Biological Technologies. Hand Proprioception & Touch Interfaces (HAPTIX).

RESEARCH. While U.S. soldier fatalities have dropped in recent years, the prevalence of powerful explosives on the battlefield has resulted in a large number of veterans suffering from upper limb amputations.

Tremendous advances have been made in the development of dexterous mechatronic prostheses, yet no clinical treatment exists to provide naturalistic control of these prostheses or to convey tactile and proprioceptive feedback to the user. As a result, prosthetic control remains un-intuitive, relies on lengthy training, requires taxing levels of visual concentration for operation, is unable to provide reflexive reaction, and ultimately limits prosthesis performance and the sense of embodiment.

In order to provide amputees with a prosthesis that feels and functions like a natural limb, the HAPTIX  by U.S. DARPA (Defense Advanced Research Projects Agency) program will develop new science and technology to achieve closed-loop control of dexterous mechatronic prostheses. HAPTIX will 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. This interface system will require novel algorithms for converting muscle and/or nerve signals into volitional commands for controlling a multi-degree-of-freedom (DoF) transradial prosthesis. Sensory encoding algorithms will be developed for generating stimulation patterns that evoke naturalistic sensations of touch forces and joint motion for the prosthesis. System performance and user impact will be evaluated in a year-long, take-home trial before the end of the HAPTIX program.

Proposed research should investigate innovative approaches that enable revolutionary advances in science, devices, or systems. Specifically excluded is research that primarily results in evolutionary improvements to the existing state of practice.

The HAPTIX program seeks innovative research proposals to develop an implantable system for restoring closed-loop sensorimotor capabilities to trans-radial amputees. Recording and stimulating interfaces are expected to use peripheral nerve or implantable electromyographic (EMG) electrodes to provide the biological link with the HAPTIX system. Implantable electronics will transport peripheral signals to and from the body and advanced algorithms will transform these data into practical motor and sensory signals. Methods for controlling the prosthesis with these signals must take into account the natural physiological processes underlying the control of wrist and hand function to achieve proportional and simultaneous control of all available DoF. It is expected that HAPTIX systems will restore specific sensory modalities, such as touch and proprioception, and that these sensations will be congruous in sensory modality and physical location with the external stimulus (e.g., an object touching a thumb sensor must elicit the percept of touch to the user’s thumb). HAPTIX will develop and test the electrodes, algorithms, electronics, and packaging technologies needed to control and sense the prosthesis. These technologies will be developed in a modular fashion using open standards to allow full system integration as the program progresses.

The final HAPTIX system is expected to demonstrate dramatically improved sensorimotor capabilities over current state-of-the-art (SOA) systems in trans-radial amputees. All technology development within the HAPTIX program must carefully consider how to achieve quantitative and qualitative outcome metrics during the year-long human subject trials. In addition, the final HAPTIX system must be suitable for daily use thus requiring a substantial level of maturity of all technology components. Proposers are expected to consider daily user operations such as configuration, re-training, and charging. All of these components must be developed using a systems engineering approach, wherein the design tradeoffs are described clearly. (