Teflon™-coated silicon apertures for supported lipid bilayer membranes

Abstract

We present a method for microfabricating apertures in a silicon substrate using well-known cleanroom technologies resulting in highly reproducible giga-seal resistance bilayer formations. Using a plasma etcher, 150μm apertures have been etched through a silicon wafer. Teflon™ has been chemically vapor deposited so that the surface resembles bulk Teflon and is hydrophobic. After fabrication, reproducible high resistance bilayers were formed and characteristic measurements of a self-inserted single OmpF porin ion channel protein were made.

Ion Channels on Silicon

“…A glass aperture has been fabricated with heavy ion irradiation and wet etching to form a low capacitance aperture suitable for low noise bilayer measurement [5][6][7]. Silicon has been used as a substrate and then coated with polytetrafluoroethylene (PTFE, Teflon) to form stable high resistance, repeatable seals between painted lipid bilayers and the device [9]. Silicon devices have also been integrated with polydimethylsiloxane (PDMS) microfluidic channels to help direct single cells to the aperture [10].…”

“…Ion channel reconstitution takes advantage of the natural properties of lipids to spontaneously form a lipid bilayer and then insert particular proteins of interest. Glass [5][6][7], Si/SiO 2 [8][9][10][11], polytetrafluoroethylene [12] and silicon elastomers [13] have been used as the substrate in these devices to span lipid bilayers and record ion channel activity. A glass aperture has been fabricated with heavy ion irradiation and wet etching to form a low capacitance aperture suitable for low noise bilayer measurement [5][6][7].…”

Investigating cellular electroporation using planar membrane models and miniaturized devices

“…Consequently, in most of the cases, an insulating (silicon-based) material is directly employed to make the membrane that contains the aperture. To achieve this, an additional layer of insulating material must be deposited on the silicon membrane, either by thermal growth (silicon dioxide) [112,[114][115][116][117] or using plasma enhanced chemical vapor deposition (PECVD) (silicon nitride) [32,[107][108]113].…”

“…Consequently, an additional (thick) layer of insulating material is required to restore the quality of the electrical measurements, and SU-8 [112,[116][117] or polyimide [108] are commonly employed for that purpose. A final step consists of coating the substrate around the aperture with a hydrophobic material, such as a fluorinated polymer [112,114,[116][117] to promote sealing of the BLM on the substrate (seal resistance > 20 GΩ) and subsequently to enhance the quality of the electrical measurements. Figure 3.11B shows one example of such a multiple-layer device.…”

“…The fabrication process is dictated by the nature of the substrate in which the orifices are made as well as their final size, as reviewed below. In this category of miniaturized devices, the substrates containing the apertures are fixed between two conventional mL-or μL-sized reservoirs usually made from polymers such as Teflon [3,114] or PDMS (polydimethylsiloxane) [32].…”