| AVS 59th Annual International Symposium and Exhibition | |
| Scanning Probe Microscopy Focus Topic | Wednesday Sessions |
| Session SP+AS+BI+ET+MI+NM+NS+SS+TF-WeM |
| Session: | Probe-Sample Interactions, Nano-Manipulation and Fabrication |
| Presenter: | J.F. Portoles, Newcastle University, UK |
| Authors: | J.F. Portoles, Newcastle University, UK P.J. Cumpson, Newcastle University, UK |
| Correspondent: | Click to Email |
Accurate measurement of biologically-relevant forces in the range of pN to μN is an important problem in nanoscience.
A number of force probe techniques have been applied in recent years. The most popular is the Atomic Force Microscope (AFM). Accuracy of force measurement relies on calibration of the probe stiffness which has led to the development of many calibration methods[1], particularly for AFM microcantilevers. However these methods typically exhibit uncertainties of at best 15% to 20% and are often very time consuming. Dependency on material properties and cantilever geometry further complicate their application and take extra operator time. In contrast, one rapid and straightforward method involves the use of reference cantilevers (the "cantilever-on-cantilever" method) or MEMS reference devices. This approach requires that a calibrated reference device is available, but it has been shown to be effective in providing measurement traceability[2].
The main remaining difficulty of this approach for typical users is the positional uncertainty of the tip on the reference device, which can introduce calibration uncertainties of up to around 6%. Here we present a new reference device based on a torsional spring of relatively large dimensions compared to the typical AFM cantilever and demonstrate how it is calibrated. This method has the potential to calibrate the reference device traceably[3] to the SI with a 1% accuracy by applying techniques typically used for the characterisation of micromechanical devices. The large dimensions of the device reduce the positional uncertainty below 1% and simultaneously allow the use of the device as an effective reference array with different reference stiffnesses at different positions ranging from 0.090 N/m to 4.5 N/m
[1] P J Cumpson, C A Clifford, J F Portolés, J E Johnstone, M Munz Cantilever Spring-Constant Calibration in Atomic Force Microscopy, pp289-314 in Volume VIII of Applied Scanning Probe Methods, Ed. B Bhushan and H Fuchs (Springer, New York, 2009)
[2] P J Cumpson PJ, J Hedley, Nanotechnology 14 (2003) pp. 1279-1288
[3] J F Portolés, P J Cumpson, J Hedley, S Allen, P M Williams & S J B Tendler, Journal of Experimental Nanoscience 1 (2006) pp51-62.