Preparation of Polystyrene Microsphere-Templated Porous Monolith for Wastewater Filtration

Porous monoliths prepared using templates are highly sought after for filtration applications due to their good mass transport properties and high permeability. Current templates, however, often lead to the formation of dead-end pores and irregular pore distributions, which reduce the efficiency of the substrate flow across the monolith column. This study focused on the preparation of a microsphere-templated porous monolith for wastewater filtration. The optimal template/monomer ratio (50:50, 60:40, 70:30) was determined, and appropriate template removal techniques were assessed for the formation of homogenous pores. The physicochemical characteristics and pore homogeneity of the monoliths were examined. The 60:40 ratio was determined to result in monoliths with homogeneous pore distributions ranging from 1.9 μm to 2.3 μm. SEM and FTIR investigations revealed that solvent treatment was effective for removing templates from the resulting solid monolith. The water quality assessments revealed reductions in the turbidity and the total number of suspended particles in the tested wastewater of up to 96–99%. The findings of this study provide insightful knowledge regarding the fabrication of monoliths with homogenous pores that are beneficial for wastewater treatment.

A Highly Sensitive Ammonia Gas Sensor Using Micrometer-Sized Core–Shell-Type Spherical Polyaniline Particles

A highly sensitive NH3 gas sensor based on micrometer-sized polyaniline (PANI) spheres was successfully fabricated. The PANI microspheres were prepared via a facile in situ chemical oxidation polymerization in a polystyrene microsphere dispersion solution, resulting in a core–shell structure. The sensor response increased as the diameter of the microspheres increased. The PSt@PANI(4.5) sensor, which had microspheres with a 4.5 μm average diameter, showed the largest response value of 77 for 100 ppm dry NH3 gas at 30 °C, which was 20 times that of the PANI-deposited film-based sensor. Even considering measurement error, the calculated detection limit was 46 ppb. A possible reason for why high sensitivity was achieved is simply the use of micrometer-sized PANI spherical particles. This research succeeded in providing a new and simple technology for developing a high-sensitivity NH3 gas sensor that operates at room temperature.

A blood-mimicking fluid with cholesterol as scatter particles for wall-less carotid artery phantom applications

Aim of the study: At present, there are few scatter particles used in preparing blood-mimicking fluids, such as nylon, sephadex, polystyrene microsphere, and poly(4-methystyrene). In this study, we present cholesterol as a new scatter particle for blood-mimicking fluid preparation. Materials and methods: The procedure for the preparation of the proposed blood-mimicking fluid involved the use of propylene glycol, D(+)-Glucose and distilled water to form a ternary mixture fluid, with cholesterol used as scatter particles. Polyethylene glycol was first used as part of the mixture fluid but the acoustic and physical properties were not suitable, leading to its replacement with D(+)-Glucose, which is soluble in water and has a higher density. A common carotid artery wall-less phantom was also produced to assess the flow properties. Results: The prepared blood-mimicking fluid with new scatter particles has a density of 1.067 g/cm3, viscosity of 4.1 mPa.s, speed of sound 1600 m/s, and attenuation of 0.192 dB/cm at 5 MHz frequency. Peak systolic velocity, end diastolic velocity and mean velocity measurements were gotten to be 40.2 ± 2.4 cm/s, 9.9 ± 1.4 cm/s, and 24.0 ± 1.8 cm/s, respectively. Conclusion: Based on the results obtained, the blood-mimicking fluid was found suitable for ultrasound applications in carotid artery wall-less phantoms because of its good acoustic and physical properties.

Preparation, Structure, and Properties of Polystyrene-Microsphere-Reinforced PEG-Based Hydrogels

To improve the mechanical strength and practicability of hydrogels, polystyrene microspheres with core–shell structure were prepared by the soap-free emulsion polymerization, polyethylene glycol hydrogels with polystyrene microspheres by the in-situ polymerization. The structure, morphology, roughness, swelling property, surface energy, and mechanical properties of the microspheres and hydrogels were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, confocal laser microscopy, swelling test, contact angle measurement, and compression test. The results showed that they have certain swelling capacity and excellent mechanical properties, and can change from hydrophobic to hydrophilic surface. The reason is that the hydrophilic chain segment can migrate, enrich, and form a hydration layer on the surface after soaking for a certain time. Introducing proper content of polystyrene microspheres into the hydrogel, the compressive strength and swelling degree improved obviously. Increasing the content of polystyrene microspheres, the surface energy of the hydrogels decreased gradually.

Polystyrene Microsphere-Based Immunochromatographic Assay for Detection of Aflatoxin B1 in Maize

Aflatoxin B1 (AFB1), a mycotoxin, is hepatotoxic, carcinogenic, and nephrotoxic in humans and animals, and contaminate a wide range of maize. In this study, an immunochromatographic assay (ICA) based on polystyrene microspheres (PMs) was developed for sensitive and quantitative detection of AFB1 in maize. The amounts of PMs, the condition for activating carboxyl groups of PMs, the amount of monoclonal antibody (mAb), and the volume of the immune probe were optimized to enhance the performance PMs-ICA for point-of-care testing of AFB1 in maize. The PMs-ICA showed the cut-off value of 1 ng/mL in phosphate buffer (PB) and 6 µg/kg in maize samples, respectively. The quantitative limit of detection (qLOD) was 0.27 and 1.43 µg/kg in PB and maize samples, respectively. The accuracy and precision of the PMs-ICA were evaluated by analysis of spiked maize samples with recoveries of 96.0% to 107.6% with coefficients of variation below 10%. In addition, the reliability of PMs-ICA was confirmed by the liquid chromatography-tandem mass spectrometry method. The results indicated that the PMs-ICA could be used as a sensitive, simple, rapid point-of-care testing of AFB1 in maize.

A Miniature Fiber Tip Polystyrene Microsphere Temperature Sensor With High Sensitivity

A fiber-optic temperature sensor based on fiber tip polystyrene microsphere is proposed. The sensor structure can be formed simply by placing and fixing a polystyrene microsphere on the center of an optical fiber tip. Since polystyrene has a much larger thermal expansivity, the structure can be used for high-sensitive temperature measurement. By the illuminating of the sensor with a broadband light source and through the optical Fabry-Perot interference between the front and back surfaces of the polystyrene microsphere, the optical phase difference (OPD) or wavelength shift can be used for the extraction of temperature. Temperature measurement experiment shows that, using a fiber probe polystyrene microsphere temperature sensor with a spherical diameter of about 91.7 µm, a high OPD-temperature sensitivity of about −0.617 96 nm/°C and a good linearity of 0.991 6 were achieved in a temperature range of 20°C–70°C.

Numerical and Experimental Investigation on the Optical Manipulation from an Axicon Lensed Fiber

Here we numerically and experimentally studied the optical trapping on a microsphere from an axicon lensed fiber (ALF). The optical force from the fiber with different tapered lengths and by incident light at different wavelengths is calculated. Numerically, the microsphere can be trapped by the fiber with tapered outline y=±x/0.5 and y=±x at a short incident wavelength of 900 nm. While for the fiber with tapered outline y=±x/2, the microsphere can be trapped by the light with longer wavelength of 1100 nm, 1300 nm, or 1500 nm. The optical trapping to a polystyrene microsphere is experimentally demonstrated in a microfluidic channel and the corresponding optical force is derived according to the fluid flow speed. This study can provide a guidance for future tapered fibre design for optical trapping to microspheres.