Unwinding a spiral of cellulose nanocrystals for stimuli responsive stretchable optics
Cellulose nanocrystals (CNCs) derived from biomass spontaneously organize into a helical arrangement, termed a chiral nematic structure. This structure mimics the organization of chitin found in the exoskeletons of arthropods, where it contributes to their remarkable mechanical strength. Here, we demonstrate a photonic sensory mechanism based on the reversible unwinding of chiral nematic CNCs embedded in an elastomer, leading the materials to display stimuli responsive stretchable optics. Vivid interference colors appear as the film is stretched and disappear when the elastomer returns to its original shape. This reversible optical effect is caused by a mechanically induced transition of the CNCs between a chiral nematic and pseudo nematic arrangement.Cellulose nanocrystals (CNCs) spontaneously organize into a helical arrangement but flexible CNC elastomer composite materials with this structure were so far not realized. Here the authors demonstrate the fabrication of a CNC based elastomer composite and its application as a photonic strain sensor.
Nature Communications