Stalling interkinetic nuclear migration in curved pseudostratified epithelium of developing cochlea

The bending of epithelial tubes is a fundamental process in organ morphogenesis, driven by various multicellular behaviours. The cochlea in the mammalian inner ear is a representative example of spiral tissue architecture where the continuous bending of the duct is a fundamental component of its morphogenetic process. Although the cochlear duct morphogenesis has been studied by genetic approaches extensively, it is still unclear how the cochlear duct morphology is physically formed. Here, we report that nuclear behaviour changes are associated with the curvature of the pseudostratified epithelium during murine cochlear development. Two-photon live-cell imaging reveals that the nuclei shuttle between the luminal and basal edges of the cell is in phase with cell-cycle progression, known as interkinetic nuclear migration, in the flat region of the pseudostratified epithelium. However, the nuclei become stationary on the luminal side following mitosis in the curved region. Mathematical modelling together with perturbation experiments shows that this nuclear stalling facilitates luminal-basal differential growth within the epithelium, suggesting that the nuclear stalling would contribute to the bending of the pseudostratified epithelium during the cochlear duct development. The findings suggest a possible scenario of differential growth which sculpts the tissue shape, driven by collective nuclear dynamics.

Development of a Modular Tensegrity Robot Arm Capable of Continuous Bending

In this study, we present a tensegrity robot arm that can reproduce the features of complex musculoskeletal structures, and can bend like a continuum manipulator. In particular, we propose a design method for an arm-type tensegrity robot that has a long shape in one direction, and can be deformed like a continuum manipulator. This method is based on the idea of utilizing simple and flexible strict tensegrity modules, and connecting them recursively so that they remain strict tensegrity even after being connected. The tensegrity obtained by this method strongly resists compressive forces in the longitudinal direction, but is flexible in the bending direction. Therefore, the changes in stiffness owing to internal forces, such as in musculoskeletal robots, appear more in the bending direction. First, this study describes this design method, then describes a developed pneumatically driven tensegrity robot arm with 20 actuators. Next, the range of motion and stiffness under various driving patterns are presented as evaluations of the robot performance.

Dual-band-notched UWB MIMO antennas with miniaturization using half-cutting technology

A compact four-element ultra-wideband (UWB) multiple-input–multiple-output (MIMO) antenna with dual polarization and dual-notched capabilities was developed and fabricated. The MIMO antenna is composed of four orthogonally placed half-cutting UWB antenna elements. This orthogonal placement improves the isolation. Furthermore, an L-shaped slot and a continuous bending slot are etched to realize the band-rejection function in the WiMAX and WLAN bands. The result shows that the antenna achieved operating bands of 2.9–16.5 GHz (140.2%, S11 < −10 dB), fully covering the UWB (3.1–10.6 GHz). The port isolation is greater than 23 dB in the frequency band of interest, excluding two rejected bands. Moreover, the MIMO antenna has excellent diversity performance, such as a low envelope correlation coefficient (<0.004), high diversity gain (approximately 10 dB), and good omnidirectional radiation characteristics.

Design, modeling and evaluation of a millimeter-scale SMA bending actuator with variable length

Millimeter-scale continuum bending actuators are useful in minimally invasive surgery to allow distal visualization and manipulation outside the line of sight. This paper presents a new continuum bending actuator based on shape memory alloy (SMA) with variable bending length. It consists of two SMA wires antagonistically configured to produce bidirectional bending under Joule heating. A linearly actuated rigid tube along the longitudinal axis enables continuous bending length adjustment, thus enhancing its workspace and force range. The proposed fabrication method tackles the challenging assembly tasks of maintaining the antagonistic configuration of long SMA wires, and robust electrical and mechanical connection during actuation. A quasi-static model of the actuator based on beam model and SMA constitutive model is presented and verified. The bending actuator was evaluated comprehensively for its workspace, blocked force, and trajectory tracking capability at different bending lengths and under different cooling conditions. It is the first work that demonstrates real-time continuous bending length adjustment in SMA-based bending actuator, leading to the potential development of compact and compliant robotic end effectors with improved distal workspace and force.

ALD Deposited ZnO:Al Films on Mica for Flexible PDLC Devices

In this work, highly conductive Al-doped ZnO (AZO) films are deposited on transparent and flexible muscovite mica substrates by using the atomic layer deposition (ALD) technique. AZO-mica structures possess high optical transmittance at visible and near-infrared spectral range and retain low electric resistivity, even after continuous bending of up to 800 cycles. Structure performances after bending tests have been supported by atomic force microscopy (AFM) analysis. Based on performed optical and electrical characterizations AZO films on mica are implemented as transparent conductive electrodes in flexible polymer dispersed liquid crystal (PDLC) devices. The measured electro-optical characteristics and response time of the proposed devices reveal the higher potential of AZO-mica for future ITO-free flexible optoelectronic applications.

Design and Analysis of Pneumatic Bending Actuator Used in Soft Robotics

Pneumatic soft actuators can change their shapes under pneumatic pressure actuation and are capable of continuous bending. However, the air chambers inside will expand during the actuation process and cause nonlinear problems. Therefore pneumatic actuators are difficulties to model. In this paper, three types of bending actuators with different air chamber shapes are designed and the finite element model (FEM) is developed to simulate the deformation under different air pressure actuation. A prototype of the bending actuator is fabricated and a method to limit the expansion of the air chamber is designed based on the FEM results, which can effectively improve the expansion and the response of the actuator under low air pressure conditions through experimental comparison.