UPDATE: Some data presented here is out of date. For up-to-date data, see my next post here. — Lately I’ve been performing comparison experiments between our NPN membranes (wafer 1132, 3 slot SEPCON, 40-48nm pores and 13-20% porosity) and commercial cellulose triacetate filtration membranes, with respect to the degree to which they hinder the diffusion…

Last week, I worked with Kevin to create a prototype cell culture device that could be compatible with his Raman system in Nottingham. The space constraints of the physical system are challenging: The overall working distance of the system must be less than 1.5 mm (smaller is better), must maintain only MgF2, media, and cells…

In this post, I’m going to discuss the results of the different PEG molecular on silane samples. We used same condition to make 4 chips for each sample. And we treat them with BSA, IgG, and PBS to rest the adsorption. We are using the SEM, contact angle and XPS as the testing method. The way we…

The following plot is an attempt to summarize recent work measuring rate of flow through a membrane as a function of concentration.  We investigated 100 nm NPs, (totally blocked), 20 nm NPs (partially blocked) and IgG (mostly passed).  In all cases, the buffer used was 1xPBS and 0.1% Tween 20.  This plot mostly shows the total…

Our recent work using NPN to separate free IgG from 20 nm NPs has shown that we can pass liquid under either forward or reverse configurations using the centrifuge.  We had thought that there would be greater resistance in the forward orientation due to cake layer formation.  We had found high resistance to flow in…

I’ve been taking lots of zetapotential measurements with my current setup. Serendipitously, it appears that the more I use the electrodes, the more stable my zetapotential measurements become. Because the system seems well behaved now, I decided to move on to a more difficult problem. Sarah and I made some nanofluidic transistors a few weeks back,…

In my last post, I described a new process for reducing fluoropolymer build up during RIE. Unfortunately, the new process had substantially lower yields (half) than the process I was using before. In this post, I am detailing my attempts to make the MgF2 nanomembranes stronger to try and improve the yield of my current etching…

In our previous post I relate how our first experience with the membranes encountered some difficulties.  These were mostly of two kinds:  clogging or braking of the membrane and somewhat arbitrary sizing of the particles.  We think we have fixed both. In our latest experiments we have used manually-extruded particles.  These are obtained after the…

Josh has just started teaching us how to play with these; some early findings: – So far, standard centrifugation results mostly on the caking of lipids that clogs the membranes. – Use of the pressure cell has shown some promise, we have passed 120nm lipid-nps through 400nm pores @10PSI.  The result?  70nm particles… – Reverse…

As discussed in a previous post, we decided to test chips from wafer #1070 because they have smaller pores than those used in the most recent forward vs. reverse study. In the forward direction, 31 uL of filtrate was passed after 30 minutes at 3 krpm. (after 30 additional minutes at 5 krpm the total…