MWCNTs-like protection layer formation on bacterial cellulose bundles as a potential material for suspended resonator

Suspended carbon naotubes (CNTs) resonator is a sensitive detector for chemical and biological applications. Small sizes of CNTs can enhance sensitivity, but increase complexity for fabrication. In order to overcome the challenges, a novel technique has been developed to produce a long, sensitive and high tensile strength carbon nanotubes (CNT) coated bacterial cellulose (BC) bundle. This study demonstrates the use of ultrasonication to perform carboxyl functionalized multi-walled carbon nanotubes (MWCNTs-COOH) self-assembling on the surface of BC bundles (BC/MWCNTs) via hydrogen bonds. Ultrasonication can disrupt dense cellulose network and produce the long BC/MWCNTs bundles ranging from 30 to 100 μm. Raman spectroscopy shows a drop at peak of hydroxyl (-OH, 3700 m^-1) and carbonyl (C=O, 1600 cm^-1). This indicates the formation of the continuous MWCNTs-like protection layer on BC surface. Electrical properties of the BC/MWCNTs bundles showed linearity from -6 V to +6 V. Composites with BC treated by higher ultrasonic powers, 100 W, show higher conductivity comparing to 80 W. Sensitivity from 10^-7 to 10^-9 A of long BC/MWCNTs composite bundles is reported in this paper. This technique may be competitive to the current state of carbon nanotubes resonator.