Ph.D Thesis

Ph.D StudentBar Meital
SubjectFlexible Sensors Based on Monolayer-Capped Nanoparticles:
Towards the Development of Electronic Skin
DepartmentDepartment of Nanoscience and Nanotechnology
Supervisor PROF. Hossam Haick
Full Thesis textFull thesis text - English Version


Flexible sensors appear to be promising components for smart sensing applications, including consumer electronics, robotics, and health care. The reliability, reproducibility, and the complexity of producing integrated flexible systems are still major impediments to the realization of flexible sensors for real-world applications. Au nanoparticles (Au-NPs)-based sensors are versatile sensing platform that can be used in the sensing of several stimuli such as humidity, temperature, strain/ pressure and volatile organic compounds (VOCs). In particular, the challenges that we are addressing include: (i) tuning the sensitivity of Au-NPs based sensors towards specific stimuli. In this context, we have used basic components in the sensors and systematically changed them while examining their influence on the sensing properties. For example, the Au-NP film morphology was switched from perforated to continuous film to change humidity sensitivity; the sensors' substrate was manipulated so that the dynamic range of the strain/pressure could be controlled. Controlling the Au-NPs diameter (mainly by sintering) affected the sensitivity to strain/pressure and temperature. This step was a building block used later in the development of a multi-parametric sensing platform. (ii) Multi-parametric sensing was achieved by using different approaches for separating the response signals. For example, at the hardware level, rigid sensing pixels based on Au-NPs films were used to sense humidity and temperature, while minimizing the sensitivity to strain/ pressure. In another example, Au-NPs based flexible sensors were bent during exposure to a range of VOCs. Separation of the different VOC signals was done with Principle Component Analysis (PCA); this showed that the bending the sensor induces new sensing states and improved separation. (iii) High resolution, human-like strain/pressure sensing was realized while minimizing related wiring and the amount of read-out data. The front line of today's pressure mapping technology requires a dense wiring network between the sensing "pixels". To overcome this limitation, a flexible linear strain sensor was developed which senses in real time the position and strain (or load) of a deformation event along the sensor on the basis of only 2 resistance measurements. The 2 sensing lines are equivalent to 20 pixels and resistance measurements in the pixelated technology.