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  1. Fracture-based design enables stronger electroadhesive clutches, which enhances the programmable stiffness and load capacity of robots.
    Free, publicly-accessible full text available November 30, 2023
  2. The most common sensing modalities found in a robot perception system are vision and touch, which together can provide global and highly localized data for manipulation. However, these sensing modalities often fail to adequately capture the behavior of target objects during the critical moments as they transition out of static, controlled contact with an end-effector to dynamic and uncontrolled motion. In this work, we present a novel multimodal visuotactile sensor that provides simultaneous visuotactile and proximity depth data. The sensor integrates an RGB camera and air pressure sensor to sense touch with an infrared time-of-flight (ToF) camera to sense proximity by leveraging a selectively transmissive soft membrane to enable the dual sensing modalities. We present the mechanical design, fabrication techniques, algorithm implementations, and evaluation of the sensor's tactile and proximity modalities. The sensor is demonstrated in three open-loop robotic tasks: approaching and contacting an object, catching, and throwing. The fusion of tactile and proximity data could be used to capture key information about a target object's transition behavior for sensor-based control in dynamic manipulation.
  3. Abstract

    Repairing fractured metals to extend their useful lifetimes advances sustainability and mitigates carbon emissions from metal mining and processing. While high‐temperature techniques are being used to repair metals, the increasing ubiquity of digital manufacturing and “unweldable” alloys, as well as the integration of metals with polymers and electronics, call for radically different repair approaches. Herein, a framework for effective room‐temperature repair of fractured metals using an area‐selective nickel electrodeposition process refered to as electrochemical healing is presented. Based on a model that links geometric, mechanical, and electrochemical parameters to the recovery of tensile strength, this framework enables 100% recovery of tensile strength in nickel, low‐carbon steel, two “unweldable” aluminum alloys, and a 3D‐printed difficult‐to‐weld shellular structure using a single common electrolyte. Through a distinct energy‐dissipation mechanism, this framework also enables up to 136% recovery of toughness in an aluminum alloy. To facilitate practical adoption, this work reveals scaling laws for the energetic, financial, and time costs of healing, and demonstrates the restoration of a functional level of strength in a fractured standard steel wrench. Empowered with this framework, room‐temperature electrochemical healing can open exciting possibilities for the effective, scalable repair of metals in diverse applications.

    Free, publicly-accessible full text available March 18, 2024
  4. Abstract

    Extracellular vesicles (EVs) – nanoscale membranous particles that carry multiple proteins and nucleic acid cargoes from their mother cells of origin into circulation – have enormous potential as biomarkers. However, devices appropriately scaled to the nanoscale to match the size of EVs (30–200 nm) have orders of magnitude too low throughput to process clinical samples (1012EVs mL−1in serum). To address this challenge, we develop a novel approach that incorporates billions of nanomagnetic sorters that act in parallel to precisely isolate sparse EVs based on immunomagnetic labeling directly from clinical samples at flow rates billions of times greater than that of a single nanofluidic device. To fabricate these chips, the ferromagnetic metals are electro‐deposited into a self‐assembled microlattice, achieving >109nanoscale magnetophoretic sorting devices in a 3D postage stamp‐sized lattice with >70x magnetic traps and >20x enrichment of magnetic nanoparticles versus our previous work. The immunomagnetically labeled EVs are isolated and achieve a ≈100% increase in yield as well as increased purity compared to conventional methods. Building on the proof‐of‐concept demonstrations in this manuscript, this new approach has the potential to enhance the future clinical translation of EV biomarkers by enabling rapid, sensitive, and specific isolation of EV subpopulations from clinical samples.

    Free, publicly-accessible full text available January 29, 2024
  5. Abstract

    Stiffness is a mechanical property of vital importance to any material system and is typically considered a static quantity. Recent work, however, has shown that novel materials with programmable stiffness can enhance the performance and simplify the design of engineered systems, such as morphing wings, robotic grippers, and wearable exoskeletons. For many of these applications, the ability to program stiffness with electrical activation is advantageous because of the natural compatibility with electrical sensing, control, and power networks ubiquitous in autonomous machines and robots. The numerous applications for materials with electrically driven stiffness modulation has driven a rapid increase in the number of publications in this field. Here, a comprehensive review of the available materials that realize electroprogrammable stiffness is provided, showing that all current approaches can be categorized as using electrostatics or electrically activated phase changes, and summarizing the advantages, limitations, and applications of these materials. Finally, a perspective identifies state‐of‐the‐art trends and an outlook of future opportunities for the development and use of materials with electroprogrammable stiffness.

  6. Abstract

    Healing metallic materials involves high temperatures and large energy inputs. This work demonstrates rapid, effective, low‐energy, and room‐temperature healing of metallic materials by using electrochemistry and polymer‐coated cellular nickel to mimic the transport‐mediated healing of bone. The polymer coating enables selective healing only at the fracture site, electrochemical reactions transport metal ions from a metal source to fractured areas, and the cellular structure of the metal allows facile ion transport to healing sites and effective recovery of strength and toughness when the cellular metal is subjected to three types of damage (scission fracture, tensile failure, and plastic deformation). Using this strategy, samples fractured in tension and by scission recover 100% of their tensile strength in as little as 10 and 4 h of healing. The healing process is stochastic, thus a statistical method is used to quantify and predict the likelihood of achieving target healing strengths based on energy input. This electrochemistry‐based approach enables the first demonstration of room‐temperature healing of structural metallic materials and requires several orders of magnitude less energy than many previously reported metal healing techniques.