The mechanism of organic dye photobleaching is not well understood, but there are a few methods out there for reducing the rate of photobleaching. Some literature suggests that photobleaching is due to excess oxygen in solution and the interaction between the dye and oxygen radicals. Actin research swears by the following “anti-bleaching buffer” to limit…
Membrane chips were amino-silanized with APTES in the YES system. I performed the standard electroosmosis tests with these chips. Here are the flow rates in comparison with non treated and oxidized membranes: Here are the calculated zeta potentials: As you can see, amino silane reduces the rate of electroosmosis and the zeta potential. We would expect…
Here is an attempt at the active area figure using the “newer” EO membranes (SC172). Here is the raw flow data for the three membrane sizes: If we take the slopes from this figure, we get the flow rates in uL/min. We can then plot against active area: We get a pretty nice fit here,…
In prep for manuscript writing I came across a paper that says they’ve created a super efficient EO pump that uses extremely low voltages. Their top flow rate (.125 mL/(min V cm2) ) is comparable to the flow rates I see with our materials (144 mL/(min V cm2)). They run their experiments at 3 V…
Back a year or more ago, we had analyzed the EO flow rates from pnc-Si and determined that the flow was much higher than any other material. We then went on to try to calculate the zeta potential using the Helmholtz-Smoluchowski equation: We figured out the velocity of the fluid, v, from our flow rate…
Ag/AgCl electrodes are used overwhelmingly in streaming potential and sometimes in electroosmosis. The benefit of using Ag/AgCl in electroosmosis should be less gas generation and the ability to make an enclosed pump. Here is some information on my attempt at Ag/AgCl EO. .2mm silver wires were coated with AgCl using protocol. Electrodes were immersed in…
All electrokinetic phenomena are connected by a form of the Helmholtz-Smoluchowski equation. In the case of electroosmosis, the equation can be written as follows: where v is the velocity (in m/s) of water flow through the pores, epsilon the permittivity, E the electric field, zeta the zeta potential, and eta the viscosity. Since we do…
I’ve tested several membrane types with the streaming potential apparatus in order to calculate zeta potential. Here are the results: All materials in the above chart have negative zeta potentials. Pnc-Si seems to have the highest overall potential, followed by PES then cellulose. Cellulose is prone to cracking and bursting at pressure above 7 PSI….
In this post I will describe recent streaming potential measurements for PES membranes and the calculated apparent zeta potentials from these measurements. Setup: 1. Fabricate Ag/AgCl electrodes: Silver wire at the anode in 1M KCl at 1mA current for 20 minutes. 2. Assemble streaming potential device: Electrodes are inserted into silicone chord o-rings and chamber…
In the next paper that I’d like to publish, I will compare protein separations for two membranes with different pore distributions to a single membrane at two salt concentrations (basically a redo of this post). My most recent trial with this had less than stellar results. I chose two wafers for movable cutoffs – SC…