Magnetic microbead detection using the planar Hall effect

Magnetic biosensor technologies for medical applications: a review

“…The AMR effect offers much scope for tailoring the shape of the device to constrain both the flow of current through it and the magnetisation to obtain a desired resistance response. 7 Accordingly, the two biosensors reported which use AMR are a cross [35,36] very similar to the Hall crosses previously mentioned and a ring [112]. The former consists of two crossed 60 9 10 lm bars of 200 Å thick Ni 80 Fe 20 or permalloy (Py).…”

“…3 (cgs units) [36,112] and so most MR sensors attempt to measure a large number of beads to obtain a high signalto-noise ratio, usually through mass coverage of the sensor surface by a monolayer of beads. Unfortunately, such averaged detection methods are unsuitable for reading of bead libraries, where each bead is supposed to be functionalised with a different DNA sequence, and so must be sensed individually.…”

Exchange-biased planar Hall effect sensor optimized for biosensor applications

“…2, [4][5][6] Exchange-biased PHE sensors with a 20 nm thick ferromagnetic ͑FM͒ layer were studied by Ejsing et al 4,5 Subsequently, the range of FM thicknesses from t = 3 to 20 nm were studied by Tanh et al 6 We present investigations of exchange-biased Permalloy PHE sensor crosses with a fixed active area of w ϫ w =40ϫ 40 m 2 and t = 20, 30, and 50 nm. The investigations include the thickness dependence of sensor sensitivity, linear operation range, and electrical noise and it is shown that the sensor response to magnetic beads can be significantly improved by increasing t. The general results are exemplified by calculations of the signal-to-noise ratio ͑SNR͒ of a single M-280 Dynabead® placed on top of the sensor center.…”

GMR sensors: Magnetoresistive behaviour optimization for biological detection by means of superparamagnetic nanoparticles

“…The detection system can be potentiometric (Hintsche et al, 1995), mechanical (Ilic et al, 2000), amperometric (Martelet, 1998), optical (Stokes and Vo-Dinh, 2001), conductometric (Park et al, 2002), piezoelectric (Tombelli et al, 2005), or based on any other physico-chemical phenomenon. In this sense, magnetoresistive sensors have gained importance in the last decades (Baselt et al, 1998;Ejsing et al, 2005;Li et al, 2006;Vopálenský et al, 2004). Nowadays, such transducers are well-stabilized in various industrial sectors for a wide range of applications due to their many advantages.…”