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CRCNS21 Computational Models of Multisensory Integration by Upper Limb in Humanoids and Amputees

This international collaborative research project between Johns Hopkins University (JHU) and the Technical University of Munich (TUM) investigated how the human brain processes and integrates multiple types of sensory information, such as touch and force, with the goal of improving prosthetic limbs for amputees and advancing sensory capabilities in humanoid robots. The research advanced our understanding of how the brain responds to sensory feedback in upper-limb amputees. Through experiments in which amputees received electrical stimulation while performing phantom hand movements, we demonstrated that sensory feedback activates the cortical sensorimotor and multisensory regions, and that these regions communicate dynamically during stimulation. Experiments with intact-limb participants explored the integration of visual, haptic, and force feedback, as well as in virtual reality motor training, further showing how the brain processes multimodal sensory information. In addition, this research inspired work on examining the reliability of where amputees perceive sensations over time, which contributed to a successful doctoral fellowship for continued investigation. Our collaborators at TUM improved multimodal sensor technology combining tactile and thermal feedback for humanoid robots, demonstrating the feasibility of integrating multiple sensor types into a unified system for detecting and responding to environmental stimuli. The experimental methods and analysis techniques developed across both teams, including functional network analysis and multimodal sensor integration, provide a foundation for future research in prosthetics and robotics. This research benefits the public by generating knowledge about how amputees process restored sensory information. Advances in humanoid sensing contribute to safer human-robot interaction. The project also fostered international collaboration and cross-disciplinary training: one TUM doctoral student spent a summer at JHU working on multimodal sensor integration, while two JHU students traveled to TUM to host workshops on neuromorphic sensory encoding and sensory integration.

42 ENGINEERING↗

Design of a Single Layer Metamaterial for Pressure Offloading of Transtibial Amputees

While using a prosthesis, transtibial amputees may experience pain and discomfort brought on by large pressure gradients at the interface between the residual limb and prosthetic socket. Current prosthetic interface solutions attempt to alleviate these pressure gradients by using soft homogenous liners to reduce and distribute pressures. This research investigates an additively manufactured metamaterial inlay with a tailored mechanical response to reduce peak pressure gradients around the limb. The inlay uses a hyperelastic behaving metamaterial (US10244818) comprised of triangular pattern unit cells which can be 3D printed with walls of various thicknesses controlled by draft angles. The hyperelastic material properties are modeled using a Yeoh 3rd order model. The 3rd order coefficients can be adjusted and optimized, which corresponds to a change in the unit cell wall thickness to create an inlay that can meet the unique offloading needs of an amputee. Finite element analysis simulations evaluated the pressure gradient reduction from: 1) a common homogenous silicone liner, 2) a prosthetist's inlay prescription that utilizes three variations of the metamaterial, and 3) a metamaterial solution with optimized Yeoh 3rd order coefficients. When compared to a traditional homogenous silicone liner for two unique limb loading scenarios, the prosthetist prescribed inlay and the optimized material inlay can achieve equal or greater pressure gradient reduction capabilities. These results show the potential feasibility of implementing this metamaterial as a method of personalized medicine for transtibial amputees by creating a customizable interface solution to meet the unique performance needs of an individual patient.

60 APPLIED LIFE SCIENCES↗

Silicone Molding and Lifetime Testing of Peripheral Nerve Interfaces for Neuroprostheses

