See my previous post for background information. It has been established that diffusion of small particles (diameter < roughly 1/3 pore diameter) across ultrathin membranes is mediated almost entirely by the ability of the particle to discover a pore, rather than by its ability to diffuse through a pore once one has been found. In…
Meghan and I continued to experiment with our PLA printed transwells. We came up with a protocol that has some cells growing on pnc-Si (albeit not to confluence yet), and less so on nonporous Silicon nitride. In the gallery below B2, B3, and B4 are 1060 nonporous silicon nitride SEPCONS (cells in trenches) and B5…
Prior to my qualifying exam about a month ago, I put together a simple model of transport (detailed in this previous post) across a nanomembrane that incorporated electrostatics as well as terms describing both convective and diffusive transport across the membrane. It was a useful model, but ultimately limited, as shown by the following image:…
Below are various SEMs of NPN membranes. (All samples were coated with metal by using the Denton Ag sputterer for 120 s) These were used samples that have been sitting out in the lab for weeks. I don’t remember the exact details of the processing. I believe they were filters we used to test the possibility…
For a while now I’ve been working on developing and testing the practicality of using nanoporous membranes as filters for highly sensitive assays. Traditional filter-based assays are restricted in their speed by both the time it takes for a particle to find a pore as well as the time it takes for the particle to…
Sketchup is a great tool for showing off your microsystem ideas, complete with animation capabilities. However, it cannot intrinsically move objects around, show how water flows in a channel, or insert pieces into a slot, which are useful for understanding how a microsystem can be assembled. Keyframe Animation is a plugin for sketchup that…
Bob and I are trying to determine which wet etch would be appropriate to use to remove the native oxide inside the pores before membrane liftoff. The issue is when removing the native oxide, we will remove part of the membrane. So far, we removed native oxide from bare silicon wafers using 50:1 HF. For…
During our meeting with Vincent Tabard-Cossa from U Ottawa, we are going to explore the concept of using nano porous silicon nitride membranes in electronic detection schemes for identifying nucleic acid:small molecule complexes. The concept was demonstrated by Wanunu et al, Nano Letters, 2011, where they showed single nanopores were able to detect complexes of…
On May 13, Jim McGrath and I are hosting Vincent Tabard-Cossa from the University of Ottawa. We will be interacting with Vincent as a sort of NRG mini-retreat day. See the information below. Vincent’s U Ottawa Page Home Visit Agenda Tuesday, May 13 9:00-10:00AM – BME Dept seminar by Vincent Tabard-Cossa 10:00-11:15AM – Nanomembrane Research…
We were targeting a TEOS layer of 300 nm for the SiO2 membrane. The wafers were patterned with ø3 µm pores using S1813 resist (~1.5 µm thick). The target etch time in the Drytek RIE is 4 min 10 s using SF6 and Ar. We will need a thicker resist coating to prevent the RIE…