Single Suspended Particle Research Articles

A microfluidic transistor for automatic control of liquids

Microfluidics have enabled notable advances in molecular biology1,2, synthetic chemistry3,4, diagnostics5,6 and tissue engineering7. However, there has long been a critical need in the field to manipulate fluids and suspended matter with the precision, modularity and scalability of electronic circuits8–10. Just as the electronic transistor enabled unprecedented advances in the automatic control of electricity on an electronic chip, a microfluidic analogue to the transistor could enable improvements in the automatic control of reagents, droplets and single cells on a microfluidic chip. Previous works on creating a microfluidic analogue to the electronic transistor11–13 did not replicate the transistor’s saturation behaviour, and could not achieve proportional amplification14, which is fundamental to modern circuit design15. Here we exploit the fluidic phenomenon of flow limitation16 to develop a microfluidic element capable of proportional amplification with flow–pressure characteristics completely analogous to the current–voltage characteristics of the electronic transistor. We then use this microfluidic transistor to directly translate fundamental electronic circuits into the fluidic domain, including the amplifier, regulator, level shifter, logic gate and latch. We also combine these building blocks to create more complex fluidic controllers, such as timers and clocks. Finally, we demonstrate a particle dispenser circuit that senses single suspended particles, performs signal processing and accordingly controls the movement of each particle in a deterministic fashion without electronics. By leveraging the vast repertoire of electronic circuit design, microfluidic-transistor-based circuits enable fluidic automatic controllers to manipulate liquids and single suspended particles for lab-on-a-chip platforms.

The influence mechanism of the main suspended particles of Yellow River sand on the emitter clogging − An attempt to improve the irrigation water utilization efficiency in Yellow River basin

The existence of suspended particles in water poses a great challenge to the adaptability of drip irrigation technology. To explore the differences in emitter clogging caused by irrigation water containing various suspended solids, this research used irrigation water containing Yellow River sand, quartz sand, and sodium bentonite as the main suspended particles (designated HW, SW and BW, respectively) to conduct a short-period emitter anti-clogging test and particle settlement test in static water. The results showed that the type of suspended particles had a very significant impact on the relative flow rate (Dra) of the emitter (P < 0.01). Emitter clogging was the most serious in the HW treatment, followed by the SW treatment, and emitters in the BW treatment had the lowest clogging degree. The clogging substance formed in the HW treatment exhibited a compact and stable structure; that in the SW treatment was a loosely structured accumulation of large particles; and that in the BW treatment had a flocculent structure with strong plasticity that flowed easily with water. These three types of suspended particles experienced two stages of sedimentation: short rapid sedimentation followed by slow sedimentation. Grid clogging at the emitter’s water inlet caused emitter clogging. The total mass of sediment in laterals in the HW treatment was the largest, and the Dra was the smallest; the total mass of sediment in laterals in the BW treatment was the smallest, and the Dra was the largest. In the SW treatment, the values of these two indexes were between those in the HW and BW treatments. Single suspended particles, such as quartz sand (powder) or sodium bentonite (clay), had more difficulty forming stable clogging structures, so the Dra was relatively high. Coarse and fine particles were balanced in Yellow River sand; thus, the emitter was easily clogged, and the degree of clogging was the most serious. This study tried to provide a basis for the differences and formation mechanisms of emitter clogging and the anti-clogging strategies of emitters in drip irrigation systems in different reaches of the Yellow River.

Surface Enhanced Raman Spectroscopy of Individual Suspended Aerosol Particles

We report the observation and measurement of surface enhanced Raman spectroscopy (SERS) signatures from individual suspended aerosol particles. To our knowledge, this is the first report of SERS from single suspended particles formed from droplets containing analyte molecules and metallic nanoparticles (MNPs). We describe our experimental setup to generate, charge, and trap microdroplets and an associated spectroscopic measurement arrangement configured to easily switch between trapped, suspended particles and bulk liquid samples of the same materials. Trapped droplets quickly dry to form micron-sized particles mainly composed of inert material, NaCl (>99%) with trace amounts of analyte molecules, and MNPs. As an initial investigation and demonstration of our method, surface enhanced resonance Raman spectroscopy (SERRS) is conducted on 3–5 μm diameter suspended solid particles containing R6G dye molecules and silver nanoparticles (NPs). SERRS signal intensities are linear with particle dye concentrations ...

The lattice Boltzmann simulation of suspended particle movement in a tapered tube

Based on the lattice Boltzmann method, the motion of single suspended particle in tapered tube is simulated numerically. The distributions of velocity and pressure in the flow field are obtained. The hydrodynamic force on the particle boundary is evaluated by conventional momentum exchange method (CME), lattice-type-dependent momentum-exchange method (LME) and stress tensor integral method (STI) separately. The variations of velocity and the trajectory of the particle which starts at different places are analyzed, the results evaluated by LME are in excellent agreement with those by STI and the results evaluated by CME are slightly different from those by the former two methods.

