Nondestructive evaluation of solids by photothermal interferometry on nonreflective surfaces

Thermal expansion interferometry is a simple and very sensitive tool for nondestructive material analysis. In its basic form highly reflective surfaces are needed however. We developed a modified experimental set-up that can be used on any surface and found a theoretical description in good agreement with the results

Remote nondestructive material analysis by photothermal interferometry

Interferometry is used for the detection of thermal waves to study material properties. A symmetrical interferometer as thermal expansion detector was developed for photothermal nondestructive material analysis. After mixing a phase shifted reference signal electrically to the interferometer signal, phase and amplitude exchange phenomena have been observed

Photothermal interferometry for nondestructive subsurface defect detection

A symmetrical interferometer as thermal expansion detector was developed for photothermal nondestructive material analysis. Phase and amplitude exchange phenomena have been observed, when introducing an electronic reference phase shifter mixed to the interferometer signal. Experimental and theoretical results obtained with this system are presented

Bisphenol detection: Screen-printed electrode comparison for rapid, cost-effective monitoring

Endocrine-disrupting chemicals (EDCs) pose significant health hazards, impacting metabolic, reproductive, and respiratory functions. Thermal paper, commonly used in receipts and tickets, contains Bisphenol A (BPA) and Bisphenol S (BPS), a concerning EDC that can easily migrate to the skin, where it disrupts the endocrine system by mimicking the estrogen hormone, so negatively influencing human health [1,2]. Given its toxicity and widespread use, there's a pressing need for analytical methods to detect EDCs like bisphenols. Screen-printed electrodes (SPEs) offer a cost-effective solution for real-time monitoring. This study compares SPEs with carbon nanoparticles (CNPs) and carbon single-wall nanotube electrodes (SWCNTs) for BPA and BPS detection. It demonstrates their sensitivity, repeatability, and suitability for rapid, low-cost detection without hazardous waste generation. SEM was employed to examine the surface of the working electrodes of SPEs. The specificity of the SPE sensors in simultaneously detecting BPA and BPS was evaluated using differential pulse voltammetry (DPV), as depicted in Figure 1. SPE electrodes based on single-wall nanotubes demonstrated a broader linear range (0.5 to 75.0 μM) and higher sensitivity towards BPA and BPS oxidation than those with carbon nanoparticles. However, due to reduced capacitive current, CNP-based SPEs exhibited a 15-fold lower limit of detection (LOD) for BPA and a 4-fold lower LOD for BPS than SPE based on SWCNTs. These findings suggest that screen-printed electrodes based on carbon materials are promising techniques for on-site and health risk assessments in various everyday scenarios

Two-wavelength double heterodyne interferometry using a matched grating technique

Two-wavelength double heterodyne interferometry is applied for topographic measurements on optically rough target surfaces. A two-wavelength He-Ne laser and a matched grating technique are used to improve system stability and to simplify heterodyne frequency generation

Dual wavelength heterodyne interferometry for rough surface measurements

For interferometric topography measurements of optically rough surfaces dual wavelength heterodyne Interferometry (DWHI) is a powerful tool. A DWHI system based on a two-wavelength HeNe laser and a matched grating technique is described. This set-up improves system stability and simple heterodyne frequency generation

Dual wavelength heterodyne interferometry using a matched grating set-up

Two-wavelength double heterodyne interferometry is applied for topographic measurements on rough target surfaces. A two-wavelength HeNe laser and a matched grating technique are used to improve system stability and to simplify heterodyne frequency generation. Results obtained with an experimental set-up will be presented. The results obtained show that a dual wavelength heterodyne interferometer is appropriate for high precision ranging. Progressing developments for large distances will be discussed

Electrochemical sensor for detection bisphenols in thermal paper

The substances of very high concern (SVHCs) can be found in a wide range of consumer products. These substances can negatively influence human health depending on the route of exposure, exposure time and duration, amount of intake the substance by body and other factors. Increased number of carcinoma, sterility, diabetes can be due to the contact with SVHCs in our everyday life. Bisphenol A (BPA) is one of the most commercialized SVHC chemicals and is used in many different products such as plastic packaging for water and food, storage media, and even in thermal paper. Thermal paper is used for receipts in stores and tickets for parking, bus, and trains. BPA is applied on thermal paper as a dye developer. As a dye developer, it is not chemically bound to the paper so it can easily migrate and be absorbed by the skin (fingers, palm). Studies showed that typical occupational exposures of work cashiers can increase concentrations of BPA and its metabolites in urine several times. Toxicokinetic studies showed that the route of exposure has a big effect on the concentration of BPA that circulates in the body. If BPA enters the body through dermal exposure, it metabolizes as unconjugated BPA, while oral exposure leads to a conjugated form of BPA. Studies showed that only the unconjugated form can bind to estrogen receptors, leading to the conclusion that the unconjugated form is hazardous. Due to that European Commission restricted usage of BPA to 0.02 mas%. The paper manufacturers replaced BPA with bisphenol S (BPS). It is expected that 61 % of all thermal paper in the EU will be BPS-based till now. However, the wide use of BPS in thermal paper raises concern because it was shown that BPS is also toxic. New studies of urine samples collected around the world showed the presance of BPS. Due to increasing production of BPS there is a need for the development of analytical methods for the detection of SVCHs. The most used are HPLCs with mass spectrometric detection, which are expensive and time-consuming. On a another hand, electrochemical sensors are low-cost and simple method for detection of SVCHs. The present study represents fast, reliable and commercial detection of bisphenols via screen-printed electrodes (SPEs) as receptor elements. Scanning electron microscopy (SEM) was used to study the surface of the SPEs working electrodes. SPE electrodes showed very good electrochemical responses toward BPA and BPS oxidation with linear ranges between 0.5 and 50.0 μM and lower limits of detection of 0.15 μM and 0.37 μM, respectively

Electrochemical sensors for detection of bisphenols

The endocrine-disrupting chemicals (EDCs) are chemicals of very high concern that have hazards with serious consequences on human health. It influences on development of metabolic disorders, reproduction and respiratory problems. They can be found in our everyday life, from food, and personal care products to medical devices, dental products, special lenses and baby drink cans. Among several EDCs, banned Bisphenol A (BPA) and his substitute Bisphenol S (BPS) have attracted attention due to high usage during the manufacturing process for water and food packaging, in the production of epoxy resins, lacquer coating and can even be found in receipt. Due to that, there is a need for the fast, reliable and commercial detection of Bisphenols in everyday life. The gold standard for the detection of Bisphenols is chromatography and enzyme-linked immunosorbent assay, expensive and robust methods. Electrochemical sensors are a new approach to the detection of EDCs in very small quantities in complex environments. The aim of this research was to study commercial screen-printed electrodes (SPEs) as receptor elements in electrochemical sensors for the detection of BPA and BPS. Scanning electron microscopic (SEM) and Fourier transform infrared spectroscopy (FT-IR) were employed for examining the surface of the SPEs working electrodes. SPE electrodes showed very good voltammetric responses toward BPA and BPS oxidation with linear ranges between 0.5 and 50.0 μM and lower limits of detection of 0.15 μM and 0.37 μM, respectively