mechanical engineering (5)

Fast Charger...


Significant Li plating capacity from Si anode. a, Li discharge profile in a battery of Li/graphite–Li5.5PS4.5Cl1.5 (LPSCl1.5)–LGPS–LPSCl1.5–SiG at current density 0.2 mA cm–2 at room temperature. Note that SiG was made by mixing Si and graphite in one composite layer. Inset shows the schematic illustration of stages 1–3 based on SEM and EDS mapping, which illustrate the unique Li–Si anode evolution in solid-state batteries observed experimentally in Figs. 1 and 2. b, FIB–SEM images of the SiG anode at different discharge states (i), (ii), and (iii) corresponding to points 1–3 in a, respectively. c, SEM–EDS mapping of (i), (ii), and (iii), corresponding to SEM images in b, where carbon signal (C) is derived from graphite, oxygen (O) and nitrogen (N) signals are from Li metal reaction with air and fluorine (F) is from the PTFE binder. d, Discharge profile of battery with cell construction Li-1M LiPF6 in EC/DMC–SiG. Schematics illustrate typical Si anode evolution in liquid-electrolyte batteries. e, FIB–SEM image (i) of SiG anode following discharge in the liquid-electrolyte battery shown in d; zoomed-in image (ii). Credit: Nature Materials (2024). DOI: 10.1038/s41563-023-01722-x

Topics: Applied Physics, Battery, Chemistry, Climate Change, Electrical Engineering, Mechanical Engineering

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a new lithium metal battery that can be charged and discharged at least 6,000 times—more than any other pouch battery cell—and can be recharged in a matter of minutes.

The research not only describes a new way to make solid-state batteries with a lithium metal anode but also offers a new understanding of the materials used for these potentially revolutionary batteries.

The research is published in Nature Materials.

"Lithium metal anode batteries are considered the holy grail of batteries because they have ten times the capacity of commercial graphite anodes and could drastically increase the driving distance of electric vehicles," said Xin Li, Associate Professor of Materials Science at SEAS and senior author of the paper. "Our research is an important step toward more practical solid-state batteries for industrial and commercial applications."

One of the biggest challenges in the design of these batteries is the formation of dendrites on the surface of the anode. These structures grow like roots into the electrolyte and pierce the barrier separating the anode and cathode, causing the battery to short or even catch fire.

These dendrites form when lithium ions move from the cathode to the anode during charging, attaching to the surface of the anode in a process called plating. Plating on the anode creates an uneven, non-homogeneous surface, like plaque on teeth, and allows dendrites to take root. When discharged, that plaque-like coating needs to be stripped from the anode, and when plating is uneven, the stripping process can be slow and result in potholes that induce even more uneven plating in the next charge.

Solid-state battery design charges in minutes and lasts for thousands of cycles, Leah Burrows, Harvard John A. Paulson School of Engineering and Applied Sciences, Tech Xplore

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As The Worm Turns...


Schematic diagram of the worm-inspired robot. Credit: Jin et al.

Topics: Applied Physics, Biomimetics, Instrumentation, Mechanical Engineering, Robotics

Bio-inspired robots, robotic systems that emulate the appearance, movements, and/or functions of specific biological systems, could help to tackle real-world problems more efficiently and reliably. Over the past two decades, roboticists have introduced a growing number of these robots, some of which draw inspiration from fruit flies, worms, and other small organisms.

Researchers at China University of Petroleum (East China) recently developed a worm-inspired robot with a body structure that is based on the oriental paper-folding art of origami. This robotic system, introduced in Bioinspiration & Biomimetics, is based on actuators that respond to magnetic forces, compressing and bending its body to replicate the movements of worms.

"Soft robotics is a promising field that our research group has been paying a lot of attention to," Jianlin Liu, one of the researchers who developed the robot, told Tech Xplore. "While reviewing the existing research literature in the field, we found that bionic robots, such as worm-inspired robots, were a topic worth exploring. We thus set out to fabricate a worm-like origami robot based on the existing literature. After designing and reviewing several different structures, we chose to focus on a specific knitting pattern for our robot."

A worm-inspired robot based on an origami structure and magnetic actuators, Ingrid Fadelli, Tech Xplore

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Like Mushrooms for Plastics...


