Energy autonomy and conformability are essential elements in the next generation of wearable and flexible electronics for healthcare, robotics and cyber-physical systems. This study presents ferroelectric polymer transducers and organic diodes for imperceptible sensing and energy harvesting systems, which are integrated on ultrathin (1-µm) substrates, thus imparting them with excellent flexibility. Simulations show that the sensitivity of ultraflexible ferroelectric polymer transducers is strongly enhanced by using an ultrathin substrate, which allows the mounting on 3D-shaped objects and the stacking in multiple layers. Indeed, ultraflexible ferroelectric polymer transducers have improved sensitivity to strain and pressure, fast response and excellent mechanical stability, thus forming imperceptible wireless e-health patches for precise pulse and blood pressure monitoring. For harvesting biomechanical energy, the transducers are combined with rectifiers based on ultraflexible organic diodes thus comprising an imperceptible, 2.5-µm thin, energy harvesting device with an excellent peak power density of 3 mW·cm⁻³.

A force, humidity, and temperature‐responsive electronic skin is presented by combining piezoelectric zinc oxide (ZnO) and poly‐N‐vinylcaprolactam‐co‐di(ethylene glycol) divinyl ether hydrogel into core‐shell nanostructures using state‐of‐the‐art dry vapor‐based techniques. The proposed concept is realized with biocompatible materials in a simplified design that delivers multi‐stimuli sensitivity with high spatial resolution, all of which are prerequisites for an efficient electronic skin. While the piezoelectricity of ZnO provides sensitivity to external force, the thermoresponsiveness of the hydrogel core provides sensitivity to surrounding temperature and humidity changes. The hydrogel core exerts mechanical stress onto the ZnO shell, which is translated to a measurable piezoelectric signal. A localized force sensitivity of 364 ± 66 pC N⁻¹ is achieved with very low cross talk between 0.25 mm² pixels. Additionally, the sensor's sensitivity to humidity is demonstrated at 25 and 40 °C, i.e., above and below the hydrogel's lower critical solution temperature (LCST) of 34 °C. The largest response to temperature is obtained at high humidity and below the hydrogel's LCST. The sensor response to force, humidity, and temperature is significantly faster than the system's intrinsic or excitation‐induced time scale. Finally, the sensor response to touch and breath demonstrates its applicability as e‐skin in real‐life environment.

Most flexible piezoelectric transducers have a vertical setup with top and bottom electrodes, which does not enable the selective, directional detection of mechanical stimuli. Here we present a paradigm shift in the design of such transducers by placing the electrodes in a single layer and fully embedding them in a ferroelectric layer. This approach enables a selective detection of in-plane strains with a linear, orientation-dependent response. Our transducers feature microstructured, densely interdigitated electrodes embedded in the ferroelectric copolymer P(VDF-TrFE) and show an in-plane strain sensitivity of up to 8.3 nC % ⁻¹ (21.3 V % ⁻¹ ), while being 23 times less sensitive to transversal loading, compared to vertical setup devices. The embedded electrodes cause a strong anisotropy for in-plane strain coupling and make it possible to distinguish both the bending orientation and the bending intensity on a time-variable curvilinear surface. A high power density of 2.3 mW cm ⁻³ was achieved during a periodic bending movement at 90 Hz. In addition to a photolithography and electroplating-assisted method, we present an alignment-free, elegant microcapillary force-based process for scalable fabrication of embedded electrodes. The presented transducers have a high potential for application as energy-autonomous sensors for condition monitoring, robotics and wearables.

The ski deflection with the associated temporal and segmental curvature variation can be considered as a performance-relevant factor in alpine skiing. Although some work on recording ski deflection is available, the segmental curvature among the ski and temporal aspects have not yet been made an object of observation. Therefore, the goal of this study was to develop a novel ski demonstrator and to conceptualize and validate an empirical curvature model. Twenty-four PyzoFlex^® technology-based sensor foils were attached to the upper surface of an alpine ski. A self-developed instrument simultaneously measuring sixteen sensors was used as a data acquisition device. After calibration with a standardized bending test, using an empirical curvature model, the sensors were applied to analyze the segmental curvature characteristic (m⁻¹) of the ski in a quasi-static bending situation at five different load levels between 100 N and 230 N. The derived curvature data were compared with values obtained from a high-precision laser measurement system. For the reliability assessment, successive pairs of trials were evaluated at different load levels by calculating the change in mean (CIM), the coefficient of variation (CV) and the intraclass correlation coefficient (ICC 3.1) with a 95% confidence interval. A high reliability of CIM −1.41–0.50%, max CV 1.45%, and ICC 3.1 > 0.961 was found for the different load levels. Additionally, the criterion validity based on the Pearson correlation coefficient was R² = 0.993 and the limits of agreement, expressed by the accuracy (systematic bias) and the precision (SD), was between +9.45 × 10⁻³ m⁻¹ and −6.78 × 10⁻³ m⁻¹ for all load levels. The new measuring system offers both good accuracy (1.33 × 10⁻³ m⁻¹) and high precision (4.14 × 10⁻³ m⁻¹). However, the results are based on quasi-static ski deformations, which means that a transfer into the field is only allowed to a limited extent since the scope of the curvature model has not yet been definitely determined. The high laboratory-related reliability and validity of our novel ski prototype featuring PyzoFlex^® technology make it a potential candidate for on-snow application such as smart skiing equipment.

Pressure sensors integrated in surfaces, such as the floor, can enable movement, event, and object detection with relatively little effort and without raising privacy concerns, such as video surveillance. Usually, this requires a distributed array of sensor pixels, whose design must be optimized according to the expected use case to reduce implementation costs while providing sufficient sensitivity. In this work, we present an unobtrusive smart floor concept based on floor tiles equipped with a printed piezoelectric sensor matrix. The sensor element adds less than 130 µm in thickness to the floor tile and offers a pressure sensitivity of 36 pC/N for a 1 cm² pixel size. A floor model was established to simulate how the localized pressure excitation acting on the floor spreads into the sensor layer, where the error is only 1.5%. The model is valuable for optimizing the pixel density and arrangement for event and object detection while considering the smart floor implementation in buildings. Finally, a demonstration, including wireless connection to the computer, is presented, showing the viability of the tile to detect finger touch or movement of a metallic rod.

A vibration energy harvesting system based on fully printed piezoelectric transducers is realized. The transducers have a butterfly‐like architecture based on two single‐optimized cantilevers with a resonance frequency tuned to 49.5 Hz and can be easily mounted to an industrial engine. By comparing single‐ and multistack configurations of the piezoelectric layers combined with full‐wave or voltage doubler rectifiers, the power transfer characteristics and impedance can be matched to the electrical requirements of the sensing circuitry. A single stack with 21 μm thickness results in the maximum power output of 14.4 μW at a vibration velocity of 11.5 mm s⁻¹, typical for industrial engines. The system is used to power a wireless sensor node on a 1 kW rotary pump in normal operation. The system can harvest up to 138 mJ within 24 h, sufficient for daily remote monitoring of the engine's vibration spectrum and temperature state. The system is thus suitable as a low‐cost, ecofriendly power source for industrial IoT applications.