Research on Holographic Sensors and Novel Photopolymers at the Centre for Industrial and Engineering Optics
29 May 2013-
TL;DR: The photopolymer materials consist of a light-sensitive film which is exposed during production to form the hologram, thereby offering versatility well beyond that of current security holograms, which are mass produced from a master using a foil stamping processes.
Abstract: The recent resurgence of interest in photopolymers for commercial holograms is a strong incentive for development of photopolymers that are as environmentally friendly as possible. Photopolymer materials consist of a light-sensitive film which is exposed during production to form the hologram, thereby offering versatility well beyond that of current security holograms, which are mass produced from a master using a foil stamping processes.
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TL;DR: An overview of recent investigations of photopolymerizable nanocomposite photonic materials in which, thanks to their high degree of material selectivity, recorded volume gratings possess high refractive index modulation amplitude and high mechanical/thermal stability at the same time, providing versatile applications in light and neutron optics.
Abstract: We present an overview of recent investigations of photopolymerizable nanocomposite photonic materials in which, thanks to their high degree of material selectivity, recorded volume gratings possess high refractive index modulation amplitude and high mechanical/thermal stability at the same time, providing versatile applications in light and neutron optics. We discuss the mechanism of grating formation in holographically exposed nanocomposite materials, based on a model of the photopolymerization-driven mutual diffusion of monomer and nanoparticles. Experimental inspection of the recorded grating’s morphology by various physicochemical and optical methods is described. We then outline the holographic recording properties of volume gratings recorded in photopolymerizable nanocomposite materials consisting of inorganic/organic nanoparticles and monomers having various photopolymerization mechanisms. Finally, we show two examples of our holographic applications, holographic digital data storage and slow-neut...
65 citations
TL;DR: In this article, the authors explored the humidity and temperature response of volume phase slanted gratings recorded in photopolymers with varied chemical composition and showed that the response of photopolymer-based holographic gratings to relative humidity (RH) and temperature (T) can be tuned by alteration of the photpolymer composition.
Abstract: This work explores the humidity and temperature response of volume phase slanted gratings recorded in photopolymers with varied chemical composition. Acrylamide and diacetone acrylamide were used as monomers and triethanolamine and N -phenylglycine were used as photoinitiators. The study demonstrates that the response of photopolymer-based holographic gratings to relative humidity (RH) and temperature (T) can be tuned by alteration of the photopolymer composition. Humidity and temperature response of the holograms has been characterized by recording Bragg selectivity curves of transmission gratings and by monitoring the position of the maximum intensity in the spectral response of reflection gratings. Investigation of the humidity response in the range of 20–90% RH reveals that photopolymers containing triethanolamine are more responsive to moisture than photopolymers containing N -phenylglycine and display significant sensitivity to relative humidity above 40%. Full reversibility of humidity induced changes in gratings recorded in diacetone acrylamide-based photopolymer is confirmed at RH ≤ 60%. Exposure to RH ≥ 70% leads to irreversible changes in these gratings. The temperature response of slanted transmission gratings was investigated in the temperature range of 20–60 °C. Exposure of the photopolymer layers containing triethanolamine to elevated temperature was found to cause layer shrinkage due to desorption of absorbed water. Sealed layers containing triethanolamine, however, demonstrated swelling due to the effect of thermal expansion. The photopolymer layers containing N -phenylglycine were found to be unresponsive to temperature changes below 30 °C and have sensitivity to temperature above 30 °C.
24 citations
01 Jan 2015
TL;DR: This chapter provides an overview of the fabrication of optical devices, and highlights holography as a practical approach for the rapid construction of optical sensors that operate in the visible spectrum and near infrared.
Abstract: Optical devices that reversibly respond to external stimuli can provide fast, quantitative, visual colorimetric readouts in real-time. They may consist of bioactive recognition elements that can transmit the signal through a transducer embedded within the system. Responsive photonic structures may have applications in chemical, biological and physical sensors for medical diagnostics, veterinary screening, environmental monitoring, pharmaceutical bioassays, optomechanical sensing and security applications. This chapter provides an overview of the fabrication of optical devices, and highlights holography as a practical approach for the rapid construction of optical sensors that operate in the visible spectrum and near infrared. It begins with describing the fundamentals of holography and origins of holographic sensors. The chapter also explains the principle of operation of these devices and discusses the design parameters that affect the readouts. The principles of laser light interference during sensor fabrication and photochemical patterning are discussed. Furthermore, computational readout simulations of a generic holographic sensor through a finite element method are demonstrated. Studied design parameters include optical effects due to lattice spacing, nanoparticle (NP) size and concentration, number of stacks, their distribution, and lattice deficiencies within the sensor. Computational simulations allow designing holographic sensors with predictive optical characteristics.
8 citations
TL;DR: In this article, the authors explored the humidity and temperature response of volume phase gratings recorded in photopolymers containing acrylamide and diacetone acryamide as monomers, and triethanolamine and N-phenylglycine as photoinitiators.
