A shape-memory chitosan scaffold (CSS) fabricated by an ice-templated method can be used as a versatile host matrix for self-assembly of a wide range of functional nanoscale building blocks, and thus it can produce a family of functional three-dimensional (3D) macroscale assemblies, which show promising practical application potential in various fields.
Materials often exhibit very different properties when shrunk down to the nanoscale. Exciting new devices can be designed when nanoscale characteristics are brought together in synergy with macroscale materials, but bespoke production processes are often needed for each new nano-composite material. Scientists in China have developed a polymer scaffold for functional nanoparticles that can be folded and mangled but will reform into its original shape if it is placed in water.
Shu-Hong Yu and colleagues at the University
of Science and Technology of China have
developed a simple shape memory polymer
scaffold from chitosan that can be used as
a host for a wide range of different functional
nanoparticles, combining benefits from the
macro- and nanoscale.
Chitosan solution is placed in a mould and shaped by ice crystal fingers that grow and push the chitosan polymer chains into place, forming an insoluble and robust sponge-like scaffold. If the scaffold is put into a solution of nanoparticles it becomes coated as it swells and the nanoparticles bind to the scaffold via electrostatic interactions
A wide diversity of nanoparticles can be attached to the scaffold to make 3D shape memory materials with properties ranging from magnetism to antibacterial activity. Multifunctional materials can be created by adding two types of nanoparticles simultaneously. And no matter how many times the scaffolds are compressed and folded, if you place them in water, they will revert to their original shape.
Shu-Hong Yu says that the universal, straightforward, low cost and scalable nature of this approach shows its versatility in its ability to retain the function of a diverse range of nanoparticles in the 3D material which will have uses in a wide range of devices. Yu’s team are now working towards incorporating nanomaterials, such as graphene sheets and nanowires, into their scaffolds to fabricate more sophisticated nanocomposites.