Integration of electrodes in Si channels using low temperature polymethylmethacrylate bonding

Abstract

Low temperature Si to glass bonding using polymethylmethacrylate (PMMA) as an adhesive layer is developed to integrate electrodes with Si channels. The integrated microsystem contains channels dry etched in Si with widths ranging from 3to100μm and depths ranging from 100nmto30μm. The channels are bonded to a 100μm thick glass consisting of 600nm thick patterned PMMA and 20∕50nm thick Cr∕Au electrodes, with PMMA as an adhesive layer. The typical bond strength is 3MPa, obtained by bonding at 110°C with 600nm thick PMMA. Fluidic flow studies are carried out in channels that are 50 and 100μm wide with a depth of 100nm. De-ionized water flows through the sealed Si channels due to capillary pressure with an initial velocity of 0.65mm∕s for 50μm wide and 100nm deep channels. Electric fields are used to induce DNA motion with velocities from 2.4to14.5μm∕s in 100μm wide and 20μm deep channels. The forces generated by the fields and the fluid flow are also used to stretch the tethered DNA molecules up to 15μm long in the microchannels.

Voltage-assisted polymer wafer bonding

“…Bonding experiments were performed with PMMA at two different bond temperatures: 90 • C and 160 • C. While the experiments at 90 • C produced higher bond strength, the samples bonded at 160 • C were much more uniform, had fewer voids and more pieces survived dicing. These results agree with the results of [27] where a higher temperature produced a more uniform bond (as explained earlier), improving uniformity and therefore chip survival. 90 • C is below the glass transition temperature for PMMA; hence, it not be to deform and fill the surface roughness of the glass.…”

The immobilization of DNA molecules to electrodes in confined channels at physiological pH

“…The fabrication technology to integrate electrodes with sealed channels is based on bonding an array of Si channels with electrodes on a thin glass substrate using PMMA as an adhesive layer [13]. PMMA bonding is used to integrate electrodes with the channel array since PMMA does not clog the channels during bonding due to its high viscosity.…”

Control of DNA motion in microchannels integrated with dual electrodes

“…10 The DNA velocity increases with the amplitude of the applied voltage and decreases with distance from the electrode pair. 11 Here we have expanded on this work by fabrication of a new system consisting of either 400 or 900 nm wide Si channels integrated with two electrode pairs. Using this dual-electrode system, we have demonstrated for the first time the ability to precisely control the motion and average position of DNA confined within microchannels using ac potential.…”