Stimuli-responsive flexible membrane via co-assembling sodium alginate into assembly membranes of rod-like cellulose nanocrystals with an achiral array.

• Nanocrystals were assembled in sodium alginate to prepare flexible sensors. • The emission and mechanical properties depended on the co-assembly ratio. • The assembled membrane emitted varied light under strain and humid stimuli. Uniaxially assembling cellulose nanocrystals (CNCs) can induce strong solid-state emission based on optical inelastic scattering, whereas the CNC assembly membranes are not flexible enough for further applications. Thus, we introduced CNC into flexible sodium alginate (SA) and further controlled the assembly structure of CNC to increase the membrane toughness and maintain the emission properties. The results indicated that the stretchability increased from 0.027 % to 37 % when 33–37% when 33 % SA was introduced. The assembly achirality was controlled by tuning CNC concentration in suspension, and the co-assembly could further control the wavelength of the assembly-induced emission from 420 nm to 440 nm. Furthermore, the improved stretchability made assembly membrane an optical sensor, whose excitation wavelength blue-shifted about 30 nm under a 30 % strain. The emission of the co-assembly membrane could also respond to humidity, and this cellulose-based material should have great potential in biosensor and wearable devices. [ABSTRACT FROM AUTHOR]