Optical Detection of Polyacrylamide Swelling Behavior in a Porous Silicon Sensor

2008 ◽  
Vol 1133 ◽  
Author(s):  
Lisa M. Bonanno ◽  
Lisa A. DeLouise
Keyword(s):  
Refractive Index ◽  
Porous Silicon ◽  
Optical Response ◽  
Crosslinking Density ◽  
Detection Sensitivity ◽  
Cross Linking ◽  
Volume Sensitivity ◽  
Swelling Capacity ◽  
Silicon Sensor

Abstract This work proves that a 1-D porous silicon (PSi) sensor is capable of monitoring the optical changes in a polyacrylamide (PAAm) hydrogel that correlate with swelling capacity. The PSi device was impregnated with PAAm hydrogel with varying crosslinking density and total solids. The optical response of the PSi sensor was utilized to distinguish the changes in refractive index of hydrogels with varying cross-linking densities. Refractive index values calculated by the composite hydrogel-PSi sensor response agree well (≤1% difference) with values measured using a bench-top refractometer. This work serves to build a foundation for creating a composite biochemical-responsive hydrogel-PSi sensor in which competitive binding of a target analyte would cause a reduction in hydrogel cross-linking density. Long-term goals of this work are to exploit the volume sensitivity of a PSi sensor and leverage the added optical response of the responsive hydrogel to increase target detection sensitivity in an affinity based biosensor.

scholarly journals Flow-Through Self-Standing Porous Silicon Sensor

Proceedings ◽  
2018 ◽  
Vol 4 (1) ◽  
pp. 17
Author(s):  
David Martín-Sánchez ◽  
Salvador Ponce-Alcántara ◽  
Jaime García-Rupérez
Keyword(s):  
Refractive Index ◽  
Porous Silicon ◽  
Multilayer Structure ◽  
Reflectance Spectra ◽  
Flow Through ◽  
Index Changes ◽  
Lift Off ◽  
Theoretical Simulations ◽  
Silicon Sensor ◽  
Good Agreement

A self-standing porous silicon (PS) multilayer structure detached from the substrate by the lift-off method and integrated with a microfluidic cell is presented. Experiments of refractive index changes sensing flow through open-ended pores are reported. We continuously recorded the reflectance spectra of the PS membrane each 30 s and measured the shift as different substances flowed through the structure. The experimental sensitivity values are in good agreement with the theoretical simulations performed.

scholarly journals Speckle Noise Removal in Image-based Detection of Refractive Index Changes in Porous Silicon Microarrays

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ruyong Ren ◽  
Zhiqing Guo ◽  
Zhenhong Jia ◽  
Jie Yang ◽  
Nikola K. Kasabov ◽  
...  
Keyword(s):  
Refractive Index ◽  
Porous Silicon ◽  
Refractive Index Change ◽  
Speckle Noise ◽  
Noise Removal ◽  
Detection Sensitivity ◽  
Gray Level ◽  
Denoising Method ◽  
Index Changes ◽  
Gray Values

Abstract Based on porous silicon (PSi) microarray images, we propose a new method called the phagocytosis algorithm (PGY) for removing the influence of speckle noise on image gray values. In a theoretical analysis, speckle noise of different intensities is added to images, and a suitable denoising method is developed to restore the image gray level. This method can be used to reduce the influence of speckle noise on the gray values of PSi microarray images to improve the accuracy of detection and increase detection sensitivity. In experiments, the method is applied to detect refractive index changes in PSi microcavity images, and a good linear relationship between the gray level change and the refractive index change is obtained. In addition, the algorithm is applied to a PSi microarray image, and good results are obtained.

Long term results of accelerated corneal collagen cross-linking in pediatric keratoconus

2021 ◽  
pp. 112067212110183
Author(s):  
Yasin Cinar ◽  
Cagla Cilem Han ◽  
Alparslan Sahin ◽  
Zeba A Syed
Keyword(s):  
Visual Acuity ◽  
Corneal Thickness ◽  
University Hospital ◽  
Long Term Results ◽  
Cross Linking ◽  
Distance Visual Acuity ◽  
The Mean ◽  
Collagen Cross Linking ◽  
Corneal Collagen

Purpose: To evaluate the long term visual, refractive, and corneal tomographic outcomes of epithelium-off accelerated corneal collagen cross-linking (ACXL) in the management of pediatric keratoconus (KC). Methods: This retrospective study included patients under 18 years old with progressive KC who underwent ACXL between 2012 and 2019 at Dicle University Hospital. Complete ophthalmic examination was performed including uncorrected distance visual acuity (UDVA), best spectacle-corrected distance visual acuity (CDVA), manifest refraction, and corneal tomography. Evaluations were performed preoperatively and at 6 months intervals postoperatively. Results: Forty-nine eyes of 49 patients were included in the study. The mean age of patients at the time of ACXL was 14.2 ± 1.8 (range: 9.5–17.3) years. Mean follow up was 4.61 ± 1.90 (range: 2.0–8.1) years. The mean LogMAR UDVA improved from 0.94 ± 0.41 to 0.81 ± 0.43, 0.69 ± 0.41, and 0.67 ± 0.33 after 1, 3, and 5 years respectively ( p = 0.001). The mean LogMAR CDVA improved from 0.58 ± 0.36 to 0.46 ± 0.31, 0.34 ± 0.23, and 0.39 ± 0.27 after 1, 3, and 5 years respectively ( p = 0.015). The mean refractive cylinder improved significantly from 6.01 ± 2.07 diopters (D) to 5.46 ± 1.87, 5.38 ± 2.18, and 5.02 ± 2.31 D after 1, 3, and 5 years respectively ( p = 0.005). As compared to preoperative values, steep keratometry and maximum keratometry were not significantly different ( p = 0.805 and 0.448, respectively) following ACXL, while flat keratometry significantly improved after ACXL ( p = 0.012). Although central corneal thicknesses decreased significantly ( p = 0.029), the decrease in thinnest corneal thickness was not statistically significant ( p = 0.205). Conclusion: Epithelium-off ACXL seems to be effective for halting KC progression with long term clinical benefits in pediatric patients.

