Zhizheng Gu

A novel two-dimensional (2-D) linear piezoelectric stepping platform using two parallel longitudinal-bending hybrid piezoelectric actuators is proposed in this paper. The proposed platform is moved in the X-direction by combing the vertical and horizontal bending motions of the parallel actuators, whereas the movement in the V-direction is realized by the vertical bending and longitudinal hybrid motions. The platform is designed and its operating principles in two orthogonal directions are described. The finite-element method simulations are performed to verify the operating principles of the 2-D platform. Two piezoelectric actuators are fabricated and a prototype of the platform is assembled. The measured results of mechanical output performance indicate that the velocities of the platform are 101.7 and 124.2 μm/s in X- and V-directions when the voltage and frequency are 400 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p-p</sub> and 5 Hz, respectively, which verifies the feasibility of the proposed mechanism for the 2-D stepping platform.

Two-dimensional materials have a wide range of applications in many aspects due to their unique properties. Here we carry out a detailed structural search and design of the BP 2 using the first principles method, and find a new PMM2 sheet. The analysis of the phonon dispersive curves shows that the 2D PMM2 is dynamic stable. The study of molecular dynamics shows that the 2D PMM2 can be stable under high temperature, even at 600 K. Most importantly, when a suitable strain is applied, the structure can exhibit other electronic properties such as direct band gap semiconductor. In addition, the small strain can tune the band gap value of the PMM2 structure to around 1.4 eV, which is very close to the ideal band gap of solar materials. Therefore, the 2D PMM2 may have potential applications in the field of photovoltaic materials.