Ultrathin epidermal piezoelectric sensors are essential in the next generation of wearable flexible electronics due to their conformal contact with the skin. However, the fabrication and peeling of ultrathin film still face great challenges, and there is an urgent need to develop a facile and effective process. Here, we propose a method of combing spin-coating and aqueous phase exfoliating to prepare the ultrathin poly(vinylidene fluoride-ran-trifluoroethylene) (P(VDF-TrFE)) piezoelectric film with a thickness of about 3 μm. And the thermal treatment is employed to improve its crystallinity and piezoelectricity, resulting in the piezoelectric coefficient of 11.67 pC N −1 and fine sensitivity of 4.56 mV kPa −1 . The ultrathin device is successfully applied to monitor the signals of arterial pulse and interactive force, which is expected to provide references for medical diagnosis and robot design. Notably, this work might motivate design principles and methods of ultrathin epidermal devices and promote its applications in wearable flexible electronics.

This paper mainly focuses on the fast and efficient design method for plant bioinspired fluidic cellular materials and structures composed of polygonal motor cells. Here we developed a novel structural optimization method with arbitrary polygonal coarse-grid elements based on multiscale finite element frameworks. The fluidic cellular structures are meshed with irregular polygonal coarse-grid elements according to their natural size and the shape of the imbedded motor cells. The multiscale base functions of solid displacement and hydraulic pressure are then constructed to bring the small-scale information of the irregular motor cells to the large-scale simulations on the polygonal coarse-grid elements. On this basis, a new topology optimization method based on the resulting polygonal coarse-grid elements is proposed to determine the optimal distributions or number of motor cells in the smart cellular structures. Three types of optimization problems are solved according to the usages of the fluidic cellular structures. Firstly, the proposed optimization method is utilized to minimize the system compliance of the load-bearing fluidic cellular structures. Second, the method is further extended to design biomimetic compliant actuators of the fluidic cellular materials due to the fact that non-uniform volume expansions of fluid in the cells can induce elastic action. Third, the optimization problem focuses on the weight minimization of the cellular structure under the constraints for the compliance of the whole system. Several representative examples are investigated to validate the effectiveness of the proposed polygon-based topology optimization method of the smart materials.

The mechanical analysis of interlayer bonding problem of asphalt pavement is performed by the elastic layered system theory or finite element method (FEM); then, a lot of specialized programs based on the above theories emerged successively, of which BISAR3.0 and EverStressFE are quite representative. In order to further clarify the characteristics of BISAR3.0 and EverStressFE for investigating interlayer bonding problem of asphalt pavement, this paper will carry out a comprehensive comparison from the specific realization viewpoint, such as the principle of interlayer bonding, modeling, calculation processing, and result treatment, and a specific example will be given to compare and analyze their functions. The results indicate that the two programs have certain comparability in analyzing the interlayer bonding problem of asphalt pavement, which will contribute to the foundation for the rational selection of asphalt pavement structure mechanical analysis program.