Abstract: Holographic sensors have significant potential in various applications ranging from in vitro diagnostics to optical security. They are capable of providing fast, real-time, reversible or irreversible, visual colorimetric or optical readouts. The main challenge in the development of holographic sensors is to improve their selectivity by functionalizing the holographic recording material and achieve a response to a specific analyte. This material should be permeable to the analyte and its properties should change under exposure to the analyte. This work explores the humidity and temperature response of volume phase gratings recorded in photopolymers containing acrylamide and diacetone acrylamide as monomers, and triethanolamine and N-phenylglycine as photoinitiators. Characterization of the humidity response of photopolymer-based gratings in the relative humidity (RH) range of 20-90 % was carried out by measuring the diffraction efficiency of slanted transmission gratings and the position of the maximum intensity in the spectral response of reflection gratings. A strong humidity dependence of the diffraction efficiency of diacetone acrylamide-based transmission gratings was observed at RH=20-90%. The humidity dependence of the spectral response of the reflection gratings showed that photopolymers containing triethanolamine are more hydrophilic than photopolymers containing N-phenylglycine. The temperature response of slanted transmission gratings was investigated in the temperature (T) range of 20–60 °C. Exposure of the photopolymer layers containing triethanolamine to elevated temperature showed that the observed Bragg angle shift was caused by layer shrinkage due to water evaporation. The application of a sealing technique allowed for the observation of the photopolymer layer swelling due to the layer’s thermal expansion. The results demonstrate an effective approach to obtaining photopolymer-based gratings with tuneable temperature and humidity sensitivity.
7 citations
Cites background from "Research on Holographic Sensors and..."
...Many examples of holographic sensors for detection of a variety of analytes have been reported in the literature.(3-17) Holographic sensors can detect analytes in both gas and liquid phase as well as different physical stimuli such as pressure and magnetic field....
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References
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TL;DR: In this article, proper orthogonal decomposition (POD) was applied to the modal vibration analysis of a metal plate, which was subject to vibrations with an electrodynamical shaker in a range of frequencies from 100 to 5000 Hz.
Abstract: The proper orthogonal decomposition (POD), also known as Karhunen–Loeve expansion, is applied to the modal vibration analysis of a metal plate. The metal plate was subject to vibrations with an electrodynamical shaker in a range of frequencies from 100 to 5000 Hz. The data were obtained from the measurements with a laser vibrometer. The plate vibration measurements were used to calculate the eigenfunctions and the eigenvalues. It was found that a large fraction of the total energy of the vibrations is contained within the first four POD modes. The essential features of the vibrations are thus described by only the first four eigenfunctions.
364 citations
TL;DR: The purpose of this investigation was to review the toxicity data, identify any new relevant data, and select those data to be used in dose-response modeling, and proposed revised cancer and noncancer toxicity values were estimated using the newest U.S. EPA guidelines for cancer risk assessment and non cancer hazard assessment.
Abstract: Acrylamide (ACR) is used in the manufacture of polyacrylamides and has recently been shown to form when foods, typically containing certain nutrients, are cooked at normal cooking temperatures (e.g., frying, grilling or baking). The toxicity of ACR has been extensively investigated. The major findings of these studies indicate that ACR is neurotoxic in animals and humans, and it has been shown to be a reproductive toxicant in animal models and a rodent carcinogen. Several reviews of ACR toxicity have been conducted and ACR has been categorized as to its potential to be a human carcinogen in these reviews. Allowable levels based on the toxicity data concurrently available had been developed by the U.S. EPA. New data have been published since the U.S. EPA review in 1991. The purpose of this investigation was to review the toxicity data, identify any new relevant data, and select those data to be used in dose-response modeling. Proposed revised cancer and noncancer toxicity values were estimated using the newest U.S. EPA guidelines for cancer risk assessment and noncancer hazard assessment. Assessment of noncancer endpoints using benchmark models resulted in a reference dose (RfD) of 0.83 microg/kg/day based on reproductive effects, and 1.2 microg/kg/day based on neurotoxicity. Thyroid tumors in male and female rats were the only endpoint relevant to human health and were selected to estimate the point of departure (POD) using the multistage model. Because the mode of action of acrylamide in thyroid tumor formation is not known with certainty, both linear and nonlinear low-dose extrapolations were conducted under the assumption that glycidamide or ACR, respectively, were the active agent. Under the U.S. EPA guidelines (2005), when a chemical produces rodent tumors by a nonlinear or threshold mode of action, an RfD is calculated using the most relevant POD and application of uncertainty factors. The RfD was estimated to be 1.5 microg/kg/day based on the use of the area under the curve (AUC) for ACR hemoglobin adducts under the assumption that the parent, ACR, is the proximate carcinogen in rodents by a nonlinear mode of action. When the mode of action in assumed to be linear in the low-dose region, a risk-specific dose corresponding to a specified level of risk (e.g., 1 x 10-5) is estimated, and, in the case of ACR, was 9.5 x 10-2 microg ACR/kg/day based on the use of the AUC for glycidamide adduct data. However, it should be noted that although this review was intended to be comprehensive, it is not exhaustive, as new data are being published continuously.
269 citations
TL;DR: Experimental results on sensitivity, spatial frequency response, particle scattering noise, and nonlinearities are discussed and a few holographic applications of the material are presented.
Abstract: Holograms have been constructed in photopolymer materials which give bright, low-noise images. These holograms are of the volume type and have no surface variations in all but a few special cases. They are constructed in virtually real time and in situ, requiring no processing. Materials sensitive to both uv and blue-green radiation have been used. In this paper, the mechanism of hologram formation is examined. Experimental results on sensitivity, spatial frequency response, particle scattering noise, and nonlinearities are discussed. A few holographic applications of the material are presented.
229 citations
"Research on Holographic Sensors and..." refers background in this paper
...The well known DuPont photopolymer [2-4] and Polaroid DMP-128 [5, 6] emerged in the 1970’s and 1980’s but commercial use was limited....
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TL;DR: The rather high and unusual toxicity of the monomer would require extensive toxicologic study in order that recommendations for safe industrial handling could be ascertained, and to evaluate the safety in commercial use of polymers or copolymers which might contain small amounts of residual acrylamide.
164 citations
"Research on Holographic Sensors and..." refers background in this paper
...This toxicity can be attributed to the carcinogenic nature of the monomer acrylamide (AA) [34-37]....
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