Multiaxis force and torque sensing for insect flight research: Design, fabrication, calibration and testing of MEMS strain gauge sensor

Flying insects are able to perform remarkable maneuvers and flying acrobats by a deceptively simple process of beating their wings. However, a closer look at insect flight reveals highly complex and sophisticated mechanisms based on unsteady aerodynamics. The focus of this research project is to develop engineering solutions, specifically using Micro Electro Mechanical Systems (MEMS) technology, to study the aerodynamics of insect flight.;To this effect, MEMS force sensors were designed, fabricated, characterized and tested with tethered flying insects. The force sensors are microfabricated with integrated pieozresistive elements that can sense changes in strain in the structure with the idea that the flight force from a fly, tethered to the sensor, can be measured quantitatively. Force sensors were designed based on two main criterions; first that they are able to measure forces with at least two degrees of freedom and second that they are sensitive enough to measure real-time flight forces from fruit flies (Drosophila melanogaster), typically less than 20microN.;Tethered flight tests are conducted inside a specialized LED flight simulator arena that was already developed prior to this project by Michael Dickinson's group at Caltech. The force sensor measures the small multidirectional forces generated by fruit flies while simultaneously supporting it inside the arena thus providing the quantitative data that allows a better understanding of sensorimotor mechanisms of flight control in flying insects.;Elastic beam theory is revisited to formulize the governing equations for the MEMS force sensor design. Finite element models of the design are used to verify theoretically predicted values of stress and strain. The sensor is fabricated using standard bulk microfabrication processes and as such, material, design and fabrication constraints are highlighted. Several design and instrumentation techniques that increase force sensitivity for piezoresistive sensors are also discussed. A new technique that uses a nanoindenter tool for the force characterization of sensors is described. The sensors are shown to have successfully measured forces from tethered flying insects inside the flight arena. Finally, future directions for research in the area of insect flight using MEMS based force sensors are discussed, as are design changes that increase force sensitivity and allow elucidation of specific features of insect flight such as take-off and landing.