Revolutionizing Prosthetics

Overview

Begun in 2006, the Defense Advanced Research Project Agency’s (DARPA) Revolutionizing Prosthetics program set out to expand prosthetic arm options for wounded warriors. The program provided funding to APL to produce a fully neurally integrated upper-extremity prosthesis to support clinical trials and manufacturing transition. This led to the development of our Modular Prosthetic Limb (MPL).

Our requirements for the MPL were aimed at reflecting the capabilities of a human upper limb, including:

mechanical components that would provide equivalent degrees of freedom, strength, and environmental tolerance (to heat, cold water, humidity, dust, etc.)
materials that would enable the limb to weight approximately as much as the upper limb of an average human
sensors for touch, temperature, vibration, and proprioception (the ability to sense the position of the arm and hand relative to other parts of the body)
power that would allow extended continuous use

With this new prosthesis, an individual who has lost their upper limb would be able to manipulate and feel objects as if with a biological hand.

Integrated Technologies

Virtual Integration Environment

The MPL was initially developed as a research platform. Because only a limited number of them could be made, APL developed the Virtual Integration Environment (VIE), a modular and configurable system to support various limb models (including the MPL) and algorithms in order to facilitate virtual demonstrations of highly dexterous control of an upper-limb prosthesis. It serves as a complete limb system simulation environment to support neural integration. The VIE is used to visualize and monitor performance of various design approaches, pilot neural signal analysis algorithms, and simulate emerging mechatronic elements. It provides a framework for synchronizing research and efforts across many geographically distributed contributors in order to turn neural research into engineering reality. From the clinical and patient perspective, the VIE can be used to train end users to control real or virtual neuroprosthetic devices, and to configure and customize clinical and take-home devices.

Neural Research

The neuroscientific goals of Revolutionizing Prosthetics were to evaluate the safety and efficacy of cortical microstimulation for tactile and proprioceptive feedback in humans; to develop active and wireless implantable microelectrodes for stimulating, recording, and demonstrating the viability of chronic implantation; and to evaluate the feasibility of bilateral closed-loop cortical control. Revolutionizing Prosthetics enabled the first-ever neuroprosthetic system controlled with signals from the posterior parietal cortex and the first-ever demonstration of closed-loop cortical control of a dexterous neuroprosthesis using recordings from the motor cortex and parietal reach region and stimulation in the primary somatosensory cortex.

Modular Prosthetic Limb

The first version of the Modular Prosthetic Limb (MPL v1.0) was completed in December 2009. It featured anthropomorphic form factor and appearance, human-like strength and dexterity, high-resolution tactile and position sensing, and a cortical neural interface for intuitive and natural closed-loop control. Made of lightweight carbon fiber and high-strength alloys, the arm had 25 degrees of freedom, or joint motions (the human arm has about 30). This limb was modular and configurable to the level of a patient’s injury. MPL v2.0 was completed in December 2010, and efforts shifted focus to refinement of the MPL system technologies by incremental design improvements for increased reliability, increased simplicity, commonality among subsystems, maximized performance, and evolved software and controls algorithms. MPL systems were used by clinical partners in neural-based research and development of cortical encoding and decoding strategies.

Proto 2

During development of Proto 1, the Revolutionizing Prosthetics team engaged in concurrent research, analysis of alternatives, design, and development efforts for design of a limb including: biomimetic operation including all degrees of freedom, speed, dexterity, and force; electromechanical actuation mechanisms; communications, signal analysis, and control strategies; and comfort and appearance (socket and cosmesis). The mechatronic culmination of these efforts was completed in August 2007. Two versions of Proto 2 were designed—one with an intrinsic hand using off-the-shelf brushless direct current motors, and one with an extrinsic hand using a cobotic device in the forearm with a single motor to control the wrist and hand. There are about 25 microprocessors (computer chips) and 80 tactile sensors built into the fingers, fingertips, hand, wrist, and elbow. The Proto 2 limbs incorporated significant advances in many technologies, leading to the ultimate design of the MPL

Proto 1

Prototype 1 (Proto 1) had eight degrees of freedom—a level of control far beyond the state of the art for prosthetic limbs at the time. As a rapid-development prototype, Proto 1 utilized many commercial off-the-shelf components with the purpose of supporting neural integration research and serving as a test bed for evaluation of haptic feedback and indirect sensory perception approaches. Additionally, Proto 1 was used to demonstrate advanced prosthetic function with classification algorithms for noninvasive and low-invasive control devices. Proto 1 was fitted for the beginning of Revolutionizing Prosthetics clinical evaluations using surface electromyographic control with targeted muscle reinnervation (TMR) patients at the Rehabilitation Institute of Chicago in January 2007.

