Half a century since the concept of a cyborg was introduced, digital cyborgs, enabled by the spread of wearable robotics, are the focus of much research in recent times. We introduce JIZAI ARMS, a supernumerary robotic limb system consisting of a wearable base unit with six terminals and detachable robot arms controllable by the wearer. The system was designed to enable social interaction between multiple wearers, such as an exchange of arm(s), and explore possible interactions between digital cyborgs in a cyborg society. This paper describes the JIZAI ARMS’ design process, an interdisciplinary collaboration between human augmentation researchers, product designers, a system architect, and manufacturers, to realize a technically complex system while considering the aesthetics of a digital cyborg. We also provide an autobiographical report of our first impressions of using the JIZAI ARMS and use our findings to speculate on a model of potential social interactions between digital cyborgs.

There are body-powered hooks and myoelectric prosthetic hands that trans-radial amputees can use for work. Though the body-powered hooks have good workability for complex operations, the design of the hook is unappealing and the harness is cumbersome. The myoelectric prosthetic hand has a natural appearance similar to the human hand and intuitive operability using a myoelectric control system. However, it is expensive and heavy. Because of these problems associated with prostheses for work, many amputees use cosmetic prostheses. In this paper, we report a lightweight, low-cost electric trans-radial prosthesis with three opposed fingers. A simple mechanism to control the fingers by a linear actuator contributes to its good workability, lightweight, and low-cost. An operation system using an inexpensive distance sensor allows intuitive operability equivalent to the myoelectric control system. A socket makes the prosthesis easily removable. The total weight of the hand and socket is 300 g, and both can be produced with a 3D printer. An evaluation using the Southampton Hand Assessment Procedure (SHAP) demonstrated that an amputee was able to operate abstract objects which require six types of grasps with the developed prosthesis.