Layer-by-layer (LbL) assembly is a method for the fabrication of polymer films exploiting the interactions between a pair of polymers

such as electrostatic interaction

hydrogen bonding

and covalent bonding. Since it is simple

requires no special instruments

and has a fine control of the film composition and thickness

it has found applications in the fabrication of devices

surface modification and various biomedical fields. Our efforts in this area include both fundenmental issues and biomedical applications. We first extended the LbL methods based on hydrogen bonding and covalent bonding from 2D systems to 3D systems and fabricated hollow capsules based on hydrogen bonds and covalent bonds. We proposed a general method for the fabrication of single component LbL films and capsules. Using poly(vinylpyrrolidone)/polyacrylic acid film as example

we studied the hydrogen-bonded LbL films extensively. We also first fabricated LbL films using the reversible covalent bond (i.e.

phenyl boronate ester bond) as the driving force. Based on these experiments

we recently proposed the conception of dynamic layer-by-layer assembled films. A new drug delivery method has been proposed which exploits the gradual disintegration of dynamic LbL films. We also proposed a new fast-responding optical sensing method based on stimuli-responsive hydrogel films fabricated via LbL assembly.