Bio-Inspired Nanostructures for Enhanced Light Management

The biological surface has developed functional structures during long-term evolution, which inspires the development of biomimic materials for optical and optoelectronic applications. For example, the micropapillae and nanofolding structures of rose petals could enhance light absorption and color saturation. Here, the authors report a successful replication of rose hierarchical surface structures by simple and cost-effective processes. A variety of rose structured surfaces were investigated, which confirmed the diversity of functional surface architecture. The polydimethylsiloxane (PDMS) negative replica was formed by casting PDMS solution on top of a rose petal followed by a temperature-assisted curing process. The hierarchical structure was further transferred into photoresist films by ultraviolet nanoimprint using the PDMS replica as molds. The imprinted photoresist films demonstrated uniform replications of rose microconvex cells with nanofolding details in the scale of a square centimeter. Super-hydrophobicity was demonstrated on both PDMS negative replica and photoresist positive replica. The incorporation of photoresist replica on the surface of photodetectors improved the responsivity by 35% to 42% due to enhanced light management effect. This bio-inspired transfer imprint process with PDMS provided a high-fidelity and cost-effective method to reproduce functional structures from biological surfaces. This study also demonstrated the potential of utilizing rose structures in photovoltaic and optoelectronic applications.