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Conductive hydrogels (CHs) have received significant attention for use in wearable devices because they retain their softness and flexibility while maintaining high conductivity. CHs are well suited for applications in skin‐contact electronics and biomedical devices owing to their high biocompatibility and conformality. Although highly conductive hydrogels for smart wearable devices are extensively researched, a detailed summary of the outstanding results of CHs is required for a comprehensive understanding. In this review, the recent progress in the preparation and fabrication of CHs is summarized for smart wearable devices. Improvements in the mechanical, electrical, and functional properties of high‐performance wearable devices are also discussed. Furthermore, recent examples of innovative and highly functional devices based on CHs that can be seamlessly integrated into daily lives are reviewed. Recent significant progress for developing conducting hydrogels is highlighted in this review. Preparation, fabrication, and application of the conducting hydrogels for wearable devices are summarized and discussed for comprehensive understanding. The challenges and opportunities of conducting hydrogels for novel devices are further discussed.

Programmable hydrogels are an emerging class of intelligent materials engineered to respond precisely to specific stimuli, offering tailored functionalities with significant potential for biomedical applications, including drug delivery, tissue engineering, and wound healing. This review comprehensively explores various programmable hydrogels responsive to diverse triggers, including temperature, gene expression, color, shape, and mechanical force. The design and fabrication methods underlying these systems are detailed, highlighting the roles of crosslinkers, adhesion groups, and photosensitive functional groups. Furthermore, the key physical, chemical, and biological properties that govern the performance and functionality of hydrogels are analyzed. The review further examines the mechanisms and recent advancements in self‐executing hydrogels, such as self‐activated, self‐oxygenated, self‐expandable, and self‐powered systems, demonstrating how these innovative designs drive the development of next‐generation programmable hydrogels. The main challenges in hydrogel design, including complexity, reproducibility, and clinical translation, are also addressed. Finally, a perspective on future research directions, highlighting the integration of the latest technologies to realize programmable hydrogels with dynamic closed‐loop responsiveness, bionic synergy, and robust clinical applicability, is offered. This review summarizes the design principles and key features of programmable hydrogels that respond to multiple stimuli. It then delves into the cutting‐edge mechanisms of self‐executing systems, highlighting their role as the cornerstone of next‐generation programmable hydrogels (NGPHs). Finally, by addressing critical challenges in complexity and translation, the review looks to the future of NGPHs, emphasizing their evolution toward dynamic closed‐loop control, biomimetic intelligence, and successful clinical integration.

Fabricating mechanically strong hydrogels that can withstand the conditions in internal tissues is a challenging task. We have designed hydrogels based on multicomponent systems by combining chitosan, starch/cellulose, PVA, and PEDOT:PSS via one-pot synthesis. The starch-based hydrogels were homogeneous, while the cellulose-based hydrogels showed the presence of cellulose micro- and nanofibers. The cellulose-based hydrogels demonstrated a swelling ratio between 121 and 156%, while the starch-based hydrogels showed higher values, from 234 to 280%. Tensile tests indicated that the presence of starch in the hydrogels provided high flexibility (strain at break > 300%), while combination with cellulose led to the formation of stiffer hydrogels (elastic moduli 3.9–6.6 MPa). The ultimate tensile strength for both types of hydrogels was similar (2.8–3.9 MPa). The adhesion and growth of human osteoblast-like SAOS-2 cells was higher on hydrogels with cellulose than on hydrogels with starch, and was higher on hydrogels with PEDOT:PSS than on hydrogels without this polymer. The metabolic activity of cells cultivated for 3 days in the hydrogel infusions indicated that no acutely toxic compounds were released. This is promising for further possible applications of these hydrogels in tissue engineering or in wound dressings. Graphical abstract

We prepared poly(vinyl alcohol) (PVA)/SiO 2 and PVA/SiO 2 /glutaraldehyde (GA) nanocomposite membranes in a single step using the solution casting method. The structure, morphology, and properties of these nanocomposite membranes were characterized by Raman spectroscopy, atomic force microscopy, small- and wide-angle X-ray scattering, thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis (DMA). The influence of silica and GA loading on the meso-scale characteristics of the composite membranes was investigated. The results showed that silica deposited in the form of small nanoparticles (~1 nm) in the PVA/SiO 2 membranes, while bigger submicron particles (>25 nm) were formed in the PVA/SiO 2 /GA membranes. The water uptake of the PVA/SiO 2 membranes increased with temperature, but the PVA/SiO 2 /GA membranes were completely dissolved above 50 °C. We can therefore conclude that the addition of GA deteriorated the properties of PVA/SiO 2 membranes. The thermal stability of the PVA/SiO 2 membranes increased with the increasing silica loading with a maximum char yield of 46 % for PVA/SiO 2 /4T. Even DMA profiles indicated a promising increase in E R (rubbery modulus) from 6 MPa (PVA membrane) to 1015 MPa (PVA/SiO 2 /4T) at 250 °C, showing high mechanical strength of these membranes.

Advances in additive manufacturing, particularly 3D and multidimensional printing, have enabled unprecedented control over the architecture, composition, and bioactivity of epidermal patches. These developments have broadened the scope of epidermal patches across biomedical and personal-care applications, supporting personalized and adaptive solutions for drug delivery, wound management, tissue regeneration, and skin-related interventions. This review summarizes next-generation printed epidermal patches, covering both conventional (non-microneedle) systems and microneedle-integrated platforms. Particular emphasis is placed on emerging material systems, including self-oxygenating hydrogels, nanomaterial-free bioinks derived from proteins and polysaccharides, and functional nanocomposite formulations. We examine key 3D printing strategies for fabricating acellular constructs, cell-laden matrices, and microneedle array patches (MAPs), alongside recent advances in multidimensional printing technologies. Biomedical applications are discussed with a focus on dermal and transdermal drug delivery, particularly insulin delivery for diabetes management as well as wound repair, regenerative therapies, photodynamic treatments, and biosensing. Additionally, the integration of printed epidermal patches with wearable sensors, smart devices, and artificial intelligence (AI) is highlighted as an emerging frontier in intelligent skin-interfaced systems, with implications for both healthcare and advanced personal-care technologies. Finally, key challenges related to clinical translation, regulatory pathways, and commercialization are addressed, providing strategic insights to guide the advancement of hydrogel-based additive manufacturing from laboratory innovation to real-world clinical and aesthetic applications. [Display omitted] •3D printing enables next-generation epidermal patches using bioinks, acellular matrices, cell-laden constructs, and microneedles.•4D and 5D printing advances smart epidermal patches with expanded functional versatility.•Printed patches and microneedles support drug delivery, wound healing, skin regeneration, photodynamic therapy, and biosensing.•Integration of printed patches with sensors and AI drives innovation in personalized cosmetics.•Clinical development, regulatory hurdles, and commercialization shape translation to market.