Ultra‐Low Power Corrosion Sensor Made of Iron Nanowires on Magnetic Tunnel Junctions

Abstract

Corrosion sensors are of critical importance for monitoring the destructive potential of a corrosive environment. Due to their large surface-to-volume area, nanowires react with a remarkably high speed, rendering them attractive corrosion-sensing elements. To avoid the difficulties related to contacting nanowires, we present a magnetic approach, exploiting the fast reaction of nanowires to the environment. Iron nanowires have a high magnetization value, which decreases upon nanowire corrosion. Due to shape anisotropy, they also possess a large remnant magnetization, which is detectable by a magnetic tunnel junction sensor. Iron nanowires were fabricated by electrochemical deposition, placed on top of the magnetic tunnel junction and aligned using a magnetic field. The nanowires provide a bias field causing a change of the characteristic curve of the tunnel junction. The corrosion sensor was tested in

Template-Assisted Iron Nanowire Formation at Different Electrolyte Temperatures

“…Because of their large aspect ratio, defined as the ratio between the nanowire length and the diameter (L/ɸ), nanowires exhibit magnetic anisotropy, which makes them better candidates for MRI (magnetic resonance imaging) contrast agents, electrochemical water splitting, hyperthermia, or targeted drug delivery [ 3 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ] than their spherical nanoparticle counterparts. The nanowire matrix, which has a high surface-to-volume ratio, enables the development of corrosion, flow, acoustic, and pressure sensors that have a significant efficiency enhancement [ 21 , 22 , 23 , 24 , 25 , 26 ]. When nanowires are embedded in polycarbonate membranes, they can serve as flexible permanent magnets [ 26 , 27 , 28 , 29 , 30 ], but when they are released from the template, they may act as responsive magnetic sensors [ 31 , 32 ].…”