A team of international researchers said that while advances have been made to make prosthetic hands and fingers look real in terms of replicating anatomical structure, skin tone, pores, and hair, they still feel artificial, and social touching for prosthetic hands has been a neglected area of research. Toward that end, the research team has demonstrated that the touch from a warm and soft rubber hand can be perceived by another person as if the touch were coming from a human hand. The results were published September 29 in the open access journal IEEE Transactions on Neural Systems and Rehabilitation Engineering.
For the hand design used in the study, the researchers took a three-step approach. First they had study participants select artificial skin samples according to their preferred warmth and softness characteristics. They then replicated the geometric features of a human subject’s hand and the softness of the hand’s skin tissue. Finally, they combined the previous results to design the artificial hands-one with embedded heat sensors and one without-for the perception experiments. For the perception experiments, participants were asked to touch a human hand, a soft and cold artificial hand, and a soft and warm artificial hand; both artificial hands were fabricated with bone structure. The study shows that the participants in the perception experiments had difficulty distinguishing touch between touch from a soft and warm artificial hand and touch from a human hand.
To touch and be touched are vital to human development, well-being, and relationships. And it can be expected that prosthetic hands will touch and be touched by others during social interactions. Thus, the researchers said that when applied to prosthetic hands, these findings have the potential to help prosthesis users cope with the functional and psychosocial effects of losing a part of their body. They also said that future work could investigate other design variables that can make social touches (e.g., a handshake or caress) from a prosthetic hand indistinguishable from a human hand and the effects of artificial fingerprint ridges on the pleasantness of touch.