Pt–Pd-Embedded Silicon Microwell Arrays

Si microwell arrays containing Pt–Pd thin film were fabricated by the chemical etching of a Si substrate through a polystyrene honeycomb mask using a patterned metal catalyst. The honeycomb mask, which was formed by the utilization of binary colloidal crystals composed of large silica spheres and small polystyrene spheres, acted as a mask for metal deposition. After immersing a locally Pt–Pd-coated Si substrate into a solution containing hydrofluoric acid and hydrogen peroxide, an ordered Si microwell array with a hexagonal arrangement could be obtained by site-selective metal-assisted chemical etching. Moreover, the notable feature of this process is that an isolated circular Pt–Pd film used as a catalyst remained at the bottom of each well after chemical etching.