Fabrication of carbon-nanotube enhanced piezoelectric membrane for biosensor application

This paper reports on a carbon-nanotube (CNT) enhanced piezoelectric membrane for the possible application as a mass sensitive biosensor. CNT possesses a hollow core and large specific surface area that could be used for bio-molecular binding. A larger number of probe molecules on the surfaces of CNT could capture more target molecules and therefore increase the detection sensitivity of the biosensor. Based on this idea, we have fabricated the piezoelectric membrane incorporated with CNT. The piezoelectric membrane with a thickness of 0.8 µm was fabricated by micro-machining technique and its Q factor in air was characterised to be as high as 219 at a frequency of about 122 kHz. The fabricated PZT membrane was then loaded into quartz tube under a pressure of 12 Torr to grow CNTs by using thermal chemical vapour deposition (TCVD) at a temperature of 700°C. CNTs were successfully synthesised on the backside of the membrane and the average length was about 10 µm. Raman spectrum showed the intensity ratio (IG/ID) of the grown CNTs in this work was 1.18. The detailed fabrication process has been reported.