Abstract
Hydrogels are a widely used ionic conductor in on-skin electronic and iontronic devices. However, hydrogels dehydrate in the open air and freeze at low temperatures, limiting their real applications when they are attached on skin or exposed to low temperatures. Polymer-ionic liquid gels can overcome these two obstacles, but synthetic ionic liquids are expensive and toxic. In this work, we present an ionic conductor based on polyacrylic acid (PAAc) and deep eutectic solvents (DESs) that well addresses the aforementioned challenges. We polymerize acrylic acid in DESs to get the PAAc–DES gel, which exhibits excellent stretchability (> 1000%), high electrical conductivity (1.26 mS cm−1), high adhesion to the skin (~ 100 N m−1), as well as good anti-drying and anti-freezing properties. We also demonstrate that the PAAc-DES gel can be used as an on-skin electrode to record the surface electromyographic signal with high signal quality, or as a transparent stretchable electrode in iontronic devices that can work at –20 °C. We believe that the PAAc–DES gels are an ideal candidate as epidermal electrodes or transparent stretchable electrodes.
Highlights
Soft ionic conductors are a vital component in on-skin electronics that can be used as an interface to transfer electrical signals between the human body and the external devices[1,2,3,4,5]
We demonstrated that the polyacrylic acid (PAAc)–Choline chloride (ChCl)–ethylene glycol (EG) gel can be used in antifreezing iontronic luminescence that works at a temperature lower than –16 °C (Fig. S13)
We demonstrated the great potential of the PAAc–Deep eutectic solvents (DESs) gel in the field of on-skin electrodes and iontronics devices
Summary
Soft ionic conductors are a vital component in on-skin electronics that can be used as an interface to transfer electrical signals between the human body and the external devices[1,2,3,4,5]. We show that a stretchable, transparent, adhesive, and anti-freezing DES gel can be prepared by polymerizing monomers in DESs, by mixing acrylic acid (AAc) with various DESs and initiating the reaction via ultraviolet (UV) radiation, similar to the method to make synthetic hydrogels. The gel exhibits a high transparency of ~ 92%, a large stretchability over 1000%, at moderate electrical conductivity of 1.26 mS cm−1, and strong adhesion (~ 100 N m−1) with the human skin, which are comparable to most IL gels. The PAAc–DES gels exhibit high compatibility on human skin without showing skin irritation after wearing for 8 h This soft ionic conductor has been applied as an on-skin electrode to record bioelectricity signals, exhibiting low impedance of the skin–electrode interface and improved signal quality compared with commercial electrodes. We believe that our work can enrich the ionic conductors with a cheaper, eco-friendly, and high-performance choice
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
