Hybrid three-dimensional printing and encapsulation process for cellulose hydrogel sensors

The advancement of three-dimensional (3D) printing technology has further promoted the scientific progression of hydrogels within the realm of wearable devices. However, when the viscosity of the hydrogel precursor is large but does not meet the self-supporting requirements, or lacks the participation of monomer with gel phase change characteristics, the 3D printing preparation of hydrogels often becomes difficult. This study delves into a novel 3D printing method aimed at combining direct ink writing (DIW) with vat photopolymerization (VPP) to achieve a broad spectrum of adjustable mechanical properties by introducing cellulose as a medium to modulate both the mechanical and rheological properties of hydrogels. This hybrid method facilitates the efficacious printing preparation of low-viscosity hydrogels, thereby mitigating the stringent viscosity prerequisites inherent in printable hydrogels. Furthermore, the employment of a dual-core coaxial printing technique for the hybrid printing of hydrogel and elastomer serves to ameliorate hydrogel water loss predicaments. As a result, this new 3D printing method broadens the mechanical properties of printable hydrogels and the adjustable range of system viscosity. At the same time, it realizes the integrated printing of encapsulation layer, and improves the service life of hydrogels, and can be applied to the hydrogel-based sensors.