As the technology to support wearable electronics advances, researchers are investigating new ways of making our clothing more "intelligent" – from smart shirts for theater ushers to the development of clothing that can respond to the wearer’s emotive state. So would it surprise you to learn that your humble underpants could one day save your life? A new study has shown that printed sensors on the elastic band of your underpants could monitor biomarkers in your sweat and tears, make autonomous diagnoses and even administer life-saving drugs.

Why use underpants? As the elastic on underpants has tight contact and direct exposure with the skin it allows for direct sweat monitoring via the chemical-sensing electrodes. And it seems elastic is a hardy textile. Engineers at the University of California, San Diego Jacobs School of Engineering discovered that even after aggressive testing by stretching, folding and pulling, the chemical sensors printed on the elastic still retained their sensing ability and could detect hydrogen peroxide and NADH – two compounds that sensors in "smart' systems will need to recognize.

The printed sensors can be incorporated into logic-based biocomputing systems that will monitor biomarkers such as lactate, oxygen, norepinephrine and glucose. It is expected that the smart system will be capable of diagnosing changes in a patient’s health status or a soldier’s battlefield injury and automatically trigger the release of drugs to begin treatment before help arrives. The sensors could also be used to detect driver’s alcohol consumption, the performance of athletes or stress levels of soldiers. The sensors, power, electronics and logic systems could all be embedded in the surface area of the clothing.

Professor Joseph Wang, from the Department of NanoEngineering at the University of California, San Diego Jacobs School of Engineering, said “…putting the electrodes on the underwear, we didn’t plan to make it so sexy. Our approach is scientific. The waistband of the underwear gives you the best contact with the skin where you expect to get a good sampling of the sweat.”

Wang, along with the UC San Diego NanoEngineers and their collaborators at Clarkson University continue to research how the sensed biomarker information is processed and how to obtain accurate, automated diagnoses that will be able to trigger the release of drugs. Wang explained that lactate, oxygen, norepinephrine and glucose are examples as the kinds of injury biomarkers that will provide biological input signals for the prototype smart system. Electrodes that contain a combination of enzymes will act as sensors to convert the biomarkers to products. This information may be analyzed by another enzyme on the electrode for further logic operations. The electrodes will also act as transducers producing a string of 1s and 0s that could activate smart materials and trigger the release of medication based on pre-determined patient treatment plans.

“We just want the ones and zeros. The digital pattern of ones and zeros will reveal the type of injury and automatically trigger the proper treatment,” said Wang.

If, for example, an injured soldier went into shock, enzymes on the electrode would sense rising levels of the biomarkers lactate, glucose and norepinephrine. This would cause the concentrations of products generated by the enzymes to change – higher hydrogen peroxide, lower norepi-quinone, higher NADH and lower NAD+. This would cause the built-in logic structure to output the signal “1,0,1,0” which indicates shock and could trigger a pre-determined treatment response. “This is biocomputing in action,” said Wang.

The peer-reviewed study called “Thick-film textile-based amperometric sensors and biosensors” was published in Analyst and was funded by the U.S. Office of Naval Research.