Holcombe Department of Electrical and Computer Engineering, Clemson University, Clemson, SC 29634.
Charles H. Townes Optical Science and Engineering Summer Research Program, Clemson University, Clemson, SC 29634.
Proc Natl Acad Sci U S A. 2020 Dec 1;117(48):30107-30117. doi: 10.1073/pnas.2009162117. Epub 2020 Nov 16.
Colorimetric sensors offer the prospect for on-demand sensing diagnostics in simple and low-cost form factors, enabling rapid spatiotemporal inspection by digital cameras or the naked eye. However, realizing strong dynamic color variations in response to small changes in sample properties has remained a considerable challenge, which is often pursued through the use of highly responsive materials under broadband illumination. In this work, we demonstrate a general colorimetric sensing technique that overcomes the performance limitations of existing chromatic and luminance-based sensing techniques. Our approach combines structural color optical filters as sensing elements alongside a multichromatic laser illuminant. We experimentally demonstrate our approach in the context of label-free biosensing and achieve ultrasensitive and perceptually enhanced chromatic color changes in response to refractive index changes and small molecule surface attachment. Using structurally enabled chromaticity variations, the human eye is able to resolve ∼0.1-nm spectral shifts with low-quality factor (e.g., Q ∼ 15) structural filters. This enables spatially resolved biosensing in large area (approximately centimeters squared) lithography-free sensing films with a naked eye limit of detection of ∼3 pg/mm, lower than industry standard sensors based on surface plasmon resonance that require spectral or angular interrogation. This work highlights the key roles played by both the choice of illuminant and design of structural color filter, and it offers a promising pathway for colorimetric devices to meet the strong demand for high-performance, rapid, and portable (or point-of-care) diagnostic sensors in applications spanning from biomedicine to environmental/structural monitoring.
比色传感器以简单且低成本的形式提供了按需传感诊断的前景，能够通过数码相机或肉眼进行快速的时空检测。然而，实现对样品性质微小变化的强烈动态颜色变化仍然是一个相当大的挑战，这通常通过在宽带照明下使用高响应材料来实现。在这项工作中，我们展示了一种通用的比色传感技术，克服了现有基于色度和亮度的传感技术的性能限制。我们的方法将结构色光学滤波器作为传感元件与多色激光光源结合使用。我们在无标记生物传感的背景下实验性地证明了我们的方法，并实现了对折射率变化和小分子表面附着的超灵敏和感知增强的色度颜色变化。利用结构赋予的色度变化，人眼能够以低品质因数（例如，Q ∼ 15）的结构滤波器分辨约 0.1nm 的光谱位移。这使得能够在大面积（约平方厘米）无光刻的传感膜中进行空间分辨生物传感，其肉眼检测限约为 3pg/mm，低于基于表面等离子体共振的行业标准传感器，后者需要光谱或角度询问。这项工作强调了光源选择和结构色滤波器设计的关键作用，并为比色器件提供了一条有前途的途径，以满足从生物医学到环境/结构监测等应用中对高性能、快速和便携式（或即时诊断）诊断传感器的强烈需求。
