Optical and Nanomechanical Characteristics of Multilayer Structure Derived from Color-changing Beetle Popillia Indgigonacea Motsch

The architecture of multilayer acting in colorful appearance has been widely reported.In spite of this,it is interesting that dense multilayer in epicuticle for Popillia indgigonacea Motsch elytra not only helps presenting angle dependence color-changing,but also showing higher reduced modulus(Er)and hardness(H)to protect soft abdomen below.The optical and nanomechanical properties of elytron were investigated by structural observation,optical experiments,nanoindentation and coupled bionic model simulations.The peak reflectance gradually varies from 588 nm to 510 nm with color change from orange and yellow to green when the incidence angle switches from 0°to 60°,which is attributed to the regulated variation from refractive spectra between the layers in different angle.In addition,the relatively higher Er and H of elytron epicuticle and endocuticle could play a role in resisting force with its multilayer.To identify the multifunctional characteristics of multilayer,optical and mechanical simulations were conducted based on coupled bionic models,and a strong consistence between the experiments and simulations is obtained.The multilayer could resist force with lowest strain and stress,and the structural thickness is the most necessary factors that could adjust the colors in color-changing process.

Cellulose nanofiber-based pH indicator integrated with resazurin-modified carbon dots for real-time monitoring of food freshness

Modified carbon dots with resazurin(R-CD)were prepared using a hydrothermal method to fabricate a CNF-based pH-responsive indicator for real-time food freshness monitoring.FE-SEM and FTIR results confirmed that the R-CD was uniformly distributed in the CNF matrix.The thermal stability of the CNF/R-CD indicator film was increased,and the water contact angle of the film was slightly lower than that of the neat CNF film.The CNF/R-CD film showed excellent UV-barrier properties,with~98.3%and 87.7%blocking the UV-B and UV-A light.The indicator film showed excellent color stability even after 2 months of storage at 25℃ and responded rapidly to alkaline pH and NH3 through a color change from yellow to brownish-red.The CNF/R-CD indicator films exhibited distinct color changes during shrimp packaging depending on pH and TVB-N concentration.Therefore,the CNF/R-CD indicator can be used as a promising pH-sensitive color-changing intelligent packaging application for freshness monitoring.

Study on preparation,characterization and application of mixed-colorants thermochromic microcapsules

In order to expand the color-change range and make the discoloration temperature suitable for the daily textiles,a new formulation of mixed-colorants thermochromic core material is designed,in which crystal violet lactone(CVL)is the basic color former,bisphenol A(BPA)is the developer,especially the solvent-based dye and dodecyl dedecanoate are used as the extended dye and the solvent,respectively.Scanning electron microscope(SEM),differential scanning calorimeter(DSC)and thermogravimetric analyzer(TGA)were applied to study the morphology,encapsulation rate,non-isothermal crystallization behavior and thermal stability of the mixed-colorant thermochromic microcapsules(MCTMs)prepared by in-situ polymerization.The results show that MCTMs have good sphericity,uniform particle size,good thermal stability and the encapsulation rate can reach 86.73%.Under the non-isothermal conditions,the encapsulation of formaldehyde-melamine resin wall material can slightly reduce the crystallization rate of the solvent,but does not affect the relative crystallinity,thermal properties and discoloration sensitivity of the core materials.With the variety of ambient temperatures in the range of 20–35℃,the printed cotton fabrics with MCTMs could change color reversibly between different tones with good reliability and durability,and exhibit more gorgeous colors than the common thermochromic materials.