Synthesis and isolation of metalloprotein on a super water-repellent umbrella-shaped pillar array with double re-entrant structure

This paper reports the generation of microdroplets on a water-repellent device equipped with an array of tiny umbrella-shaped pillar structures. The microdroplets were used for chemical synthesis, docking, and crystallization of a functional protein. The umbrella-shaped water-repellent devices were easily fabricated from SU-8 by soft micro-electromechanical systems technology, which would suit mass production. We used simulations to visually clarify how water and methanol were repelled and quantitatively determined the umbrella-shaped structure's water-repellency by measuring a microdroplet's contact angle. Pillar array devices reduce the amount of reagents used in chemical synthesis experiments and facilitate chemical analysis. Furthermore, the reaction speed in microdroplets is often faster. The synthesis of a Zn(ii) complex, which usually takes 4 h in a beaker, was completed in less than 120 s. The reaction inside the microdroplets was observed with a high-speed camera, and the products were identified by optical analysis. A metal complex and protein were docked and crystallized in microdroplets on the water-repellent device. The crystallization was observed under an optical microscope, producing beautiful single protein crystals. The metal complex and protein docking was confirmed by elemental analysis of the crystals.