Bonding of Macromolecular Hydrogels Using Perturbants

This Communication describes the use of low molecular weight solutes to bond patterned macromolecular hydrogels and provides evidence that bonding occurs via reversible perturbation of the gels. The ability to form biologically relevant gels with complex microscale architectures may provide useful scaffolds for studies in cell biology and physiology and for microfluidic devices.1 One promising route to these structures is layer-by-layer stacking, a widely used technique in the microfabrication of polydimethylsi-loxane (PDMS).2 Passive adhesion between hydrogels, however, is much weaker than that between PDMS structures (most likely due to an intervening thin layer of water). Stacked gels are thus unlikely to resist stresses imparted by mechanical pumping or by cells. Recent work by Stroock and co-workers has shown that alginate gels can be irreversibly bonded by removal and reintroduc-tion of free calcium ion.3 Here, we describe a general strategy fo