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This paper provides a tutorial introduction to recently devised technologies for transducers embedded within the organic coatings of metallic (or, more generally, of electrically conductive) mechanical components, such as organically coated flat sheet steel, and three-dimensional machine parts, such as bearing supports and mold jaws. The integration of sensors and actuators into the surface coating of these components is of particular interest: first, it allows assessment of physical parameters at locally defined positions that are not accessible with usual discrete transducers; and second, a functionalized component equipped with sensory intelligence adds value for producer and customer. However, realization of embedded transducers entails challenges posed by (i) any potential preexisting protective organic coating and (ii) the shape and surface roughness of the underlying metallic substrate. This tutorial addresses the major issues that arise when sensors or actuators are to be integrated into the organic coating of an electrically conductive machine part, and provides hints and guidelines for successful realization based on recent research.

We present a method to design specific heater electrode distributions on substrates with high thermal conductivity such as sheet metal. The substrate is covered with a thin polymer insulation layer on both sides, which are, in turn, carrying screen printed, electrically conductive heater electrodes and another protective polymer layer. The temperature inside a predetermined optimization area is demanded to be as uniform as possible, which is required for various high-precision heating applications. A uniform temperature distribution is required when realizing a newly proposed "lab on metal" approach. For this purpose, an optimization algorithm yields the required distances between the electrodes. The resulting electrode distribution was numerically obtained for certain optimization areas. We show the electrode positions relative to the distance from the centermost electrode and the optimization error for each distribution. Finally we describe the fabrication of a test device and show infrared measurements of the FEM modeled uniform temperature distribution on the experimental realized device.

This work reports on the characterization of the strain response of printed strain gauges particularly with respect to achievable gauge factors and associated spurious effects. In particular, three different effects are observed, first a set-in effect, which only occurs after production, second a nonlinear response that is more or less only visible without mechanical stabilizing top coating. Third and finally, a hysteresis behavior was found. We subsequently investigated the performance over an extended period of time, which revealed interesting and partially unexpected material properties of printed strain gauges made from silver and carbon. Both silver- and carbon-based strain gauges show a hysteresis behavior of the gauge factor and non-negligible nonlinear characteristics. Furthermore, the carbon-based sensors show a strong initial base line drift within the first 50–100 cycles. All three effects, namely hysteresis, nonlinear gauge factor and initial base line drift, are confirmed within their respective standard deviations.

In this work, we present a method for the realization of printed strain gauges on pre-coated sheet steel substrates. The state of the art is to glue strain gauges on foil onto a substrate. This, however, has inherent disadvantages in terms of force coupling between the bent substrate and the glued strain gauge sensors. The fact that the glue and the substrate have in general different moduli of elasticity affects the achievable gauge factor of the final sensor stack. The method presented in this work circumvents these problems completely by eliminating the gluing process and integrating the sensor into a cover layer on the substrate. In the considered case, the substrate is a steel sheet with an organic coating. We integrate the sensor in this coating by screen-printing it on a pre-coated layer. The results in terms of the various determined gauge factors including the influence of a top coating layer, as well as temperature dependences of the strain sensors fabricated with carbon black and silver ink are presented in this work.

We report on the design, fabrication and optical properties of large core multimode optical polymer splitter fabricated using fill up core polymer in substrate that was made by 3D printing technology. The splitter was designed by the beam propagation method intended for assembling large core waveguide fibers with 735 μ m diameter. Waveguide core layers were made of optically clear liquid adhesive, and Veroclear polymer was used as substrate and cover layers. Measurement of optical losses proved that the insertion optical loss was lower than 6.8 dB in the visible spectrum.

In this contribution we present an approach towards programmable shape memory transformations utilizing the intrinsic physical properties of a ternary polymer-based composite. The underlying idea is to use an open porous elastic skeleton as the base, where the pores are filled with a component that can alter its elasticity abruptly upon an external stimulus. In this study we use PDMS as the base network, and Paraffin as the pore filler, which causes a huge change in elasticity of the composite when undergoing the solid to liquid phase change at elevated temperature. This binary composite, already featuring shape memory characteristics, is then additionally made controllable by adding nano-particles with specific stimulus responsive properties. We demonstrate the programmable shape transformation capability of the devised ternary composite by the example of carbon black and ferromagnetic iron oxide nano-particles.

