ties allow them to be dried by exposure to the ambient atmosphere and swelled reversibly by immersion in water. Several researchers have reported the reusability of hydrogel-based electronic devices after drying and swelling. [4] For instance, Liu et al. reported hydrogel-based strain sensors that were reusable after drying and swelling. [4a] Preserving hydrogel-based electronic devices in a dry state can suppress the changes in device performance due to the oxidation of conductive structures as well as the spontaneous leakage of liquids, providing a low-cost and facile method for storing and delivering these devices.Because most hydrogel-based electronic devices are fabricated by combining hydrogels and conductive structures, their fabrication requires the patterning of conductive structures on the hydrogels. Previously, conductive structures were patterned on hydrogels using transfer printing [5] and laser-based ablation. [6] Transfer printing can be divided into three steps: preparation of conductive structures and a mask or mold, patterning of conductive structures on the donor material, and transfer of conductive structures from the donor material to the hydrogel for patterning. Rahimi et al. reported the patterning of conductive structures on hydrogels by laser-based ablation as a technique that realized spatially selective processing. [6a] The patterning procedure involved preparing the hydrogel and a conductive Zn film separately, placing the Zn film on the hydrogel, and laser irradiation to selectively remove the Zn film, followed by the removal of the excess film via peeling.Organic materials can be directly modified into conductive graphitic carbon by laser irradiation, which is generally referred to as laser-based graphitization. By utilizing this technique, conductive structures can be directly patterned along the trajectory of laser scanning. Laser-based graphitization has been used to pattern conductive structures on supporting materials for the fabrication of electronic devices. Several studies have been conducted on the fabrication of energy-storage devices such as lithium-oxygen batteries [7] and electric double-layer capacitors (i.e., supercapacitors), [8] by laser-based graphitization. To date, various materials including polyimide, [9] paper, [10] and coconut [11] have been used as precursor materials for laserbased graphitization. However, to the best of our knowledge, the direct patterning of conductive structures on hydrogels by laser-based graphitization has yet to be demonstrated. Establishing a novel method for patterning conductive structures on Hydrogels have emerged as promising supporting materials for wearable or implantable electronic devices, owing to their high biocompatibility. Among the many techniques for patterning conductive structures on supporting materials, laser-based graphitization allows the simultaneous synthesis and patterning of conductive structures. Here, it has been demonstrated for the first time, the direct patterning of conductive structures on hydrogels...
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