Fig. 3. Design and fabrication of densely packed, stretchable electronic system based on SMNM.

(A) Schematic illustration of the device system in an exploded view. The system contains 42 ICs, with lateral dimensions of ~11.2 mm by 10.1 mm and an areal coverage ratio of ~110%. Subcircuits are aligned and electrically connected through vertical vias, highlighted by dashed lines. (B) Photographs of the SMNM-based stretchable electronic system mounted on an index finger (top) and wrapped around a glass rod (bottom). (C) System-level deformations determined by FEA and experimental photographs for the top and middle circuit layers, during different levels of biaxial stretching (0, 20, and 30%). (D) Areal coverage ratio versus elastic stretchability for various stretchable skin-integrated electronic devices, including the current work and those reported previously. (E) Block diagrams of the functional components for physiological tracking, including monitoring of human motion, temperature, and humidity. The system mainly consists of a nine-axis MEMS motion-processing unit (MPU-9250; including three-axis gyroscope, three-axis accelerometer, and three-axis magnetometer), a digital high-accuracy temperature and humidity sensor (HTU21D), a microcontroller unit (Atmega328P), 2.4-GHz RF wireless transceivers (nRF24L), and five LEDs. Scale bars, 5 mm (B and C). Photo credit: H.S., Tsinghua University.