Conventionally, robots have rigid metallic bodies, moving awkwardly and not so smoothly. The development of soft robots turns this popular image of robots upside down, and soft robots are now making progress at an alarming pace.
One of the pioneers of soft robotics studies, Shinichi Hirai, has explored robotic functions different from conventional robots, by actively using soft materials. He has especially focused on developing robots that can manipulate flexible materials, capable of holding soft and deformable objects. He assumes foodstuffs as objects to be held. The target is to use robots in packaging operations at food processing plants in the near future. “The number of bento [lunchboxes] sold at convenience stores each day is about two to three million sets in Japan, with all packing done manually by human hand at factories,” Hirai says, as an explanation as to why he is so devoted to this development. “On manufacturing floors, automation using robots has made substantial progress. However, robots cannot replace human workers regarding the performance of delicate tasks that require the adjustment of force for food materials of different shapes, sizes, and softness, thus not being able to finally pack such food materials. At the same time, however, in an industry where a lack of human resources is a serious issue, demand for the automatic packaging of food has certainly grown.”

The first method that Hirai came up with was holding an object by surrounding it with an elastic thread and tightening it. This is a mechanism where an elastic thread is stretched around the ends of four poles resembling fingers, with an object placed inside the enclosure. Then, the fingers are closed to tighten the thread, thereby picking up the object. Pressure-sensitive conductive threads for which the electric potential changes when an object comes close or makes contact are employed as elastic threads. He came up with a contrivance where in response to the hardness of an object, the gripping force is adjusted so that it could be picked up while keeping deformation to a minimum.

Hirai put jelly beans into a Pyrex container for subdividing food materials and lifted up the container with this binding hand without ever dropping any of the materials. To further strengthen gripping force, he developed a binding hand with dual elastic threads and successfully lifted up an egg using these elastic threads.

As an extension of binding hands using elastic threads, Hirai and Zhongkui Wang, studying under Hirai, are developing flexible fingers driven by air pressure. The gripping section made of rubber and other soft materials has a shape with bellows-like indentations on one side. When air flows inside, the joint sections inflate and bend like fingers. Three of the flexible fingers are mounted onto a pneumatic control system to pick up various objects.