Skin Sensitivity Assessment Using Smartphone Haptic Feedback.

Goal: This work presents a smartphone application to assess cutaneous sensory perception by establishing Vibrational Perception Thresholds (VPTs). Cutaneous sensory perception diagnostics allow for the early detection and symptom tracking of tactile dysfunction. However, lack of access to healthcare and the limited frequency of current screening tools can leave skin sensation impairments undiscovered or unmonitored. Methods: A 23-participant cross-sectional study in subjects with a range of finger sensation tests Smartphone Established VPTs (SE-VPTs) by varying device vibrational intensity. These are compared against monofilament test scores, a clinical measure of skin sensitivity. Results: We find a strong positive correlation between SE-VPTs and monofilament scores ([Formula: see text] = 0.86, p = 1.65e-07). Conclusions: These results demonstrate the feasibility of using a smartphone as a skin sensation screening tool.

A Wearable Testbed for Studying Variable Transmission in Body-Powered Prosthetic Gripping.

For those with upper limb absence, body-powered prostheses continue to be popular for many activities despite being an old technology; these devices can provide both inherent haptic feedback and mechanical robustness. Yet, they can also result in strain and fatigue. Body-powered prosthetic graspers typically consist of a simple lever providing a relatively constant transmission ratio between the input forces from the user's shoulder harness and the grip force of their prosthetic prehensor. In the field of robotic hand design, new continuously varying transmissions demonstrate particular promise in generating a wide range of grasping speeds without sacrificing grip strength. These benefits, if applied to shoulder-driven prosthetic grippers, have the potential to both reduce shoulder exertion and fatigue. This work presents the integration of a continuously variable transmission into a body-powered, voluntary close prosthetic testbed. We introduce the design and validate its performance in a benchtop experiment. We compare constant transmission conditions with a force-dependent, continually varying condition. The device is mounted on a prosthetic emulator for a preliminary wearable demonstration.

"Self-care selfies": Patient-uploaded videos capture meaningful changes in dexterity over 6 months.

OBJECTIVE: Upper extremity function reflects disease progression in multiple sclerosis (MS). This study evaluated the feasibility, validity, and sensitivity to change of remote dexterity assessments applying human pose estimation to patient-uploaded videos. METHODS: A discovery cohort of 50 adults with MS recorded "selfie" videos of self-care tasks at home: buttoning, brushing teeth, and eating. Kinematic data were extracted using MediaPipe Hand pose estimation software. Clinical comparison tests were grip and pinch strength, 9 hole peg test (9HPT), and vibration, and patient-reported dexterity assessments (ABILHAND). Feasibility and acceptability were evaluated (Health-ITUES framework). A validation cohort (N = 35) completed 9HPT and videos. RESULTS: The modality was feasible: 88% of the 50 enrolled participants uploaded ≥3 videos, and 74% completed the study. It was also usable: assessments easy to access (95%), platform easy to use (97%), and tasks representative of daily activities (86%). The buttoning task revealed four metrics with strong correlations with 9HPT (nondominant: r = 0.60-0.69, dominant: r = 0.51-0.57, P < 0.05) and ABILHAND (r = -0.48, P = 0.05). Retest validity at 1 week was stable (r > 0.8). Cross-sectional correlations between video metrics and 9HPT were similar at 6 months, and in the validation cohort (nondominant: r = 0.46, dominant: r = 0.45, P < 0.05). Over 6 months, pinch strength (5.8-5.0 kg/cm2 , P = 0.05) and self-reported pinch (ABILHAND) decreased marginally. While only 15% of participants worsened by 20% on 9HPT, 70% worsened in key buttoning video metrics. INTERPRETATION: Patient-uploaded videos represent a novel, patient-centered modality for capturing dexterity that appears valid and sensitive to change, enhancing its potential to be disseminated for neurological disease monitoring and treatment.

Efficient reciprocating burrowing with anisotropic origami feet.

Origami folding is an ancient art which holds promise for creating compliant and adaptable mechanisms, but has yet to be extensively studied for granular environments. At the same time, biological systems exploit anisotropic body forces for locomotion, such as the frictional anisotropy of a snake's skin. In this work, we explore how foldable origami feet can be used to passively induce anisotropic force response in granular media, through varying their resistive plane. We present a reciprocating burrower which transfers pure symmetric linear motion into directed burrowing motion using a pair of deployable origami feet on either end. We also present an application of the reduced order model granular Resistive Force Theory to inform the design of deformable structures, and compare results with those from experiments and Discrete Element Method simulations. Through a single actuator, and without the use of advanced controllers or sensors, these origami feet enable burrowing locomotion. In this paper, we achieve burrowing translation ratios-net forward motion to overall linear actuation-over 46% by changing foot design without altering overall foot size. Specifically, anisotropic folding foot parameters should be tuned for optimal performance given a linear actuator's stroke length.

Characterizing the Force-Motion Tradeoff in Body-Powered Transmission Design.

