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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.

A piezoresistive low-pressure sensor featuring a variety of advantages because of its novel design is introduced. The main objective of this development was to realize a sensor with high sensitivity, high overload capacity, and low linearity error. This publication describes the theory for the design of the piezoresisitve low-pressure sensor. In comparison to familiar sensor concepts, the sensor developed for the pressure range of plus minus 10 kPa exhibits excellent properties (sensitivity is equal to 35 mV/V full-scale output and linearity error is equal to 0.05%). The sensor characteristics determined theoretically were by measurements on realized pressure sensors.

Für das Design von Dickschicht-Drucksensoren werden in zunehmendem Maße Simulationswerkzeuge eingesetzt. Die Simulation im mechanischen Bereich erstreckt sich von der Bestimmung der Plattenform über die Berücksichtigung der Einspannverhältnisse und der Montage des Sensors bis zur Bestimmung nichtlinearer Abhängigkeiten. Aus bisher mangelnder Kenntnis der physikalischen Mechanismen, die zum piezoresistiven Effekt bei Widerstandspasten führen, wird der Einfluß der Widerstände auf die Ausgangskennlinie des Sensors durch eine experimentelle Bestimmung der Kennwerte in die Simulation miteinbezogen.