No abstract

Hydrogel bioadhesion technology has offered unprecedented opportunities in minimally-invasive surgeries, which are routinely performed to reduce postoperative complication, recovery time, and patient discomfort. Existing hydrogelbased adhesives are challenged either by their inherent weak adhesion under wet and dynamic conditions, or potential immunological side-effects, especially for synthetic hydrogel bioadhesives. Here, a kind of synthetic hydrogel bioadhesives from a variety of polymer precursors are reported, featuring instant formation of tough biointerface, allowing for wet and robust adhesion with highly dynamic biological tissues. Moreover, by getting rid of monomers during the hydrogel fabrication, these hydrogel adhesives do not cause any inflammatory response during the in vivo wound sealing, promising for immediate vascular defects repairing and surgical hemostasis. Additionally, they could also serve as human-electronics interfacing materials, enabling bioelectronics implantation for real-time physiological and clinical monitoring.

Flexible and stretchable light emitting devices are driving innovation in myriad applications, such as wearable and functional electronics, displays and soft robotics. However, the development of flexible electroluminescent devices via conventional techniques remains laborious and cost-prohibitive. Here, we report a facile and easily-accessible route for fabricating a class of flexible electroluminescent devices and soft robotics via direct ink writing-based 3D printing. 3D printable ion conducting, electroluminescent and insulating dielectric inks were developed, enabling facile and on-demand creation of flexible and stretchable electroluminescent devices with good fidelity. Robust interfacial adhesion with the multilayer electroluminescent devices endowed the 3D printed devices with attractive electroluminescent performance. Integrated our 3D printed electroluminescent devices with a soft quadrupedal robot and sensing units, an artificial camouflage that can instantly self-adapt to the environment by displaying matching color was fabricated, laying an efficient framework for the next generation soft camouflages.

Nature builds structurally ordered and environmentally adaptive composite materials by harnessing biologically catalyzed mineralization under mild conditions. Despite recent advancements in engineering conventional materials with microorganisms through biomimetic mineralization, it remains difficult to produce mineralized composites that integrate the hierarchical structure and living attributes of their natural counterparts. Here, a kind of functional material is developed by integrating 3D printed hydrogel architectures with enzyme-induced biomineralization. It is shown that the enzyme-induced mineralization intensely transforms flexible and soft hydrogels (modulus of 125 kPa) to rigid (150 MPa) and highly mineralized hydrogel composites. Coupling with embedded 3D printing, sophisticated and mineralized freeform architectures are fabricated in the absence of sacrificial inks, which were previously unattainable through conventional manufacturing strategies. Moreover, by exploiting multi-material 3D printing to tailor the construct composition, exquisite control over the mineral distribution within the hydrogel constructs can be achieved, thus composite materials with tessellated architectures and unconventional mechanics could be obtained. The study provides a viable means to fabricate composite materials with highfidelity architectures and tailored mechanical properties, unlocking paths to the next generation of functional materials and structures by integrating 3D printing with biomineralization.

Coating conventional metallic electrodes with conducting polymers has enabled the essential characteristics required for bioelectronics, such as biocompatibility, electrical conductivity, mechanical compliance, and the capacity for structural and chemical functionalization of the bioelectrodes. However, the fragile interface between the conducting polymer and the electrode in wet physiological environment greatly limits their utility and reliability. Here, a general yet reliable strategy to seamlessly interface conventional electrodes with conducting hydrogel coatings is established, featuring tissue‐like modulus, highly‐desirable electrochemical properties, robust interface, and long‐term reliability. Numerical modeling reveals the role of toughening mechanism, synergy of covalent anchorage of long‐chain polymers, and chemical cross‐linking, in improving the long‐term robustness of the interface. Through in vivo implantation in freely‐moving mouse models, it is shown that stable electrophysiological recording can be achieved, while the conducting hydrogel–electrode interface remains robust during the long‐term low‐voltage electrical stimulation. This simple yet versatile design strategy addresses the long‐standing technical challenges in functional bioelectrode engineering, and opens up new avenues for the next‐generation diagnostic brain‐machine interfaces.