UT Acoustic MEMS
We build microphones that work while on fire.
We build microphones inspired by insects.
We build seismometers that can detect events anywhere on earth.
We are building a system that uses acoustic waves to communicate with CO2 storage sites deep beneath the surface.
Fly-Inspired Microphones
Check out this link to listen to an NPR radio interview: UT Researchers Creates Device That Mimics Fly's Hearing Power
An additional link here: How a Tiny Fly's Ear Could Help You Hear Better
Optically-Read Seismic Sensors
Professor Hall started a company, Silicon Audio, INC. that today makes and sells the highest dynamic range seismometer in the world. Check out www.siaudio.com and once there, be sure to check out this video: Silicon Audio Optical Seismometer
The seismic sensor is competing for a mission to Europa, the icy moon of Jupiter thought to embody conditions needed to support life. Earth-based testing of the sensor has taken place in Alaska and Greenland: A glacier in Interior Alaska is a testing ground for equipment intended for use in space
photograph by Meghan Murphy, showing Silicon Audio engineer Brad Avenson installing Silicon Audio sensors on Alaska's Gulkana Glacier.
The sensor uses an optical diffraction grating to split an incident laser beam into a reference beam and a beam that passes through the grating to reflect off a moving mass. Design of the sensor requires modeling the interaction of light with the grating. Image produced by graduate student Randy Williams using a Fourier Optics simulation coded in Python.
Elastic Wave Telemetry for CO2 Storage Sites
Capturing and storing CO2 inside the earth can help reduce climate change. Safe storage requires communication with sensors miles beneath the surface. Wired communication is undesirable for various reasons. Electromagnetic waves used in wireless communication do not propagate well inside the earth. We are exploring how elastic waves (i.e. vibrations) can be used to carry digital information from deep inside the earth to the surface. The image carousel features acoustic propagation modes in a steel casing as simulated by graduate student Ehsan V. using COMSOL.
High-Temperature Microphones
Hypersonic flight is flight at speeds 5x faster than sound. Such speeds are realized by vehicles developed by the Air Force and in atmospheric entry of space probes and weapons. Dynamic pressure signals (i.e., sound) in such flows contains information related to laminar-to-turbulent transition, shocks, and combustion. We are creating microphones for ground test facilities and flight vehicles that detect audible and ultrasonic sound and operate in an extreme temperature environment, greater than 1,000K.
The image shows a microphone recording sound while under butane flame. Video link here: Microphone Recording Under Butane Flame. Microphone designed and fabricated by graduate student Yoonho Seo.
Infrasonic Microphones
Infrasound is sound in the 0.01 Hz to 20 Hz frequency range. Large events create infrasound - earthquakes, volcanos, hurricanes, avalanches, tornadoes, and man-made explosions. We are creating infrasonic microphones for the detection and monitoring of nuclear test activity, a key element to enforcing the comprehensive test-ban treaty. The image is a silicon piezoresistor fabricated on a pressure-sensitive diaphragm. Remote explosions hundreds of miles from the microphone produce nanometer deflections of the diaphragm, inducing a measurable change in piezoresistance.
Sensor shown is fabricated and tested by a team of graduate students (Yoonho Seo, Randy Williams, Carly Stalder) and group alumni Donghwan Kim.
Capacitive and Piezoelectric Ultrasonic Transducers
Ultrasonic transducers are used to launch and receive ultrasound in air, enabling objects in the path of the sound to be detected and even imaged. We have built capacitive and piezoelectric micromachined ultrasonic transducers (CMUTS and PMUTS) for industrial applications. The image at left is an ultrasonic tone burst in air operating at 240 kHz and measured optically using modulated refractive index (optical measurement of sound). The tone burst is generated by a PMUT fabricated by Donghwan Kim.