**3.9 Surfaces that react to stimuli**

Tissue culture techniques have leveraged the shift in surface characteristics of thermally sensitive smart polymeric materials from hydrophilic well above threshold temperature to hydrophobic underneath it. Human cells are grown on hydrophobic solid culture plates and are normally separated from them using a protease therapy that causes the cells to be damaged. Because of the close connectivity among cells and cells, this allows for a high level of effectiveness whenever transplanted into individuals. The intensity of each molecule's reaction to variations in stimuli is a combination of single monomer unit modifications that are weak on their own, and these modest reactions combine to generate a force that drives biochemical mechanisms. Likewise, the chromatographic matrix has been modified using surfaces with thermally responsive hydrophobic/hydrophilic qualities. For protein-rich selectivity with minimal non-specific couplings, thermally responsive size-exclusion chromatography is utilized. Smart polymeric mats are distinguished by their non-linear behavior [88, 89]. A minor stimulus can cause a substantial change in structure and characteristics (**Table 2**). Once that shift happens, the polymer exhibits a predictable all-or-nothing reaction with full homogeneity throughout [96].
