Functional solid-state photonic droplets with interpenetrating polymer network and their applications to biosensors

초록

Complete solid-state cholesteric liquid crystal (CLCsolid) balls with an semi interpenetrating polymer network (IPN) structure (CLCsolid-IPN) were fabricated using uniformly sized CLCsolid balls intertwined with poly(acrylic acid) (PAA). The CLCsolid balls were produced from a reactive mesogen mixed with a nonreactive chiral dopant using a microfluidic device after ultraviolet curing and dopant extraction. The CLCsolid-IPN balls were prepared by allowing AA monomers to infiltrate the space remaining after dopant removal. The CLCsolid balls could be applied to a small strain sensor because they exhibited excellent elastic properties which led to the reflected color change with the magnitude of the blueshift proportional to the applied strain. The CLC(solid-IPN )balls showed pH responsive color change, which property could be applied to a small pH sensor. The urease-immobilized CLCsolid-IPN (CLCsolid-IPN-urease) balls could be applied to a small urea sensor after urease immobilization. The enzymatic reaction with urea redshifted the reflected color of the CLCsolid-IPN-urease balls because the increase in local pH induced by the enzymatic reaction led to swelling of the intertwined PAA. The highly swollen KOH-treated CLCsolid-IPN (CLCsolid-IPN-KOH) balls were used to sense divalent metal ions. The replacement of K+ ions with divalent metal ions (M) led to a blueshift in the reflected color due to the bridged -COO-M-COO- structure. Thus, the proposed photonic CLCsolid-IPN balls, which are not affected by the viewing angle, represent a potential new sensor platform that can offer simple functionalization, requires only small test samples and does not need sophisticated analytical instruments.

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