3D printing of hydrogels for flexible micro-supercapacitors

Advances in hydrogel technology have paved the way for novel and valuable capabilities that are being applied to a diverse spectrum of energy storage applications. Hydrogels, originally renowned for their biomedical applications, are now finding translation into the energy storage domain. These versatile materials exhibit promising potential for various energy-related applications, including but not limited to acting as highly flexible electrolytes, facilitating the development of flexible supercapacitors, and contributing to advancements in energy conversion devices. The tunable properties of hydrogels, their high ion accessibility, and desirable mechanical characteristics position them as promising candidates for enhancing the performance and efficiency of energy storage systems. In this review, we emphasize the integration of hydrogels into flexible micro-supercapacitors through 3D printing technology, unraveling the charge transport mechanisms inherent in hydrogels. We discuss methods for developing hydrogels with enhanced physicochemical properties, such as improved mechanical strength, flexibility, and charge transport, offering new prospects for next-generation energy storage devices. With a deeper understanding of gelation chemistry, we showcase significant progress in fabricating stimuli-responsive, self-healing, and highly stretchable hydrogels. Furthermore, we present compelling examples highlighting the versatility of hydrogels, including tailorable architectures, conductive nanostructures, 3D frameworks, and multifunctionalities. The application of innovative 3D printing techniques in hydrogel design is poised to yield materials with immense potential in the realm of energy storage.