Design & development of microorganism activity monitoring transducer using ultrasonic sensors

Abstract

This thesis presents the design and development of a microorganism activity monitoring transducer by using ultrasonic sensors as the main part in detecting the signal of microorganism activity. Three types of samples which are Saccharum Officinarum in tap water, Saccharomyces Cerevisiae and Aspergillus Niger in distilled water are used in the experiments and are found to give differents voltage signals. This indicates that the transducer is able to detect changes of concentrations and the number of cells in the samples tested. The proposed design consists of two parts. In the first part, the selection of electronic components that is able to produce an appropriate output signal has been made and tested. The design of the circuit is done by combining the application circuit for each component based on the detail that is supplied by each component manufacturer. In this stage, a Computer-Aided Design (CAD) software is used to design a Printed Circuit Board (PCB). The second part is the design of a container that is used to place the sample and also the sensor. A material with properties such as glass, light weight, temperature resistant and chemically stable has been chosen as the main material to build the container. A CAD software is used to design the shape of the container and fabricate it. The functionality of the transducer is tested by using pseudo bacteria liquids, real microorganisms and the results obtained shows that the output signal of the transducer is dependent on the density and concentration of the tested liquid. During the testing of the microorganisms, a proposed method of cell counting is done to show the relationship between the signal magnitude and the number of cells. The increment or decrement of live cells has been used as indicator of microbe activity. The experiment results show that the use of ultrasonic sensors for microorganism monitoring has a potential to be further investigated and developed towards a reliable and fast monitoring system required in certain industries.