A device apt to detect a single magnetic nano-particle placed in its proximity is disclosed. The device is a ferromagnetic corner-shaped nano-structure with 4 gold contacts deposited on it: two contacts are for injecting a small electric current (injection contacts) and the other two are used to measure the voltage drops in the ring portion between them (reading contacts). The voltage drops depend on the magnetization configuration inside the nano-structure (anisotropic magnetoresistance effect, AMR), in particular the configuration in the corner of the structure flanked by the reading contacts. The magnetization configuration can be manipulated in a controlled manner by the application of an external field and probed unambiguously by measuring the voltage drop in the reading contacts. The highly predictable magnetization switching and abrupt transition allow the nano-structure to be used for nano-particle detection as follows. The proximity of a magnetic nano-particle affects the values of the external field required to modify the magnetization configuration, hereby providing a practical way to detect its presence. Since magnetic nano-particles can be attached to biomolecules, the device can be used for molecular recognition. Single molecule detection can be achieved as the effect of a single magnetic bead on the micromagnetic configuration of the nanostructure is very high. This relies on the fact that the domain wall and magnetic beads have comparable dimensions. In addition it is described how suitable arrangements of such nano-structures in arrays can be used to detect and count multiple magnetic nano-particles allowing for a quantitative determination of molecules concentration in biological samples. Very low limits of detection (LOD) can be achieved, theoretically below 1 pM, with a sizable improvement with respect to standard detection systems for molecules (i.e. fluorescence).
Biosensori spintronici con area attiva localizzata su una parete di dominio magnetico
VAVASSORI, Paolo
2008
Abstract
A device apt to detect a single magnetic nano-particle placed in its proximity is disclosed. The device is a ferromagnetic corner-shaped nano-structure with 4 gold contacts deposited on it: two contacts are for injecting a small electric current (injection contacts) and the other two are used to measure the voltage drops in the ring portion between them (reading contacts). The voltage drops depend on the magnetization configuration inside the nano-structure (anisotropic magnetoresistance effect, AMR), in particular the configuration in the corner of the structure flanked by the reading contacts. The magnetization configuration can be manipulated in a controlled manner by the application of an external field and probed unambiguously by measuring the voltage drop in the reading contacts. The highly predictable magnetization switching and abrupt transition allow the nano-structure to be used for nano-particle detection as follows. The proximity of a magnetic nano-particle affects the values of the external field required to modify the magnetization configuration, hereby providing a practical way to detect its presence. Since magnetic nano-particles can be attached to biomolecules, the device can be used for molecular recognition. Single molecule detection can be achieved as the effect of a single magnetic bead on the micromagnetic configuration of the nanostructure is very high. This relies on the fact that the domain wall and magnetic beads have comparable dimensions. In addition it is described how suitable arrangements of such nano-structures in arrays can be used to detect and count multiple magnetic nano-particles allowing for a quantitative determination of molecules concentration in biological samples. Very low limits of detection (LOD) can be achieved, theoretically below 1 pM, with a sizable improvement with respect to standard detection systems for molecules (i.e. fluorescence).I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
