Liquid phase immunoassay utilizing magnetic marker and high Tc superconducting quantum interference device

We have developed a liquid phase immunoassay system utilizing a magnetic marker and a superconducting quantum interference device (SQUID). In this system, the magnetic marker was used to detect the biological material called antigen. The magnetic marker was designed so as to generate a remanence, and the remanence field of the markers that bound to the antigens was measured with the SQUID. The measurement was performed in a solution that contained both the bound and free (or unbound) markers, i.e., without using the so-called bound/free (BF) separation process. The Brownian rotation of the free markers in the solution was used to distinguish the bound markers from the free ones. Using the system, we conducted the detection of biological material called IgE without BF separation. At present, we could detect the IgE down to 7 pg (or 39 amol

Noise properties of direct current SQUIDs with quasiplanar YBa2Cu3O7 Josephson junctions

We describe the noise performance of dc SQUIDs fabricated with quasiplanar ramp‐type Josephson junctions on the basis of c‐axis‐oriented YBa2Cu3O7/PrBa2Cu3O7 thin‐film heterostructures. The noise spectrum of the dc SQUIDs was measured with dc‐ and ac‐bias schemes at different temperatures and showed values below 10−5 Φ0/Hz1/2 down to frequencies of about 1 Hz at 70 K. Up to now for the magnetic fluxnoise and the energy resolution obtained at 1 kHz and 77 K the best values were 2.5×10−6, Φ0/Hz1/2 and 3×10−31 J/Hz, respectively. A study of the white and 1/fnoises of the SQUIDs was performed. The influence of magnetic flux, bias current, high static magnetic fields, and aging on the SQUID noise were investigated. The junctions and devices do not degrade due to aging in air or thermal cycling

Switching between dynamic states in intermediate-length Josephson junctions

The appearance of zero-field steps (ZFS’s) in the current-voltage characteristics of intermediate-length overlap-geometry Josephson tunnel junctions described by a perturbed sine-Gordon equation (PSGE) is associated with the growth of parametrically excited instabilities of the McCumber background curve (MCB). A linear stability analysis of a McCumber solution of the PSGE in the asymptotic linear region of the MCB and in the absence of magnetic field yields a Hill’s equation which predicts how the number, locations, and widths of the instability regions depend on the junction parameters. A numerical integration of the PSGE in terms of truncated series of time-dependent Fourier spatial modes verifies that the parametrically excited instabilities of the MCB evolve into the fluxon oscillations characteristic of the ZFS’s. An approximate analysis of the Fourier mode equations in the presence of a small magnetic field yields a field-dependent Hill’s equation which predicts that the major effect of such a field is to reduce the widths of the instability regions. Experimental measurements on Nb-NbxOy-Pb junctions of intermediate length, performed at different operating temperatures in order to vary the junction parameters and for various magnetic field values, verify the physical existence of switching from the MCB to the ZFS’s. Good qualitative, and in many cases quantitative, agreement between analytic, numerical, and experimental results is obtained

SQUIDs in biomagnetism : A roadmap towards improved healthcare

This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 686865.Peer reviewedPublisher PD