The deformation and mechanical properties of hybrids formulated from thiol-ene PDMS and thiol-ene hydrogel based on PDMAEMA-Pent were investigated first (Figure ). The samples tested displayed relatively linear tensile deformation profiles up to fracture, with relatively low elongations at break. The modulus clearly varied based on the initial polymer concentration used to formulate the gel, with a nearly 4-fold increase when the polymer concentration doubled. In all cases, within the range of formulations tested, fracture of the hybrid samples was observed in the bulk of the hydrogel phase, indicating relatively strong adhesion sustained by thiol-ene bonding between the two phases. Similarly, hybrids generated between thiol-ene PDMS and PEGDA hydrogels displayed apparent moduli that increased gradually as a function of monomer concentration, in the range of 70-550 kPa, over the range of formulations tested (Figure ). Hybrid samples generated from thiol-ene PDMS and CMC-Allyl hydrogels displayed significantly weaker mechanical properties (Supplementary Figure ). Not surprisingly, as relatively low polymer concentrations were used for the formulation of the hydrogel, the apparent Young's modulus of corresponding hybrids was significantly lower (2.4 and 24 kPa for hydrogels formulated from 20 and 50 mg/mL CMC-Allyl, respectively; Figure ). However, CMC-Allyl based hybrids displayed higher elongations at break, perhaps as a result of the higher molecular weight of the base polymer selected as backbone, compared to PDMAEMA-Pent (250 kDa for the former compared to 68 kDa for the latter), and its reduced crosslinking density. The sharper increase in apparent modulus observed for these samples is also in good agreement with the evolution of shear moduli typically reported for these materials . This is presumably the result of more pronounced network defects generated at lower concentrations, associated with faster kinetics of cyclisation and loop formation . However, interestingly, CMC-Allyl based hybrids displayed adhesive failure profiles that contrasted with the cohesive failure observed for PDMAEMA-Pent based samples (Supplementary Figure ). This was also associated with a more gradual fracture, resulting in seesaw profiles as hydrogels domains remained adhered to the elastomer surface and elongated prior to further fracture (Supplementary Figure ).