Use of a GMR-SV Device Below a Single Coil and Channel to Detect the Deformation Properties of Red Blood Cell Membranes

Abstract

A dual-type giant magnetoresistance-spin valve (GMR-SV) multilayer of Ta/NiFe/CoFe/Cu/CoFe/IrMn/CoFe/Cu/CoFe/NiFe/Ta was prepared by ion beam deposition. The bottom exchange coupling field (Hex) and coercivity (Hc), the top Hex and Hc, magnetoresistance (MR) ratio, and magnetic sensitivity (MS) of the as-grown sample were 480 Oe and 120 Oe, 240 Oe and 60 Oe, 6.3%, and 2.3%/Oe, respectively. The two electrodes of the GMR-SV device, a single turn coil of micrometer size, and a valley formed using a photoresist (PR) process to produce a channel of 10 μm as a biosensor were patterned by using a lithography process and an electron cyclotron resonance (ECR) Ar-ion milling system. The MR ratio and the MS of the patterned GMR-SV device were 3.5% and 0.88%/Oe, respectively. Computer simulations revealed that a single turn coil resulted in sufficient field strength to induce a magnetic field in the red blood cell (RBC)’s membrane of 12 Oe at an applied current of 10 mA. A valley channel, formed by the PR process, with a thickness of 10 μm and a width of 8 μm, occurred on the upper layer above the coil at the center of the GMR-SV device. Four types of RBCs, including normal circular and deformed elliptical membranes, were bonded to the edge and the central portion of the RBC due to the arrangement of the magnetic beads (MBs) with dipole moments. The differentially detected output signals of the normal and deformed RBC membranes, which were combined with MBs, were distributed the region of 5–30 μV.