A wearable microfluidics-integrated impedimetric immunosensor based on Ti3C2Tx MXene incorporated laser-burned graphene for noninvasive sweat cortisol detection

In this study, we newly developed a wearable electrochemical impedimetric immunosensor with a microfluidic channel and chamber based on a Ti3C2Tx MXene-loaded laser-burned graphene (LBG) flakes 3D electrode network for noninvasive point-of-care cortisol biomarker detection in human sweat. Polydimethylsiloxane (PDMS) was used as a substrate to fabricate flexible and stretchable patch sensor. Then, LBG was transferred onto the PDMS substrate by removing the polyamide (PI) film. A laser line gap creates a disconnection between the laser-burned graphene flakes, which consequently decreases the electrochemical performance of the LBG electrode. To solve the inter-flake disconnection problem caused by burning and transferring, highly conductive Ti3C2Tx MXene was loaded onto the electrode. The proposed flexible microfluidic system was fabricated using three-dimensional (3D) printed mold and PDMS. The fabricated sensor was attached to the skin to collect sweat, which then moved by natural pressure through the channel to the chamber. The successful loading of Ti3C2Tx MXene was confirmed using field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). Under optimized parameters, the Ti3C2Tx MXene/LBG/PDMS-based patch cortisol immunosensor exhibited linearity and a detection limit of 0.01-100 nM and 88 pM, respectively. Based on the analyses, it can be concluded that the developed strategy is well suited and conformable for point-of-care cortisol biomarker detection.

Automated summary

A wearable sweat sensor based on MXene and graphene was developed, with a 3D printed microfluidic system for noninvasive cortisol detection in human sweat. The sensor exhibited linear detection with a low limit of 88 pM.