可拉伸无机柔性电子采用传统无机功能材料和创新力学结构设计，可同时实现良好的电学性能和大变形能力，因而得到了广泛关注。本文针对医疗、航天等复杂力学环境，提出可拉伸无机柔性电子的界面不敏感设计原理，设计了基于力学结构的应变传感与超声驱动大变形柔性器件，发展出相应力学模型与制备工艺，保证优良的力学与电学性能，对柔性电子落地实际应用具有示范意义。具体如下：

  可拉伸无机柔性电子通常在自由界面条件下进行设计和标定性能，然而在实际应用中器件与人体/物体的界面条件是相对复杂的（自由、可滑移、固结等），并且可相互切换。理想情况下，器件的性能应该对界面条件不敏感，以保证其精确性和稳健性。本文通过理论、有限元及实验方法研究了不同构形可拉伸无机柔性电子的界面条件对其力学与电学性能的影响，提出了通用的界面不敏感设计原理，即器件/互联导线周期长度应该与封装厚度在同一量级或更小。

  传统观点认为高灵敏系数代表应变传感器具有高分辨率，大量柔性应变传感器研究利用接触电阻原理提高灵敏系数（有高达10⁷），其可拉伸性和电阻变化来源于导电微结构的不稳定接触关系变化，因而重复性和线性度不够理想。本文通过理论研究发现了灵敏系数并不是越大越有利于提高测量精度，过大的灵敏系数会产生较大的测量误差（典型测量条件下灵敏系数=5×10⁴对应测量误差可达50%），为传感器设计提供了理论指导；提出了一种基于偏轴蛇形叠层结构的非接触电阻原理柔性大应变传感器，在高达50%的应变范围内保持了优异的重复性（重复误差=1.58％）和线性度（拟合优度>0.999），该传感器成功用于人体活动监测、医疗手术和中国首次火星探测任务“天问一号”的地面试验。

  超声促渗技术利用超声的物理效应促进药物经皮导入，然而目前还未发现有研究者发展出相关柔性超声器件进行可穿戴应用探索。本文提出一种具有超声促渗功能的可拉伸电子面膜（SEFM），为了克服人脸大面积复杂曲面带来的技术挑战，发展了单面软压等可拓展到其他可拉伸电子的新型封装方法，通过有限元方法和实验验证了SEFM的力学、热学、电学和超声性能，最后通过动物实验和人脸实验证明了SEFM促进药物导入的作用。

  柔性传感与驱动器一般需要柔性电池为其供能，而目前柔性电池很难同时实现优异可弯曲性、高毛体积能量密度和面积能量密度。受骨骼和珍珠层微观结构的启发，本文设计了一种由子电池和软胶组成的交错阵列结构柔性电池；解析地研究了其弯曲力学行为，得到不同参数对应变降低程度的影响；实验验证了其优异可弯曲性、高毛体积能量密度和面积能量密度，由于只需很薄的软胶就可大大减少薄子电池间的相互作用，毛体积能量密度达到了传统电池的92.3%。

    Stretchable inorganic electronics adopt conventional inorganic functional materials and innovative mechanically guided structure design, to achieve excellent stretchability and functionality simultaneously. For the complex environment in medical treatment and aerospace, this paper puts forward an interface-insensitive design principle for stretchable inorganic electronics, designs several stretchable and flexible electronics for strain sensing and ultrasound actuating based on mechanically guided structure designs, develops corresponding mechanical models and fabricating processes, and ensures the excellent mechanical and electrical performances, which has demonstration significance for the practical application of flexible electronics. The main contents are as follows:

    Stretchable inorganic electronics are usually designed and calibrated under free interface condition, while the interface conditions between the devices and body/object in practical applications are rather complex (free, slidable or bonded) and may switch among them. In the ideal situation, the mechanical and electrical performances should be insensitive to the interface conditions, to ensure the accuracy and robustness of the devices. Here, the effect of interface conditions on the mechanical and electrical performances is studied for stretchable inorganic electronics with different configurations by theoretical analysis, finite element analysis and experiment. A universal interface-insensitive design principle is proposed for stretchable inorganic electronics, i.e., the period length of the devices/interconnects should be the same order of magnitude or less as the encapsulation thickness.

    Plenty of works about stretchable strain sensors have been devoted to enlarging the gauge factor (GF) (reaching as high as 10⁷), since the conventional wisdom holds that a high GF indicates a high resolution of a sensor. Most of the existing stretchable strain sensors are based on contact-resistance mechanism, where the stretchability and resistance variation depend on the contact relationship change of the conductive microstructures. These sensors usually exhibit unsatisfactory repeatability and linearity of the electrical response because the contact is unstable. Here, we find that the GF is not the bigger the better for the improvement of the measurement accuracy. The overlarge gauge factor yields a large measuring error for stretchable strain sensors (reaching the measuring error of 50% for GF=5×10⁴ under a typical measurement condition). This finding is of much significance for providing theoretical guidance for the sensor design. Then we report a completely different design for stretchable strain sensors based on a contact-resistance-free structure, i.e., the off-axis serpentine sandwich structure, which guarantees the excellent repeatability (repeatability error=1.58%) and linearity (goodness-of-fit>0.999) while the sensor undergoes a large applied strain (50%). The present sensors are successfully applied to monitoring human activities, medical surgery and the ground tests of Tianwen-1, China’s first Mars exploration mission.

    Sonophoresis promotes the delivery of drugs into/through the skin by the physical effects of ultrasound, however, it has not been found that researchers have developed relevant flexible ultrasonic devices for wearable applications. Here, we introduce a novel stretchable electronic facial mask (SEFM) for sonophoresis. To overcome the technical challenges brought by the large-area complex surface of human face, several unique approaches including the single-side soft pressing (SSSP) technique for the encapsulation are exploited in this work, which could be extended to the design and fabrication of other stretchable electronics. The mechanical, thermal, electrical and ultrasonic characteristics of the SEFM are all verified by the finite element analysis and experiments. Finally, we prove the effect of the SEFM on accelerating the delivery of drugs through animal experiments and human facial experiments.

    Flexible batteries are generally needed to power flexible sensors and actuators. However, few of the batteries have both superior bendability, high bulk volumetric energy density and high areal energy density. Here, inspired by the microstructures of bone and nacre, a staggered-array structure composed of thin sub-cells and soft adhesives is reported for flexible batteries. An analytic model is presented to study the mechanical behavior of the structure bending on a cylinder, which exhibits the effects of different parameters on strain reduction. A flexible Li-ion battery is prepared with superior bendability, high bulk volumetric energy density and high areal energy density. Owing to the thin soft adhesives, the interactions among thin sub-cells are substantially reduced, and the bulk volumetric energy density of the battery reaches more than 92.3% of that in conventional ones.