(Invited) Single Cell Detection Using Magnetic Zigzag Nanowire Biosensor

Monday, October 12, 2015: 10:55
Ellis West (Hyatt Regency)
H. T. Huang (National Tsing Hua University) and Z. H. Wei (National Tsing Hua University)
Among various types of biosensors, magnetoresistance-based biosensors possess several advantages including high sensitivity and being less interfered by the environment, and are therefore suitable for sensitive biodetection [1-4]. Besides, the magnetic is not shielded by chemical compounds, microstructures, or another biomaterials, so the signals detected by the magnetoresistance-based biosensors are not influenced by the surrounding objects. In this report we present wave Permalloy (Ni81Fe19) nanowires with various line widths as a biomolecular sensing device. In this design, the magnetic poles on the apexes and valleys of the wave Permalloy nanowires can actively attract the magnetic beads immobilized biomolecular onto the nanowires for detection.
Permalloy nanowires with line widths 300 and 500 nm deposited onto wave silicon grooves were designed as biosensing devices of nano magnetic beads, which modified by biomolecule. Figure 1 shows the SEM image of the wave ferromagnetic nanowires. We applied a magnetic field along x axis, and measured the magnetoresistance curves of the nanowires before and after the attachment of magnetic beads by four-probe method. The stray field generated by the magnetized beads are against the magnetic moments of the wave sheet surfaced film, therefore making it harder for the switching process to occur. It was observed that the sensitivity 43.29% in switching field variation after magnetic beads were attached can be obtained when the field was applied perpendicular to the plane of the 300 nm wide nanowire. The sensitivity 45.78% in magnetoresistance variation occurred in the 500 nm wide nanowire for the same field direction.
Further work, we will focus on different wire width (150, 300, 500, and 800 nm) before and after attaching nano magnetic beads on the nanowires, when magnetic fields were applied in various directions,x, y, and z (out-of-plan) axes.

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