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High-Tc SQUID gradiometer system for immunoassays

Fredrik Öisjöen (Institutionen för mikroteknologi och nanovetenskap, Kvantkomponentfysik) ; Per Magnelind (Institutionen för mikroteknologi och nanovetenskap, Kvantkomponentfysik) ; Alexei Kalaboukhov (Institutionen för mikroteknologi och nanovetenskap, Kvantkomponentfysik) ; Dag Winkler (Institutionen för mikroteknologi och nanovetenskap, Kvantkomponentfysik)
Superconductor Science and Technology Vol. 21 (2008), 3, p. Art. Nr. 034004.
[Artikel, refereegranskad vetenskaplig]

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.

Nyckelord: SQUID, Gradiometer, Magnetic nanoparticles, Immunoassays

Denna post skapades 2008-02-21. Senast ändrad 2016-07-19.
CPL Pubid: 68414


Institutioner (Chalmers)

Institutionen för mikroteknologi och nanovetenskap, Kvantkomponentfysik


Övrig annan teknik

Chalmers infrastruktur