Ultrasensitive magnetic nanoparticle detector for biosensor applications

Yu Chi Liang, Long Chang, Wenlan Qiu, Arati G. Kolhatkar, Binh Vu, Katerina Kourentzi, T. Randall Lee, Youli Zu, Richard Willson, Dmitri Litvinov

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Ta/Ru/Co/Ru/Co/Cu/Co/Ni80Fe20/Ta spin-valve giant magnetoresistive (GMR) multilayers were deposited using UHV magnetron sputtering and optimized to achieve a 13% GMR ratio before patterning. The GMR multilayer was patterned into 12 sensor arrays using a combination of e-beamand optical lithographies. Arrays were constructed with 400 nm × 400 nmand 400 nm × 200 nm sensors for the detection of reporter nanoparticles. Nanoparticle detection was based on measuring the shift in high-to-low resistance switching field of the GMR sensors in the presence of magnetic particle(s). Due to shape anisotropy and the corresponding demag field, the resistance state switching fields were significantly larger and the switching field distribution significantly broader in the 400 nm × 200 nm sensors as compared to the 400 nm × 400 nm sensors. Thus, sensor arrays with 400 nm × 400 nm dimensions were used for the demonstration of particle detection. Detection of a single 225 nm Fe3O4 magnetic nanoparticle and a small number (~10) of 100 nm nanoparticles was demonstrated. With appropriate functionalization for biomolecular recognition, submicron GMR sensor arrays can serve as the basis of ultrasensitive chemical and biological sensors.

Original languageEnglish (US)
Article number1296
JournalSensors (Switzerland)
Issue number6
StatePublished - Jun 6 2017


  • Bioinstrumentation
  • Biosensor
  • Magnetic particle detection
  • Magnetoresistive sensors

ASJC Scopus subject areas

  • Analytical Chemistry
  • Information Systems
  • Instrumentation
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering
  • Biochemistry


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