In this contribution we present a minimum effort approach to sensors for physical quantities like, e.g., force, pressure, strain, and temperature without the need for cost-intensive lab equipment. Only adhesive tape, carbon black, some kind of cutting tool, and a heat source are needed to fabricate sensors that can easily be affixed also to unusual and curved surfaces. We demonstrate the ease of fabrication and usage at the example of a rather generic sensor structure that can be used to measure strain, force/pressure, and temperature at virtually any chosen point of interest.

We present the first realization of printed capacitive touch buttons and touch pads integrated into the organic coatings on sheet steel. The properties of coated sheet steel relevant for printing are discussed and compared with substrates, commonly used for printed electronics. Different designs and read-out methods for capacitive buttons on sheet steel have been screen printed and their sensitivity in dependence on design parameters is rated.

This work demonstrates a low-cost fabrication method for Electrowetting-on-Dielectric (EWOD) structures for microsystem and Lab-on-a-chip applications. The electrowetting effect allows droplet movement by manipulating the surface tension equilibrium in an EWOD system. A voltage-induced imbalance of the contact angle (CA) at the triple contact line leads to droplet actuation into the direction of the smaller CA. The presented low-cost EWOD stack consists of a suitable substrate, actuation electrodes and dielectric/hydrophobic layers. Screen printed silver electrodes on glass substrates were investigated and characterized. Indium Tin Oxide (ITO) glass slides with a top coated Teflon fluoropolymer were used as electrical counter electrodes. As an application, a demonstrator of a simple optofluidic (OF) switch is simulated in terms of optical path switching time and fabricated using the silver screen printed setup. The incident beam of a laser light source becomes deflected depending on the position of an EWOD actuated droplet inside the device.

In this work we present a method for the fabrication of all-printed strain gauges on pre-coated sheet steel substrates. The state of the art is to glue strain gauges on foil onto a substrate. This, however, has inherent disadvantages in terms of force coupling from the surface strain within the bent substrate to the glued strain gauge sensors. The fact that the glue and the strain gauge substrate have in general different moduli of elasticity affects the maximum achievable gauge factor of the final sensor stack. The method presented in this work circumvents these problems completely by removing the glue and the substrate layer from the stack and by printing the sensor layer directly on top of the pre-applied organic coating. We present comparative measurements of carbon black based sensors, as well as two different polymeric silver ink based sensors.

In recent years, the implementation of printed strain gauges as cost-effective alternatives to conventional glued strain gauges was investigated. Printed strain gauges are, in general, not temperature compensated due to the lacking availability of appropriate materials. Their accuracy (and applicability) therefore is strongly affected by temperature drifts. In this contribution, we propose a concept for temperature compensated strain measurement with printed strain gauges based on two nested, meander shaped strain gauges consisting of different materials. Due to the proximity of the sensors, they are both affected by the same strain and the same local temperature. It is shown that, by measurement of the resistance of both strain gauges, the strain applied to the strain gauges can accurately be determined even if the sensors are subject to temperature fluctuations.

The paper reports on temperature behavior of strain sensitivity of recently introduced screen printing technology facilitating the realization of silver and carbon black piezoresistors embedded in organic coatings. Piezoresistive layers were prepared by screen printing directly on the top of the organic coating. Since no glue or carrying substrates are between the sensitive element and the device under test, the coupling factor is high and the strain is efficiently transferred to the sensing element. The strain induced changes in resistance (piezoresistive effect) are generally lower compared to the changes induced by temperature. The temperature dependence of the sensitivity to strain was investigated utilizing both single element piezoresistors and piezoresistors connected to a Wheatstone bridge. The study analyzes strain-gauges under longitudinal tensile and compressive strain and temperatures up to 80 °C. Screen printed strain gauges can provide reliable and robust strain measurements for coated metallic substrates, the sensor performance is comparable to the conventional solution with glued sensors.

In this work we report on the integration of all-printed multi-layer ferroelectric sensor stacks into organic coatings on metallic surfaces like sheet steel. Manufacturing techniques for realizing thin film sensor layers on top of organic coatings using screen printing are presented. Results for the piezo/pyroelectric sensor layer with variable printing parameters are then analysed and compared.

We present the first realization of printed capacitive touch buttons and touch pads integrated into the organic coatings on sheet steel. The properties of coated sheet steel relevant for printing are discussed and compared to substrates, commonly used for printed electronics. Different designs and read-out methods for capacitive buttons on sheet steel have been screen printed and their sensitivity in dependence on design parameters is rated.