Green solid films with tunable mechanical properties made from deoxyribonucleic acid

Promoting green innovation to establish a worldwide low-carbon society is an urgent priority. Effective utilization of natural resources excluding fossil fuels is one of the efforts that will contribute to the resolution of this issue. Here, we show that solid-state films made from deoxyribonucleic acid (DNA) can be used as a structural material. The great advantage of the DNA films over the ones made from synthetic polymers is that the mechanical properties are controllable, from glassy to rubbery, via semicrystalline by simply regulating the water content in the film. Why and how such unique mechanical properties can be manifested by the DNA films is determined from detail structural analyses using Fourier-transform infrared spectroscopy and wide-angle X-ray diffraction measurements. With an increasing water content, the conformation of double-stranded DNA (dsDNA) was changed from the A-form in an amorphous state to the B-form in a partially packed one. dsDNA in the B-form became densely packed as the film was stretched.