CAREER: Multi-chrome metasurfaces for dynamic structural color and naked eye diagnostics

高灵敏度、快速和准确的传感器和医疗诊断对社会福祉、国民健康产生积极影响，并有助于制定具有经济后果的决策。然而，现代科学仪器和传感技术往往体积庞大、价格昂贵、速度缓慢和/或操作繁琐；在条件不利、偏远或欠发达的社区可能无法获得实验室级诊断。另一方面，比色传感器为这些问题提供了一个有希望的解决方案，因为它们可以通过数码相机或肉眼以高分辨率进行分析。然而，到目前为止，比色传感器的性能通常不如笨重/昂贵的替代品，因为它很难将小的传感器变化转换为大的颜色响应。本研究介绍并探讨了一种通过优化传感器设计，配合光源设计来解决和克服这一问题的方法。这项研究为新型高性能比色传感器打开了大门，它可能与笨重/昂贵的替代品竞争和/或提供更大的功能。结构着色面临着基本的限制，目前阻止实现由光谱性质的微小变化引起的强烈的动态色彩响应。因此，动态显色和比色传感设备目前严重依赖于利基物理/化学效应，这些效应必须放大光谱变化才能产生比色响应。建立在这种方法上的比色传感器是不可推广的，最终无法与实验室级台式设备的性能相媲美，这些设备通常体积大，速度慢，操作成本高/复杂。提出的研究提出了一种变革性和通用的技术，用于颜色转导和感知，可以克服这些挑战。本研究的最终目标是打破目前动态结构颜色设备的性能限制，并研究一类新的基于结构颜色的诊断，可通过肉眼读取，可以媲美甚至超过台式替代品的性能。该项目的目标包括：(1)为我们的高级方法“超色结构色”（HSC）建立理论框架，同时绘制和研究动态颜色转导的局限性，以及如何在响应目标刺激时最大化感知颜色变化；(2)研究多铬激光光源的超表面优化设计和定制比色轨迹；在解决集成和纳米制造挑战的同时，制造、表征和分析它们的性能；(3)实验表征了新开发的多铬超表面的比色传感性能，推动了裸眼诊断领域的发展；(4)实施一项教育计划，旨在解决已观察到的高中和本科水平的光学和光子学方面的教育差距，以努力：(a)增加本地高中生接触STEM的机会，(b)向代表性不足的群体和少数民族推广STEM和研究生水平的教育机会，以及(c)弥合光学和光电行业本科教育与工业机会之间的差距。使用多铬激光光源对动态结构颜色的研究是引人注目的，因为它从根本上提供了最高的比色灵敏度，因此没有替代方法（即宽带或单色照明）可以在响应给定的光谱扰动时主要产生更强的颜色变化。我们专注于研究多铬超表面和响应纳米材料的集成，将促进我们对以下方面的理解：多共振和微波光子系统，中低折射率超表面和生物传感器的设计和优化，如何从非常规介质中制造可扩展的芯片级光学器件，以及如何从阵列和像素化结构中定制光谱特性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

High sensitivity, fast, and accurate sensors and medical diagnostics offer positive impacts on societal well-being, national health, and aid decision making with economic consequences. However, modern scientific instrumentation and sensing technologies are often bulky, expensive, slow, and/or cumbersome to operate; and may be unavailable in disadvantaged, remote, or under-developed communities where access to laboratory grade diagnostics is sparse. Colorimetric sensors on the other hand offer a promising solution to these problems, as they can be analyzed with high resolution by digital cameras or the naked eye. However, the performance of colorimetric sensors is so far typically inferior to the bulky/expensive alternatives as it can be difficult to convert small sensor variations into a large color response. This research introduces and investigates a means to address and overcome this problem through optimization of the sensor design, coordinated with the design of the light source. This research opens the door to new types of high-performance colorimetric sensors, which may be competitive with and/or offer greater functionality than the bulky/expensive alternatives.Structural coloration faces fundamental limits which presently prevent the realization of strong dynamic color responses arising from small variations in spectral properties. As such, dynamic coloration and colorimetric sensing devices currently rely heavily on niche physical/chemical effects which must amplify spectral changes to yield their colorimetric response. Colorimetric sensors built on such approaches are not generalizable and ultimately fail to rival the performance of laboratory grade benchtop equipment which is often bulky, slow, and costly/complex to operate. The proposed research presents a transformative and general technique for color transduction and sensing which can overcome these challenges. The ultimate goal of this research is to break the present performance limits of dynamic structural color devices and to investigate a new class of structural color based diagnostics, readable by the naked eye, which can rival or even exceed the performance of benchtop alternatives. Objectives of this project include: (1) Establish the theoretical framework for our high-level approach, ‘hyperchromatic structural color’ (HSC), while mapping out and investigating the limits of dynamic color transduction and how to maximize perceived color variations in response to targeted stimuli; (2) Study the design of metasurfaces optimized for multi-chrome laser illuminants and tailored colorimetric trajectories; and fabricate, characterize, and analyze their performance while addressing integration and nanomanufacturing challenges; (3) Experimentally characterize the colorimetric sensing performance of the newly developed multi-chrome metasurfaces and advance the field of naked eye diagnostics; and (4) Implement an educational plan aimed at addressing an observed educational gap in high-school and undergraduate level optics and photonics in an effort to: (a) increase STEM exposure to local high-schoolers, (b) promote both STEM and graduate level education opportunities to underrepresented groups and minorities, and (c) bridge the gap between undergraduate education and industrial opportunities in optics and opto-electronic industries. The investigation of dynamic structural color using multi-chrome laser illuminants is compelling because it fundamentally offers access to the highest colorimetric sensitivities, and hence no alternative approach (i.e. broadband or monochromatic illumination) can principally produce stronger color variations in response to a given spectral perturbation. Our focus on studying multi-chrome metasurfaces and the integration of responsive nanomaterials will advance our understanding of: multi-resonant and moiré photonic systems, the design and optimization of moderate to low index metasurfaces and biosensors, how to nano-manufacture scalably chip-scale optics derived from unconventional media, and how to tailor spectral properties from arrays and pixelated structures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.