The preconcentration of proteins with low concentrations can be used to increase the sensitivity and accuracy of detection. A nonlinear electrokinetic flow is induced in a nanofluidic channel due to the overlap of electrical double layers, resulting in the fast accumulation of proteins, referred to as the exclusion-enrichment effect. The proposed chip for protein preconcentration was fabricated using simple standard soft lithography with a polydimethylsiloxane replica. This study extends our previous paper, in which gold nanoparticles were manually deposited onto the surface of a protein preconcentrator. In the present work, nanofractures were formed by utilizing the self-assembly of gold-nanoparticle-assisted electric breakdown. This reliable method for nanofracture formation, involving self-assembled monolayers of nanoparticles at the junction gap between microchannels, also decreases the required electric breakdown voltage. The experimental results reveal that a high concentration factor of 1.5×104 for a protein sample with an extremely low concentration of 1 nM was achieved in 30 min by using the proposed chip, which is faster than our previously proposed chip at the same conditions. Moreover, an immunoassay of bovine serum albumin (BSA) and anti-BSA was carried out to demonstrate the applicability of the proposed chip.

The oxide roughness of metal-oxide-silicon diodes can be intentionally controlled by the very high vacuum pre-bake and the growth conditions during rapid thermal oxidation. Both surface and Si/oxide interface have the similar magnitude of roughness measured by atomic force microscopy, indicating the conformal growth of oxide. At accumulation bias (positive gate bias), the holes tunnel from gate electrode to n-type Si through the ultrathin oxide, and recombine with the electrons in the accumulation region radiatively if phonon scattering and roughness scattering provide the necessary momentum. The light emission intensity increases with increasing oxide roughness. Strong electroluminescence with an external quantum efficiency of ∼ 2 × 10 −6 at room temperature was observed from a rough metal-oxide-silicon tunneling diode.

No abstract