Particle trapping techniques

Paunov VN, Cayre OJ. Supraparticles and Janus particles fabricated by replication of particle monolayers at liquid surfaces using a gel trapping technique. Adv Mater 2004 16 788-791. 

The mass versus particle size distribution of several polymer latices with diameters in the range of 30 nm to 1500 nm was determined in less than 20 minutes using an integrated hydrodynamic chromatograph. Distributions obtained were compared with those found by other particle sizing techniques such as electron microscopy to verify validity of the technique. The instrument employed was able to analyze latices re-producibly with different optical properties, even though some of the injected particles may have been trapped within the column. Latex properties were correlated with particle size distribution data to illustrate the benefit of this particle sizing technique. 

Figure 2. Free radical release, measured by means of ESR/spin trapping technique, from micronsized and nano-sized Fe203 particles compared with amosite (asbestos).27...

During STI and oxide CMP, defects can come from sources such as oversized particles, polishing debris, diamond particles from the pad conditioner, and particles trapped in the polishing pad. In addition to the techniques discussed in this chapter, could you think of additional solutions for the reduction of these defects ... 

In 1986, Ashkin and coworkers reported on the first successful single-beam gradient-force trap, or laser tweezers, for dielectric particles [21]. They were able to trap particles of glass, silica, and polystyrene (PS) in the range from 25 nm to 10 pm in water. Optical trapping techniques have since been integrated to a range of different... 

The second important point on which the CICR technique is based is the strict control of the average number of reactants deposited on the clusters. This is is achieved by using the pick-up technique originally developed by Scoles and coworkers [291]. It consists in capturing the reactants by sticky collisions between the clusters and a low-pressure gas. Of course, the number of particles trapped is not the same for every cluster, but the important point is that the capture process has known statistics, being a random Poisson process. Hence the probability distribution Pq (m ) of finding exactly q reactant molecule per cluster follows the Poisson law of order q ... 

Contact angles of microscopic particles against another phase boundary can be determined interferometrically, by means of a film trapping technique It consists of capturing of... 

F. G. Major et al., Physics and Techniques of Charged Particle Traps. Springer Ser. Atom. Optical and Plasma Physics, vol. 37 (Springer, Berlin, 2005) ... 

The major application of dielectrophoresis in micro- and nanofluidic systems continues to be the manipulation of particles and cells. Popular applications include particle trapping, dielectrophoretic microsystems, traveling wave dielectrophoresis, and determination of cell dielectric properties. The specific dielectrophoretic techniques used in existing applications are too numerous to cover in this entry. This entry does provide a brief overview of some of the established manipulation techniques. 

Figure 7. Trapping thresholds ofparticles studied as a function of device fabrication technique. The particle trapping threshold is observed to be a function of particle size, particle conductivity, and morphology.

Particle-initiated breakdown is one of the most severe imperfections in gas-insulated apparatus, seriously reducing the dielectric strength of gases and the reliability of gas-insulated apparatus. Obviously, the best way to alleviate the effect of conducting particles is to remove them from the equipment. Various techniques to remove them and to promote particle motion or scavenging into low-field particle traps have been studied and are in use in gas-insulated equipment. 

AC Dielectrophoresis Lab-on-ChIp Devices, Rgure 2 DIelectrophoretIc manipulation techniques (a) electrorotation, (b) electro-orientation, (c) particle trapping and (d) traveling wave dielectrophoresis... 

We will first describe spectroscopy on collimated atomic beams and on kinematically compressed ion beams. Two groups of nonlinear spectroscopic tecliniques will be discussed saturation techniques and two-photon absorption techniques. We will also deal with the optical analogy to the Ramsey fringe technique (Sect. 7.1.2). In a subsequent section (Sect. 9.8) laser cooling and atom- and ion-trap techniques will be discussed. Here, the particles are basically brought to rest, ehminating the Doppler as well as the transit broadening effects. 

A. Hadjiiski, R. Dimova, N. D. Denkov, I. B. Ivanov, and R. Borwankar, Film trapping technique precise method for three-phase contact angle determination of solid and fluid particles of micrometer size, Langmuir, 12(26), 6665-6675 (1996). 

In the same period, it was understood that the trapping of atoms by laser light might give birth to what is now called particle-trapping spectroscopy (Letokhov 19756). This would be an important supplement to the Doppler-free laser spectroscopy techniques developed earlier, namely standing-wave absorption saturation spectroscopy... 

Different oils (mainly hydrocarbons or silicone oils) and their mixtures with hydrophobic solid particles are widely used for destruction of undesirable foam. For a long time, the entry, E, spreading, S, and bridging, B, coefficients (which can be calculated from the oil-water, oil-air, and water-air interfacial tensions) were used to evaluate the activity of such oil-based antifoams (AFs). However, recent studies showed that there was no correlation between the magnitudes of E, S, and B and the antifoam activity—the only requirement for having an active AF, in this aspect, is to have positive E and B. Instead, it was shown that the so-called entry barrier, which characterizes the ease of entry of pre-emulsified oil drops in the solution smface, was of crucial importance an easy entry (low entry barrier) corresponded to an active AF and vice versa. We developed a new method, the film trapping technique (FTT), which allows one for the first time to measme directly the critical capillary pressure, P , which induces the entry of micrometer-sized oil drops, identical to those in real AFs. This chapter describes the main results obtained so far by the FTT with various systems. 

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