Electrical porous silicon sensor for detection of various organic molecules in liquid phase

2015 ◽  
Vol 212 (8) ◽  
pp. 1851-1857 ◽  
Author(s):  
Farid A. Harraz ◽  
Adel A. Ismail ◽  
Houcine Bouzid ◽  
Saleh A. Al-Sayari ◽  
Ali Al-Hajry ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Porous Silicon ◽  
Organic Molecules ◽  
Silicon Sensor

scholarly journals Significant photoinduced refractive index change observed in porous silicon Fabry–Pérot resonators

2000 ◽  
Vol 76 (15) ◽  
pp. 1990-1992 ◽  
Author(s):  
Morio Takahashi ◽  
Yuichi Toriumi ◽  
Takahiro Matsumoto ◽  
Yasuaki Masumoto ◽  
Nobuyoshi Koshida
Keyword(s):  
Refractive Index ◽  
Porous Silicon ◽  
Refractive Index Change ◽  
Index Change ◽  
Fabry Perot

The scattering of light. I. The optical response of a finite molecular fluid

1984 ◽  
Vol 312 (1521) ◽  
pp. 251-293 ◽  
Keyword(s):  
Refractive Index ◽  
Cross Section ◽  
Complex Refractive Index ◽  
Scattered Light ◽  
Optical Response ◽  
Scattering Cross Section ◽  
Material System ◽  
Optical Extinction ◽  
Many Body Theory ◽  
Scattering Cross

We present a classical many-body theory of the optical response of a molecular fluid. The unified treatment provides mutually consistent expressions for the dielectric constant, the refractive index, the optical extinction coefficient, and the optical scattering cross section. The theory treats a finite material system and handles all surface effects associated with transmitted and scattered light. The complex refractive index and the scattering cross section will be analysed in two future papers.

Investigation of the third-order nonlinear optical properties in porphyrin solutions in the picosecond regime

2015 ◽  
Vol 24 (03) ◽  
pp. 1550030 ◽  
Author(s):  
M. Chniti ◽  
C. Cassagne ◽  
J. L. Godet ◽  
G. Boudebs
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Time Dependence ◽  
Nonlinear Optical ◽  
Optical Response ◽  
Spectral Width ◽  
Incident Laser ◽  
Third Order ◽  
The Third ◽  
532 Nm

The D4σ-Z-scan technique is used to evaluate the sign and the magnitude of the nonlinear (NL) refractive index and the NL absorption (NLA) coefficient with a laser delivering single pulses in the picosecond regime at 355 nm, 532 nm and 1064 nm. The NL optical response of the zinc porphyrins (Pph) has been found to be significantly enhanced. The study of the NLA and refraction is performed, taking into account the time dependence and the spectral width of the incident laser. The variations of the NL coefficients as a function of the intensity and the concentration are provided and are found to be linear.

Impact of oral contraceptive use and menstrual phases on patellar tendon morphology, biochemical composition, and biomechanical properties in female athletes

2013 ◽  
Vol 114 (8) ◽  
pp. 998-1008 ◽  
Author(s):  
Mette Hansen ◽  
Christian Couppe ◽  
Christina S. E. Hansen ◽  
Dorthe Skovgaard ◽  
Vuokko Kovanen ◽  
...  
Keyword(s):  
Patellar Tendon ◽  
Female Athletes ◽  
Maximum Voluntary Contraction ◽  
Biomechanical Properties ◽  
Cross Sectional Area ◽  
Cross Linking ◽  
Sectional Area ◽  
Cross Sectional ◽  
Collagen Cross Linking

Sex differences exist with regards to ligament and tendon injuries. Lower collagen synthesis has been observed in exercising women vs. men, and in users of oral contraceptives (OC) vs. nonusers, but it is unknown if OC will influence tendon biomechanics of women undergoing regular training. Thirty female athletes (handball players, 18–30 yr) were recruited: 15 long-term users of OC (7.0 ± 0.6 yr) and 15 nonusers (>5 yr). Synchronized values of patellar tendon elongation (obtained by ultrasonography) and tendon force were sampled during ramped isometric knee extensor maximum voluntary contraction to estimate mechanical tendon properties. Furthermore, tendon cross-sectional area and length were measured from MRI images, and tendon biopsies were obtained for analysis of tendon fibril characteristics and collagen cross-linking. Overall, no difference in tendon biomechanical properties, tendon fibril characteristics, or collagen cross-linking was observed between the OC users and nonusers, or between the different phases of the menstrual cycle. In athletes, tendon cross-sectional area in the preferred jumping leg tended to be larger than that in the contralateral leg ( P = 0.09), and a greater absolute ( P = 0.01) and normalized tendon stiffness ( P = 0.02), as well as a lower strain ( P = 0.04), were observed in the jumping leg compared with the contralateral leg. The results indicate that long-term OC use or menstrual phases does not influence structure or mechanical properties of the patellar tendon in female team handball athletes.

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