Micropillar Arrays for High Sensitivity Sensors.

Abstract

In this thesis, a soft and sensory skin-like electronic structure is developed. A capacitance-type pressure sensor is developed that is not only flexible but also stretchable, has a wide sensing regime (up to 10 kPa), and high sensitivity (0.34 kPa-1). Micropillar sensor arrays inspired by cilia structures found in nature are fabricated using a soft nanolithography technique and electroded with sputtered gold. The arrays are configured for capacitance type pressure sensing in the tactile – touch regime. Several designs are proposed, fabricated, and evaluated to optimize sensitivity and detectability in the low pressure range. Techniques for fabricating asymmetric easy to buckle pillar structures and a multi-level hierarchical design platform are developed. Here, we present the highest reported sensitivity [0.34 kPa-1] of a passive capacitance type sensor that is both flexible and stretchable. There is experimental evidence to suggest that the sensor can be configured to detect very low pressures, and or used for proximity sensing.

The influence of pillar design parameters on sensor performance is explored using experimental and computational simulation techniques. The relationship between different pillar deformation modes and sensor characteristics is established and quantified. Computational simulations are carried out in COMSOL to investigate how large conformational changes of the pillars during deformation influence the capacitance readings for the different sensor designs. The simulations are an important tool in solving coupled multiphysics problems and for visualizing complex nonuniform three dimensional electrostatic fields. The simulation results show identical trends to the experiments and excellent correlation is achieved for the full device model. Finally, the microstructured sensor array naturally lends itself to the development of pixel-type pressure sensors and biomedical monitoring devices – the potential for both applications are demonstrated here.