High-Tc SQUID gradiometer system for immunoassays
Journal article, 2008

A high-Tc dc SQUID (superconducting quantum interference device) gradiometer was developed for magnetic immunoassays where magnetic nanoparticles are used as markers to detect biological reactions. The gradiometer was fabricated on a 5 × 10 mm2 SrTiO3 bicrystal substrate and has a gradiometer resolution of 2.1 pT cm−1 Hz−1/2. A magnetic signal was detected from a sample of 1 μl of Fe3O4 nanoparticles in a 40 mg ml−1 solution kept in a microcavity fabricated on Si wafers with Si3N4 membranes using MEMS (micro-electro-mechanical-systems) technology. It was found that volumes as small as 0.3 nl in principle would be detectable with our present device. This corresponds to a total number of particles of 2.2 × 107. The estimated average dipole moment per particle is 4.8 × 10−22 Am2. We are aiming at reading out immunoassays by detecting the Brownian relaxation of magnetic nanoparticles, and we also intend to integrate MEMS technology into our system.

Gradiometer

Magnetic nanoparticles

Immunoassays

SQUID

Author

Fredrik Öisjöen

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Per Magnelind

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Alexei Kalaboukhov

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Dag Winkler

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Superconductor Science and Technology

0953-2048 (ISSN) 1361-6668 (eISSN)

Vol. 21 3 Art. Nr. 034004-

Subject Categories

Physical Sciences

Other Engineering and Technologies not elsewhere specified

DOI

10.1088/0953-2048/21/3/034004

More information

Created

10/8/2017