Characterizing fruit fly flight behavior using a microforce sensor with a new comb-drive configuration

This paper reports a MEMS microforce sensor with a novel configuration of bulk micromachined differential triplate comb drives that overcomes the difficulty of electrically isolating the two stationary capacitor comb sets in bulk micromachining. A high-yield fabrication process using deep-reactive ion etching (DRIE) on silicon-on-insulator (SOI) wafers and only three lithographic masks was utilized to construct the high aspect ratio devices. The process features dry release of both suspended structures and the entire device in order to protect fragile components. The sensor has a high sensitivity (1.35 mV/μN), good linearity (<4%), and a large bandwidth (7.8 kHz), and is therefore well suited for characterizing flight behavior of fruit flies (Drosophila melanogaster). The technique allows for the instantaneous measurement of flight forces, which result from a combination of aerodynamic forces and inertial forces generated by the wings, and demonstrates a novel experimental paradigm for exploring flight biomechanics in the fruit fly. The average lift force is determined to be 9.3 μN (±2.3 μN), which is in the range of typical body weights of fruit flies. The potential impact of this research extends beyond gathering flight data on Drosophila melanogaster by demonstrating how MEMS technology can be used to provide valuable tools for biomechanical investigations.