On the occasion of OTWorld 2020, the largest trade fair dedicated to prosthetics, we officially presented the new version of Adam’s Hand, the World First Fully-Adaptive Bionic Hand together with its accessories: ThunderCell Battery power system, EMG Wave Electrodes, MyoUnit , DemoUnit and MyoLogic App.
Adam’s Hand is a myoelectric prosthetic hand that uses a single motor to move all the fingers, making them automatically adapt to grasped objects’ shape and size. The innovation is that, unlike the other bionic devices available on the market, the users will no longer have to perform difficult co-contractions, double or triple pulses to choose a preset grip pattern, but they simply decide to open or close the hand, which will autonomously conform to the grasped object.
How does a myoelectric prosthesis work?
Any myoelectric prosthesis consists of four basic components:
- the terminal device (the actual “hand”)
- the EMG sensors for its control
- a power system necessary for all the components
- a socket, tailored to the user by the orthopedic technician, which connects the previous modules to each other and to the user’s residual limb.
We often hear about prostheses “controlled by thought”, when speaking of myoelectric prostheses. But is this statement correct?
Before operating a myoelectric prosthesis, it is necessary to “think”, that means to have the intention to make a movement. However, thinking is not enough: it is essential that the intention is translated into a muscle contraction.
Indeed, the myoelectric prostheses work by exploiting the surface electromyographic signal (EMG), deriving from the electrical activity of muscle fibers. At this point the question is: how is the EMG signal translated into a command that can be performed by the prosthesis?
The first step is to detect the signal thanks to the surface electrodes, that are non-invasive electrodes, positioned on the user’s skin. In particular, in the case of upper-limb prostheses, the electrodes are inside the prosthetic socket, in contact with the residual muscles of the arm or the forearm.
In this way, when the user performs a muscle contraction, the corresponding EMG signal is first recorded and, after an initial processing, transmitted to the electronic board integrated in the prosthesis. At this point, thanks to a calibration procedure, the contraction performed by the user is associated with a command to be performed by the prosthesis (for example: fingers’ opening or closing).
Adam’s Hand: the importance of user and orthopedic technicians’ experiences
To define the new design of Adam’s Hand and its specific characteristics, our Team have conducted several in-depth analyses, carrying out interviews and directly asking users what they are looking for in a prosthesis, as well as listening to the opinion of orthopedic clinics, which know user’s needs and are therefore valuable collaborators to develop a prosthesis with the best characteristics.
During the studies conducted, we have constantly involved our interlocutors, placing them at the center of the process of designing, developing and improving of the Adam’s Hand, a device that is the result of upper limb amputees’ needs.
This investigation has led, today, to obtain a prosthesis that stands out from all the currently available devices.
Adam’s Hand: the innovation at the basis of our technology
The Adam’s Hand technology leverages the concept of underactuation, for which a single degree of actuation – which in our case is a high-power density DC motor – can lead to the actuation of several degrees of freedom.
In this way, all the fingers move together, but if one of them stops because it’s blocked by the grasped object, the other fingers keep bending, until they completely envelope the object.
You can think that this actuation mode leads to a limitation in the prosthetic hand functionality. Actually, the concept behind the Adam’s Hand functioning is inspired by the human hand synergistic behaviour, for which the complexity of the human hand movements can be reduced in some fundamental combinations of finger movements – or synergies – which occur during the most common hand postures.
In particular, it has been demonstrated that just two synergies are able to reproduce nearly the 80% of the variance of the human hand postures.
It’s important to note that many bionic hands available today implement the underactuation concept within each single finger, and thus they propose an “adaptive grip”. The difference with the Adam’s Hand is that our device implements underactuation also among different fingers, from which the term “fully-adaptive” grip.
Compared to traditional bionic devices, this leads to a higher adaptability to objects’ shape and force distributions, resulting in an improved grasp robustness, above all when the grasped object moves within the hand.
With our solution, the final user is able to control the device in an extremely intuitive way and to learn really quickly how to use it, also thanks to the automatic force distribution between fingers, which leads to a highly stable grip.
This feature helps facilitate the embodiment of the device, which is no more perceived by the user as an external tool, but rather as an extension of the user’s own body, and it also helps reduce the high rejection rate generally associated with upper-limb prosthetic hand.
Adam’s Hand technical features
Compared to the beta prototype, the new version of Adam’s Hand is improved in terms of aesthetic design and it has reduced dimensions and weight, to ensure maximum comfort to the user.
In order to obtain these features, the robustness has not been overlooked and it was achieved thanks to a stainless steel core and aviation-grade aluminium finger joints.
Moreover, soft finger pads ensure increased adherence and stability during grip actions, together with a pressure sensor integrated in the thumb which implements an automatic grasp to avoid slipping of grasped objects.
The new version of the Adam’s Hand is water resistant, with an IP44 protection rate. This is an important upgrade because it makes the device protected from accidental dripping water, coming from any direction, and from the entry of solid bodies with dimensions greater than 1 mm.
Another new feature is the robust mechanism which allows for the passive abduction and adduction of the thumb, that can be locked by the user in three locked positions: neutral (45°), lateral (0°) and in opposition (90°).
Particular attention has also been given to the possibility of customizing the device, which is available in five basic colors: white, solid black, desert sand, carbon fiber and spectrum – a grey camouflage motif.
The modular design at the base of the Adam’s Hand allows for easy maintenance and repair, with fingers that can be replaced directly by orthopedic technicians, in order to speed up and optimize time and costs of routine and extraordinary maintenance of the device.
Moreover, the Adam’s Hand is compatible with the major upper-limb prosthetic systems available on the market (EMG electrodes, battery systems, wrist prono-supinators and elbow modules) thanks to the integrated Quick Disconnect Wrist.
Together with the hardware of the device, the software was also optimized: the machine learning algorithm integrated in the Adam’s Hand was in fact improved along with the development of “MyoLogic Pro“, the App dedicated to the Orthopedic Technicians, with the aim of guiding them through the fast configuration and calibration of the Adam’s Hand.
Besides the Adam’s Hand, our Team has also developed the new EMG “Wave Electrodes” and the “ThunderCell Battery” power system, that allow to optimize the prosthesis functioning, as you can discover soon in the next articles of our blog!
If you want to discover now the technical features of the Adam’s Hand, visit our website and download the brochures and the content dedicated to our new products!