A Defense Advanced Research Projects Agency program is developing ways to deliver naturalistic sensations, such as touch and position sense, to amputees while enabling prosthetic control and reducing phantom limb pain.
“We have the opportunity to not only significantly improve an amputee’s ability to control a prosthetic limb, but to make a profound, positive psychological impact,” Doug Weber, Defense Advanced Research Projects Agency (DARPA) program manager of HAPTIX, stated in a press release. “Amputees view existing prostheses as if they were tools, like a wrench, used only to perform a specific job, so many people abandon their prostheses unless absolutely needed. We believe that HAPTIX will create a sensory experience so rich and vibrant that the user will want to wear his or her prosthesis full-time and accept it as a natural extension of the body. If we can achieve that, DARPA is even closer to fulfilling its commitment to help restore full and natural functionality to wounded service members.”
The Hand Proprioception & Touch Interfaces for Prosthetic Limbs (HAPTIX) program is the most recent development in DARPA’s prosthetics research. Previously, through the Revolutionizing Prosthetics program, DEKA Integrated Solutions and the Johns Hopkins University Applied Physics Laboratory created two advanced, electromechanical prosthetic arm and hand systems capable of unprecedented levels of dexterity, speed and strength, Weber told O&P Business News. To build on the success of Revolutionizing Prosthetics, DARPA launched the Reliable Neural Interface Technology (RE-NET) program, which developed the technologies to reliably extract information from the human nervous system to provide life-long control of many degree-of-freedom (DOF) machines. HAPTIX was designed to advance this work by developing a system that allows the daily use of prosthetics in the field.
“The HAPTIX program aims to develop implantable neural-interface microsystems to extract volitional motor command signals from muscles and nerves and provide tactile and proprioceptive feedback by patterned microstimulation of sensory nerves,” Weber said. “While DARPA’s primary goal is to create a system that achieves these objective in upper limb prostheses, the hope is that the technology will be modular and scalable to serve a variety of applications, including lower limb prostheses and advanced neuromodulation devices.”
Through HAPTIX, DARPA plans on outfitting an existing prosthesis that provides two degrees of freedom each at the wrist, in the thumb and with finger motion, with approximately 10 pressure sensors and joint angle and velocity sensors for all six degrees of freedom. Additional sensing and motor capabilities may be added to the prosthesis, which will be suitable for daily use.
Call for proposals
To help develop an implantable system for restoring sensorimotor capabilities to transradial amputees, DARPA released a call for research proposals with an anticipated total funding of approximately $40 million to be awarded in three technical areas and advanced studies.
In the technical area, phase I will develop and test a variety of electronics, electrode technologies and coding algorithms for extraction of volitional motor control signals and application of sensory feedback, according to DARPA’s program announcement. The selected components from phase I will be integrated into a working prototype of the HAPTIX system in phase II. Finally, phase III will test systems that receive investigational device exemption approval and achieve phase II program metrics under conditions including laboratory and take-home trials of the complete system for 12 or more months in transradial amputee volunteers, according to the announcement.
DARPA is also interested in creating technologies that support the next generation of HAPTIX. Through the Advanced Studies area, DARPA “seeks to develop science and technology to extend capabilities of neural interface systems for future applications in prosthetics and other applications that require monitoring and modulation of neural activity.”
According to Weber, DARPA is hoping to start the program with selected proposals in November after proposal reviews and contract negotiations.
“During the trial, system performance is expected to demonstrate achievement of naturalistic sensation of the missing limb through activation of neural pathways that encode touch and proprioception for the missing limb. The system should also demonstrate intuitive motor control by directly accessing volitional motor control signals from muscles or peripheral motor nerves,” Weber said. “Anticipating a successful study outcome, we hope this long-term trial will provide a credible path to human translation by providing the necessary foundation for this novel medical device technology to obtain regulatory approval for clinical use within the United States.” — by Casey Tingle
Disclosure: Weber is employed by DARPA.