Recently, triboelectric energy nanogenerators (TENGs) have been paid the most attention by many researchers to convert mechanical energy into electrical energy. TENGs usually have a simple structure and a high output voltage. However, their high internal resistance results in low output power. In this work, we propose a flexible triboelectric energy nanogenerator with the double-side tribological layers of polydimethlysiloxane (PDMS) and PDMS/multiwall carbon nanotube (MWCNT). MWCNTs with different concentrations have been doped into PDMS to tune the internal resistance of triboelectric nanogenerator and optimize its output power. The dimension of the fabricated prototype is ~3.6 cm3. Three-axial force sensor is used to monitor the applied vertical forces on the device under vertical contact-separation working mode. The Prototype with 10 wt% MWCNT (Prototype I) produces higher output voltage than one with 2 wt% MWCNT (Prototype II) due to its higher dielectric parameter measured by LRC impedance analyzer. The triboelectric output voltages of Prototype I and Prototype II are 30 V and 25 V under the vertical force of 3.0 N, respectively. Their maximum triboelectric output powers are ~130 μW at 6 MΩ and ~120 μW at 8.6 MΩ under vertical forces, respectively.

The severe crosstalk effect is widely present in tactile sensor arrays with a sandwich structure. Here we present a novel design for a resistive tactile sensor array with a coplanar electrode layer and isolated sensing elements, which were made from polydimethylsiloxane (PDMS) doped with multiwalled carbon nanotubes (MWCNTs) for crosstalk suppression. To optimize its properties, both mechanical and electrical properties of PDMS/MWCNT-sensing materials with different PDMS/MWCNT ratios were investigated. The experimental results demonstrate that a 4 wt% of MWCNTs to PDMS is optimal for the sensing materials. In addition, the pressure-sensitive layer consists of three microstructured layers (two aspectant PDMS/MWCNT-based films and one top PDMS-based film) that are bonded together. Because of this three-layer microstructure design, our proposed tactile sensor array shows sensitivity up to − 1.10 kPa − 1 , a response time of 29 ms and reliability in detecting tiny pressures.

It has been shown in a previous work that the directional pattern of underwater sound scattered from an object insonified by an incident plane wave can be efficiently predicted based on a reversal of diffraction tomography. The method uses the Fourier diffraction theorem with the first order Born approximation. In this paper, modification to the Born approximation is proposed by taking into account the difference in acoustic impedance between the object and water. The impedance difference was ignored in the original derivation of the Fourier diffraction theorem, leading to inaccuracy in the computation. In a two-dimensional case, the proposed modification causes a shift of a circle in the 2D Fourier transform domain, from which spectral samples are taken to give a more accurate generalized projection in the sound field. This leads to improved prediction of acoustic scattering. Extension to 3D is straightforward. The Fourier diffraction theorem with modified Born approximation is applied to produce far-field directional patterns of scattered sounds from several objects of different shapes. Comparison with the original method shows effectiveness of the proposed method. The work was supported by the Natural Science Foundation of China under the Grant No. 61071187.