Development of shear horizontal surface acoustic wave with silicon dioxide nanoparticles waveguide sendor for escherichia coli O157: H7 detection

Abstract

Escherichia coli O157:H7 (E.coli O157:H7), a dangerous strain among 225 E. coli unique serotypes. A few cells of this bacterium are able to cause young children to be most vulnerable to serious complications. The presence of higher than 1 cfu E .coli O157:H7 in 25 g of food has been considered as a dangerous level. Thus, highly sensitive sensor is needed for this. The aim of this research work is to develop nanostructure waveguide shear horizontal surface acoustic wave (SHSAW) sensor for the detection of E.coli O157:H7. The interdigital transducer (IDT) is the heart of SHSAW sensor. It deterrmines the resonant frequency and the sensitivity of the sensor. In generally, the higher the resonant frequency, the higher sensitive the sensor will be, the width of IDT has to fabricated to sub micrometer. These involve more expensive cost and complicated methods. However, few reports mentioned IDT design parameters such number of transmission and receiving electrode fingers, electrode length or acoustic aperture and length of delay line or propagation path, can increase the SHSAW sensor sensitivity. Herein, COMSOL Multiphysics simulations were implemented for this investigation, the delay line length and aperture sizes are found that can increase the mass loading sensitivity. The research was continued by the development and evaluation of fabrication SHSAW device by using the improved conventional lithography process was conducted. The results show that the dimension of devices were precisely(less than 1%, relative standard deviation (RSD)) and accurately (less than 4% error from theoretical calculation) fabricated in laboratory for experimentally study on the effects of IDT parameters toward mass loading sensitivity. From the response surface methodology, 12 μm pitch sizes IDT with 0.72 mm aperture size, 2.1 mm delay line length and 385.1607 MHz average resonant frequency were identified as the most optimum parameters to achieve highest sensitive of devices.