University of Twente Student Theses


Modeling, design and characterization of a 3D-printed capacitive shear stress sensor

Oprel, Jens (2021) Modeling, design and characterization of a 3D-printed capacitive shear stress sensor.

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Abstract:This bachelor assignment concerns the modelling, design, fabrication and characterization of a 3D-printed shear stress sensor. The design is optimized for application in measurements on the human foot, which are interesting for health related applications. More specifically, shear stress monitoring could help to prevent development of diabetic foot ulcers. This application imposes some requirements and objectives. Measurement range, accuracy of peak measurements and the sensor dimensions are the most crucial points of attention. Based on these requirements and objectives, capacitive sensing and Fused Deposition Modelling printing are selected as most promising sensing and printing principles. Theoretical models are developed to study the electrostatic (capacitive) andmechanical behavior of sensing structures. The electrostatic model introduces an approximation for structures of parallel wires. The mechanical model is based upon an hyperelastic beam model. Finite ElementMethods are used for verification of the models. These models are used to optimize the design of the sensor, which consists of 3 sets of 3 electrodes in a beam structure. These are used tomeasure differential capacitance changes using a capacitance to digital converter. The results show that it is possible to measure shear stresses. The smallest fabricated sensor with dimensions of 8.75 £ 8.75 £ 11mm has a sensitivity of 0.9 pF/MPa in the measurement range of 0 to 140 kPa. The fabricated sensors show a linear displacement-capacitance relation. The mechanical behavior of the sensor shows some hysteresis. The durability and repeatability of measurements are main points of attention that need further research if the sensor is to be applied for shear force measurements on the foot.
Item Type:Essay (Bachelor)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering BSc (56953)
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