A Biomimetric Lactate Imprinted Smart Polymers as Capacitive Sweat Sensors

This paper demonstrates a non-enzymatic biomimetric flexible sweat sensor. Fabricated by multi-layered assembly, the layers comprised a conductive nanoporous carbon nanotube-cellulose nanocrystals (CNC/CNT) porous films entrained with poly (N-isopropylacrylamide) (pNIPAM) based microgel. The pNIPAM microgels based sensor films are effective for detection of ionic strength. The pNIPAM microgels coated with lactate imprinted poly (aniline/phenylboronic acid) (pANI/PBA) moieties switch off their responsivity to NaCl and instead effectively respond to lactate. As such, the printed pNIPAM microgels have been demonstrated as flexible capacitive sensor for multiplex detection of electrolyte (e.g. NaCl) and lactate levels in sweat analysis. The linear concentration range obtained for pNIPAM @CNC/CNT sensor in response to NaCl was 3-80 mM, with a limit of detection (LOD) of 0.23 mM NaCl. The lactate imprinted pANI/PBA- pNIPAM @CNC/CNT sensor resulted in a linear range of 1 mM-25 mM, and a LOD of 0.10 mM, an order of magnitude higher than the non-imprinted form. For both analytes, the sensor precision ranged from 0.5-5.0%, indicative of the overall reliability and validity. The fabricated flexible sensors were demonstrated to be effective in quantitation of electrolytes (principally NaCl) and lactate in a real sweat sample.