Printed Magnetic Field Sensors: From Wearable Devices To Interactive Surfaces

Printing electronics is developing as an on-site fabrication approach to obtaining customized functional devices. [1] In particular, printed devices can be designed to suit
the specifications of each user, e.g. size, location, and functionality. Our research focuses on developing touchless devices that interact via printed magnetic field sensors. Here we will show our approach to fabricating magnetoresistive printable pastes containing magnetosensitive particles embedded in a polymeric binder. The engineering of the printed sensors relies on the properties of the paste fillers, binder, substrate, and processing techniques. The properties of the fillers change the output response of the printed sensors. For example, flake particles showing anisotropic magnetoresistance [2] and giant magnetoresistance [3] have excellent sensitivity below 1 mT making them attractive for wearable and on-skin applications. On the other hand, we studied the capabilities of bismuth-based printed sensors [4] showing non-saturating large magnetoresistance; the output characteristics of these devices made them attractive for wide-range magnetic field sensors. Tuning the mechanical properties of the binder gives special deforming capabilities to
the printed sensors. Polymeric binders used to print our sensors on flexible foils allowed us to laminate our printed systems on objects with complex geometries and even on the
human skin. For instance, we achieved stretchable (100% strain) magnetic field sensors by using a styrene-butadiene-styrene block copolymer as a binder. We demonstrated
that these printed sensors are functional after bending to 16 µm bending radius. [3] We demonstrated the scalability of printing magnetic field sensors using automatized
dispenser printing and laser sintering. This technique offers large-area, affordable, customized fabrication of flexible fully printed magnetic field sensors with minimal material requirements. [4] Such fabrication capabilities open the path for extended interactive smart surfaces and touchless terminal boards. We foresee further developing flexible printed touchless devices in 2D and even 3D printed [5] fully embedded systems for navigation, gaming, personal dosimeters, and health monitoring.
[1] Y. Khan, et al. Adv. Mater. 32, 1905279 (2020)
[2] E.S. Oliveros Mata, et al. Appl. Phys. A 127, 280 (2021)
[3] M. Ha, et al. Adv. Mater. 33, 2005521 (2021)
[4] E.S. Oliveros‐Mata, E. S., C. Voigt, et al. Adv. Mater. Technol. 2200227 (2022)
[5] E.M. Palmero, et al. IEEE Trans. Magn. 55, 1 (2018)