Generation of liquid aerosols by electrospraying has been a well-studied technique [28,29]. Electrostatic charges are used to decrease the surface tension of a liquid to facilitate or cause breakup of the surface. The placement of charge on the surface in practice necessitates a sufficiently conductive liquid for electric current flow to replenish charge carried away by the aerosol released. In an assist mode, a potential difference is placed on the liquid to decrease the droplet size for pneumatic atomization or vibrating-orifice droplet generation. For an electrostatic spray where a high potential at a liquid surface causes droplets to be ejected, different modes of droplet formation occur where polydisperse or monodisperse droplets are produced. Recent work has shown that with a combination of a constant-pressure feed through a capillary tube and electrospraying, a stable, high-concentration 107cm~3), ultrafine 10 nm) aerosol can be produced . A commercial version of an electrospray aerosol generator is shown in Fig. 5. A small volume of the liquid (conductivity ~ 0.2S/m) to be sprayed is placed in the sample vial. Nonvolatile liquids, solutions, or suspensions of ultrafine particles can be used. Pressurizing the chamber forces a slow flow of the liquid up the capillary tube. A high voltage of several kilo volts applied to the platinum wire causes electrospraying of the liquid surface exiting the capillary tube, producing droplets approximately 200-2000 nm in diameter. The aerosol flow of a few liters per minute consist of highly charged droplets that are neutralized in the ionizer chamber. Careful control of the process parameters result in a monodisperse aerosol.
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If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.