Formation of poly(ethylene glylcol) diacrylate (PEGDA) hydrogel precursor solutions. PEGDA was dissolved in PBS (pH7.4) at a concentration of 500 mg/mL. The stock solution of photointiator (Irgacure 2959, 100 mg/mL in ethanol) and an additional volume of PBS were added to the polymerisation mixture containing PEGDA stock to achieve final concentrations of polymer of 125, 200, 300 and 400 mg/mL, in PBS. The molar equivalent of photoinitiator that was used was 1:40 with respect to PEGDA. The UV curable mixtures were finally vortexed thoroughly before use.