doi:10.1038/nindia.2017.150 Published online 5 December 2017
Using a novel "sequential elemental de-alloying" technique to make porous metal oxides, researchers at the Indian Institute of Science (IISc) in Bengaluru have fabricated a humidity sensor that doubles as an electronic ear1.
Highly porous materials, with variable chemical compositions belong to the family of 'functional' materials used for making devices capable of reproducing human senses. The electronic nose is one such device.
The IISc's humidity sensor based on porous stannic oxide (SnO2) can measure changes in relative humidity with an accuracy of 1% — a property that will enable online monitoring of hospitalised patients of asthma, cancer, diabetes, and dehydration by measuring the humidity changes between their inhaled and exhaled breath.
According to the researchers, their humidity sensor responds distinctly towards speaking, breathing, and whistling. It is able to recognise and create a distinct response pattern for words spoken by different users indicating its potential to differentiate between words like the human ear. The observed abilities of the sensor "will facilitate its utilisation for electronic listening as well as for biomedical applications," says the report.
Besides, the two-step strategy developed for the synthesis of three-dimensional porous SnO2 microstructures "can be applied to fabricate other porous metal oxides also."
1. Solanki, V. et al. Sequential elemental de-alloying approach for the fabrication of porous metal oxides and chemiresistive sensors thereof for electronic listening. ACS Appl. Mater. Interfaces 9, 41428−41434 (2017) doi: 10.1021/acsami.7b12127