New Technology Restores Cold Sensation in Amputees’ Phantom Limbs

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Black Prosthetic Arm

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Researchers have actually established the thin-film thermoelectric cooler (TFTEC), among the world’s tiniest and fastest refrigeration gadgets, for applications like enhanced prosthetics and enhanced truth. Collaboration with neuroscientists has actually permitted amputees to view temperature level with phantom limbs, a first-of-its-kind improvement that has ramifications for prostheses, haptics, and other applications like cooling electronic devices and energy harvesting in satellites. (Artist’s Concept)

Researchers at Johns Hopkins Applied Physics Laboratory (APL) have actually established among the tiniest, most extreme, and fastest refrigeration gadgets, called the wearable thin-film thermoelectric cooler (TFTEC). They have actually signed up with forces with neuroscientists to assist amputees feel temperature level with their phantom limbs.

This pioneering advancement opens a large range of helpful brand-new performances, consisting of improved prosthetics, tactile feedback in unique increased truth (AR) formats, and thermally-regulated treatments for usage cases like discomfort relief. The innovation is likewise possibly important in a variety of commercial and research study contexts, such as cooling electronic devices and lasers, and energy harvesting in satellites.

TFTEC advancement at APL began in 2016, when Rama Venkatasubramanian, a semiconductor gadget engineer and chief technologist for APL’s thermoelectrics research study, started establishing sophisticated nano-engineered thermoelectric products and gadgets for the Defense Advanced Research Projects Agency (< period class ="glossaryLink" aria-describedby ="tt" data-cmtooltip ="<div class=glossaryItemTitle>DARPA</div><div class=glossaryItemBody>Formed in 1958 (as ARPA), the Defense Advanced Research Projects Agency (DARPA) is an agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. DARPA formulates and executes research and development projects to expand the frontiers of technology and science, often beyond immediate U.S. military requirements, by collaborating with academic, industry, and government partners.</div>" data-gt-translate-attributes="[{" attribute="">DARPA) MATRIX program. To support MATRIX, APL developed advanced thin-film thermoelectric materials called Controlled Hierarchically Engineered Superlattice Structures (CHESS), to enable an entirely new set of transduction capabilities for several Department of Defense applications, including cooling computer chips and engine components.

Venkatasubramanian’s strides in CHESS thermoelectrics were so significant by the end of 2019 that Bobby Armiger, who supervises APL’s Exploratory Science Branch, wondered if his devices could be used to facilitate temperature sensation in phantom limbs of amputees for improved prostheses. Since 2006, APL had been leading DARPA’s Revolutionizing Prosthetics program, an effort focused on creating a mentally controlled artificial limb that will restore near-natural motor and sensory capability to upper-extremity amputee patients.

Johnny Matheny Testing

Johnny Matheny, a prosthetics tester, determines which cola can is the coldest using a modular prosthetic limb and thin-film thermoelectric device, both developed by the Johns Hopkins Applied Physics Laboratory. Credit: Ed Whitman / Johns Hopkins University Applied Physics Laboratory

“We’ve known that we can stimulate specific parts of someone’s amputated limb to feel sensations of touch and vibration, but no one has been able to create a cooling sensation with the speed, intensity, and efficiency to restore natural thermal perception with a prosthetic system,” Armiger said. “Restoring temperature sensation has practical applications — like identifying a cold beverage — as well as having the potential to improve the emotional embodiment of the prosthetic device, perhaps by feeling the warmth of a loved one’s hand.”

Venkatasubramanian and the thermoelectrics team began collaborating with Armiger and a team of neuroscientists and roboticists as part of a study supported by the Center for Rehabilitation Sciences Research within the Department of Physical Medicine & Rehabilitation (PM&R) at the Uniformed Services University of the Health Sciences (USU), through a sub-award from The Henry M. Jackson Foundation for the Advancement of Military Medicine to create a wearable thermoelectric cooler fast and intense enough to match the human body’s ability to rapidly sense temperature changes.

From that, the wearable TFTEC was created.

“Our TFTEC is just a little more than one millimeter thick, weighs only 0.05 grams, similar to a thin adhesive bandage, and can provide intense cooling in less than a second,” said Venkatasubramanian. “It’s also two times more energy efficient than today’s most common thermoelectric devices, and can be readily manufactured using semiconductor tools that are also used for manufacturing light-emitting diodes [LEDs] It’s an amazing advancement that might have big ramifications for prostheses and haptics applications.”

