Selective patterning of Si-based biosensor surfaces using isotropic silicon etchants

Abstract

Ultra-sensitive, label-free biosensors have the potential to have a tremendous impact on fields like medical diagnostics. For the majority of these Si-based integrated devices, it is necessary to functionalize the surface with a targeting ligand in order to perform both specific biodetection. To do this, silane coupling agents are commonly used to immobilize the targeting ligand. However, this method typically results in the bioconjugation of the entire device surface, which is undesirable. To compensate for this effect, researchers have developed complex blocking strategies that result in selective patterning of the sensor surface. Recently, silane coupling agents were used to attach biomolecules to the surface of silica toroidal biosensors integrated on a silicon wafer. Interestingly, only the silica biosensor surface was conjugated. Here, we hypothesize why this selective patterning occurred. Specifically, the silicon etchant (xenon difluoride), which is used in the fabrication of the biosensor, appears to reduce the efficiency of the silane coupling attachment to the underlying silicon wafer. These results will enable future researchers to more easily control the bioconjugation of their sensor surfaces, thus improving biosensor device performance.

Nonlinear nanophotonic devices in the ultraviolet to visible wavelength range

“…To realize the potential of small organic molecules in integrated photonics, fabrication methods which allowed oriented and ordered monolayers of molecules had to be developed. One such route was inspired by earlier work in the biosensor field [232][233][234][235][236][237][238]. By self-assembling and covalently attaching nonlinear organic molecules onto the device surface, these criteria can be achieved.…”

“…One such route was inspired by earlier work in the biosensor field (232)(233)(234)(235)(236)(237)(238). By selfassembling and covalently attaching nonlinear organic molecules onto the device surface, these criteria can be achieved.…”

Review Label-free detection with high-Q microcavities: a review of biosensing mechanisms for integrated devices

“…For example, for the modification of glass (and the thermal oxide layer on silicon) one can use silanization of the glass-silanol groups [13, 16] or physisorption of proteins and hydrogels [57, 107]. In multiplexed arrays, each sensor element can be individually functionlized, by, for example fluids controlled with microfluidics [23, 24], or ink-jet printing [113] or patterning with silicon etchants [114]. Also very recently, one and two-dimensional photonic crystal resonators have been explored to detect biomolecules, including interleukins 4, 6 and 8 [115] and bovine serum albumin [116] as well as immunoglobulins [106].…”

Hybrid Integrated Label-Free Chemical and Biological Sensors

“…Developing new surface chemistries for optical sensors is crucial in order to achieve specific and sensitive detection. By optimizing the surface functionalization procedures, optical sensors can be developed which are capable of detecting single molecules, cells, and nanoparticles [ 15 , 120 , 173 , 174 ]. Effective detection of analytes is especially crucial in medical and diagnostic applications.…”