Solids behaviour in a dilute gas–solid two-phase mixture flowing through monolith channels

This paper reports, for the first time, the solids behaviour in a dilute gas–solid two-phase mixture flowing through monolith channels. The non-intrusive positron emission particle tracking (PEPT) technique was used in the work, which allowed investigation of three-dimensional solids motion at the single suspended particle level. Processing of the PEPT data gave solids velocity and occupancy in the monolith channels. The results showed a non-uniform radial distribution of both the solids velocity and concentration. The highest axial solids velocity occurred in monolith channels located in the central part of the column, whereas the highest solids concentration took place at a position approximately 0.7 times the column radius. The axial distribution of the axial solids velocity showed an entrance region with a length of approximately 33 times the hydrodynamic diameter of a monolith channel under the conditions of this work. Analysis of the PEPT data also gave distributions of particle residence time and tortuosity in terms of solids motion. The distributions were approximately Gaussian-type with the tortuosity distribution more skewed toward the right hand side. The peak residence time and tortuosity decreased with increasing superficial gas velocity and the distributions were broadened at lower superficial gas velocities. The results of this work also provided a possible explanation to our previously observed early laminar-to-turbulent flow transition in monolith channels.

Lattice-Boltzmann Simulation of Particle Suspensions in Shear Flow

Inclusion of short-range particle–particle interactions for increased numerical stability in a lattice-Boltzmann code for particle-fluid suspensions, and handling of the particle phase for an effective implementation of the code for parallel computing, are discussed and formulated. In order to better understand the origin of the shear-thickening behavior observed in real suspensions, two simplified cases are considered with the code thus developed. A chain-like cluster of suspended particles is shown to increase the momentum transfer in a shear flow between channel walls, and thereby the effective viscosity of the suspension in comparison with random configurations of particles. A single suspended particle is also shown to increase the effective viscosity under shear flow of this simple suspension for particle Reynolds numbers above unity, due to inertial effects that change the flow configuration around the particle. These mechanisms are expected to carry over to large-scale particle-fluid suspensions.

Solids behaviour in a gas–solid two-phase mixture flowing through a packed particle bed

This paper reports the solids behaviour in a dilute gas–solid two-phase mixture flowing through a packed bed. The positron emission particle tracking (PEPT) technique was used in the work, which allowed investigation of three-dimensional solids motion at the single suspended particle level. Processing of the data gave solids velocity, the residence time of suspended particles, bed tortuosity in terms of solids motion, as well as solids occupancy in the cross-section of the packed bed. The results suggest that the wall effect on the motion of suspended particles is limited to approximately one packed particle diameter under the conditions of this work. Both the average axial and radial velocities of suspended particles, normalised by the superficial gas velocity, change periodically with radial position, but the periodicity does not correspond exactly to the packed particle diameter. The peak and trough values of the average axial velocity of the suspended particles in the bulk region are, respectively, ∼ 25 % and ∼ 15 % of the superficial gas velocity under the conditions of this work and the superficial gas velocity shows little effect. The peak and trough values of the average radial velocity of the suspended particles in the bulk region are, respectively, +5% (positive) and - 5 % (negative) of the superficial gas velocity. The results of the residence time and tortuosity of the suspended particles show an approximately Gaussian distribution with the peak residence time and tortuosity increasing with decreasing superficial gas velocity. The occupancy data suggest that particles spend more time in an annular region close to the wall, indicating a non-uniform particle distribution across the packed bed cross-section.

Further development of temperature determination for a heated micron-sized particle from forced convection

A novel method for determining temperature of a micron-sized particle from forced convective force has been developed. The force was measured for a single suspended particle in an electrodynamic chamber. Particle heating was achieved by focused CO 2 laser radiation. With negligible free convection, a correlation was formulated between the forced convective force and temperature-dependent viscosity of the gas, on the basis of the Stokes expression. According to this correlation, the ratio of hot to cold forced convective forces on a particle depends on the gas viscosity, and the particle temperature can be attained from this ratio. Particle temperature was determined for a non-reacting glassy carbon particle of 100 μm and a pyrolyzing polystyrene particle of 157 μm . It was shown that the developed method is straightforward and quite accurate with an uncertainty of less than 2.5%, and applicable to both reacting and non-reacting particles.

Theoretical and experimental investigations of the interdependence of the dielectric, dielectrophoretic and electrorotational behaviour of colloidal particles

New theoretical relationships are derived to link the dielectric properties of a suspension of colloidal particles to both the dielectrophoretic (DEP) and electrorotation (ROT) behaviour exhibited by a single suspended particle. It is found that the relaxation frequencies that characterize the dielectric spectrum of a colloidal suspension are close to, but different from, those that characterize the DEP and ROT responses. The extent of this difference is dependent on particle volume fraction and the intrinsic dielectric properties of both particle and suspending medium. Experimental results obtained for yeast cells in the frequency range from 1 kHz to 10 MHz provide confirmation of the theory.

