Transferable crack-free colloidal crystals on an elastomeric matrix with surface relief

Crack-free three-dimensional (3D) colloidal silica crystals are fabricated on an elastomeric polydimethylsiloxane (PDMS) stamp via the lift-up method. A surface relief structure is fabricated on the PDMS substrate to enable the formation of colloidal crystal assemblies that cannot be achieved on a plane PDMS substrate owing to the hydrophobic nature of its surface. Four samples of uniform silica particles having different sizes are prepared for colloidal crystal assembly on PDMS substrates with various relief patterns. This strategy not only provides a means for the assembly of crack-free colloidal crystals on a soft hydrophobic surface via the lift-up method but enables the transfer of the crack-free colloidal crystals onto a curved surface. 3D Crack-free colloidal assembly onto soft hydrophobic surface via the lift-up method is demonstrated. A surface relief structure on a PDMS substrate enables the formation of colloidal crystal assemblies that cannot be achieved on a plane PDMS substrate owing to the hydrophobic nature of its surface. Different relief patterns (cylindrical, cross-shaped, and long rectangular) and different sizes of uniform silica particles from 190 to 300 nm are investigated.