The first one magnetically controlled robotic hand it’s a prosthesis latest generation. It is capable of reproducing the residual movements of the wearer’s forearm, so that he can carry out small daily actions and more. After years of research at the Sant’Anna of Pisathe prosthesis It was tested for 6 weeks by Daniel, a 34 year old boy.
The results are promising. The prosthesis allows the user to perform “simple” tasks such as open a jar or close a zip, but also to perform actions that require more precision such as using a screwdriver or a knife. All this without cables or electrical connection, because this new type of prosthesis exploits the control of the muscles using magnets and a algorithm.
How the new magnetically controlled robotic hand works
The device was developed by a group of Italian researchers from BioRobotics of Sant’Anna in Pisa. The study was developed within the project Myki funded by the European Commission and coordinated by Professor Christian Cipriani.
The idea comes from the fact that there are 20 muscles in the forearm and many of these control the hand. Often people with an amputated arm can feel the sensation that the hand is still in their place because there are some in the forearm residual muscles that move in response to the command that comes from the brain. So the movement signal can reach the end of the limb, interrupting itself. So there are some residues of movement that can be translated into signals to move the hand.
The idea that guided the project was to exploit these movements and translate them into signals for the prosthesis. This can be done by combining small magnets to the various muscles that remain in the amputated arm, implanting them with surgery.
In this way it is possible to map the position of the magnets thanks to their magnetic field natural, which allows them to be tracked in space. When the muscle contracts, the magnet moves and the algorithm detects the change and generates a corresponding movement on the robotic hand. Then the residual movements of the arm are mapped and translated into signals sent to the prosthesis. Then, to improve the connection between the arm and the prosthesis, the researchers also created a carbon fiber structure custom-made for Daniel, the patient who started the experiment. The prosthesis was created starting from the cast of Daniel’s arm and contains the electronic system which localizes the movement of the magnets.
The muscle contracts, the magnet moves, the algorithm detects the movement, translates it and sends the signal to the actual hand which moves the fingers as if the movement of the muscles could actually reach them.
This control system is called myokineticthat is, relating to the movement of the muscles. The great result of the researchers in Pisa is that of having associated different magnets to the different muscles of the forearm, in order to obtain very diversified movements of the prosthesis.
The research team developed both the hardware and software for this project. The prosthesis used for the hand is called My Hand It was developed by the startup Prensilia. This prosthesis is among the winners of the Compasso d’Oro 2022the Italian industrial design award, and was already awarded the Red Dot Design Award in 2019.
With its 5 grips, Mia Hand can perform 7 of the 10 main gestures used in 80% of daily movements and is also the fastest upper limb prosthesis on the market.
Magnetic prosthesis testing on the first patient
Myokinetic control was studied for 7 years before the experimentation. After several scientific publications, in 2023 the time came to test the robotic hand. The person testing this magnetic hand was Daniel, a volunteer, who underwent surgery during which he was implanted with 6 magnets in the forearm. For each magnet it was necessary to locate and isolate a muscle, to implant the magnet corresponding to the desired movement.
The magnets were covered with biocompatible material to be inserted into the human body. Because of the magnetic material, the surgery was performed with plastic instruments. An ultrasound scan then ensured that the magnets were in the right place. After a few weeks of rest, the wounds healed and Daniel was ready to try on the prosthesis.
The test was a success. Daniel was able to control the movements of his fingers and perform simple actions such as picking up and moving objects. The results also seem promising for the dosage of force. Daniel was able to pick up a coin, pour water. All this through an instinctive movement, which actually comes from his own arm.
The trial has provided important guidelines for future studies. First, optimal candidates should have a recent amputation, trained and non-atrophied muscles, without fibrosis or denervated areas, so that the residual muscles move well. Another aspect that can be improved is the positioning of the magnets in the muscles, which moved a few millimeters during the 6-week test. This is affected by some aspects that need to be better considered, such as the movement of the elbow muscles that also influence those of the forearm. Other research will concern a way to optimize the reception of the magnetic field and translate the signals better.
In any case, the results are very promising and the research team is already hopeful of extending the research to a wider range of amputations.
