What is the patent for interference scattering microscopy with photonic crystal guided resonance about?

The patent describes a method and system that uses photonic crystal guided resonance to enhance interference scattering microscopy (iSCAT). This approach improves sensitivity for label-free imaging of nanoparticles and biomolecules by leveraging resonant modes in photonic crystals to amplify scattering signals.

How does photonic crystal guided resonance improve interference scattering microscopy?

Photonic crystal guided resonance increases the local electromagnetic field intensity at the sensor surface, which enhances the scattering signal from nanoparticles. This results in higher contrast and sensitivity in iSCAT imaging, allowing detection of smaller particles or molecules compared to conventional methods.

Who owns the patent for interference scattering microscopy with photonic crystal guided resonance?

The patent is typically assigned to research institutions or companies involved in advanced microscopy, such as universities or biotech firms. Specific ownership details require checking the patent document, but it is often filed by inventors from institutions like the University of Cambridge or MIT.

What are the key applications of this patented technology?

Key applications include label-free single-molecule imaging, nanoparticle tracking, and biosensing. It is particularly useful for studying dynamic biological processes, such as protein interactions or virus detection, with high spatial and temporal resolution.

How does this patent differ from standard iSCAT patents?

This patent integrates photonic crystal guided resonance into iSCAT, which is a departure from standard iSCAT that relies on simple interference from a reference beam. The resonance enhances the signal-to-noise ratio, enabling detection of smaller scatterers and reducing the need for complex optical setups.

Interference Scattering Microscopy Photonic Crystal Guided

Interference scattering microscopy (iSCAT) is a label-free optical technique that detects single nanoparticles and proteins by measuring the light they scatter. A photonic crystal guided resonance (PC-GR) structure can amplify this scattering signal, making detection more sensitive. The core idea behind an interference scattering microscopy photonic crystal guided resonance patent is to combine these two technologies: using a photonic crystal slab to create a sharp resonance that enhances the local electric field, which in turn boosts the scattered signal from a nanoparticle bound to the surface. This patent space covers the specific designs, materials, and methods that make this combination work for biosensing and single-molecule detection.

How Interference Scattering Microscopy Works

Interference scattering microscopy measures the weak scattered light from a nanoscale object by mixing it with a reference beam. In a typical iSCAT setup, a laser beam is split into two paths. One path illuminates the sample, and the light scattered by the particle is collected. The other path serves as a reference, often reflected from a glass coverslip. The two beams are recombined on a camera, where they interfere. The resulting signal is proportional to the product of the scattered and reference fields, which amplifies the tiny scattered signal above the background noise.

This technique allows researchers to detect particles as small as single proteins, gold nanoparticles, and viruses in real time. The main limitation is that the signal strength depends on the particle’s polarizability and the local intensity of the illuminating field. For very small molecules or weakly scattering objects, the signal can drop below the detection threshold. This is where photonic crystal structures become useful.

Photonic Crystal Guided Resonances

A photonic crystal is a periodic structure of materials with different refractive indices. When designed correctly, it can support guided resonances — modes that are trapped in the crystal plane but can leak out as radiation. These resonances appear as sharp features in the reflection or transmission spectrum of the crystal. At the resonance wavelength, the electric field inside and near the crystal surface is strongly enhanced.

The quality factor (Q-factor) of a guided resonance determines how narrow the resonance is and how strong the field enhancement becomes. A higher Q-factor means a sharper resonance and stronger field confinement. Typical photonic crystal slabs can achieve Q-factors ranging from a few hundred to tens of thousands, depending on the design. The field enhancement at the surface can be ten to a hundred times greater than the incident field.

This field enhancement is the key property that makes photonic crystals attractive for sensing. When a nanoparticle binds to the surface of the photonic crystal, it interacts with this enhanced field, producing a larger scattered signal. The combination with iSCAT then allows this signal to be read out with high sensitivity.

The Patent Landscape for iSCAT and Photonic Crystals

Patents in this area typically cover the integration of an iSCAT detection system with a photonic crystal sensor chip. The United States Patent and Trademark Office (USPTO) and other international patent offices have granted several patents that describe apparatus and methods for using photonic crystal surfaces in label-free imaging. A search on Google Patents for terms like “interference scattering” and “photonic crystal” returns a focused set of filings, mostly from research institutions and biotechnology companies.

