Wearable microneedle dual electrochemical sensor for simultaneous pH and cortisol detection in sweat

We report herewith an inexpensive flexible dual target electrochemical sensor for simultaneous detection of pH and cortisol in human sweat. The sensor was fabricated by printing layer by layer (LbL) on a conductive microneedle polydimethylsiloxane (PDMS) flexible substrate. The dual sensor integrates two detection chambers comprising polyaniline (PANi) and cortisol imprinted poly (glycidylmethacrylate-co ethylene glycol dimethacrylate) (poly (GMA-coEGDMA)). The dual wearable sensor rapidly (< 1 min) responded linearly to pH in the range of 3-9, while the cortisol sensor chamber had a linear range of 0-100 ng/mL. The cortisol sensing region had an excellent limit of detection (LOD) of 1.4 +/- 0.3 ng/mL, with intra-batch reproducibility of 2.4% relative standard deviation (%RSD). The inter-batch precision (%RSD for three different sensors) was determined to be 4.7%. Demonstrating excellent stability and reusability, a single patch of cortisol sensor was used for 15 times over a 30-day period, with minimal change in response. The dual analyte wearable sensors were effective for detection of pH and cortisol in real human sweat.