Emerging soft ionotronics better match the human body mechanically and electrically compared to conventional rigid electronics. They hold great potential for human-machine interfaces, wearable and implantable devices, and soft machines. Among various ionotronic devices, ionic junctions play critical roles in rectifying currents as electrical p-n junctions. Existing ionic junctions, however, are limited in electrical and mechanical performance, and are difficult to fabricate and degrade. Herein, the design, fabrication, and characterization of tough transient ionic junctions fabricated via 3D ionic microgel printing is reported. The 3D printing method demonstrates excellent printability and allows one to fabricate ionic junctions of various configurations with high fidelity. By combining ionic microgels, degradable networks, and highly charged biopolymers, the ionic junctions feature high stretchability (stretch limit 27), high fracture energy (>1000 Jm −2 ), excellent electrical performance (current rectification ratio >100), and transient stability (degrade in 1 week). A variety of ionotronic devices, including ionic diodes, ionic bipolar junction transistors, ionic full-wave rectifiers, and ionic touchpads are further demonstrated. This study merges ionotronics, 3D printing, and degradable hydrogels, and will motivate the future development of high-performance transient ionotronics.

The mechanical properties of sutures are important for wound closure and meniscus repair. A tough gel coating technology has been developed to modify and functionalize sutures, but its effects on suture degradation remain unexplored. Our aim is to investigate how a tough gel coating mediates the properties of the suture. The Polyglactin910 (Vicryl) suture was chosen because it is widely used, strong, easy to handle, and degradable. This study compared six pristine Vicryl sutures and six coated Vicryl sutures at 0, 2, 4, and 6 weeks. All the sutures were soaked in phosphate-buffered saline (PBS), to mimic degradation in physiological conditions, and tensile strength was tested at each time point.The pH of the soaking mediums was measured weekly and compared at 4, 5, and 6 weeks. No significant difference (p = 0.059 and p = 0.576) was found between the absolute and normalized breaking force of coated and pristine Vicryl sutures at 0, 2, 4, and 6 weeks. After 4 weeks of immersion, the soaking medium became more acidic for both suture types. The decrease in pH was less significant for coated Vicryl sutures than for pristine ones (p < 0.001) at 4, 5, and 6 weeks of immersion. Although coating does not affect the strength of Vicryl sutures soaked in PBS, it can effectively act as a buffer to the acidic environment caused by suture degradation, which could help reduce inflammation.Hydrogel coating is a promising technology to modify suture characteristics.

Ionotronics An hourglass measures time by a regulated flow of sand through a narrow neck. In article number 2213677, Jianyu Li and co‐workers show that with similar shapes, ionic junctions regulate ion flow, allowing unidirectional current conduction. Like sand in an hourglass, microgels can be the building blocks of such ionotronics to achieve printability and tough mechanics. The ionic junctions are critical elements in the world of soft and stretchable circuits. Cover illustration by SciFig (Mitra, Aram, and Farzan; https://sci‐fig.com/).