652 publications from this institution
Blossman-Myer and Burggren (Comp. Biochem. Phys. A, 155, 2010,259-263) found that the cocoon of the silkworm, Bombyx mori , while creating a tough barrier offering mechanical protection to the pupa, imposes no barrier to the diffusion of oxygen or water vapor. In view of its mechanical properties, silk cocoon is an "emperor's new clothes" for pupa. A theoretical analysis is given to explain the fascinating phenomenon by a fractal hydrodynamic model for discontinuous membrane composed of hierarchical silk cascade. The model reveals that when the fractal dimensions of the microstructure of the cocoon meet a special condition, air and water vapor can flow through the cocoon as if there were no cocoon. However, at extremes of weather, the cocoon is an excellent thermal protection for both high and cool temperatures. A better understanding of the cocoon mechanism could help the further design of bio-mimetic artificial clothes for special applications.
Adsorption of fine particles in air by a leaf is studied experimentally. It is found that each leaf can absorb only a kind of particles with almost same size, and it also exhibits high selectivity over other particles. The SEM study reveals that the size of nanopore on the epidermis is a main factor of the highly selective adsorption; the smaller nanopores can absorb larger nanoparticles in air. The morphology of a lotus leaf, which is waterproof and dustproof, has, on the other hand, many short nanofibrils instead of nanopores. It is concluded that the nanoscale geometrical structure of a surface affects its attraction/repulsion property. The experiment also shows that one square millimeter surface with nanopores in diameter of 18 nm can absorb 2 million nanoparticles of about 200 nm in diameter from air in 24 hours. A better understanding of the adsorption/repulsion mechanism could help the further design of bio-mimetic waterproof/dustproof artificial materials and artificial porous materials/fabrics/nonwovens for adsorption of nanoparticles in air.