Implantable peripheral nerve cuffs have a large application in neuroprostheses as they can be used to restore sensation to those with upper limb amputations. Modern day prosthetics, while lessening the pain associated with phantom limb syndrome, have limited fine motor control and do not provide sensory feedback to patients. Sensory feedback with prosthetics requires communication between the nervous system and limbs, and is still a challenge to accomplish with amputees. Establishing this communication between the peripheral nerves in the arm and artificial limbs is vital as prosthetics research aims to provide sensory feedback to amputees. Peripheral nerve cuffs restore sensation by electrically stimulating certain parts of the nerve in order to create feeling in the hand. Cuff electrodes have an advantage over standard electrodes as they have high selective stimulation by bringing the electrical interface close to the neural tissue in order to selectively activate targeted regions of a peripheral nerve. In order to further improve the selective stimulation of these nerve cuffs, there is need for finer spatial resolution among electrodes. One method to achieve a higher spatial resolution is to increase the electrode density on the cuff itself. Microfabrication techniques can be used to achieve this higher electrode density. Using L-Edit, a layout editor, microfabricated peripheral nerve cuffs were designed with a higher electrode density than the current model. This increase in electrode density translates to an increase in spatial resolution by at least one order of magnitude. Microfabricated devices also have two separate components that are necessary to understand before implantation: lifetime of the device and assembly to prevent nerve damage. Silicone molding procedures were optimized so that devices do not damage nerves in vivo, and lifetime testing was performed on test microfabricated devices to determine their lifetime in vivo. Future work of this project would include fabricating some of the designed devices and seeing how they compare to the current cuffs in terms of their electrical performance, lifetime, shape, and mechanical properties.

59 BASIC BIOLOGICAL SCIENCES↗

The Dynamic Socket: A Better Prosthesis

The issues that amputees experience with current prosthetic devices are discussed and how Sandia National Laboratory is working to make them both functional and comfortable to wear.

42 ENGINEERING↗

High Dexterity Robotics for Safety and Emergency Response - 17104

Recently, significant advances in robotics have led to increased use in industrial and military applications. For example, the military has used explosive ordnance disposal (EOD) robots to enable responders to remotely investigate hazardous environments. While EOD robots have saved many lives, their utility is hampered by: 1) limited ability to manipulate complex objects and mechanisms (e.g. open a car door, operate power tools or turn valves), and 2) the requirement for significant operator training using joystick-type interfaces. Most robots today have simplistic manipulators and cannot easily operate in environments designed for humans as evidenced by the recent Amazon Picking Challenge and the DARPA Robotics Challenge. Simple tasks that humans perform easily, such as picking up objects or operating a cutting tool, require customized rigs that are expensive and time-consuming to use. The specialized nature of these robots limits their utility in highly unstructured environments, for example during emergency situations where a robot may need to be rapidly re-purposed for an unanticipated situation (i.e. the Fukushima nuclear disaster). Robots are needed that can perform complex human-like tasks and are easy to use for everyday and emergency tasks. In 2005 the Defense Advanced Research Projects Agency (DARPA) initiated the Revolutionizing Prosthetics (RP) Program with the goal of creating prosthetics as capable as the human arm and a human-machine interface enabling highly intuitive operation. The Johns Hopkins University Applied Physics Laboratory (JHU/APL) created the Modular Prosthetic Limb (MPL), originally developed for amputees and paralyzed individuals as part of the RP Program, to replicate the capability of the human hand and arm to the extent technologically possible. With 26 joints and over 180 sensors, it is one of the most sophisticated and fully integrated robotic arms in the world. We have also demonstrated human-machine interface techniques that are highly intuitive requiring minimal training. While the MPL was originally designed as a prosthetic, it has also been incorporated into mobile robotic systems to project human capability. Using tele-operation, we have demonstrated the ability to perform dual-arm remote operations in complex environments. For nuclear facilities, high dexterity robots combined with tele-operation offer the potential to enhance worker safety, productivity and quality. Safety enhancements include enabling remote operation in hazardous environments, remote handling of heavy or dangerous materials, and elimination of injury due to repetitive motions. Because the MPL is designed to function like a human limb, the robot can work in environments designed for humans with limited need for specialized tools. When used for routine operations, it can also maintain a level of familiarity and confidence that effectively accomplishes reinforcement training for use in emergency situations, unlike a specialized robot that might sit unused for months or years at a time. In August 2016 we demonstrated the use of the MPL at the Portsmouth Gaseous Diffusion Plant in Piketon, Ohio. Two robotic platform technologies were demonstrated to familiarize the DOE Emergency Management's (EM) workforce on the potential benefits of this technology. Here we present the results of those efforts, highlight the lessons learned during 'EM Week,' and outline potential future developments that could further advance application of these technologies to enhance worker safety. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