IEEE Robotics & Automation Magazine - June 2014 - 89

self-rectify when applying the wrong
amount of pressure on an object during the movement itself, due to the
communication flow between the
prosthesis and the brain, in a reaction
time of less than 100 ms
● manage, in real time, the different
levels of exerted force for the two different nerve sensory areas (index finger, thumb, and small finger) while
holding an object in the palm of the
hand (with 93% accuracy).
The experimentation also highlighted the importance of reactivating
tactile feedback to enable the patient to
use the robotic prosthesis with dexterity. On the one hand, when the artificial
circuit taking sensory information
from the prosthesis to the brain was
deactivated, the patient's dexterity
markedly diminished despite his being
able to see. On the other hand, holding
exercises with active sensory feedback
were undertaken blindfolded and in
acoustic isolation.
Starting from the demonstration of
the possibility of restoring fine motor
control capabilities in amputees by
exploiting learning processes based on
sensory feedback, it is expected that
LifeHand2 can trigger many new
research developments in the field of
robotic prostheses and robot-based
rehabilitation and assistive solutions. To
read more on the LifeHand2 experimental studies, visit www.unicampus.it/
lifehand/lifehand-2-the-project and
www.project-time.eu.
●

Figure 3. Using restored sensory feedback
for recognizing a rigid object shape.

Figure 4. A comparative view of the
shape and dimension of the robotic hand
used for the LifeHand2 experiments with
respect to the human hand.

LifeHand2, the prosthesis was fitted
onto the arm of the amputated patient,
thereby creating a more natural physical
condition than in 2008, even though the
device is still experimental.
The communication hardware
between the nerve fibers and computer
were the intraneural electrodes placed in
the patient's nerves, based on the technology known as transverse intrafascicular multichannel electrodes and designed,
made, and tested to be placed transversally to the nerve fascicles (with a minimum diameter of 220 µm, equivalent to
about three human hairs). The transversal implant onto the nerves is aimed at
establishing the largest possible amount
of contact points between the communication channels of the electrodes and the
nervous fibers to amplify the possibility
of communicating with the central nervous system. The 16 electrical contacts
(or active sites) that are incorporated in
the electrodes are made from platinum
and iridium oxide on a sublayer of polyimide, guaranteeing their isolation and
flexibility. During experimentation, the
electrodes (80 µm in diameter each)
proved to have an extremely high level
of selective activation of the nerve fiber
distributed across the length of the

nerve. This helped to generate sensations in the patient's nervous system
using much lower intensity level
impulses than with the LifeHand1 2008
experimentation.
An analysis of experimental data of
LifeHand2 provided researchers with
scientific feedback that confirmed the
possibility of restoring, to a patient
whose upper limb had been amputated,
tactile sensations and the ability to handle objects in a near-natural way. Specifically, as displayed in Figures 1-4, the
patient was quickly able to learn how to
use an anthropomorphic robotic prosthetic hand to
● combine the sensory areas to
robustly manipulate the overall palm
force
● distinguish the different consistencies
of hard, medium, and soft objects
(with more than 78.7% accuracy)
● recognize the basic shape and size of
objects, such as the cylinder of a bottle, the sphere of a baseball, and the
oval of a mandarin (88% accuracy)
● understand the location of an object
in relation to the hand, therefore
sending to the prosthesis the most
appropriate command to shape the
best grasp (97% accuracy)

References

[1] S. Raspopovic, M. Capogrosso, F. M. Petrini, M.
Bonizzato, J. Rigosa, G. D. Pino, J. Carpaneto, M.
Controzzi, T. Boretius, E. Fernandez, G. Granata, C.
M. Oddo, L. Citi, A. L. Ciancio, C. Cipriani, M. C.
Carrozza, W. Jensen, E. Guglielmelli, T. Stieglitz, P.
M. Rossini, and S. Micera, "Restoring natural sensory
feedback in real-time bidirectional hand prostheses,"
Sci. Trans. Med., vol. 6, no. 222, p. 222ra19, 2014.
[2] P. M. Rossini, S. Micera, A. Benvenuto, J. Carpaneto, G. Cavallo, L. Citi, C. Cipriani, L. Denaro,
V. Denaro, G. Di Pino, F. Ferreri, E. Guglielmelli,
K.-P. Hoffmann, S. Raspopovic, J. Rigosa, L. Rossini, M. Tombini, and P. Dario, "Double nerve
intraneural interface implant on a human amputee
for robotic hand control," Clin. Neurophysiol., vol.
121, no. 5, pp. 777-783, 2010.

june 2014

IEEE ROBOTICS & AUTOMATION MAGAZINE

http://www.unicampus.it/ http://www.project-time.eu

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