Breath figure technique

The breath figures technique is one of the most widely employed methods for the fabrication of organized porous polymer films [30, 31] and, as fiuther depicted in detail, in this approach the template consists of an ordered array of water droplets that can be removed by simple evaporation. Indeed, the simultaneous evaporation of a volatile solvent and condensation of water vapor in combination with thermocapillary effects and Marangoni convection allow the formation and precise organization of water droplets at the polymer solution-air interface [30]. This array of water droplets will evaporate upon complete evaporation of the solvent of the polymeric solution, and the surface will reflect its presence in the form of pores. 

Whereas the polymers employed by Qiao et al. [133, 206] concerned only star polymers with low Tg (below 48 °C), Li and coworkers [207] studied the construction of macroporous polymeric films on various nonplanar substrates with static breath figures technique, using linear polymers with high Tg. For this purpose, two kinds of linear polymers with high Tg, polystyrene-6-poly(acrylic acid) and polystyrene without polar end groups, were employed to prepare three-dimensional macroporous films on different nonplanar substrates. 

Another technique utilizing hquid droplets is breath figure templating, which was reported by Francois et al. [43-45]. Under the influence of a moist air flow, water droplets condense on the surface of a polymer solution. They form a hexagonal array and sink into the polymer solution, thereby serving as template. After complete evaporation of the solvent and water droplets, a polymer film remains with hexagonally arranged pores. 

Hierarchical structures in the micrometer and/or submicrometer scale from blends can also be prepared by combination of the BF and a different patterning technique, in general, lithographic techniques. For instance, Ge and Lu [205] prepared multiscale stmctured films by combining the breath figures formation with embossing techniques (Fig. 10.9). More precisely the authors prepared porous... 

Fig. 10.9 Formation of multiscale structures by combination of the breath figures approach and embossing techniques. The immiscibility between both homopolymers added (PS and PVP) due to the different hydrophilicity produces hierarchical ordered patterns where the PVP is located inside the pore and the PS at the pore wall. In addition, embossing produces an additional level of order at the micrometer length-scale as well as replicas. Reproduced with permission from ref. [205]...

The study shown in Figure 3.3 addresses the biochemical mechanism of lactose intolerance and uses the technique of breath collection and H2 analysis. Breath Hj rose after a lactose-intolerant child consumed a dose of lactose, but did not rise after a dose of equal weights of glucose and galactose. These results are consistent with the fact that lactose intolerance arises from a deficiency in lactase. 

Figure 4 Cartoon depicting technique for quantification of nebulizer output and measurement of deposition. On the left, a patient inhales nebulized particles via a Y piece. The exhalation filter captures exhaled particles. On the right, the same patient performs a similar maneuver. The inhaled mass filter captures particles that would have been inhaled. Differences between filters measure deposition. Breathing pattern can be monitored using a pneumotachograph represents the sum of minute ventilation plus nebulizer flow leaving the expiratory arm of the Y piece). (From Ref. 9.)...

Figure 6 Sketch depicting technique for bench measurements of inhaled mass and particle distribution. Breathing pattern defined by settings on Harvard pump. Particles presented to patient are captured on the inhaled mass filter. In separate experiments, the cascade impactor measures inspired aerosol isokinetically. (From Ref. 10.)...

FIGURE 17.8 Arrangement of equipment for the nitrogen-washout technique. Valve V allows the subject to breathe room air until the test is started. The test is started by operating valve V at the end of a normal breath, that is, the subject starts breathing 100% Oj through the inspiratory valve (I) and exhales the Nj and Oj mixture into a collecting spirometer via the expiratory valve EX. 

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