An optical detector has been fabricated that is specific for targeted bacterial cells, by stamping an antibody grating pattern on a silicon surface. The antibody grating alone produces insignificant optical diffraction, but upon immunocapture of cells, the optical phase change produces a diffraction pattern. This technique eliminates much of the surface modifications and the secondary immunochemical or enzyme-linked steps that are common in immunoassays. Microcontact printing provides an alternative to previously reported photolithographic-mediated antibody patterning processes and uses a photolithographic process simply to produce the elastomeric stamp. We have stamped antibodies directly onto clean native oxide silicon substrates with no other chemical surface treatments. Direct binding of the antibodies to the silicon occurs in a way that still allows them to function and selectively bind antigen. The performance of the sensor was evaluated by capturing Escherichia coli O157:H7 cells on the antibody-stamped lines and measuring the intensity of the first-order diffraction beam resulting from the attachment of cells. The diffraction intensity increases in proportion to the cell density bound on the surface.

Microcontact printing was used to pattern silicon, aluminum, and titanium substrates using octadecyltrichlorosilane as the ink and an elastomer as the stamp. Patterns were transferred into the substrates using both dry and wet etching. The Al and Ti were etched using an electron cyclotron resonance (ECR) plasma source at low ion energies and low pressure. Silicon was etched in HF to remove the native oxide, followed by KOH. Microcontact printing using OTS ink is a convenient and easy way to pattern both semiconductor and metal surfaces without the extended use of photolithography.

No abstract

No abstract

No abstract