Optical waveguide for common path simultaneous refractive index and broadband absorption measurements in small volumes

Goddard, N J

doi:10.1016/j.snb.2016.07.162

Cited by 10 publications

(14 citation statements)

References 19 publications

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“…The instrumentation used to test the porosity of hydrogels and performance of waveguide biosensors has been previously described. [4][5][6] Briefly, a BK7 equilateral prism (Qioptic Photonics, Denbighshire, UK) was used to couple light in and out of the hydrogel waveguide (Fig. 1).…”

Section: Instrumentationmentioning

confidence: 99%

“…Optical biosensors can also work at wavelengths where haemoglobin has low absorption, and can thus potentially be used with whole blood. One such biosensor is based on leaky waveguides (LWs) [3][4][5][6][7] or Hydrogel Optical Waveguides (HOWs). [8][9][10] In LWs, light is confined by phenomena other than total internal reflection (TIR) at either one or both of the waveguide interface(s).…”

Section: Introductionmentioning

confidence: 99%

“…The resonance angle of LWs is visualised either by depositing a metal layer or immobilising a suitable dye in the waveguide or fabricating strips of waveguides. [3][4][5][6][7] The resonance angle is determined by the effective refractive index of the waveguide, which may change as a result of binding of the analyte to bioreceptors immobilised in the waveguide, forming the biosensing mechanism.…”

Section: Introductionmentioning

confidence: 99%

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A feasibility study of a leaky waveguide aptasensor for thrombin

Alamrani

Greenway

Pamme

et al. 2019

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Section: Instrumentationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A feasibility study of a leaky waveguide aptasensor for thrombin

Alamrani

Greenway

Pamme

et al. 2019

Analyst

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“…Usually, the latter have higher sensitivities, especially when combined with optical interferometry [10]. These techniques can also be combined with absorption spectroscopy [11][12][13]. Nowadays, these methods are well established and also available in highthroughput format [8,9,[14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…The quasihomogeneous adlayer refractive index in the function of surface coverage for seven different adlayer film thicknesses. The dashed line represents the average value of the refractive index, n A θ , calculated from equation(12).…”

mentioning

confidence: 99%

Modeling of Label-Free Optical Waveguide Biosensors with Surfaces Covered Partially by Vertically Homogeneous and Inhomogeneous Films

Kovàcs

Horváth

2019

Journal of Sensors

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Optical Waveguide Lightmode Spectroscopy (OWLS) is widely applied to monitor protein adsorption, polymer self-assembly, and living cells on the surface of the sensor in a label-free manner. Typically, to determine the optogeometrical parameters of the analyte layer (adlayer), the homogeneous and isotropic thin adlayer model is used to analyze the recorded OWLS data. However, in most practical situations, the analyte layer is neither homogeneous nor isotropic. Therefore, the measurement with two waveguide modes and the applied model cannot supply enough information about the parameters of the possible adlayer inhomogeneity and anisotropy. Only the so-called quasihomogeneous adlayer refractive index, layer thickness, and surface mass can be determined. In the present work, we construct an inhomogeneous adlayer model. In our model, the adlayer covers the waveguide surface only partially and it has a given refractive index profile perpendicular to the surface of the sensor. Using analytical and numerical model calculations, the step-index and exponential refractive index profiles are investigated with varying surface coverages from 0 to 100%. The relevant equations are summarized and three typically employed waveguide sensor structures are studied in detail. We predict the errors in the calculated optogeometrical parameters of the adlayer by simulating the OWLS measurement on an assumed inhomogeneous adlayer. We found that the surface coverage has negligible influence on the calculated refractive index below film thicknesses of 5 nm; the calculated refractive index is close to the refractive index of the adlayer islands. But the determined quasihomogeneous adlayer refractive index and surface mass are always underrated; the calculated quasihomogeneous thickness is heavily influenced by the surface coverage. Depending on the refractive index profile, waveguide geometry, and surface coverage, the thickness obtained from the homogeneous and isotropic modeling can even take negative and largely overestimated values, too. Therefore, experimentally obtained unrealistic adlayer values, which were dismissed previously, might be important indicators of layer structure.

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Photofunctionalizable Hydrogel for Fabricating Volume Optical Diffractive Sensors

Pal

Labella

Goddard

2019

Macro Chemistry & Physics

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Volume amplitude gratings made of mesoporous hydrogels are beneficial for sensing, but are difficult to fabricate because they involve creating high aspect ratio features in soft materials. A novel photofunctionalizable hydrogel is reported and its suitability for fabricating grating sensors is demonstrated comprising of features with an aspect ratio of ≈3.2. To make a photofunctionalizable hydrogel with high optical quality that can be patterned using widely available light sources, a water‐soluble photoactive monomer and sensitizer are synthesized. A transmission amplitude grating is subsequently fabricated in a ≈100 µm thick photofunctionalizable hydrogel film by reaction of the free amines generated in the photoexposed regions with pH‐responsive fluorescein isothiocyanate. The volume hydrogel grating described herein is shown to be suitable for real‐time sensing of pH as an exemplar analyte. This work will have a significant impact on the fabrication of diffractive optical structures in thick films of hydrogels that are highly promising for biomolecular sensing in disease diagnosis and healthcare monitoring.

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Optical waveguide for common path simultaneous refractive index and broadband absorption measurements in small volumes

Cited by 10 publications

References 19 publications

A feasibility study of a leaky waveguide aptasensor for thrombin

A feasibility study of a leaky waveguide aptasensor for thrombin

Modeling of Label-Free Optical Waveguide Biosensors with Surfaces Covered Partially by Vertically Homogeneous and Inhomogeneous Films

Photofunctionalizable Hydrogel for Fabricating Volume Optical Diffractive Sensors

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