There are three areas in which conventional AFM has limitations: (i) low imaging rate, (ii) probe-sample force interaction, and (iii) the planar nature of the sample. We are developing two high-speed force microscopy techniques. One high-speed AFM (HS AFM) technique is a DC method in which the tip is in continuous contact with the specimen. This routinely allows video-rate imaging (30 frames per second, fps) and has achieved imaging at over 1000 fps, i.e., 100,000 times faster than conventional AFM. Damage to specimens resulting from this high-speed contact-mode imaging is surprisingly less than would be caused at normal speeds. The behavior of the cantilever and tip at these high velocities has been investigated and superlubricity is a key component in the success of this technique. The other high-speed force microscope is a non-contact method based on shear-force microscopy (ShFM). In this HS ShFM, a vertically-mounted laterally-oscillating probe detects the sample surface at about 1 nm from it as a result of the change in the mechanical properties of the water confined between the probe tip and the sample. With this technique, very low normal forces are applied to the specimen. Conventional AFMs require planar samples because the probe scans in a plane. It is as if the tip is only 'seeing' the sample from above. We have overcome this limitation be steering the tip of a nanorod in a three dimensional scan with six degrees of freedom using holographically generate optical traps such that it is possible to scan around a sample.

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.

High-speed atomic force microscopy (AFM) is important for following processes that occur on sub-second timescales for studies both in biology and materials science, and also for the ability to examine large areas of a specimen at high resolution in a practical length of time. Further developments of the previously reported high-speed contact-mode AFM are described. Two instruments are presented: (i) a high-speed flexure stage arrangement capable of imaging at a video rate of 30 fps, and (ii) an ultra-high speed instrument using a combined tuning fork and flexure-stage scanning system capable of ultra-high-speed imaging in excess of 1000 fps. Results of imaging collagen fibres under ambient conditions at rates of up to 1300 frames s−1 are presented. Despite tip–specimen relative velocities of up to 200 mm s−1, no significant damage to the collagen specimen was observed even after tens of thousands of frames were acquired in the same area of the specimen.

Atomic force microscopy (AFM) has many advantages over other microscopy techniques for the study of both synthetic polymer systems and biological structures. Its ability to acquire high-resolution images under ambient conditions and also in liquid environments is particularly important for biomolecular systems and both biological and polymer systems benefit from the lack of radiation damage associated with electron microscopy. However, in its conventional implementations, AFM suffers from low image acquisition rates, which are typically less than one frame per minute. This results in two significant disadvantages of this and indeed other SPM techniques: (i) the inability to follow processes occurring in much less than a one-minute time period, and (ii) the inability to image large areas of the specimen because there is no low-magnification mode and the low imaging rate means it is impractical to image large areas by multiple scans.