The outstanding properties of graphene have initiated myriads of research and development; yet, its economic impact is hampered by the difficulties encountered in production and practical application. Recently discovered laser-induced graphene is generated by a simple printing process on flexible and lightweight polyimide films. Exploiting the electrical features and mechanical pliability of LIG on polyimide, we developed wearable resistive bending sensors that pave the way for many cost-effective measurement systems. The versatile sensors we describe can be utilized in a wide range of configurations, including measurement of force, deflection, and curvature. The deflection induced by different forces and speeds is effectively sensed through a resistance measurement, exploiting the piezoresistance of the printed graphene electrodes. The LIG sensors possess an outstanding range for strain measurements reaching >10% A double-sided electrode concept was developed by printing the same electrodes on both sides of the film and employing difference measurements. This provided a large bidirectional bending response combined with temperature compensation. Versatility in geometry and a simple fabrication process enable the detection of a wide range of flow speeds, forces, and deflections. The sensor response can be easily tuned by geometrical parameters of the bending sensors and the LIG electrodes. As a wearable device, LIG bending sensors were used for tracking body movements. For underwater operation, PDMS-coated LIG bending sensors were integrated with ultra-low power aquatic tags and utilized in underwater animal speed monitoring applications, and a recording of the surface current velocity on a coral reef in the Red Sea.npj Flexible Electronics (2019) 3:15 ; https://doi.

Magnetic field sensors are an integral part of many industrial and biomedical applications, and their utilization continues to grow at a high rate. The development is driven both by new use cases and demand like internet of things as well as by new technologies and capabilities like flexible and stretchable devices. Magnetic field sensors exploit different physical principles for their operation, resulting in different specifications with respect to sensitivity, linearity, field range, power consumption, costs etc. In this review, we will focus on solid state magnetic field sensors that enable miniaturization and are suitable for integrated approaches to satisfy the needs of growing application areas like biosensors, ubiquitous sensor networks, wearables, smart things etc. Such applications require a high sensitivity, low power consumption, flexible substrates and miniaturization. Hence, the sensor types covered in this review are Hall Effect, Giant Magnetoresistance, Tunnel Magnetoresistance, Anisotropic Magnetoresistance and Giant Magnetoimpedance.

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Flexible and wearable magnetoelectronics add intriguing new functionalities to our natural perception. Of particular interest regarding these artificial skins are wireless sensing and touchless interactions. Biocompatibility and imperceptibility are the most significant features of wearable devices attached to our bodies. In this work, a biocompatible magnetic skin is introduced. It offers extreme flexibility, stretchability (>300%), and lightweight while maintaining a remanent magnetization up to 360 mT. The magnetic skin is comfortable to wear, can be realized in any desired shape or color, and adds tunable permanent magnetic properties to the surface it is applied to. It provides remote control functions and combined with magnetic sensors; it implements a complete wearable magnetic system. For example, eye tracking is realized by attaching the magnetic skin to the eyelid. The advantage that it does not require any wiring makes it an extremely viable solution for soft robotics and human-machine interactions. Wearing the magnetic skin on a finger or integrated

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The detection of small forces is of great interest in any robotic application that involves interaction with the environment (e.g. objects manipulation, physical human-robot interaction, minimally invasive surgery), since it allows the robot to detect the contacts early on and to act accordingly. In this work, we present a sensor design inspired by the ciliary structure frequently found in nature, consisting of an array of permanently magnetized cylinders (cilia) patterned over a giant magnetoresistance sensor (GMR). When these cylinders are deformed in shape due to applied forces, the stray magnetic field variation will change the GMR sensor resistivity, thus enabling the electrical measurement of the applied force. In this paper we present two 3×3 mm 2 prototypes composed of an array of 5 cilia with 1 mm of height and 120 µm and 200 µm of diameter for each prototype. A minimum force of 333 µN was measured. A simulation model for determining the magnetized cylinders average stray magnetic field is also presented.

Tunable, Flexible composite magnets for marine monitoring applications**

The classical equations of de Sitter for the hydrostatic figure of the earth are modified to make their development independent of the external potential theory. The modification is essential to demonstrate clearly the correct structure of the problem of hydrostatic equilibrium for the earth. An expression is obtained giving the hydrostatic flattening in terms of other parameters, which seems to have the advantage of easy numerical manipulation. If J and H of the hydrostatic earth are taken to be equal to those determined observationally for the real earth and only the hydrostatic equations are used (as advocated by most of the post‐satellite investigators), the value of hydrostatic flattening obtained is 1/296.70 ± 0.05, in contrast to the value of 1/299.86 as found from de Sitter's equations. Of course, it is possible to obtain the value of 1/299.86 for hydrostatic flattening, but the approach involved is different from the approach advocated in most of the recent investigations. It is not our intention to prove that the value of hydrostatic flattening reported in this paper is necessarily the correct value but to show that if the presently accepted method of computing hydrostatic flattening is adopted the value will be 1/296.70 ± 0.05.