Fifteen million people worldwide live with spinal cord injuries that limit their daily functioning, but technology is opening up new avenues to independence.
A team of engineers from the University of Berkeley has developed a device that could radically change the lives of those who have suffered spinal injuriesIt is called Back Grasper and uses robotic fingers positioned on the back of the hand to restore the ability to grasp large, heavy objects.
A new perspective on spinal cord injuries
Spinal cord injuries between the cervical levels of C5 and C7 can have a devastating impact on the mobility sectors of the upper limbs. The loss of the ability to voluntarily flex the fingers and wrist makes it particularly difficult to grasp large or heavy objects. The engineers of the research group Embodied Dexterity they decided to face this challenge with a completely innovative approach.
Their device does not attempt to replicate the natural grip of the hand, but instead uses a completely new way of interacting with objects. This design choice has proven to be particularly effective, as demonstrated in a study recently published in the magazine IEEE Transactions on Neural Systems and Rehabilitation Engineering.
The key to success lies in the device's ability to exploit the residual functionality of patients with spinal cord injuries, particularly wrist extension, which often remains intact.
Human-robot collaboration for effective gripping
One of the most interesting features of the Dorsal Grasper is the concept of collaborative grip. As the associate professor explains Hannah Stuart, the device has been designed to work in synergy, as mentioned, with the patient's residual capacities:
People with tetraplegia often retain the ability to extend their wrist backwards but cannot flex it forwards. We wanted to enhance this ability by allowing the grasp, but in a way that the person is an active part of the gesture.
The robotic fingers, positioned on the back of the hand, create a system that does not interfere with the residual natural movements. This approach avoids the conflicts typical of robotic devices that adapt around the patient's fingers, where a "conflictual" tension often arises between the intentions of the person and those of the robot.
Expansion of the grasping space in spinal cord injuries
The PhD student Andrew McPherson, who contributed to the development of the device, highlighted another significant advantage of the Dorsal Grasper. For people who use a wheelchair, It can be difficult to reach head-on into surfaces like counters or refrigerators to grab objects, due to the bulk of the chair legs.
The device's unique configuration allows you to grab objects virtually anywhere your arm can reach, without having to rotate your body (a movement that could compromise your balance in a wheelchair). This feature greatly expands the work space accessible to the user.
Intuitive control and quick response
The post-doctoral researcher Jungpyo Lee he emphasized how laboratory tests have demonstrated the extreme intuitiveness of the device control. The possibility of using wrist extension, a movement that patients use daily, makes the operation natural and immediate.
The person is an active partner, controlling the robotic finger and wrist extension. If the robotic finger strength is not enough to grasp a heavy object, the person can further extend the wrist and increase the grip strength.
This direct collaboration between user and device also allows for a faster response than fully robotic systems, especially when releasing objects.
The Future of the Dorsal Grasper
The team is already working on a version of the device specifically designed for home use. This new iteration will be fully autonomous, with motors and batteries integrated into the wrist. The main challenge is to make it robust enough to withstand everyday use, which is less predictable than the controlled environment of the laboratory.
The Berkeley team's approach to designing assistive devices demonstrates the importance of considering not just technical functionality, but also practical usability and social acceptability. As McPherson emphasized, the success of an assistive device depends not only on its technical effectiveness, but also on its ability to integrate naturally into the user's daily life.