Timeline

Major Events

2022	Revolutionizing Prosthetics Participant 4 uses neural control paired with robotic autonomy algorithms to cut and eat a Twinkie with knife and fork
2022	Revolutionizing Prosthetics Participant 4 demonstrates first-ever focal stimulation of fingertip sensation, spanning 8 fingertips across both hands
2019	First human (Revolutionizing Prosthetics Participant 4) is implanted with six microelectrode arrays bilaterally, two in the primary motor cortex (M1) hand area and two in the primary sensory cortex (S1) hand area of the left hemisphere of the participant (the dominant one, because the participant is right-handed), and one in M1 and one in S1 of the right (nondominant) side.
August 2017	FDA approves implantation of microelectrode arrays in the motor cortices and somatosensory cortices on both hemispheres in a human candidate.
2016–2017	Revolutionizing Prosthetics Participant 3 demonstrates control over multiple virtual aircraft in a pilot simulator.
2016–2017	Revolutionizing Prosthetics Participant 3 is able to perceive forces placed on sensors in each of the fingertips of the MPL through stimulation of the somatosensory cortex.
2015	First human (Revolutionizing Prosthetics Participant 3) is implanted with four microelectrode arrays, two in the motor cortex and two in the sensory cortex of the left side of the participant (dominant, because the participant is right-handed).
2014	First human (Revolutionizing Prosthetics Participant 2) demonstrates non-anthropomorphic control of a flight simulator.
May 2014	MPL v3.0 is completed.
2013	FDA approves implantation of microelectrode arrays in somatosensory (S1) cortex for recording and imparting electrical stimulation.
April 2013	First human is implanted with two microelectrode arrays in parietal cortex (AIP and BA5), with no device-related adverse events to date.
December 2012	“Breakthrough: Robotic limbs moved by the mind” is featured on CBS’ 60 Minutes.
December 2012	Clinical trial results are published in The Lancet.
September 2011	The MPL is controlled by a patient using ECoG during a UPMC and University of Pittsburgh experiment.
February 2011	First human is implanted with two microelectrode arrays in primary motor cortex (M1) hand area, with no device-related adverse events to date.
December 2010	MPL v2.0 is completed.
September 2010	Phase 3 Kickoff meeting for APL Revolutionizing Prosthetics team.
December 2009	Version 1 of the Modular Prosthetic Limb (MPL v1.0) was completed with 17 degrees of freedom.
April 2008	Phase 2 Kickoff meeting for APL Revolutionizing Prosthetics team.
August 2007	Two versions of Proto 2 were completed with 22 degrees of freedom. The extrinsically actuated hand employed a cobot in the forearm driving the hand, wrist, and radial rotator. The intrinsically actuated hand was motor driven.
January 2007	Prototype 1 (Proto 1), with 8 degrees of freedom, began preclinical evaluations using surface myoelectric control. The Virtual Integration Environment (VIE) was used for clinician interface and patient training.
January 2006	Phase 1 Kickoff meeting for APL Revolutionizing Prosthetics team.

Program Background

DARPA contracted more than $107 million for the APL-led Revolutionizing Prosthetics program to create a fully functional upper limb that responded to direct neural control. The groundbreaking work done under this program capitalized on previous DARPA investments in neuroscience, robotics, sensors, power systems, and actuation. In particular, this program built on DARPA’s Human Assisted Neural Devices program, which decoded the brain’s motor signals with such fidelity that movements of a robotic arm could be controlled entirely by direct brain control.

The following items illustrate DARPA’s rationale, goals, and commitment to Revolutionizing Prosthetics and associated programs.

Partners Build High-Tech Hands for Wounded Warriors, by Cheryl Pellerin (American Forces Press Service, December 15, 2010)
DARPA’s Bio-Revolution, by Jonathan Beard (DARPA: 50 Years of Bridging the Gap, April 2008, pp. 158–160)
DARPA Revolutionizes Prosthetics: How and Why?, by Judith Philipps Otto (The O&P Edge, November 2007)
DARPA’s Cutting-Edge Programs Revolutionize Prosthetics, by Donna Miles (American Forces Press Service, February 8, 2006)

Partners

The Revolutionizing Prosthetics team brought together the most respected scientific researchers in their fields, as well as commercial leaders from the prosthetics industry. The project was shaped by a multidisciplinary team that included experts in signal processing and pattern recognition, electrodes for brain implants, mechatronics, neuroscience, electrical engineering, cognitive science, signal processing, battery design, nanotechnology, and even behavioral science.

Revolutionizing Prosthetics

Overview

Virtual Integration Environment

Neural Research

Modular Prosthetic Limb

Proto 2

Proto 1

Major Events

Sponsors

Program Background

Partners

Contact Information

Media Relations

Paulette Campbell

Technology Transfer

Heather Curran

Other Inquiries

Revolutionizing Prosthetics Team