After the disaster with the fridge freezing our gold nanoparticles and causing them to irreversibly aggregate, I figured that it would be a shame to waste the ruined gold solutions and so I took some conductivity and pH measurements with them. I found that conductivity could vary by a factor of 1.5 between the solutions (from…
This is a summary I wrote ~3 weeks ago of the work Josh Miller and I are doing under the CEIS grant for NPN Lift-off. Summary: Josh and I have been working for about four weeks so far on this program. During that time we have done preliminary lift-off (LO) tests on two wafers: one…
You may recall that last year I spent some time working on a proof-of-concept experiment for a high-throughput, non-specific drug discovery assay. The experiment involved binding up a FLAG-peptide sequence-tagged alkaline phosphatase (AP) enzyme with a biotinylated anti-FLAG antibody, in turn bound to a large avidin bead. This very large complex was unable to move…
The NPN tenting mechanism I’ve described in a few different posts has relied solely on mechanical technique. I poke the substrate with tweezers, or delaminate it with high electrical forces, or heat it up and let it contract while in contact with each other. It would scale very poorly if we tried to make this…
I have been using ITO electrodes deposited on PTFE sheets for my TEER measurements. A 100 nm thin ITO is deposited on ~300 micron PTFE sheets, and have a sheet resistivity of 60 ohms/sq. This sheet is commercially available from Sigma; so the electrode properties are consistent within the experiments. Although ITO has a huge…
I used the following parameters in the Simple Sieving Model (pardon the MATLAB syntax) Am = 1; %cross sectional area in cm^2 Do = 1*10^-7;% diffusion coefficient in the membrane in cm^2/sec P = .15;% membrane porosity; t = linspace(0,420,500); %time vector sec Qo = 1*0.00166; %militers per second (0.00166 = 10 ul/min) L =…
Hi all, Currently I am working on a cell culture system to mimic the blood-brain-barrier (BBB). Essentially, growing endothelial cells (bEnd3) on one side of the membrane, and pericyte and/or astrocyte on the other. Below is the layout of the cell culture system: a, b, c, and d are custom-cut silicone gaskets. f is the…
I spent some more time in understanding the numbers I am getting for our device simulations. In my simulations, I am assigning a conductivity value for my cell layer. Technically, from this information and by knowing the thickness and area of the cell layer, I can analytically calculate the value of resistance that the cell…
Paper can be found here I am working on developing an analytical model to understand how to accurately post-process the resistance values I obtain from my TEER measurements. This paper addresses a similar issue and comes up with a correction factor to match the TEER values obtained in a microsystem with the ones obtained from a…
From my last two posts (Anodic Bonding, Ozone Bonding), it is clear that we have some sort of bonding going on between the freestanding membrane and the posts intended to support the membrane. However, we do not understand the nature of the transfer. To gain more insight into this process, I took more SEMs of…