Thermoelectric Polymer Aerogels for Pressure–Temperature Sensing Applications

The unrivaled capability of sensors to respond to physical, chemical and biological stimuli from our surroundings and transform them into communicable data has made them key components of emerging sophisticated technologies. Even though, depending on their application, sensor reading and fabrication can get quite intricate, especially where several types of sensors are involved. Luckily, the latter shortcoming can be satisfied by creating advanced functional materials that have the ability to react to multiple stimuli. Currently, several techniques are feasible for resolving this issue but this work focuses on the most eye-catching method: conducting aerogels. It is known that conducting polymers such as PEDOT:PSS upon dispersion in water, can form aerogels upon freeze drying.  Previous studies have demonstrated dual parameter sensors with this material. Unfortunately, the pressure/temperature sensing operation of such devices has been seen to suffer from a significant cross-talk, which is related to the inherent charge transport mechanism in the conducting aerogels.

A team of researchers led by Professor Xavier Crispin at Linköping University in Sweden developed a dual-parameter sensors based on thermoelectric polymer aerogels with fully decoupled temperature and pressure sensing capability. They hoped that their work would develop a strategy on how to fully decouple temperature and pressure readings, in a dual-parameter sensor based on thermoelectric polymer aerogels. Their work is now published in the research journal, Advanced Functional Materials.

The research methods employed by the researchers involved fine tuning the transport properties of the conducting aerogels with exposure to the vapor of high boiling point dimethylsulfoxide polar solvent. The team also employed thermoelectric polymer aerogels that had been prepared by freeze drying the water dispersion of three organic materials: PEDOT: PSS, nano-fibrillated cellulose, and glycidoxypropyl trimethoxysilane.

The authors observed that post treatment with the dimethylsulfoxide polar solvent vapor enhanced the pressure sensitivity by two orders of magnitude, and led to an absence of cross-talk in the dual-parameter sensors. Additionally, it was seen that the aerogels made of PEDOT: PSS displayed semiconductor properties lying at the transition between insulator and semimetal due to exposure to the polar solvent vapor. Most important, the team noted that due to temperature-independence charge transport nature of the dimethylsulfoxide-treated PEDOT-based aerogel, a decoupled pressure and temperature sensing could be achieved without crosstalk in the dual-parameter sensor devices.

The optimized dual-parameter sensors developed by Shaobo Han and colleagues in the study can potentially be utilized in various electronic-skin applications.

PNG aerogels – PEDOT: PSS, nano-fibrillated cellulose, and glycidoxypropyl trimethoxysilane based aerogels.

PEDOT: PSS – poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate)