Hydrogels' flexibility is similar to natural tissue. They are hydrophilic and uncharged. Their volume increases in aqueous solutions allowing analytes to easily diffuse in the swollen gel layer . Hydrogels are used extensively as scaffolds in tissue engineering and drug delivery systems. Their structure is often too weak to withstand implantation, for this reason layers might benefit from additional crosslinking. Apart from physical barrier, hydrogels can also prevent fouling through strong repulsive hydration forces of the tightly bound water layer .