Scanning probe microscopy (SPM) remains one of the most vibrant areas of technical development for microscopic imaging. In SPM, a nanopositioning system brings a physical probe with an ultrafine tip very close to the sample surface under study. Depending on the nature of the tip and the particular measurement mode being used, interactions between the surface and the tip lead to measurable changes in the system, which can be detected and recorded.

A plethora of such measurement modes exist, bearing on the physical, electrical, magnetic and other properties of the surface. As the positioning system moves across the sample, the instrument can assemble an “image” of the sample out of the measurements made at each location, or a particular location can be studied over time as conditions are varied. One specific measurement mode is scanning electrochemical microscopy (SECM), in which the probe is an ultramicroelectrode formed from a fine wire embedded in a glass probe, with just the tip of the wire exposed for detection. These electrodes can be less than a micron in diameter at the tip.

Typically, SECM measurements are carried out in an aqueous electrolytic medium to allow current flow, with the probe submerged and brought to the sample surface. When the probe is close enough, the readings from the electrode become very specific to the local area beneath the probe. In addition to providing readings of current, electrical potential and other electrochemical variables, the electrode can also be used to direct current to a particular location on the sample, manipulating the local conditions for an experiment. This active use of the electrode can also be used to create or modify nanostructures on the sample through deposition, etching or other processes.

The largest market for SECM is academia, and there are applications in a variety of disciplines from the chemistry of surfaces to the characterization of cell membranes. Research into catalysts, corrosion and deposition is found both in academia and also in industrial labs focusing on advanced materials and metals. Fuel cell design is another important area of study for SECM in the energy industry. Electronics materials and other nanotechnological devices can also be studied and manipulated with SECM. In the life sciences, in addition to studying cell membranes, the technique can be used for measuring enzymatic activity, biostructures and biosensors.

Since SECM remains a rarer specific technique, not all of the relevant SPM vendors provide SECM options. Bruker, the dominant market leader, has long supported the technique, and in September, the company introduced a PeakForce SECM mode for its Dimension Icon AFM, which provides high resolution simultaneous imaging of both topography and electrochemical properties. Princeton Applied Research (AMETEK) has wide expertise in electrochemistry, including systems for SECM. In September, AMETEK partnered with the Laboratory of Physical and Analytical Electrochemistry—École Polytechnique Fédérale de Lausanne to market the Swiss research institute’s soft probe technology (see IBO 10/31/16), which overcomes difficulties that topographic effects can cause in SECM. When Agilent Technologies spun off some of its businesses into Keysight Technologies, its SPM business was included in that, making the new company the third largest vendor of SECM.

Other major SPM vendors that offer SECM probes include Park Systems, JPK, Asylum Research (Oxford Instruments) and Nanonics. There are also a few smaller vendors that are highly focused on the SECM technique; these include Sensolytics, Heka (acquired by Harvard Bioscience in 2015, see IBO 1/31/15), CH Instruments and BioLogic Science Instruments.

SECM at a glance:

Leading SECM Suppliers:

• Bruker
• AMETEK
• Keysight

Largest Markets:

• Academia
• Metals
• Energy

SECM System Cost: $50,000­–$200,000