Advanced prosthesis technology delivers humanlike sense of touch

Johns Hopkins University engineers developed a prosthetic hand that can grip everyday objects like a human, carefully conforming and adjusting its grasp to avoid damaging or mishandling whatever it holds.

The hybrid design offers a promising solution for people with hand loss and could improve how robotic arms interact with their environment.

“The goal has been to create a prosthetic hand that we model based on the human hand’s physical and sensing capabilities – a more natural prosthetic that functions and feels like a lost limb,” says Sriramana Sankar, a Johns Hopkins biomedical engineer who led the work. “We want to give people with upper-limb loss the ability to safely and freely interact with their environment, to feel and hold their loved ones without concern of hurting them.”

The device, developed by the same Neuroengineering and Biomedical Instrumentations Lab that created the first electronic ‘skin’ with a humanlike sense of pain, features a multifinger system with rubberlike polymers and a rigid 3D-printed internal skeleton. Its three layers of tactile sensors, inspired by the layers of human skin, allow it to grasp and distinguish objects of various shapes and surface textures, rather than just detect touch. Each soft air-filled finger joint can be controlled with the forearm’s muscles, and machine learning algorithms focus the signals from the artificial touch receptors to create a realistic sense of touch.

“The sensory information from its fingers is translated into the language of nerves to provide naturalistic sensory feedback through electrical nerve stimulation,” Sankar says.

In the lab, the hand identified and manipulated 15 everyday objects, achieving the best performance compared with the alternatives, successfully handling objects with 99.69% accuracy and adjusting its grip as needed to prevent mishaps.

“We’re combining the strengths of rigid and soft robotics to mimic the human hand,” Sankar says. “The human hand isn’t completely rigid or purely soft – it’s a hybrid system, with bones, soft joints, and tissue working together. That’s what we want our prosthetic hand to achieve.”

To help amputees regain the ability to feel objects while grasping, prostheses will need three key components: sensors to detect the environment, a system to translate that data into nerve-like signals, and a way to stimulate nerves so the person can feel the sensation, says Nitish Thakor, a Johns Hopkins biomedical engineering professor who directed the work.

The bioinspired technology allows the hand to function this way, using muscle signals from the forearm, like most hand prostheses. These signals bridge the brain and nerves, allowing the hand to flex, release, or react based on its sense of touch. The result is a robotic hand that intuitively knows what it’s touching, much like the nervous system does, Thakor says.

“This hybrid dexterity isn’t just essential for next-generation prostheses,” Thakor says. “It’s what the robotic hands of the future need because they won’t just be handling large, heavy objects. That’s why a hybrid robot, designed like the human hand, is so valuable – it combines soft and rigid structures, just like our skin, tissue, and bones.”

Johns Hopkins University – Neuroengineering and Biomedical Instrumentation Laboratory
https://neuroengineering.bme.jhu.edu/