Two-dimensional (2D) layered materials are ideal for micro- and nanoelectromechanical systems (MEMS/NEMS) due to their ultimate thinness. Platinum diselenide (PtSe2), an exciting and unexplored 2D transition metal dichalcogenide material, is particularly interesting because its low temperature growth process is scalable and compatible with silicon technology. Here, we report the potential of thin PtSe2 films as electromechanical piezoresistive sensors. All experiments have been conducted with semimetallic PtSe2 films grown by thermally assisted conversion of platinum at a complementary metal–oxide–semiconductor (CMOS)-compatible temperature of 400 °C. We report high negative gauge factors of up to −85 obtained experimentally from PtSe2 strain gauges in a bending cantilever beam setup. Integrated NEMS piezoresistive pressure sensors with freestanding PMMA/PtSe2 membranes confirm the negative gauge factor and exhibit very high sensitivity, outperforming previously reported values by orders of magnitude. We employ density functional theory calculations to understand the origin of the measured negative gauge factor. Our results suggest PtSe2 as a very promising candidate for future NEMS applications, including integration into CMOS production lines.

The two-dimensional material graphene promises a broad variety of sensing activities. Based on its low weight and high versatility, the sensor density can significantly be increased on a structure, which can improve reliability and reduce fluctuation in damage detection strategies such as structural health monitoring (SHM). Moreover; it initializes the basis of structure–sensor fusion towards self-sensing structures. Strain gauges are extensively used sensors in scientific and industrial applications. In this work, sensing in small strain fields (from −0.1% up to 0.1%) with regard to structural dynamics of a mechanical structure is presented with sensitivities comparable to bulk materials by measuring the inherent piezoresistive effect of graphene grown by chemical vapor deposition (CVD) with a very high aspect ratio of approximately 4.86 × 108. It is demonstrated that the increasing number of graphene layers with CVD graphene plays a key role in reproducible strain gauge application since defects of individual layers may become less important in the current path. This may lead to a more stable response and, thus, resulting in a lower scattering.. Further results demonstrate the piezoresistive effect in a network consisting of liquid exfoliated graphene nanoplatelets (GNP), which result in even higher strain sensitivity and reproducibility. A model-assisted approach provides the main parameters to find an optimum of sensitivity and reproducibility of GNP films. The fabricated GNP strain gauges show a minimal deviation in PRE effect with a GF of approximately 5.6 and predict a linear electromechanical behaviour up to 1% strain. Spray deposition is used to develop a low-cost and scalable manufacturing process for GNP strain gauges. In this context, the challenge of reproducible and reliable manufacturing and operating must be overcome. The developed sensors exhibit strain gauges by considering the significant importance of reproducible sensor performances and open the path for graphene strain gauges for potential usages in science and industry.

Im Rahmen eines kooperativen Forschungsprojekts der Universität Siegen zwischen der Arbeitsgruppe Technische Mechanik (ATM) des Departments Maschinenbau und des Lehrstuhls Stahlbau und Stahlverbundbau des Departments Bauingenieurwesen wurde eine Methode zur zerstörungsfreien Schadensdetektion an Schrauben und Bolzen entwickelt und auf ihre grundsätzliche Anwendbarkeit hin überprüft. Die Methode basiert auf der Messung von elektromechanischen Impedanzspektren, welche sich bei variierenden Strukturzuständen ändern und so eine Zustandsbewertung ermöglichen. Die Untersuchungsmethode könnte bspw. im Monitoring von Brückenbauwerken etabliert werden. Im Zuge des Projekts wurden Untersuchungen an Stahlplatten mit orthogonal aufgeschweißten Gewindebolzen durchgeführt. Um bei den Probekörpern das generelle Verhalten von elektromechanischen Impedanzspektren bei unterschiedlichen Zuständen festzustellen, wurden Voruntersuchungen gemacht. Hierbei ist eine gegenläufige Entwicklung der untersuchten Frequenzspektren unter den Einwirkungen „Vorspannung“ und „Sägeschnitt am Bolzenfuß“ festgestellt worden. Nachfolgend durchgeführte zyklische Versuche haben schließlich die Anwendbarkeit des Verfahrens gezeigt. Im Beitrag werden erste Versuchsergebnisse vorgestellt und darüber hinaus wird die Anwendbarkeit der Messmethodik für das Bauwerksmonitoring diskutiert.

Many recent investigations in the context of graphene nanoplatelets (GNPs) coatings report surface strain measurements by using piezoresistive sensing capabilities. An often underestimated problem is that the strain field is unknown and the principal strain components as well as their orientations must be determined. Herein, GNP films subjected to multiaxial strain are examined. Experimental results show that although the sensitivity to longitudinal strain is the highest, the ratio between transverse and longitudinal sensitivity exceeds 0.5. The sensitivity to shear strain is much lower. A model assisted study of a random network provides additional guidelines for the different electromechanical sensitivities. In practice, the GNP film is usually subjected to different strains simultaneously so that the multiaxial strain measurement becomes difficult. Therefore, two novel approaches for sensing plane strain components with circular GNP films are developed and successfully verified in experiments. The numerical approach is called strain‐differential electrical impedance tomography (SD‐EIT), where the proposed piezoresistive model elementwise in a finite element model is implemented and the strain components of a strain rosette are reconstructed. Moreover, an analytical approach is derived from SD‐EIT and exhibits further the opportunity to detect anomalies within the piezoresistive sensing behavior of GNP films.