To test the TFTEC’s effectiveness, scientists mapped thermal experiences in the phantom hands of 4 amputees.

“When someone loses part of a limb, the nerves within the residual limb are still there, which can lead to the ‘phantom’ limb sensation,” stated Luke Osborn, a neuroengineering scientist who leads much of APL’s noninvasive nerve simulation work. “You can place electrodes on different parts of an amputee’s upper arm where those nerves have regrown and stimulate sensation — typically pressure, but in the current case, temperature —and the individual can tell us where in their phantom hand they feel those sensations.”

Nature Biomedical Engineering just recently released arise from APL’s substantial TFTEC research study for such sensory applications, that included lab-scale characterization, trials with amputees, and a real-life presentation of the method. The research study keeps in mind that the TFTEC generated cooling experiences in the phantom limbs of all individuals throughout a cold detection job, whereas standard thermoelectric innovation just did so in half of them– and the TFTEC did so 8 times much faster and with 3 times the strength. Additionally, TFTEC utilized half the energy compared to present thermoelectric gadgets.

“We found that the TFTEC device was significantly better at creating faster and more intense cooling sensations compared to traditional devices, even though the target temperature was the same,” statedOsborn “And that helped participants make faster decisions and observations.”

The stimulation websites on test individuals stayed the exact same over 48 weeks of screening, recommending that the innovation might make it possible for users to feel the temperature level in their missing out on hands for many years. This temporal stability in addition to a wearable noninvasive treatment are appealing for adoption to real-world usage.

“When we started our work in March 2020, we realized that within just a couple of trials, we could stimulate the phantom limbs of an amputee,” statedVenkatasubramanian “We heard participants say, ‘Yes, I felt an immediate cold feeling here and a tingle there.’”

The APL group continued to best its method through screening on numerous people with amputation in addition to those with an undamaged limb. “These are the developments we dream of as scientists,” Venkatasubramanian continued. “We spend years in the lab, and to see our technology have an impact on someone’s quality of life, like an amputee to perceive the natural thermal world, is incredibly satisfying.”

Capable of creating practical and useful thermal signals for human understanding– at a portion of the energy and size compared to today’s cooling innovations– the gadgets’ low profile, high-speed, and light-weight nature make them appropriate for skin surface area applications without limitations that might impact motion.

“It has been great to see the translation of this APL-developed thermoelectric technology into the healthcare domain through this first-of-kind demonstration in an amputee,” stated David Drewry, a biomedical engineer and program supervisor within APL’s National Health MissionArea “We look forward to expanding the results in more robust clinical trials and integrating the device into other wearable form factors that can be readily deployed to individuals in need of sensory restoration or haptic feedback.”

Katy Carneal, a biomedical engineer and assistant program supervisor a biomedical engineer and assistant program supervisor who leads ingenious health-related research study at APL sees a large set of future applications for the miniaturized thermoelectric innovation. “There are so many ways that pressure and temperature sensations impact the human body,” statedCarneal “In addition to improving the quality of life for amputees, we’ve opened a lot of research doors that can help us study and find new treatments for neuromuscular diseases or chronic pain.”

Dr Paul Pasquina, the chair of PM&R at USU, echoed that interest while applauding the work of the APL group. “What a privilege it is to work with such expert engineers to come up with solutions to help real-world patients, including our wounded warriors with limb loss,” he stated.

APL is distinctively certified to advance the art-of-the-possible for unique health applications by exploring this crossway of products science and electronic gadget engineering with biology and neuroscience. In addition to the Revolutionizing Prosthetics program, APL is making considerable advances in neural user interface research study, enhancing genomics tools, and keeping an eye on physical tiredness to avoid warfighter injuries amongst numerous other improvements in the National Health Mission Area.

Reference: “Evoking natural thermal perceptions using a thin-film thermoelectric device with high cooling power density and speed” by Luke E. Osborn, Rama Venkatasubramanian, Meiyong Himmtann, Courtney W. Moran, Jonathan M. Pierce, Priya Gajendiran, Jared M. Wormley, Richard J. Ung, Harrison H. Nguyen, Adam C. G. Crego, Matthew S. Fifer and Robert S. Armiger, 27 July 2023, Nature Biomedical Engineering
DOI: 10.1038/ s41551-023-01070- w