To address these limitations, a new and simple strategy of
“layer-by-layer adhesion” has been proposed to construct
hydrogel-based microfluidics with accurate 3D microchannels and hybrid
materials (Figure 1B). The approach involves preparing predefined
microgrooves on the hydrogel surface using soft lithography techniques18 and bonding other hydrogels layer-by-layervia an adhesive. By sealing two or more hydrogel layers, closed
and perfusable microchannels are formed inside the chip. This approach
is simple and allows for the assembly of various materials into a single
chip, greatly improving its designability.
The choice of adhesive is critical for this new concept. Commercial
glues are unsuitable due to their fragility, toxicity and
incompatibility with the wet surfaces of hydrogels11,19. To address this issue, this paper synthesizes a
wet-surface adhesive based on the biopolymer chitosan20. To improve the solubility and stability of native
chitosan, a hydrosoluble and UV-crosslinkable chitosan methacryloyl
(CS-MA) will be prepared at physiological pH via N-acylation
reaction. Finally, the CS-MA adhesive will be used to stitch various
hydrogel layers and construct liver-on-a-chip to compare with that made
using sacrificial templates.