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…

Hemodialysis chips are not surviving the priming process and the 4 hour dialysis treatment. We want to verify that the membranes are being weakened and also to determine if coating with oxide will ameliorate the problem. Using single slot chips from wafer 1153 I performed burst pressure tests on three groups of chips. 1. Bare chips…

We have wondered if we can skip anodic bonding and bond the chips using our UV ozone process. There are pros and cons to this approach, mainly that the setup and procedure is easy, but the contact and alignment is difficult. So I gave it a try.   Here are a few SEMs of ozone bonded…

This is an addendum to the results I posted in my previous blog. I am trying to simulate cell growth on a transwell device and perform TEER measurements using a small chopstick electrode pair configuration. I modeled transwell membrane with different membrane areas, and observed the effect of cell growth on TEER values. TEER values,…

In my previous posts so far, I performed simulations to understand the behavior of TEER variation upon changes in electrode and membrane configuration. None of those models addresses the effects of cell growth on the TEER values. In real experiments, people measure the TEER of system before adding the cells (background TEER), and then monitor…

In an effort to better understand and check Karl’s model of sieving, I’ve built a significantly simpler version. The goal is to investigate the potential benefits of thinner membranes in dead-end filtration and separations. In my model 1 ml of water is displaced from the top bucket to an originally empty bottom bucket with a…