Fluid manipulations using a piezo electric transformer for sensing and spray generation applications

摘要

A steady effort has been made on the development of fluid manipulation techniques for sensing and actuating systems. Conventional techniques of fluid manipulation for sensing and spray generation purposes, often need trained staff or high input power and they are complicated, time consuming and expensive. Therefore, it is necessary to develop new systems which can overcome these drawbacks.;In this dissertation, the author has developed piezoelectric-based systems for fluid manipulation. The focus of this dissertation involves novel approaches of enhancing the sensing and actuating systems using the piezoelectric devices. This includes designing a system, which theoretically can overcome the limitations associated with conventional fluid manipulation systems, fabricating the device and examining the functionality of the system to prove the claim.;The purpose of the first project of this research work was to design and fabricate a piezoelectric based system to enhance the sensitivity of the system towards the sensing of toxic materials in liquid media. The functionality of the designed sensing system was investigated towards several toxic heavy metals including lead, cadmium, nickel and mercury. The SHSAW sensor was fabricated on a 64° YX-LiNbO3 piezoelectric substrate using photolithography techniques and placed in the sensor groove of an acrylic based material flow cell. Then, varying concentrations of target analytes were injected into the flow cell using a programmable syringe pump. A network analyzer was used to measure the phase response (S21) of the SH-SAW sensor towards the test analytes. System control, data acquisition and post processing of the network analyzer measurements was performed using a LabView(TM) based application. The significance of this research was based on the contribution that this sensing system could enhance the detection of the toxic heavy metal ions to pico molar concentration levels while conventional methods often work in the micro molar concentration levels.;Further, a piezoelectric based system which can be utilized for spray generation from a desired liquid was designed and fabricated. A linear 128° Y-cut lithium niobate (LiNbO3) crystal was used and a 3D printed stand was designed to pin the piezoelectric transformer on the second resonance standing wave nodes. The piezoelectric transformer (PT) was actuated by a signal generator connected to a radio frequency (RF) amplifier. To generate the spray, various aqueous solutions prepared using deionized (DI) water was filled in an adjacent reservoir and a paper bridge was placed from the reservoir and in contact with the surface of the PT. The generated piezoelectric driven spray resulted in a broad area, uniform, continues spray appropriate for coating applications. The spray generation system also made it possible to generate the spray out of the liquid by applying around 15 Vamp, AC input voltage amplitude, while traditional techniques typically require around 100 Vamp for spray formation.;Finally, the PT driven spray generation technique was used for membrane coating applications. Different polymers such as poly(allylamine hydrochloride) (PAH)/ poly(styrene sulfonate) (PSS) and poly(diallyl-dimethylammonium chloride) (PDADMAC) were sequentially sprayed on to a polycarbonate track-etched (PCTE) membrane. The polymer coated membrane was tested towards water permeability and ion rejection ratio to investigate the functionality of this novel spray generation system for membrane coating purposes.