Supercapacitors are widely used in various fields due to their high power density, fast charging and discharging speeds, and long service life. However, with the increasing demand for flexible electronics, integrated supercapacitors in devices are also facing more challenges, such as extensibility, bending stability, and operability. Despite many reports on stretchable supercapacitors, challenges still exist in their preparation process, which involves multiple steps. Therefore, we prepared stretchable conducting polymer electrodes by depositing thiophene and 3-methylthiophene on patterned 304 stainless steel (SS 304) through electropolymerization. The cycling stability of the prepared stretchable electrodes could be further improved by protecting them with poly(vinyl alcohol)/sulfuric acid (PVA/H₂SO₄) gel electrolyte. Specifically, the mechanical stability of the polythiophene (PTh) electrode was improved by 2.5%, and the stability of the poly(3-methylthiophene (P3MeT) electrode was improved by 7.0%. As a result, the assembled flexible supercapacitors maintained 93% of their stability even after 10,000 cycles of strain at 100%, which indicates potential applications in flexible electronics.

Stretchable, adhesive, and conductive hydrogels have been regarded as ideal interfacial materials for seamless and biocompatible integration with the human body. However, existing hydrogels can rarely achieve good mechanical, electrical, and adhesive properties simultaneously, as well as limited patterning/manufacturing techniques posing severe challenges to bioelectronic research and their practical applications. Herein, we develop a stretchable, adhesive, and conductive Ti₃C₂T_x-polyacrylic acid hydrogel by a simple pre-crosslinking method followed by successive direct ink writing 3D printing. Pre-polymerization of acrylic acid can be initiated by mechanical mixing with Ti₃C₂T_x nanosheet suspension, leading to the formation of viscous 3D printable ink. Secondary free radical polymerization of the ink patterns via 3D printing can achieve a stretchable, adhesive, and conductive Ti₃C₂T_x-polyacrylic acid hydrogel. The as-formed hydrogel exhibits remarkable stretchability (~622%), high electrical conductivity (5.13 S m⁻¹), and good adhesion strength on varying substrates. We further demonstrate the capability of facilely printing such hydrogels into complex geometries like mesh and rhombus patterns with high resolution and robust integration.