A magnetic nanocomposite for biomimetic flow sensing

Abstract

A magnetic nanocomposite has been implemented as artificial hair on a giant magnetoimpedance (GMI) thin-film sensor for flow sensing. The 500 μm long and 100 μm in diameter pillars are composed of iron nanowires incorporated in polydimethylsiloxane (PDMS). The nanowires' length and diameter are 6 μm and 35 nm, respectively. Upon fluid flow, the pillars are deflected, causing a change in the magnetic field at the GMI element and a corresponding change in impedance. The permanent magnetic behavior of the nanowires in combination with the GMI sensor and the high elasticity of the PDMS pillars result in a high-performance flow sensor with low power consumption and potential for remote detection. No additional magnetic field is required to magnetize the nanowires or bias the sensor, which simplifies miniaturization and integration in microsystems. At a power consumption of 31.6 μW, air flow rates up to 190 mm s⁻¹ can be detected with a sensitivity of 24 mΩ (mm)⁻¹ s and a resolution of 0.56 mm s⁻¹ while the range for water flow is up to 7.8 mm s⁻¹ with a sensitivity of 0.9 Ω (mm)⁻¹ s and a resolution of 15 μm s⁻¹. When power consumption is reduced to as low as 80 nW a high resolution of 32 μm s⁻¹ is still maintained.