Drew McPherson and Hannah Stuart present the updated Dorsal Grasper in the Embodied Dexterity Group laboratory at UC Berkeley. (Photo by Adam Lau/Berkeley Engineering)
Among the circa 15 million people worldwide who live with spinal cord injuries (SCI), many lose critical hand function, making everyday tasks like picking up a water bottle or reaching into a cupboard extraordinarily difficult. Now, a team of UC Berkeley researchers has developed a “backhand” robotic grasper that is showing promising results—enabling individuals with SCI who have cervical injuries in the C5–C7 range to grasp heavier, larger objects and do so anywhere within arm’s reach. In early tests, the new Dorsal Grasper achieved a 100% task success rate among SCI users in device-assisted modes. By contrast, they saw roughly 65% (64.7%) success when trying to grasp objects unassisted. Beyond simply restoring grip strength, the device also cuts down on awkward body compensations and could enhance users’ independence. split cord grip
“The first thing a device needs to do is not get in the way.”
Yet for the millions of people with SCI, these gains address only part of a broader challenge. Conventional mobility solutions, including wheelchairs and exoskeletons, focus mostly on walking or trunk support. Meanwhile, countless daily tasks—preparing meals, grocery shopping, or retrieving items around the house—still require functional hand and arm movement. Specifically, many people with mid-level cervical injuries (C5–C7) can extend their wrists but have difficulty flexing their fingers, limiting their ability to grasp heavier items unimanually. Understanding that specific problem illuminates why the Dorsal Grasper’s “backhand” approach may offer a new and more intuitive method.
Success rate of the grasp and release test in the SCI population. “Unassisted grasping” includes both unimanual and bimanual actions performed without the wearable device. Asterisks indicate statistical significance from paired t-tests with Bonferroni correction (*p < 0.05). From J. Lee et al., IEEE Trans. Neural Syst. Rehabil. Eng., vol. 33, pp. 22–33, 2025, doi:10.1109/TNSRE.2024.3514135.
In a study recently published in IEEE Transactions on Neural Systems and Rehabilitation Engineering, the researchers explain the development and evaluation of the Dorsal Grasper, a novel assistive device for enhancing grasping function in individuals with spinal cord injuries.
UC Berkeley’s Embodied Dexterity Group developed the Dorsal Grasper specifically for people with mid-level cervical spinal cord injuries. The design emerged from years of research into “supernumerary” robotics, focusing on lightweight wearability and real-world usability. Rather than completely taking over the hand, the Dorsal Grasper leverages existing wrist extension—an ability often preserved in C5–C7 SCI. This user-and-robot collaboration allows individuals to actively control gripping force and timing, reducing the need for complex sensor systems.
“The person is a partner, controlling the robotic finger.”
Unlike many assistive exoskeletons that wrap around or constrain the fingers, this device positions additional robotic digits on the back of the hand, providing support during grasp while leaving the natural palm and fingers unobstructed. Any residual dexterity a user has remains fully available. Moreover, users can momentarily extend their wrists more mid-grasp if they sense they need extra grip strength—highlighting active collaboration with the robotic “backhand.” To operate the Dorsal Grasper, users simply extend their wrists, which triggers the supernumerary fingers to close in a “backhand” grip. A small onboard sensor detecting wrist angle replaces the need for EMG or neural implants, streamlining setup, reducing false signals, and offering near-instantaneous adjustments in grip force or release.
The UC Berkeley–developed Dorsal Grasper assistive device supports human-robot collaborative grasping. (Image from Adam Lau/Berkeley Engineering)
In a Functional Workspace & Body Compensation Test (FWBCT), participants with SCI achieved a perfect success rate when using the Dorsal Grasper—surpassing the 64.7% success observed without assistance. During testing, individuals with C5–C7 SCI overwhelmingly preferred using the Dorsal Grasper over unassisted methods. They cited greater confidence in handling heavier objects, noting that tasks like lifting items from shelves or reaching into cupboards became far more manageable.
“We’ve realized that even though someone has tetraplegia, they might still retain a lot of dexterity and ability,” said Hannah Stuart in the official UC Berkeley press release announcing the device. “And we’ve grown an appreciation for the abilities that a person has in the absence of the device that we’re introducing. Our testing allows us to then see if the introduction of the device might negatively impact them or add new abilities.”
“If you can do the task without the device, and now it’s even harder… there’s no reason to put the effort in to use the device.”
Despite the overall improvements, the researchers also observed that simply wearing the device (without powering or using it) could reduce unassisted tenodesis success in some users—from 41.7% to 12.5% in one case—largely owing to the added weight of the 370g system (compare this to a typical roughly 170g smartphone). But for larger or heavier objects, participants found the backhand support invaluable.
Overall comfort scored around 4 out of 5, thanks to a soft forearm brace and a back-of-hand design that leaves natural finger motion unobstructed. Notably, placing the device dorsally avoids interference with finger contractures common in chronic SCI. A few participants felt the device was slightly heavy or that the supernumerary fingers could be shortened, but those concerns were outweighed by the added functionality and independence.
Participants found that joystick control modes offered a stronger grip for heavier objects, though it requires using the contralateral hand to drive the joystick. Meanwhile, the wrist-angle control mode provided a more seamless, intuitive experience for lighter tasks and freed both hands for other actions—particularly helpful for wheelchair users who may need to stabilize themselves during object retrieval.
While these findings are promising, the team emphasizes that much of the current data comes from controlled lab-based testing with standardized objects. Real-world tasks—such as reaching for items on high shelves or manipulating objects of varying fragility—pose new challenges. Future trials in home environments are planned to see how the Dorsal Grasper holds up under everyday conditions and whether it needs further tweaks in weight, sensor integration, or sizing.
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