A sessile droplet array of 4’-pentyl-biphenyl-4-carboxylic acid (PBA) doped 5CB sessile droplets (12 −104 µm) is prepared by inkjet printing and applied for label-free sensing of penicillin G according to the configuration transition from axial to windmill based on the molecular alignment of 5CB at the LC-aqueous interface. Selective determination of penicillin G is achieved according to the target-selective enzymatic hydrolysis catalyzed by penicillinase, exhibiting sensitive detection and fast response with a detection limit of 0.178 ng/mL within 3–5 min. The sensitivity is linear depending on LC droplet size. Under the optimized conditions, the linear detection range is 1.78–178.0 ng/mL. Such a droplet array sensor has also been successfully applied to determine penicillin G in real river and lake water samples with RSD of 102–119%. Such a platform possesses the advantages of simple and cheap construction of an ordered array for multiplex sensing, and easy characterization via a polarizer . The quantification range of this proposed label-free optical penicillin G sensor covers the maximum residue limits in raw milk and river water defined in the European Union Regulation, and thus being applicable for food and environmental monitoring. By engineering LC-based probes, this approach could be extended to sense various molecules and ions in biomedical and chemical scenarios. And the sessile droplets on polymer substrates would also bring the possibility for employing in flexible and wearable devices in the future.
Mengjia Cen,Jiawei Wang,Jianxun Liu,Huilin He,Ke Li,Wenfeng Cai,Tun Cao,Yan Jun Liu
Chiral metasurfaces can exhibit a strong circular dichroism, but it is limited by the complicated fabrication procedure and alignment errors. Here, a new type of self-aligned suspended chiral bilayer metasurface with only one-step electron beam lithography exposure is demonstrated. A significant optical chirality of 221° µm −1 can be realized using suspended metasurfaces with a thickness of 100 nm. Furthermore, this study experimentally demonstrates that such a structure is capable of label-free discrimination of the chiral molecules at zeptomole level, exhibiting a much higher sensitivity (orders of magnitude) compared to the conventional circular dichroism spectroscopy. The fundamental principles for chiral sensing using molecules–metasurfaces interactions are explored. Benefiting from the giant chiroptical response, the proposed metadevice may offer promising applications for ultrathin circular polarizers, chiral molecular detectors, and asymmetry information processing.
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