WJP, PHY381 (2014) Wabash Journal of Physics v1.3, p.1

Analysis of a Low-Cost Aerosol Generator

Jacob Caddick, Max Millot, Kelly Sullivan, and Martin Madsen

Department of Physics, Wabash College, Crawfordsville, IN 47933

(Dated: October 20, 2014)

This paper presents an innovative method of atomizing a methanol solution in an

effort to isolate the polyurethane nanospheres so that they may be further analyzed

within an ion trap. This was achieved by modifying a solenoid controlled valve and

spray mechanism powered by low voltage relay and a microcontroller printed circuit

board to produce a fine spray. Our most efficent volume per shot ratio comes from

a 12 volt, 30 psi pressue, 35 ms pulse with a 54.2 ± 1.0 µL/shot).

WJP, PHY381 (2014) Wabash Journal of Physics v1.3, p.2

From the creation of the cathode ray tube to potentially making trapped ion quantum

computer, ion traps clearly have prevalance in the physics society today. However, the ion

trap is useless without ions. Therefore those attempting to perform analysis with an ion

trap would require a mechanism that can inject the desired ions into the ion trap. In many

cases, the ions must be extracted from a liquid.

We found that there are many paths that can be taken to aerosolize a liquid. A very

common method is creating an aerosol mist of the liquid particles by forcing the liquid out

of a small hole that is under a certain pressure. The droplets that are expelled from the

hole quickly evaporate becoming a fine mist much like a spray paint can. In a very similar

manner, we found that the medical field produces aerosols using a nebulizer that produces

the same result as before, but instead can utilize ultrasonic power instead of compressed

air [1]. Some would simply use electricity to produce their aerosols, also known as the

electrospray [2].

However, to perform our task, we decided that we would pursue the method of ion

isolation that involves creating a fine spray of the liquid that mainly contains the desired

ions [3]. But instead of instead of using vibrations to generate our aerosols, we focused on

manipulating the pressures of a solenoid controlled valve and spray mechanism held to a

constant voltage. We then determined the efficay of such a mechanism by analyzing the

density of nanospheres produced from a specific volume of a methanol solution.

To determine the efficacy of our apparatus, we need a model that shows the number of

microspheres that are contained witin a shot of the desired fluid, with various pressures and

pulse widths. At a constant pressure P and constant voltage V , we need to know the change

in volume ∆V , the number of shots N fired by the injector and the percentage of the fluid

that is made up of the nanospheres Persp to give the number of spheres per shot S:

S =∆V

NPersp. (1)

To perform the experiment, we first filled the reservoir tube with isoproenol past the

upper portion of the metal opening (found on the left portion of FIG 2). We the pressurized

the tube using an air compressor with a tank. We varied the pressures from 25 psi to 35 psi

in increments of 5 psi. At the desired pressure, we fired a set number of shots (40, 80, 100,

120), with a duration of 35 ms per shot, into a graduated cylinder. We measured the volume

of the fluid found in the in the graduated cylinder after giving it ample time to settle in the

WJP, PHY381 (2014) Wabash Journal of Physics v1.3, p.3

FIG. 1. Drawing of the circuit diagram that shows how the Arduino Mega 2650, the low voltage

relay and the Deplphi gasoline electronic fuel injector were connected to perform the experiment.

container.

TABLE I shows the mL per shot found for each pressure tested.

psi mL/shot uncertainty (95% CI, t-dist)

25 0.04310 0.00091

30 0.05422 0.00092

35 0.0489 0.0011

TABLE I. This is a table listing the mL per shot found at a specific pressure.

After running tests at 25, 30 and 35 psi, we found that the greatest yield of volume

per shot comes from the 12 volt, 30 psi pressue, 35 ms pulse, yielding 0.0542 ± 0.0010

mL/shot. We feel that it is only necessary to supply the graphical analysis of the highest

yield experiment, which is shown in FIG 3. However, we also felt that it was necessary

to include the data points in a chart to show the change in volume consistency found at a

WJP, PHY381 (2014) Wabash Journal of Physics v1.3, p.4

FIG. 2. Figure of how the fuel injector was mounted and how the spray would enter the ion trap

apparatus.

Number of Shots Change in Volume (mL)

40 1.90

40 1.95

40 1.95

60 3.00

60 3.00

60 3.00

100 5.19

TABLE II. This is a table showing the data points of our experiment with the highest yield, 12

volt, 30 psi pressue, 35 ms pulse.

specific number of shots. This is shown in TABLE II

WJP, PHY381 (2014) Wabash Journal of Physics v1.3, p.5

We feel that a comparison of efficiencies of volume per shot coming from an array of

liquids is the best way to determine the true efficiency of our apparatus. We came to this

conclusion because we believe that there is a possibility of the results differing when using a

different fluid for acquiring nanospheres, such as finding the most efficient pressure to be 25

for one liquid and 35 for another. Therefore, further we think that there is plenty of room

for further experimentation to be done to find the pressure that gives the highest yield for

other liquids.

40 50 60 70 80 90 100 110Number of Shots

2

3

4

5

6VolumeHmLL

FIG. 3. This is the graph showing the ml of isopropanol released from the fuel injector vs the

number of shots fired at 35 ms per shot with a pressure of 30 psi.

WJP, PHY381 (2014) Wabash Journal of Physics v1.3, p.6

[1] Warren H. Finlay, “The Mechanics of Inhaled Pharmaceutical Aerosols: An Introduction,”

Academic Press, (2001).

[2] Ronald L. Grimm, “Fundamental Studies of the Mechanisms and Applications of Field-Induced

Droplet Ionization Mass Spectrometry and Electrospray Mass Spectrometry” (Ph.D.). Caltech

Library, (2006).

[3] Lars Strom, “The Generation of Monodisperse Aerosols by Means of a Disintegrated Jet of

Liquid, Rev. Sci. Instrum., 40, 778, (1969).