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Specialty film surface strain measurement method developed

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Published: July 14, 2014

Specialty film surface strain measurement method developed
- Bringing power to the production of wearable devices and flexible displays -

Summary

A research group including Associate Professor Atsushi Shishido and Graduate Student Norihisa Akamatsu, of the Chemical Resources Laboratory at the Tokyo Institute of Technology, Professor Jun Takeya, of the Department of Advanced Materials Science belonging to the Graduate School of Frontier Sciences at the University of Tokyo, and Associate Professor Shigenori Fujikawa, of the International Institute for Carbon-Neutral Energy Research (WPI-I2CNER) at Kyushu University, has developed a simple measurement method for surface strain on specialty films. By labeling light diffraction gratings (1) to film surfaces, they proved they could carry out simple quantitative measurement of surface strain (2) due to film bending.

Furthermore, they discovered that layered films comprised of photoresponsive films and silicon rubber display deformation behavior largely diverging from conventional solid mechanics. This shows that the mechanics of soft materials (soft mechanics) differs largely from conventional solid mechanics, which deals with hard materials, and is expected to provide impetus for the development of wearable devices and flexible displays accompanying progress in soft mechanics.

The development of wearable devices and flexible displays requires the layering of functional flexible films, but until now there had been no simple method to measure surface strain, which is the key to preventing deformation and destruction.

The results of this research appeared in the electronic version of the English scientific journal “Scientific Reports” on June 20th.

Surface expansion and contraction accompanying film bend-deformation. Even with the same film, different external stimulus results in different outer surface strain. This proved that mechanics unique to soft materials exist.
Surface expansion and contraction accompanying film bend-deformation. Even with the same film, different external stimulus results in different outer surface strain. This proved that mechanics unique to soft materials exist.

Explanation of Technical Terms

1. Grating:
A diffraction grid that diffracts light. Is formed by the periodic structure of the refractive index. Some have periodic refractive index changes on the inside, while others have periodic corrugations on the outside. Either kind of grating can be used in the surface-labelled grating method.
2. Surface strain:
A scale to express the state of deformation of a surface, defined by the ratio of displacement to length in initial state. The surface of a film expands when it is bent, causing device destruction and wear. A simple method for quantitative measurement of surface strains had been desired.

Reference

Authors:
Norihisa Akamatsu, Wataru Tashiro, Keisuke Saito, Jun-ichi Mamiya, Motoi Kinoshita, Tomiki Ikeda, Jun Takeya, Shigenori Fujikawa, Arri Priimagi, & Atsushi Shishido
Title of original paper:
Facile strain analysis of largely bending films by a surface-labelled grating method
Journal volume and pages:
Scientific Reports, 4, 5377/1-5377/6
DOI:

Further information
Atsushi Shishido
Chemical Resources Laboratory,
Tokyo Institute of Technology
TEL: 81-45-924-5242
Email: ashishid@res.titech.ac.jp

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