Real-time force reconstruction in a transverse dynamic force microscope

Abstract

One major functionality of force microscopes is their ability to measure forces at a high sensitivity, thereby, allowing understanding of vital mechanisms: for instance, in bio-specimens. The investigation of a specimen’s viscoelasticity on nano-scale can have significant scientific impact, but has been inhibited by the lack of fast, comprehensive scanning instruments. In principle, transverse dynamic force microscopes (TDFMs) permit the measurement of interaction forces within delicate samples in a non-contact manner. The force measurements are reconstructed via complicated offline analysis in TDFMs, therefore, they can hardly be utilised as an online force measuring tool. This paper introduces a novel integrated robust design for practical scanning using the TDFM system. The digital design is implemented in fixed-point arithmetic using Field Programmable Gate Array (FPGA) devices, thereby, permitting measurement of the interaction force at a high sampling rate. The novel digital design tackles different implementation issues achieving fast and robust force measuring performance. This enables a new force-scan mode for the TDFM, realising for the first time, online force mapping of sample-surfaces in real-time.