrodes. Gold nanoink was deposited under optical micrograph using the fountain-pen method. Nanomanipulation inside a scanning electron microscope using a calibrated atomic force microscope cantilever was conducted to calibrate the assembled force sensors, and the values were compared with finite-element-method simulation results. With their strong piezoresistive response, low stiffness, large-displacement capability, and good fatigue resistance, these force sensors are well suited to function as sensing elements for high-resolution and large-range electromechanical sensors.