title: Experimental and theoretical investigation of the precise transduction mechanism in giant magnetoresistive biosensors.
abstract: Giant magnetoresistive (GMR) biosensors consisting of many rectangular stripes are being developed for high sensitivity medical diagnostics of diseases at early stages, but many aspects of the sensing mechanism remain to be clarified. Using e-beam patterned masks on the sensors, we showed that the magnetic nanoparticles with a diameter of 50 nm located between the stripes predominantly determine the sensor signals over those located on the sensor stripes. Based on computational analysis, it was confirmed that the particles in the trench, particularly those near the edges of the stripes, mainly affect the sensor signals due to additional field from the stripe under an applied field. We also demonstrated that the direction of the average magnetic field from the particles that contributes to the signal is indeed the same as that of the applied field, indicating that the particles in the trench are pivotal to produce sensor signal. Importantly, the same detection principle was validated with a duplex protein assay. Also, 8 different types of sensor stripes were fabricated and design parameters were explored. According to the detection principle uncovered, GMR biosensors can be further optimized to improve their sensitivity, which is highly desirable for early diagnosis of diseases.
authors.affiliation: Department of Mechanical Engineering, Stanford University, Stanford, California, USA.
authors.forename: Jung-Rok
authors.initials: JR
authors.lastname: Lee
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California, USA.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Sato
authors.affiliation: Department of Mechanical Engineering, Stanford University, Stanford, California, USA.
authors.forename: Daniel J B
authors.initials: DJ
authors.lastname: Bechstein
authors.affiliation: MagArray Inc., 521 Cottonwood Drive, Milpitas, California, USA.
authors.forename: Sebastian J
authors.initials: SJ
authors.lastname: Osterfeld
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California, USA.
authors.forename: Junyi
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California, USA.
authors.forename: Adi Wijaya
authors.initials: AW
authors.lastname: Gani
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California, USA.|Department of Electrical and Computer Engineering, University of California, San Diego, USA.
authors.forename: Drew A
authors.initials: DA
authors.lastname: Hall
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California, USA.|Department of Materials Science and Engineering, Stanford University, Stanford, California, USA.
authors.forename: Shan X
authors.initials: SX
authors.lastname: Wang
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods; D006801:Humans; D060526:Magnetic Fields; D008280:Magnetics / Q000295:instrumentation / Q000379:methods; D058185:Magnetite Nanoparticles; D008962:Models, Theoretical
chemical_list: D058185:Magnetite Nanoparticles