The claims in these patents usually focus on three aspects: the structure of the photonic crystal, the optical setup for interference detection, and the method of using the combination for specific assays. For example, a patent might claim a photonic crystal slab with a periodic array of holes, designed to support a guided resonance at a specific wavelength, combined with an iSCAT microscope that illuminates the slab and detects scattered light from particles bound to the surface.

One key patent describes a method where the photonic crystal is used as a substrate for a biosensor. The crystal is illuminated at the resonance wavelength, and the iSCAT signal from bound nanoparticles is measured. The enhanced field from the resonance increases the signal-to-noise ratio, allowing detection of smaller particles or lower concentrations.

Key Design Parameters in the Patents

The patents specify several design parameters that affect performance. The period of the photonic crystal lattice is typically in the range of 400 to 800 nanometers, chosen to place the guided resonance in the visible or near-infrared spectrum. The thickness of the photonic crystal slab is usually between 100 and 500 nanometers. Common materials include silicon nitride, titanium dioxide, and silicon dioxide, chosen for their low optical absorption and high refractive index contrast.

The Q-factor of the resonance is a critical parameter. Patents often claim Q-factors above 500, and sometimes above 5,000, to achieve sufficient field enhancement. The resonance must also be spectrally aligned with the laser wavelength used in the iSCAT system. Some patents describe tuning methods, such as adjusting the angle of incidence or using a temperature-controlled stage, to match the resonance to the laser.

Another design parameter is the surface chemistry. The photonic crystal surface must be functionalized to capture specific biomolecules. Patents describe methods for attaching antibodies, DNA probes, or other capture agents to the surface, often using silane chemistry or biotin-streptavidin binding. The combination of the photonic crystal’s optical properties and the surface chemistry enables specific detection of target analytes.

Applications and Use Cases

The primary application of this patented technology is in biosensing and single-molecule detection. Researchers have used iSCAT with photonic crystals to detect single proteins, such as antibodies and enzymes, without fluorescent labels. This is valuable for studying protein interactions, binding kinetics, and conformational changes at the single-molecule level.

Another application is in virus detection. The enhanced sensitivity allows detection of individual virus particles, which is useful for early diagnosis of infections. The label-free nature of the technique means samples do not need to be prepared with dyes or tags, simplifying the workflow.

The technology also has potential in drug discovery. By measuring the binding of small molecules to immobilized targets, researchers can screen candidate drugs without the need for radioactive or fluorescent labels. The real-time nature of iSCAT allows measurement of association and dissociation rates, providing kinetic data that is useful for lead optimization.

Limitations and Considerations

While the combination of iSCAT and photonic crystals offers high sensitivity, there are practical limitations. The photonic crystal must be fabricated with high precision, which requires cleanroom facilities and advanced lithography. This increases the cost of the sensor chips compared to simple glass coverslips.

The resonance wavelength is sensitive to temperature and to the refractive index of the surrounding medium. Small changes in temperature can shift the resonance, affecting the signal. Some patents address this by including temperature control or by using a reference channel to correct for drift.

Another limitation is the binding specificity. While the photonic crystal enhances the signal from bound particles, it also enhances the signal from any non-specifically bound material. Careful surface chemistry and blocking steps are needed to minimize false positives. For medical or diagnostic applications, users should consult a professional to validate the assay performance.

Key Takeaways

Interference scattering microscopy photonic crystal guided resonance patents cover the integration of iSCAT detection with photonic crystal slabs that support guided resonances.
The photonic crystal enhances the local electric field, increasing the scattered signal from nanoparticles bound to the surface.
Patents typically claim specific structures, materials, and methods for achieving high Q-factor resonances and aligning them with the iSCAT laser.
Applications include single-protein detection, virus sensing, and label-free drug screening.
Practical limitations include fabrication cost, temperature sensitivity, and the need for specific surface chemistry to avoid non-specific binding.

Interference Scattering Microscopy Photonic Crystal Guided Resonance Patent Guide