Bioinspired conductive structural color hydrogels as a robotic knuckle rehabilitation electrical skin.

Electronic skins have attracted significant research interest in the biomedical engineering field including wearable devices, artificial prostheses, software robots, and so on. However, the integration of electronic skin for use in rehabilitation exercise remains unexplored. Here, we propose a novel, conductive structurally colored composite hydrogel for use as a robotic knuckle rehabilitation skin. It was found that the composite structure has an obvious color variation and electromechanical properties during the bending process. Therefore, this film could be used as a multi-signal response electronic skin to achieve real-time color sensing and electrical response, as well as for the human knuckle rehabilitation robot. These results indicated that the structurally colored composite hydrogels are valuable for use in many practical biomedical rehabilitation exercises where they are used as an electronic skin to give real-time color sensing and electrical response, and as well can be used in a human knuckle rehabilitation robot.

Integral equation approach to time-dependent kinematic dynamos in finite domains.

The homogeneous dynamo effect is at the root of cosmic magnetic field generation. With only a very few exceptions, the numerical treatment of homogeneous dynamos is carried out in the framework of the differential equation approach. The present paper tries to facilitate the use of integral equations in dynamo research. Apart from the pedagogical value to illustrate dynamo action within the well-known picture of the Biot-Savart law, the integral equation approach has a number of practical advantages. The first advantage is its proven numerical robustness and stability. The second and perhaps most important advantage is its applicability to dynamos in arbitrary geometries. The third advantage is its intimate connection to inverse problems relevant not only for dynamos but also for technical applications of magnetohydrodynamics. The paper provides the first general formulation and application of the integral equation approach to time-dependent kinematic dynamos, with stationary dynamo sources, in finite domains. The time dependence is restricted to the magnetic field, whereas the velocity or corresponding mean-field sources of dynamo action are supposed to be stationary. For the spherically symmetric alpha2 dynamo model it is shown how the general formulation is reduced to a coupled system of two radial integral equations for the defining scalars of the poloidal and toroidal field components. The integral equation formulation for spherical dynamos with general stationary velocity fields is also derived. Two numerical examples--the alpha2 dynamo model with radially varying alpha and the Bullard-Gellman model--illustrate the equivalence of the approach with the usual differential equation method. The main advantage of the method is exemplified by the treatment of an alpha2 dynamo in rectangular domains.

Effect of soft-iron impellers on the von Kármán-sodium dynamo.

The explanation for the observed axisymmetric magnetic field in the von Kármán-sodium (VKS) dynamo experiment is still an unresolved question. In this paper, the integral equation approach is extended to investigate the VKS dynamo action by taking into account the discontinuity of the magnetic permeability and electrical conductivity in the conducting region. When the relative magnetic permeability of the soft-iron impellers is set to 65, a steady toroidal field that is apparently axisymmetric is excited at the critical magnetic Reynolds number, Rmc≈27.23, which is close to the experimental result, Rmc≈30. Our results show that the critical magnetic Reynolds number declines as the relative magnetic permeability of the impellers increases. Furthermore, when the relative magnetic permeability is not greater than 37, an equatorial magnetic field with an azimuthal wave number m=1 is the dominant mode, otherwise a steady toroidal field with an azimuthal wave number m=0 predominates the magnetic field generated by the VKS dynamo action.