Beyond the optical and analytical performance of the sensor itself, the development of an optical detection tool in response to a pressing research or diagnostic need requires consideration of a host of additional factors. This talk will provide an overview of two photonic sensor systems developed for profiling the human immune response to COVID-19 infection and/or vaccination. One, focused on the design goal of high multiplexing (many targets per sensor), was built on the Arrayed Imaging Reflectometry (AIR) platform. AIR is a free-space optics technique that relies on the creation and target molecule binding-induced disruption of an antireflective coating on the surface of a silicon chip. The second method, focused on low cost and high speed, uses a small (1 x 4 mm) ring resonator photonic chip embedded in a plastic card able to provide passive transport of human samples. This “disposable photonics” platform is able to detect and quantify anti-COVID antibodies in a human sample in a minute, making it attractive for high-throughput testing applications.
Detection of antibodies to upper respiratory pathogens is critical to surveillance, assessment of the immune status of individuals, vaccine development, and basic biology. The urgent need for antibody detection tools has proven particularly acute in the COVID-19 era. Array-based tools are desirable as methods for assessing broader patterns of antigen-specific responses, as well as providing information on SARS-CoV-2 immunity in the context of pre-existing immunity to other viruses. Also, methods that rapidly and quantitatively detect antibody responses to SARS-CoV-2 antigens using small (fingerstick) quantities of blood are essential for monitoring immunity at a global scale. This talk will describe the development of two optical sensor platforms (Arrayed Imaging Reflectometry, and an integrated photonics platform fabricated at AIM Photonics) for quantifying antibodies to SARS-CoV-2 and other upper respiratory pathogens, and oriented towards the needs of multiplex detection and speed.
Point-of-Care diagnostics are instrumental to patient care and are broadly applied in the clinical setting. The simplest such device is the lateral flow assay, which is used to influence clinical decisions ranging from pregnancy to malarial infection. Lateral flow assays are ubiquitous; however, they are semi-quantitative, require labeled reagents, and are often less sensitive than comparable clinical laboratory technology. We hypothesize that an attractive method to introduce label-free quantification to Point-of-Care diagnostics is to couple them to photonic sensors. Photonic sensors are attractive as biological measurement tools, as they have low size, weight, and power requirements while providing high sensitivity. In this manuscript we describe post-processing of foundry-prepared photonic sensor chips in preparation for integration with a lateral flow format.
Ring resonators fabricated in silicon or silicon nitride constitute one of the most versatile and widely studied platform photonic technologies for biosensing. As part of an effort by AIM Photonics to advance the photonics manufacturing infrastructure of the United States, we have designed, fabricated, and tested a series of silicon nitride ring resonators for biosensing. Optimized designs will be incorporated into the AIM Photonics photonic design kit (PDK) and made available to the broader community. This talk will describe the evolution of our designs and their performance, with a particular focus on the detection of cytokines under microfluidic flow.
Cost-effective Point-of-Care (POC) diagnostics are of considerable interest to modern healthcare. Current POC devices are typically disposable, low-complexity, and qualitative, with quantitation only achievable at significant additional cost. Clinical diagnostic tools in centralized labs provide better quantitation, but are cumbersome, time-inefficient, expensive, and require trained operators. We hypothesized that Si3N4 and SU-8 photoresist ring resonators would allow for quantitative and inexpensive sensing of clinically relevant serum biomarkers. To test this hypothesis, we designed silicon nitride-based ring resonators that were then fabricated at the American Institute for Manufacturing Integrated Photonics (AIM Photonics). We also designed SU-8 polymer ring resonators, and fabricated those using in-house facilities. Single mode waveguides were designed for transverse electric and transverse magnetic polarizations at λ=1550 nm using COMSOL Multiphysics® and PhoeniX OptoDesigner. Devices were addressed by end-fire coupling and characterized by assessing spectral features including quality factor, finesse, and free spectral range. Bulk solution refractive index sensitivity was achieved using sucrose solutions. Specific interaction was shown by spiking C-Reactive Protein (CRP), an indicator of inflammatory response, into fetal bovine serum and identifying concentration dependent wavelength shift. This discussion will focus on device design, characterization, and the ability of silicon photonics to sense clinically relevant biomolecules in the label-free regime.
An effective response to human biowarfare agent exposure events requires the availability of simple, sensitive, reliable, and manufacturable sensing and diagnostic tools. While ring resonators fabricated on a silicon-on-insulator platform have found wide application as enabling components for biosensors, and have even been commercialized successfully, silicon nitride-based ring resonators have received less attention. We hypothesized that silicon nitride would provide both manufacturing and performance advantages over silicon in a biosensing context. To test that hypothesis, we designed a series of silicon nitride ring resonators. Designs were fabricated at the American Institute for Manufacturing Integrated Photonics (AIM Photonics) foundry. We will discuss the design process, optical performance of the manufactured devices, and their use in the label-free detection of biomedically relevant protein targets.
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