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Prosthetic Hand Hannes Mimics Key Biological Properties of Human Hand

The biomimetic prosthetic hand Hannes is featured on Science Robotics' cover today; in the current issue researchers from Istituto Italiano di Tecnologia (IIT- Italian Institute of Technology) and Centro Protesi INAIL (the prosthetic unit of the National Institute for Insurance against Accidents at Work) in Italy reported about its ability to replicate the key biological properties of the human hand: natural synergistic and adaptable movement; biomimetic levels of force and speed; high anthropomorphism and grasp robustness.

Developed involving researchers, orthopaedists, industrial designers together with patients, Hannes is able to restore over 90% of functionality to people with upper-limb amputations. It owns CE marking and it is ready to enter the international medical market, but its future commercialization will be possible only when researchers will identify investors and industrial partners.

The robotic system Hannes was born out of the IIT's Rehab Technologies Lab, that is the joint-lab between Istituto Italiano di Tecnologia in Genova and Centro Protesi INAIL in Budrio (Bologna), coordinated by Lorenzo De Michieli; the collaboration started at the end of 2013 with the aim of creating innovative high-tech cost-effective solutions for patients with physical impairment.

Among the solutions developed so far, Hannes is the most recent result, whose name is a tribute to Professor Johannes "Hannes" Schmidl, technical director of the Centro Protesi Inail in the 1960s and pioneer in upper limb prosthetics. On September 9th 2020, the hand Hannes was awarded the international industrial design prize Compasso d'Oro, due to its original and highly innovative concept.

Hannes is an anthropomorphic, poly-articulated upper limb prosthetic system including hand and wrist, whose main characteristics are the softness and the ability to dynamically adapt themselves to the shape of objects to grasp. It is uniquely similar to a human hand and, being developed directly with patients, it is of practical use. To evaluate the effectiveness and usability of Hannes, pilot trials on amputees were performed at Centro Protesi Inail and researchers found that, after a training period of less than one week, patients could autonomously use Hannes domestically to perform activities of daily living.

The prosthesis is a myoelectric system that can be worn all day long and adjustable to different upper limb impairments. Therefore, an array of surface electromyographic sensors, placed within a custom socket, detects the activity of the residual limb muscles - in the lower or higher part of the arm, which are actively contracted by the user to perform multiple movements. Moreover, through a specially developed software and a bluetooth connection, it is possible to customize the operating parameters of the hand, such as the precision and speed of movements, to ensure the most optimized experience for each user.

Hannes hand has been tested for durability and robustness in a setting that simulated more than 1 year of usage of a so called "pro-user" (almost 500000 life cycles).

The true intelligence of Hannes lies in the mechanical design, which is completely unique in its market sector, and it gives to the prosthesis the versatility and the movement of a natural hand. The underlying mechanism of the hand is a mechanical differential system that allows Hannes to adapt to the object being grasped by using just a single motor. This also permits to dramatically enhance performance due to its efficiency, at the same time, to be coherent with the 50th percentile human hand size. Hannes is provided in two different sizes, 7 ¾ and 8 ¼, for right and left handed and suitable to female and male subjects. Its weight is 450 grams.

Fingers can flex and be positioned in a natural manner, even at rest. In particular, the thumb can be oriented in 3 different positions to replicate a wide variety of grips, including a fine grip that allows to pick up small objects, a lateral grip, which allows to grasp thin objects, and finally a power grip capable of grasping and moving even heavy loads. The overall grasp is efficient, robust against external conditions and natural. The system also permits to pronate and supinate the wrist ('key turning movement'), allowing grasps in different orientation without relying on harmful patient compensation.

Hannes can perform a full closed grasp in less than 1 second and, at the same time, it can exert a maximum grasp force of 150 N, that is well beyond other commercial and research poly articulated hands, and it has an autonomy of a whole day of standard use (battery life of 1 day: 12 V power supply for a battery capacity of 1300 mAh).

Researchers conducted experiments to validate Hannes's performance and the human-likeness of its grasping behaviour and they demonstrated an improved performance compared with existing research or commercial devices.

The fundamental principles and design of Hannes are covered by IIT-INAIL patent applications. Moreover, the prosthetic hand obtained CE marking, which is fundamental for future commercialization in the European market and a precondition for international sale. Researchers are looking for investors and companies to industrialize and produce Hannes on a large scale, benefiting patients with physical impairment.

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