Concentration and particle size distribution in smoke from marijuana cigarettes with different Δ 9-tetrahydrocannabinol content

Particle size and mass concentration are important determinants of site and quantity of respiratory tract deposition of aerosols. Particle concentrations and size distributions of smoke from marijuana cigarettes with different concentrations (as measured in the marijuana leaf) of Δ 9-tetrahydrocannabinol (Δ 9-THC) were measured using a single particle aerodynamic relaxation time (SPART) analyzer. The SPART analyzer measures aerodynamic diameter of single suspended particles at a rate of 3000/min. Cigarettes were smoked using a 35-cc, 2-sec puffing device attached to a diluter; dilution and analysis were completed within 4 sec of puff generation. The size distribution of smoke from all marijuana cigarettes was similar to that for tobacco cigarettes, ranging from 0.35 to 0.43 μm (count median aerodynamic diameter). The particle number and mass concentration increased as Δ 9-THC concentration increased, being, respectively, 2.2- and 3.8-fold higher in the marijuana cigarette leaf with highest Δ 9-THC concentration compared to the placebo marijuana cigarette. These data indicate the need for quantitative comparisons of other potentially toxic constituents in marijuana cigarettes of different Δ 9-THC concentrations.

Concentration and Particle Size Distribution in Smoke from Marijuana Cigarettes with Different Δ9-Tetrahydrocannabinol Content

Concentration and Particle Size Distribution in Smoke from Marijuana Cigarettes with Different Δ9-Tetrahydrocannabinol Content. HILLER, F. G., WILSON, F. J., JR., MAZUMDER, M. K., WILSON, J. D., AND BONE, R. C. (1984). Fundam. Appl. Toxicol. 4, 451–454. Particle size and mass concentration are important determinants of site and quantity of respiratory tract deposition of aerosols. Particle concentrations and size distributions of smoke from marijuana cigarettes with different concentrations (as measured in the marijuana leaf) of Δ9-tetrahydrocannabinol (Δ9-THC) were measured using a single particle aerodynamic relaxation time (SPART) analyzer. The SPART analyzer measures aerodynamic diameter of single suspended particles at a rate of 3000/min. Cigarettes were smoked using a 35-cc, 2-sec puffing device attached to a diluter, dilution and analysis were completed within 4 sec of puff generation. The size distribution of smoke from all marijuana cigarettes was similar to that for tobacco cigarettes, ranging from 0.35 to 0.43 μm (count median aerodynamic diameter). The particle number and mass concentration increased as Δ9-THC concentration increased, being, respectively, 2.2- and 3.8-fold higher in the marijuana cigarette leaf with highest Δ9-THC concentration compared to the placebo marijuana cigarette. These data indicate the need for quantitative comparisons of other potentially toxic constituents in marijuana cigarettes of different Δ9-THC concentrations.

A unified model for particulate expansion of fluidised beds and flow in fixed porous media

A model is derived for a fluidised bed that enables its steady state particulate expansion to be predicted as a function of superficial velocity from the initial (packed bed) condition to the final fully expanded (single suspended particle) state. These predictions are in good agreement with the empirical correlations and functional dependencies found by Richardson and Zaki[1,2] over the full range of flow conditions. The derivations incorporat revisions in the form of the pressure drop correlations for flow in porous media that are justified on theoretical and empirical grounds.

Effect of Low and High Relative Humidity on Metered-dose Bronchodilator Solution and Powder Aerosols

Physical properties of two metered-dose bronchodilator aerosols packaged as solutions and two aerosols packaged as finely ground powders were measured at low and high relative humidity. The aerodynamic size distribution and particle concentration were measured in real time using the single-particle aerodynamic relaxation time analyzer, which can measure the aerodynamic diameter of single suspended particles in the respirable size range. The count median aerodynamic diameter, the mass median aerodynamic diameter, the total particles per dose, and the total aerodynamic mass per dose were calculated. Significant increases were noted in the count median aerodynamic diameter for three aerosols and in the mass median aerodynamic diameter for two aerosols. The number of particles in the measured size range increased 3.6- and 4.1-fold for the droplet aerosols and 1.4-fold for the powder preparations. The aerodynamic mass per dose in the measured size range increased 5.7- and 11.4-fold for the droplet aerosols and 3.1- and 1.6-fold for the powder aerosols. These data indicate that all aerosols tested increased in size at high humidity and that aerosols dispensed as droplets may be more unstable than those dispensed as powders.