A multifunctional biomimetic nanocomposite tactile sensor is developed that can detect shear and vertical forces, feel texture, and measure flow with extremely low power consumption. The sensor's high performance is maintained within a wide operating range that can be easily adjusted. The concept works on rigid and flexible substrates and the sensors can be used in air or water without any modifications.

We have synthesized nanowires with an iron core and an iron oxide (magnetite) shell by a facile low-cost fabrication process. The magnetic properties of the nanowires can be tuned by changing shell thicknesses to yield remarkable new properties and multi-functionality. A multi-domain state at remanence can be obtained, which is an attractive feature for biomedical applications, where a low remanence is desirable. The nanowires can also be encoded with different remanence values. Notably, the oxidation process of single-crystal iron nanowires halts at a shell thickness of 10 nm. The oxide shell of these nanowires acts as a passivation layer, retaining the magnetic properties of the iron core even during high-temperature operations. This property renders these core-shell nanowires attractive materials for application to harsh environments. A cell viability study reveals a high degree of biocompatibility of the core-shell nanowires.

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.

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A magnetoresistive tactile sensor is reported, which is capable of working in high temperatures up to 140 °C. Hair-like bioinspired structures, known as cilia, made out of permanent magnetic nanocomposite material on top of spin-valve giant magnetoresistive (GMR) sensors are used for tactile sensing at high temperatures. The magnetic nanocomposite, consisting of iron nanowires incorporated into the polymer polydimethylsiloxane (PDMS), is very flexible, biocompatible, has high remanence, and is also resilient to antagonistic sensing ambient. When the cilia come in contact with a surface, they deflect in compliance with the surface topology. This yields a change of the GMR sensor signal, enabling the detection of extremely fine features. The spin-valve is covered with a passivation layer, which enables adequate performance in spite of harsh environmental conditions, as demonstrated in this paper for high temperature.