Upper-limb prosthesis users continue to reject devices despite continued research efforts. Today, the passive topology of body-powered prehensors, which physically transmits grasp force and position data between user and device, results in improved performance over myoelectric alternatives. However, the loads and postures on the user's body also result in discomfort, fatigue, and worsened grasp force control. Despite the long history and everyday adoption of body-powered prehensors in society, the measurement of how specific body loads and postures affect grasp performance and user experience has yet to be systematically studied. In this work, we present a body-powered prosthesis emulator to independently change required input forces and motions to study the positive and negative effects provided by the inherent haptic feedback. Using a simulated grasping task, we collect functional and qualitative data from 15 participants using a shoulder harness interface. Outcomes show that lowering required input motions and forces independently reduces negative outcomes, with diminishing returns below 1:1 output mappings. Given the tradeoff between force and motion in traditional body-powered transmissions, a transmission ratio of 1:1 balances both requirements. The purpose of this study is to inform future prehensor designs that leverage the transparency of body-power to deliver high functionality while mitigating user discomfort.

Mole crab-inspired vertical self-burrowing.

We present EMBUR-EMerita BUrrowing Robot-the first legged robot inspired by the Pacific mole crab, Emerita analoga, capable of burrowing vertically downward. We choose Emerita analoga as a model organism for its rapid downward burrowing behaviors, as it is four times as fast as the most rapid bivalve mollusk. Vertical burrowing in granular media is a challenging endeavor due to the tendency for the media to create upwards resistive forces on an intruder, even during purely horizontal motions. Our robot is capable of vertically burrowing its body in granular substrate primarily through excavation using two leg pairs, which are functionally analogous to groupings of leg pairs of the mole crab. We implement a novel leg mechanism with a sweeping trajectory, using compliant fabric to enable an anisotropic force response. The maximum resistive force during the power stroke is 6.4 times that of the return stroke. We compare robot body pitch and spatial trajectories with results from biomechanical studies of the mole crabs. We characterize the sensitivity of the robot to initial depth, body pitch and leg pose, and propose bounds on initial conditions which predict various burrowing failure modes. Parametric studies utilizing Granular Resistive Force Theory inform our understanding of robot behavior in response to leg phasing and orientation. Not only does this robotic platform represent the first robophysical model of vertical mole crab-inspired burrowing, it is also one of the first legged, primarily excavative small-scale burrowing agents.

Effect of variable transmission on body-powered prosthetic grasping.

Body-powered upper-limb prostheses remain a popular option for those with limb absence due to their passive nature. These devices typically feature a constant transmission ratio between the forces input by the user and the grasp forces output by the prosthetic gripper. Work incorporating continuously variable transmissions into robotic hands has demonstrated a number of benefits in terms of their motion and forces. In this work, we use a custom prosthesis emulator to evaluate the viability of applying variable transmissions to a body-powered prosthetic context. With this haptics test bed, we measured user performance during a grasping and lift task under a variety of transmission ratio conditions and with three different test objects. Results indicate that use of a variable transmission leads to the successful manipulation of a wider variety of objects than the constant transmission ratio systems, while requiring less shoulder motion. Analysis also shows a potential tendency for users to apply higher grasp forces than necessary, when compared to constant transmission conditions. These findings suggest a multifaceted effect on grasp performance with both benefits and drawbacks when considering a variable approach that supports the continued study of variable transmissions in assisted grasping.

Motor-Augmented Wrist-Driven Orthosis: Flexible Grasp Assistance for People with Spinal Cord Injury.

This paper presents the design of a motor-augmented wrist-driven orthosis (MWDO) for improved grasp articulation for people with C6-C7 spinal cord injuries. Based on the traditional passive, wrist-driven orthotic (WDO) mechanism, the MWDO allows for both body-powered and motorized actuation of the grasping output thus enabling more flexible and dexterous operation. Here, the associated control scheme enables active decoupling of wrist and finger articulation, which can be useful during certain phases of manipulation tasks. An additional modification to the traditional WDO is the integration of a magnetic latch at the Distal Interphalangeal (DIP) joint allowing for improved pinching. These abilities are demonstrated with common activities of daily living (ADL).

Hands in the Real World.

Robots face a rapidly expanding range of potential applications beyond controlled environments, from remote exploration and search-and-rescue to household assistance and agriculture. The focus of physical interaction is typically delegated to end-effectors-fixtures, grippers or hands-as these machines perform manual tasks. Yet, effective deployment of versatile robot hands in the real world is still limited to few examples, despite decades of dedicated research. In this paper we review hands that found application in the field, aiming to discuss open challenges with more articulated designs, discussing novel trends and perspectives. We hope to encourage swift development of capable robotic hands for long-term use in varied real world settings. The first part of the paper centers around progress in artificial hand design, identifying key functions for a variety of environments. The final part focuses on the overall trends in hand mechanics, sensors and control, and how performance and resiliency are qualified for real world deployment.