Abstract
In this paper, we propose a design for a 2D slab photonic crystal (PhC) virus sensor and an associated signal analysis methodology that together enable single-virus detection while rejecting false positives that occur due to non-specific interactions of serum proteins and small molecules with the sensor surface. The slab-PhC design takes advantage of both the optical and geometrical properties of its incorporated structures by physically limiting virus infiltration to only the most sensitive region of the PhC sensor, while allowing simultaneous measurement of both site-selective virus infiltration and non-specific small molecule accumulation across the device. Notably, the proposed sensor transducer is compatible with both standard semiconductor fabrication procedures and lab-on-a-chip style microfluidic delivery systems. 3D finite-difference time-domain electromagnetic field computation results are presented, the outcomes of which indicate that both specific (target) virus capture and non-specific (non-target) binding can be simultaneously measured and discerned from one another. This type of capacity for background-corrected, single-pathogen target detection would provide a new and novel advancement toward sensitive, label-free virus diagnostics.
Highlights
Referencing in optical sensors typically involves the use of parallel structures that either lack recognition elements or are not exposed to target [1], nonreactive microarray spots [2], or completely separate reference chips in some cases
Like many slab-photonic crystal (PhC) sensors that are regularly fabricated on silicon-on-insulator (SOI) substrates, the PhC sensor modeled in this analysis (Fig. 1(a)) was composed of three principle components: a triangular lattice of low-refractive index (RI) holes in a thin high-RI dielectric slab, a W1 waveguide, and a defect structure that supports a point-like localized optical resonance
A top-oxide hard-mask layer with a thickness of 0.2a covered the device-silicon layer and shared the PhC pattern of the silicon below it. This top oxide layer was included in the simulations for two reasons: first, this type of layer is commonly used as a gas-etch mask during typical fabrication processes, and second, the top oxide reduces the vertical mode asymmetry that exists in the slab-PhC due to the underlying buried oxide
Summary
Referencing in optical sensors typically involves the use of parallel structures that either lack recognition elements or are not exposed to target [1], nonreactive microarray spots [2], or completely separate reference chips in some cases. While these referencing methods control for instrument effects (optical drift, temperature changes, etc.), they often do not adequately control for sample effects. A major challenge in the development of label-free sensors is that of differentiating specific capture of the target of interest from nonspecific adsorption of other materials in the sample being analyzed.
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