While my focus will be on packaging a single multi-channel chip device, I have captured here an initial concept for packaging multiple channels. The technique required is the application of verticle PDMS structures to direct blood and dialysate to and…
Author: Dean Johnson
Dr. Johnson is a Research Assistant Professor in Nephrology who was awarded an R01 in 2020. He earned his Ph.D. in Microsystems Engineering from RIT and is currently working on hemodialysis devices based on the ultrathin nanoporous membranes developed earlier by this group.
The effect of pump rate and channel height on Urea clearance (COMSOL modeling)
Comsol modeling was done to find the ideal channel height and volumetric flow rate. What is clear from the simulation is that ever increasing flow rates in the model lead to increased clearance and decreasing channel heights give some benefit…
Urea clearance in the presence of BSA in PBS
In this experiment I use a syringe pump to move urea dissolved in ddH2O through a 10 mm long, 300 µm high, 500 µm wide dialysis channel. The retentate is collected in a fraction collector then measured using a urea…
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Adsorption of F-BSA on PEGylated pnc-Si, PEGylated Glass, Glass
This study was run to test test the efficacy of PEGylation in blocking BSA adsorption. Three surface types were used, glass, PEGylated glass, and PEGylated pnc-SI. The glass was cleaned in Ethyl Alcohol, dried and UV treated, PEGylated glass was…
Long Term Urea Clearance (8 hours)
SET-UP Syringe pump: 5 mL of 7.6-nmol/100µL, 5.6 µL/min pump rate. Single Channel dialyser, 10 mm long, 0.5 mm wide, 0.3 mm high in stirred beaker of DI water Fraction Collector programed to rotate every 30 min. Set up in…
BSA Retention in Single Channel Dialyzer
Regarding the single channel dialyzer chip with 20-nm thick nano-porous silicon membrane: 10 mm long, 300 µm deep, 500 µm wide channels. Now that we’ve shown that a measurable quantity of urea is filtered out of DI water in one…
Single Channel Dialyzer
The main difficulty with creating a simulation of the single channel dialysis chip is that the membrane is so very thin (20 nm). This is especially true when compared to its length of 10 mm but also when compared to…
Single Channel 20 nm membrane breakage…
There is a reliability/handling issue with the single slot chips. 0.5 mm x 10 mm slots, 20 nm thick membranes with 40 nm SiN reinforcement. The membranes are easily packaged in an upper fluidic PDMS layer with inlet/outlets and two…
Rapid Prototype of Single Channel Dialysis Device
In order to rapidly test the entire setup for dialysis evaluation, including piezoelectric micro motor and recirculating fluid path, a means of quickly evaluating PDMS designs is needed. A mold was created with a multi-print technique in which printer toner…
Urea Reduction Ratio, URR
As discussed in a previous post “Clearance, Kt/V, and Concentration…”, we will use the Kt/V metric to measure the effectiveness of dialysis. There are other methods that are used: one of these is the Urea Reduction Ratio, URR. URR is…
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