Researchers at Nanomix Inc., in Emeryville, Calif., devised the breathing sensor by creating a transistor that fuses carbon nanotubes, polymers, and silicon into a capnography sensor — a human breathing monitor. Working with the University of California, Los Angeles, the company found carbon nanotube transistors fused with carbon dioxide-detecting polymers can determine CO2 concentrations in both ambient and exhaled air.

Capnography sensors detect subtle changes in the concentration of carbon-dioxide gas in a person's breath. This can reveal respiratory diseases and allow anesthesiologists to monitor a patient's breathing during surgery. In the field, emergency responders may be able to use the new sensor to verify proper breathing tube placement, monitor respiratory patterns, and assess the effect of life support measures.

The Nanomix device can monitor human breathing in laboratory settings. Company researchers are collaborating with anesthesiologists and other specialists at UC San Francisco to design and test a field-ready medical device.

The nanotube transistors may also find application in optoelectronic memories. Electronic interactions between polymers and carbon nanotubes that sense CO2 can also yield photosensitive devices that record binary on and off patterns, thus providing optically written memory elements.

When researchers shine light on the polymer-coated nanotube transistors, electric charge gets stored in the nanotubes. Because different polymers absorb light differently, engineers can tune the device to work under specific light frequencies. By changing the voltage in the device, one can control the read and erase functions.

Philip E. Bickler, Dept. of Anesthesia and Perioperative Care, UC San Francisco believes this sensing technology will break new ground. "Being able to continuously and accurately measure carbon dioxide in exhaled breath with a small, inexpensive and precalibrated device is a significant development in clinical care. It will improve emergency care in the field by helping guide resuscitation efforts and also provide important feedback about adequacy of ventilation."