High Sensitivity InSb Ultra-Thin Film Micro-Hall Sensors for Bioscreening Applications

Abstract

A high sensitivity, 4.5 µm×4.5 µm InSb thin film micro-Hall sensor (micro-HS) with a minimum field detection (B min) of 77 nT/(Hz)1/2 was developed for bioscreening applications and used for the detection of a single 2.8 µm diameter superparamagnetic microbead by monitoring its ac magnetic susceptibility. The scalability of the InSb micro-HS was demonstrated by fabricating 500 nm×500 nm InSb nano-Hall sensors with B min of 0.72 µT/(Hz)1/2 that could potentially be used to detect 100 nm sized superparamagnetic particles.

Magnetic biosensor technologies for medical applications: a review

“…Phase-sensitive detection using InSb Hall crosses has also been demonstrated by Sandhu et al [146], in which 2.8 lm diameter beads were detected using an AC excitation field now applied in-plane and a perpendicular DC field applied by a permanent magnet. In this measurement geometry, the Hall voltage is again measured at the first harmonic, but now increases when the DC field is applied if a bead is present over the sensor.…”

Sensitivity dependence of Hall biosensor arrays with the position of superparamagnetic beads on their active regions

“…There have already been reports on the detection of superparamagnetic beads with diameters in the range of 200 nm to 2.8 m using Hall sensors and lock-in measurements, 4,6 where an alternating magnetic field is applied parallel to the surface of the Hall sensor. The presence of the magnetic beads is confirmed by using the lock-in amplifier to monitor the Hall voltage due to changes of the magnetization of magnetic beads under a dc magnetic field applied perpendicular to the sensor surface.…”

High efficiency Hall effect micro-biosensor platform for detection of magnetically labeled biomolecules

“…On the other hand, studies on the sensitivity of Hall sensors clearly indicate that the opposite would be more desirable in order for high sensitivity, where the size of the beads and sensor should be more or less equal for best results (Sandhu et al, 2004). For reliable qualitative analysis, the full surface coverage is desired, and if quantitative interpretation is undertaken the surface coverage should be a function of the concentration of target molecules only, which can be achieved when the step of magnetic labeling is conducted in highly reproducible conditions.…”

“…Further, prototype platforms include magnetoresistive (Baselt et al, 1998;Graham et al, 2005) and Hall effect platforms (Besse et al, 2002;Sandhu et al, 2004) that employ superparamagnetic beads as labels which potentially enable manipulation of individual biomolecules and cells (Wang et al, 2001). Collecting beads at active sensor regions decreases the time required for the analytical process (localized immobilization) using reduced volumes of beads.…”