Development of nanomanipulator using a high-speed atomic force microscope coupled with a haptic device.

The atomic force microscope (AFM) has been widely used for surface fabrication and manipulation. However, nanomanipulation using a conventional AFM is inefficient because of the sequential nature of the scan-manipulation scan cycle, which makes it difficult for the operator to observe the region of interest and perform the manipulation simultaneously. In this paper, a nanomanipulation technique using a high-speed atomic force microscope (HS-AFM) is described. During manipulation using the AFM probe, the operation is periodically interrupted for a fraction of a second for high-speed imaging that allows the topographical image of the manipulated surface to be periodically updated. With the use of high-speed imaging, the interrupting time for imaging can be greatly reduced, and as a result, the operator almost does not notice the blink time of the interruption for imaging during the manipulation. This creates a more intuitive interface with greater feedback and finesse to the operator. Nanofabrication under real-time monitoring was performed to demonstrate the utility of this arrangement for real-time nanomanipulation of sample surfaces under ambient conditions. Furthermore, the HS-AFM is coupled with a haptic device for the human interface, enabling the operator to move the HS-AFM probe to any position on the surface while feeling the response from the surface during the manipulation.

Methods for imaging DNA in liquid with lateral molecular-force microscopy.

Shear force microscopy is not normally associated with the imaging of biomolecules in a liquid environment. Here we show that the recently developed scattered evanescent wave (SEW) detection system, combined with custom-designed vertically oriented cantilevers (VOCs), can reliably produce true non-contact images in liquid of DNA molecules. The range of cantilever spring constants for successful shear force imaging was experimentally identified between 0.05 and 0.09 N m(-1). Images of λ-DNA adsorbed on mica in distilled water were obtained at scan rates of 8000 pixels s(-1). A new constant-height force mapping mode for VOCs is also presented. This method is shown to control the vertical position of the tip in the sample plane with better than 1 nm accuracy. The force mode is demonstrated by mapping the shear force above λ-DNA molecules adsorbed on mica in a liquid environment at different tip-sample separations.

High-speed AFM of human chromosomes in liquid.

Further developments of the previously reported high-speed contact-mode AFM are described. The technique is applied to the imaging of human chromosomes at video rate both in air and in water. These are the largest structures to have been imaged with high-speed AFM and the first imaging in liquid to be reported. A possible mechanism that allows such high-speed contact-mode imaging without significant damage to the sample is discussed in the context of the velocity dependence of the measured lateral force on the AFM tip.