Credit: VTT Technical Research Centre of Finland

Topics: Biology, Biotechnology, Chemistry, Materials Science, Mechanical Engineering

A research group from VTT Technical Research Center of Finland has unlocked the secret behind the extraordinary mechanical properties and ultra-light weight of certain fungi. The complex architectural design of mushrooms could be mimicked and used to create new materials to replace plastics. The research results were published on February 22, 2023, in Science Advances.

VTT's research shows for the first time the complex structural, chemical, and mechanical features adapted throughout the course of evolution by Hoof mushroom (Fomes fomentarius). These features interplay synergistically to create a completely new class of high-performance materials.

Research findings can be used as a source of inspiration to grow from the bottom up the next generation of mechanically robust and lightweight, sustainable materials for various applications under laboratory conditions. These include impact-resistant implants, sports equipment, body armor, and exoskeletons for aircraft, electronics, or windshield surface coatings.

Mushrooms could help replace plastics in new high-performance ultra-light materials, VTT Technical Research Centre of Finland,

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The microfiber actuators on the metal mesh collector (top left), under SEM (bottom left), under heat activation (top right), and integrated into an artificial arm (bottom right). | Credit: Qiguang He et al./Science Robotics

Topics: Materials Science, Mechanical Engineering, Nanotechnology, Robotics

A new artificial fiber spun from a polymer called liquid crystal elastomer (LCE) using high-voltage electricity replicates the strength, responsiveness, and power density of human muscle fibers, scientists report. When powered by heat or near-infrared light, the fibers pulled upward and downward or oscillated back and forth.

"Our work may open up an avenue to build soft robotics or soft machines using liquid crystal elastomers as the actuator," the authors write in their paper, published in the August 25 issue of Science Robotics.

When applied to a variety of potential applications, the fiber actuators successfully controlled the pinching motion of a micro-tweezer, directed the movement of a microswimmer and a tiny artificial arm, and pumped fluids into a light-powered microfluidic pump.

Inspired by the utility of tiny fibers in nature, scientists sought to create artificial fibers that could also serve as ubiquitous tools in robotics, as sensors or assistive devices, for example. In the past few years, researchers succeeded in constructing fiber actuators driven by heat or light that are as strong and flexible as natural fibers. However, many of these artificial threads respond to their stimulus very slowly, due to their large size or complex actuation processes. When fibers can respond quickly, there's a trade-off in size or quality; for example, micro-yarns made of carbon nanotubes are fast actuators but aren't as strong as other fibers.

"Animal muscle fiber exhibits superior mechanical properties and actuation performance," said senior author Shengqiang Cai, associate professor of mechanical and aerospace engineering at the University of California, San Diego. "Only a few existing materials show similar actuation behaviors as animal muscle, and the fabrication of fibers from those materials with a size and quality comparable to muscle fiber is not easy."

Electrically Spun Artificial Fibers Match Performance of Human Muscle Fibers, Juwon Song, American Association for the Advancement of Science




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Quadrupedal Robots...


Image Source: Link below

Topics: Autonomous Vehicles, Mechanical Engineering, Research, Robotics


Legged locomotion can extend the operational domain of robots to some of the most challenging environments on Earth. However, conventional controllers for legged locomotion are based on elaborate state machines that explicitly trigger the execution of motion primitives and reflexes. These designs have increased in complexity but fallen short of the generality and robustness of animal locomotion. Here, we present a robust controller for blind quadrupedal locomotion in challenging natural environments. Our approach incorporates proprioceptive feedback in locomotion control and demonstrates zero-shot generalization from simulation to natural environments. The controller is trained by reinforcement learning in simulation. The controller is driven by a neural network policy that acts on a stream of proprioceptive signals. The controller retains its robustness under conditions that were never encountered during training: deformable terrains such as mud and snow, dynamic footholds such as rubble, and overground impediments such as thick vegetation and gushing water. The presented work indicates that robust locomotion in natural environments can be achieved by training in simple domains.

Learning quadrupedal locomotion over challenging terrain, Joonho Lee1, Jemin Hwangbo 1,2, Lorenz Wellhausen1, Vladlen Koltun3, and Marco Hutter1

Science Robotics  21 Oct 2020:
Vol. 5, Issue 47, eabc5986
DOI: 10.1126/scirobotics.abc5986

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