Device for the transport, storage as well as the chemical or physical treatments of
AFM
tip series
Authors: Gaillard Cédric 
Published: December 2016

Atomic force microscope ‐ AFM ‐ is a scanning probe microscope used to probe surfaces with a high degree of accuracy. AFM is based on the measurement of forces of interaction between, on one hand, atoms of the surface of a sample and, one the other hand, the last atoms of an AFM tip or probe. AFM is also a tool to measure the local forces allowing access, through the acquisition of force spectra, to the nanomechanical properties of a sample (adhesion, deformation, elasticity, dissipation, etc.). An AFM probe consists of a tip positioned at the end of a lever, which is itself attached to a support (“chip” or “wafer”). An AFM probe is only a few millimeters long and is very fragile and expensive.

When new or unused AFM probes can be stored in plastic transport boxes or more rarely cassettes suitable for packaging and transporting dry these probes without risk of damaging them. The ground of these boxes is covered by a layer of adhesive polymer (gel) designed to maintain AFM probes on the surface of the wafer by adhesion. However, this direct contact with the gel may cause contamination of the tips and the presence of gel avoids the physical or chemical treatment of the probes in this box, as well as their conservation in liquid medium, which is required for any chemically grafted tip.

We introduce here a new generation of AFM device that has been specifically developed to provide both the transport and storage of AFM probes in air or in liquid (water, buffers, alcools,…). It is also well adapted for physical treatments (UV/ozone treatment, plasma, metal sputtering,…) and chemical application (tip chemistry). The device is mainly based on an originally way to hold a large series of AFM probes for all the applications, preventing them from any breakage or damage. [1]

By fixing a series of AFM probes in the box, the successive steps of UV/ozone for tip surface cleaning, piranha activation of SiN tip surface, chemical reactions, bio‐functionalization, water and buffer washing and long term storage in buffer can be operated with keeping the AFM probes in their initial position. The liquid reactants, water and buffers are simply injected and removed using a (micro)syringe. Application of the AFM boxes was useful to prepare series of tips using rigorously the same experimental conditions. Antibodies functionalized tips may be prepared in one experiment to further analysis the nanomechanical properties of different substrates by AFM and force spectroscopy and mapping. Tips may also be prepared at a first place (for example, in a lab expert in chemistry of biomolecules) and be sent by mail to another place for analysis (for example, in a lab expert in AFM imaging and force measurements).

The figure 1 shows pictures of the device and an example of application to study the adhesive properties of lactalbumine milk proteins. This device takes the advantage to have internal containers that can be used independently from the outer lager container. This feature is very well adapted for chemical grafting of series of AFM tips according to different protocols.