Peripheral neuromodulation has been widely used throughout clinical practices and basic neuroscience research. However, the mechanical and geometrical mismatches at current electrode-nerve interfaces and complicated surgical implantation often induce irreversible neural damage, such as axonal degradation. Here, compatible with traditional 2D planar processing, we propose a 3D twining electrode by integrating stretchable mesh serpentine wires onto a flexible shape memory substrate, which has permanent shape reconfigurability (from 2D to 3D), distinct elastic modulus controllability (from ~100 MPa to ~300 kPa), and shape memory recoverability at body temperature. Similar to the climbing process of twining plants, the temporarily flattened 2D stiff twining electrode can naturally self-climb onto nerves driven by 37°C normal saline and form 3D flexible neural interfaces with minimal constraint on the deforming nerves. In vivo animal experiments, including right vagus nerve stimulation for reducing the heart rate and action potential recording of the sciatic nerve, demonstrate the potential clinical utility.

Despite the increasingly important role of stretchable electronics for use as the human–machine interface, their manufacturing in a commercially realistic manner remains an unresolved challenge. The bottleneck lies in the efficiency and scalability of transfer printing that is typically employed in the fabrication process to enable device stretchability via strain isolation. Here, the use of a polymer substrate with programmable rigidity for direct manufacturing of stretchable electronics is reported, forgoing the need for transfer printing while significantly enhancing strain isolation. The process starts with a stretchable elastomeric substrate synthesized via the thiol‐acrylate click chemistry. Designable rigid islands can be introduced via spatially confined oxidation of the elastomer. Strain‐sensitive microdevices can then be directly fabricated onto the rigid islands without transfer printing. Following this manufacturing scheme, a fast‐responding stretchable temperature sensor is demonstrated, with unusual accuracy and real‐time temperature monitoring capability suitable for use in a highly dynamic environment. Importantly, the critical fabrication step that introduces the programmable substrate rigidity is fully integrated into a well‐established lithographic process. Therefore, the methodology not only reduces greatly the complexity in fabricating prototype devices but also points to a highly effective way for potential manufacturing in a commercial setting.

Model composites consisting of SiC fiber and Yb2SiO5 were processed by the spark plasma sintering (SPS) method. The mechanical compatibility and chemical stability between Yb2SiO5 and SiC fiber were studied to evaluate the potential application of Yb monosilicate as the interphase of silicon carbide fiber reinforced silicon carbide ceramic matrix composite (SiCf/SiC CMC). Two kinds of interfaces, namely mechanical and chemical bonding interfaces, were achieved by adjusting sintering temperature. SiCf/Yb2SiO5 interfaces prepared at 1450 and 1500 °C exhibit high interface strength and debond energy, which do not satisfy the crack deflection criteria based on He-Hutchison diagram. Raman spectrum analyzation indicates that the thermal expansion mismatch between Yb2SiO5 and SiC contributes to high compressive thermal stress at interface, and leads to high interfacial parameters. Amorphous layer at interface in model composite sintered at 1550 °C is related to the diffusion promoted by high temperature and DC electric filed during SPS. It is inspired that the interfacial parameters could be adjusted by introducing Yb2Si2O7−Yb2SiO5 interphase with controlled composition to optimize the mechanical fuse mechanism in SiCf/SiC CMC.

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High-temperature structural materials undergo oxidation during the service, and stress would generate in the oxide film. Understanding the coupling effect between stress and oxidation contributes to the understanding of material degradation and failure during the oxidation process. Here, we propose a model to investigative the coupling effect of stress and oxidation at high temperature by considering the three-stage oxidation process, where both the interface reaction and the diffusion process are present. The governing equations including the oxidation kinetics and stress equilibrium for isothermal oxidation under stress-oxidation coupling effect have been derived. The theory is validated by comparing with the experimental results of SiO2 grown on Si substrate. Results show that the coupling of stress and oxidation influences the growth of the oxide film by affecting all three stages of the oxidation process.

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