# The Attachment of Carbon Nanotubes to Atomic Force Microscopy Tips Using the Pick-Up Method
## 4 Discussion  
Early indications of the routine use of CNT-AFM probes in AFM have not occurred and are due to a number of reasons including the difficulty in attaching CNTs to AFM tips, scaling up the attachment process to multiple probes, the tendency of CNT attachment methods to only be applied to high spring constant tapping mode probes and the technological development of silicon probes. While there are numerous techniques for attaching CNTs to AFM probes these methods are almost exclusively applied to one AFM tip at a time. Attaching CNTs to multiple AFM tips means that these types of probes could become more commonplace than they currently are. Indeed, very few manufacturers provide CNT-AFM probes and they are typically greater than 100 US dollars each (e.g., FN-1 series  
Figure 6: Shows AVD curves for two 1930-00 clever AFM probes located on the same chip using the procedure outlined in Section 2.3. (**a**) is for a 1930-00 clever-C probe and (**b**) is for a 1930-00 clever-D probe. Buckling signatures showing evidence of CNT attachment can be observed in both AVD curves.  
Figure 7: (**a**) and (**b**) Show tapping mode images with (**a**) acquired using a 1930-00 clever-C probe and (**b**) acquired using a 1930-00 clever-D probe. The height colour scale for both images is 5 nm.  
K-Tek Nanotechnology). In this work we demonstrate that the pick-up method, one of the simplest techniques to attach CNTs, can adhere CNTs to two AFM probes simultaneously. While this is not at the wafer scale it does demonstrate the proof of concept. There are a number of ways this technique can be improved. For example, by optimizing the CNT substrate and probe parameters such as spring constant. [PERSON] et al. [PERSON] et al. (2018) coated AFM tips with a thin film of plasma polymerized hexane before using the pick-up method to create CNT-AFM probes. This coating presents the CNT with a highly hydrophobic coating to which it can adsorb and improved the success rate and robustness of the CNT-AFM probes. This approach combined with the methods employed in this work could allow larger scale production of CNT-AFM probes and is the subject of further research. If this procedure could be scaled up then larger arrays of probes could be functionalized with CNTs with a wide range of applications including, but not limited to, providing the AFM community with high resolution durable probes and data storage density research.  
In this work we also demonstrated that the pick-up method can be applied to contact mode probes with spring constant less than 0.30 N/m. CNT attachment allows these low spring constant probes to operate in tapping mode. Contact mode probes operating in tapping in air with attached CNTs will allow soft biological samples to be imaged with much less force than standard tapping mode probes, which have much higher spring constants.  
We also reviewed the advantages and disadvantages of the different methods that can be used to detect CNT attachment which include improved image resolution, AVD curves and EM imaging. This will be useful for any scientists entering this area of research.  
This research was partly funded by EPSRC Basic Technology Award (EP/C523857).  
The author wishes to acknowledge [PERSON] for useful discussions, [PERSON] for assistance in acquiring SEM images, [PERSON] and [PERSON] for producing CNT covered substrates. The author also acknowledges the use and support of the South Australian node of Microscopy Australia at Flinders University, South Australia.  
The author declares no conflict of interest.