Numerical modeling and experimental study of microstamping process for fabricating microchannels using thin sheets of titanium

Ultra-thin sheets of titanium for fabricating microchannels have been used in fuel cells due to their good corrosion resistance and high strength-weight ratio. This paper presents a constitutive model for studying the anisotropy effects of pure titanium(CP-Ti) sheet on the springback behavior and forming properties during the microstamping process. Thin sheets of CP-Ti specimens with different orientations were examined using uniaxial tensile tests to assess the effects of anisotropy on their mechanical properties. Then an anisotropic constitutive model considering the off-axis elastic modulus was developed based on orthotropic elasticity and Hill's yield criterion. Numerical modeling and simulation of the microstamping process for fabricating multi-channel structures were performed. The effects of anisotropy on the springback of multi-channels were investigated and compared with experimental results;the effects of tool dimension parameters on the formability of microchannel structures were also analyzed. The results showed that the anisotropy of thin titanium sheets causes various degrees of forming loads and springback in the microstamping of microchannels at different orientations. This study accurately predicts the springback of thin titanium sheet used to fabricate microchannel structures and is a good guide to the formation of such structures.

Vibrational characteristics of rotating soft cylinders

Rotating structural components are omnipresent in engineering structures and natural world. This work investigates the effects of the centrifugal and Coriolis forces on the free vibrational characteristics of soft cylinders rotating with respect to the axis of symmetry based on the nonlinear elasticity and linear incremental theories. The formulations indicate that the biasing deformation, instantaneous elastic moduli, and incremental equations of motion strongly depend on the rotating speed. The characteristic equation for the natural frequency is derived using the state-space method and approximate laminate technique.The numerical examples included in this work demonstrate that the centrifugal and Coriolis forces might have significant effects on the vibrational characteristics of the cylinder. Results of this work will benefit the design and control of novel engineering systems with rotating soft cylinders or shafts.

Huge permittivity and premature metallicity in Bi2O2Se single crystals

Bi_(2)O_(2) Se is a promising material for next-generation semiconducting electronics.It exhibits premature metallicity on the introduction of a tiny amount of electrons,the physics behind which remains elusive.Here we report on transport and dielectric measurements in Bi_(2)O_(2) Se single crystals at various carrier densities.The temperature-dependent resistivity(p)indicates a smooth evolution from the semiconducting to the metallic state.The critical concentration for the metal-insulator transition(MIT)to occur is extraordinarily low(nc~10^(16) cm^(-3)).The relative permittivity of the insulating sample is huge(∈r≈155(10))and varies slowly with temperature.Combined with the light effective mass,a long effective Bohr radius(a_(B)^(*)≈36(2)nm)is derived,which provides a reasonable interpretation of the metallic prematurity according to Mott’s criterion for MITs.The high electron mobility(μ)at low temperatures may result from the screening of ionized scattering centers due to the huge∈r.Our findings shed light on the electron dynamics in two dimensional(2D)Bi_(2)O_(2) Se devices.

Analysis and control for a bioinspired multi-legged soft robot

Untethered soft miniature robots are considered to have a wide range of applications in biomedical field.However,researchers today still have not reached a consensus on its configuration design and actuation method.Here,inspired by the tentacles of a certain kind of echinodermata,we propose a soft multi-legged robot with a total weight of 0.26 g capable of multiple locomotion modes.Based on the magnetic field distribution of a square permanent magnet,we qualitatively analyze the motion mechanism of the robot.Finally,we carried out relevant experimental research.The research shows that the robot can move forward,backward,steering and cross obstacles under the control of the magnetic field,and can combine these abilities to navigate the maze.

Chinese Woman Reaches Peak of Neuroscience Research

Hu Hailan,executive director of the Neuroscience Center of Zhejiang University,and four other women received the 2022 L'Oreal-UNESCO For Women in Science Awards for their groundbreaking discoveries.The award ceremony was held at the headquarters of the United Nations Educational,Scientific and Cultural Organization(UNESCO),in Paris,on June 23.