Project "LifeHand 2"
A group of European universities and the Department of Microsystems Engineering of IMTEK, developed 2 advanced prosthetic, the first on was developed in the project LifeHand of 2008, the prosthetic hand was able to receive neural impulses from the brain via intraneural electrodes, but it lacked feedback to the brain, nevertheless this was the starting point to the second project LifeHand 2 of 2013, the results of this projected enabled an amputee to control the grasping force without the aid of visual or hearing sensation and distinguish force levels to avoid breaking objects. For this project a special electrode was designed in order to stimulate the peripheral nerves median and ulnar, but the activation of the prosthetic hand was via myoelectric to prevent Electromagnetic interference.
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LifeHand 2 electrodes – Transverse intrafasciular Multi-channel Electrodes (TIME)
The electrodes were developed at the Laboratory of Biomedical Microtechnology at the IMTEK (Institut für Mikrosystemtechnik) of the University of Freiburg, the superviser was Prof. Thomas Stieglitz. Completely bio-compatible, made and tested to be placed transversely to the nerve fascicles constituting a nerve. The widest part inserted into the nerve is approximately 350 micrometers. Their overall thickness is approximately 22 micrometers.
The electrode are made of platinum, iridium oxide (IrO2) on a polyimide substract with a thickness of 80µ that guaranties flexibility and isolation, each electrode can handle a charge of 120nC, one interface has 16 active sites in contact with the nerve. |
Results from LifeHand
After receiving over 25 million electric impulses the electrodes were still functionally, the four electrodes did not cause any type of discomfort or irritation to the patient during the 30 days of the test. Even after their removal, the TIME implants were fully functional. The inflammation risk in this project was lower, since the impulses generated were smaller, nevertheless cuff electrodes represent a lower risk compared to TIME implants
Evolution of the project
After receiving over 25 million electric impulses the electrodes were still functionally, the four electrodes did not cause any type of discomfort or irritation to the patient during the 30 days of the test. Even after their removal, the TIME implants were fully functional. The inflammation risk in this project was lower, since the impulses generated were smaller, nevertheless cuff electrodes represent a lower risk compared to TIME implants
Evolution of the project
Further details can be accessed on the following link LifeHand 2.
Project from the Case Western Reserve University and DARPA
Project from the Case Western Reserve University and DARPA
The Case Western Reserve University and the Defense Advanced Research Projects Agency (DARPA) are conducting experiments that also use artificial feedback in upper limb prosthesis, two patients were able to feel complex textures and control grasping force.
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A total of 24 electrodes were used to deliver electrical signals to the nerve fibers, the approach was different from the penetrating electrodes that represent a higher risk. The sheath-penetrating interfaces of TIME implants offer higher resolution, but with a potentially higher risk of signal degradation or nerve damage over the long term, for this reason cuff electrodes were used. For each nerve (ulnar, radial and median) 8 electrodes were used, according to professor Dustin Tyler in the initial phase a basic pulsed train was applied in the patient, but the sensation resembles as paresthesia (limb "falling asleep"), a slightly variation in the stimulus amplitude on the neural code permitted to activate some axons adjusting the sensations.
Note: A paper about Nerve stimulation threshold and selectivity using multi-contact nerve Cuff electrodes is "mentioned" on the report "Artificial sensory feedback" - José Dias |
Results
The stimulation trials applied in the two patients made them virtually pain-free from phantom pain. The cuff electrodes used in this project were very reliable and a good interface for the peripheral nervous system, compared to penetrating electrodes, the trials last almost 2 years. One patient was able to pop out multiple cherry steams without crushing the cherry.
For more information consult the RE-NET program from DARPA.
The stimulation trials applied in the two patients made them virtually pain-free from phantom pain. The cuff electrodes used in this project were very reliable and a good interface for the peripheral nervous system, compared to penetrating electrodes, the trials last almost 2 years. One patient was able to pop out multiple cherry steams without crushing the cherry.
For more information consult the RE-NET program from DARPA.
Reference:
- “Human Nerve Stimulation Thresholds and Selectivity Using a Multi-contact Nerve Cuff Electrode”IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING, VOL. 15, NO. 1, MARCH 2007 - Katharine H. Polasek, Student Member, IEEE, Harry A. Hoyen, Michael W. Keith, and Dustin J. Tyler, Member, IEEE.