The SPM is only two decades old but it has had a major impact on science and technology [Wiesendanger 1994]. SPMs are typically used for imaging surfaces, often with atomic resolution. But a growing body of research shows that SPMs can function both as sensors and as actuators. They can modify surfaces and structures at the nanometer scale. For example, a Scanning Tunneling Microscope (STM) can draw lines on a hydrogen-passivated silicon surface by hydrogen removal, and can deposit gold dots or lines on a surface – see e.g. [Wiesendanger 1994, Salling 1996] for reviews of some of this work, which has been able to produce features that range from a few to hundreds of nm. And recently a "desktop factory" has been proposed for producing integrated circuits by STM-induced material deposition [Tabib-Azar & Litt 1997]. This application is roughly analogous to robotic spray-painting or welding in the macro-world. In our own lab we have built patterns of nanoparticles with diameters of 5-30 nm by using an Atomic Force Microscope (AFM) [Bauret al. 1997, Requicha et al. 1998], and others have also tackled challenging nanomanipulation tasks. These are examples of robotic manipulation and assembly at the nanoscale. Despite their remarkable achievements, SPM methods for fabrication or manipulation suffer from a major drawback: they are inherently serial, and therefore have low throughputs.
