Supplemental
Charge Measurement Apparatus
In order to measure the nanocolumbic charge on the droplets formed using the IBF the electromagnetic
interference (EMI) had to be negated so the Kiethley 6514 electrometer could obtain accurate nano
coulmbic charge measurements.
Figure 3 shows the schematic diagram of the overall set up for
obtaining the charge measurements. Figure 3 shows the nanoliter LLC IBF device outfitted with a 10μL
Hamilton syringe with a 20cm long polyamine coated fused silica (FS) needle (a), an Aluminum (1.5cm
mesh) Faraday Cage 10cm x 5cm x 5cm connected to electrical ground (b), Copper Faraday Cup 2cm X
1cm x 1cm (c) connected with triaxial cable to a Keithley 6514 electrometer (d).
Figure 3. (a) Nanoliter LLC IBF device, (b) Faraday cage, (c) copper Faraday cup, (d) Kiethley 6514
electrometer.
HCl Supplemental
Figure 4 shows charge (Q) to surface area (SA) measurements for HCl at varied concentrations. The
experiments reveal a strongly correlated, potentially linear relationship between surface areas and
charge on droplets as seen with NaCl. This data is in agreement with previous studies (2, 13) and with
Gauss’s Law. The charge can also be correlated to volume, non-linearly, as shown in figure 5 showing
HCl at varied concentrations
Figure 4:Charge (nC) versus Surface area (nm2) shows linear relation for all concentrations of HCl: ▲HCl
0.33M; ■HCl 0.166M; ♦HCl 0.091M error bars represent standard deviation of charge.
Figure 5. Charge (nC) versus Volume (nm3) NaCl. ▲HCl 0.33M; ■HCl 0.166M; ●HCl 0.091M error bars
represent standard deviation of charge.
2-HEMA Supplemental
Figure 6 shows the structure of 2-HEMA a common organic monomer used in polymerizations. Figure 7
shows the same linear SA to Q relation as seen with the electrolyte solutions (NaCl & HCl). 2-HEMA
demonstrates that viscous organic monomers can also be quantified via real time charge measurement.
Again it can be seen in figure 8 that real time volume verification can be possible using IBF and possibly a
MALDI target plate as a faraday cup.
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O
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2-hydroxyethyl methacrylate
Figure 6. Structure of 2-HEMA
Figure 7. Charge (nC) versus Surface area (nm2) for ♦ 2-HEMA. Linear relationship betweeen
surface area and charge is demonstrated. Error bars represent standard deviation of charge.
Figur
e 8. Charge (nC) versus Volume (nm3) 2-HEMA.
bars represent standard deviation of charge.
● (2-HEMA) pure liquid monomer. Error