Traditional optical microscopy is a powerful tool used by the majority of scientists, but it is not without limitations. Namley that a wavelength of light has an amplitude of approximately 550 nm (green light in air) (1). This means that in practice optical microscopy cannot visualize a sample below 550 nm, precluding the study of many important biological players (2). The resolution of an optical microscope also depends on the materials used to refract the light as well as the aperture of the lens; advancements it these aspects of optical microscopy have lowered resolution to ~200 nm for specialized microscopes. 

Figure 1: Sizes of major biomolecules compared to optical and scanning electron microscopy resolutions. Reproduced from 2.  

Despite the advancements in optical microscopy, the detection limits are still far larger than features of interest, see Fig. 1, in naturally occuring and synthetic systems. The advents of scanning probe techniques (SPM) have propelled the advances in microscopy over the last decade, particularly because of the insight they provide into the structure and function of many interfacial reactions. Amongst the SPM techniques developed, scanning electrochemical microscopy (SECM) with shear-force imaging (SF) enables the concurrent mapping of electrochemical data along with surface topography. The technique utilizes a specialized probe that is scanned over a region of interest to obtain surface topography with nanoscale features. SPM holds valuable applications in fields such as nanofabrication, biotechnology, self-assembly, and nanomedicine (3). 

Figure 2: A schematic of a scanning electrochemical microscope.

SECM provides researchers with much higher resolution (~1nm) than optical microscopy, as well as the ability to monitor or control local electrochemical reactions. Continued advances in scanning probe microscopy, namely SECM, will increase the number of biological and engineering phenomena that we can study, manipulate, and eventually translate into products. For further reading please see the Integrated Systems Laboratory website, and the wikipedia pages on optical microscopy and scanning electrochemical microscopy.

References

(1.)  Davidson, M.W.., Abramowitz, M., "Optical Microscopy," [Encyclopedia of Imaging Science and Technology] (2002).
(2.)  Ob, R. on M., Cell Biology by the numbers. 
(3.)  Northcutt, R. G.., Sundaresan, V-B., "Mechanoelectrochemistry of PPy(DBS) from correlated characterization of electrochemical response and extensional strain," Phys. Chem. Chem. Phys. 17(48), 32268-32275 (2015)

Written by TPS Fellow, Parker Evans