Design, Development, and Construction of a Biologically Inspired Sensing System for Real Time Flow Visualization

Abstract

Bats exhibit complex and sophisticated flight behavior. Because of their inability to rely on eyesight when flying, bats constantly utilize complex sensing mechanisms, such as echolocation, in order to place themselves and make rapid spatial and flight pattern decisions. In recent years, attention and research have been devoted to tiny hair-shaped sensors that extend from bats’ wings into the fluid flow over their surface. Various studies so far have shown the hairs’ importance in the flight dynamics of the bat and their apparent role in allowing the animal to perform complex flight maneuvers.

This Bachelors Thesis aims to mimic the hair sensors found on bats’ wings for applications in fluid flow visualization. Analytical computations and approximations for flat-plate fluid flow as well as for flow over an airfoil surface have been performed to design and size the sensor. The initial design has then been iterated using computational tools such as ANSYS and MATLAB to optimize the sensor and to predict its functionality and operation when immersed in flow.

The manufacturing process was designed using lithographic techniques. Each layer was designed individually and superimposed over the preceding layer. The sensor was constructed in the Princeton University Micro/Nano Fabrication Laboratory using standard lithographic techniques and processes such as plasma etching and electron- beam vapor deposition. The sensor is made of Silicon, Silicon Dioxide Titanium, Platinum, and Polyimide.

The data collection system, including circuits, firmware, and software was designed and built to develop the backbone of the sensing system. It includes a Graphical User Interface, called Bat Flow Sensing, to allow the user to interface with the sensor system and to visualize flow in real-time. For this experiment, the sensing system was built into a NACA 0018 airfoil to be tested in a wind tunnel in order to simulate real-world conditions.

Device and process development in the cleanroom are iterative procedures that take time and significant repetition. Given the academic year time frame for the entire project, the sensor did not reached full completion. However, as shown in this report, the sensor manufacturing process has been developed refined up to the final phase. Reaching a complete and functional sensor is hopefully, not too far away.