New Technology Presentation Meetings of Waseda University
Rigid device is changed to flexible device by use of art of folding paper structure

Picture 1. Flexible device using art of folding paper structure

June 6, 2019, “New Technology Presentation Meetings of Waseda University “was held in JST (Tokyo). In this here, an oral presentation of Prof. Eiji Iwase about flexible device using art of folding paper structure are picked up.

The research group has developed a flexible device by making use of art of folding paper (Miura folder) structure, which is adopted for a part of solar panel. In the conventional flexible device, soft and stretchable organic materials are used in general. On the other hand, in this new device, existing hard electronic component and low stretch metal wiring are used. For this reason, it's not necessary to newly specific materials, and also, easy to advance quality and increase functions of device.

However, there is a problem in the conventional Miura folder structure. Concretely, if its device is bended toward a certain direction, it is warped. In short, it cannot change shape completely. Therefore, a hole (space) is formed at intersection of folder. As a result, it's possible to fold and bend completely. As you image easily, if hole is large, changing level is increased. By contrast, if hole is large, practical space for device and wiring becomes to be decreased. Considering above two points, practical hole area is approximate 30 %.

Figure 1. Change of shapes of device1)

By the way, as figure 1, change of shape is divided into 3 main classes, in short, �@bending, �Astretching, �Bart of folding paper. If the substrate is thin, it's easy to be bended. And also, there is zero distortion plate (neutral plane), which is balanced between tension stress and compression stress. On the other hand, stretch change is obtained by tension stress only. By contrast, neutral plane exists in art of folding paper. For this reason, it's possible to stretch in all by local bending. Figure 2 shows device structure using these characteristics effectively. In this device, rigid devices such as LED and sensor are mounted in flat plane, on the other hand, wiring is mounted in neutral plane.

Picture 2. Pilot-produced device1)

Figure 2. Structure example of device1)

Picture 2 shows pilot-produced samples. As picture 2, devices can be enlarged greatly and easily. Furthermore, if Cu wiring sample is continuously folded and bended, its sheet resistance was not changed.

Main applications are the following；�@deforming area, for example, tire of automotive, elbow and knee of human, �Afree bending plane, for example, body of automotive and helmet, �Bfull-flexible device (it's folded in mobile time, it's expanded in using time).

Reference
1)Iwase：Bendable and stretchable flexible electric device using art of folding paper structure, New Technology Presentation Meetings of Waseda University, pp.17-19 (2019.6)
※This title is translated arbitrarily by Stella News Site because of without English edition of presentation material.