To achieve mass measurement of biological molecules in viscous fluids using carbon nanotube resonators, we investigated the vibration of nanotube cantilevers in water using the optical detection technique. In vacuum, we often found a few resonance modes of nanotube vibrations. However, the nanotube lost its fundamental oscillation once immersed in water, suggesting a great viscous resistance to the nanotube vibration in water. The resonant frequency of the nanotube in water decreased with lowering the water temperature, corresponding to the natural phenomenon by which liquid viscosity tends to increase at lower temperatures.

No abstract

We demonstrated the measurement of interaction force between molecules using a multi-walled carbon nanotube cantilever under light microscopy. The deflection of the nanotube cantilever was monitored at the video frame rate during the force measurement. We also investigated the detection sensitivity and stability of our deflection detection system, and indicated that the measurement of “nm order” displacement can be achieved in water by our optical detection technique. The interaction force we measured using a cantilevered nanotube was 230 pN, possibly indicating the force required to rupture the weak bonds between the adsorbed polymers on the tungsten tip and proteins at the tip of the nanotube cantilever