EPJ Techn Instrum (2015) 2: 1
https://doi.org/10.1140/epjti/s40485-014-0011-5

Research article

Characterization of a gold coated cantilever surface for biosensing applications

¹ Department of Physics, McGill University, 3600 Rue University, Montreal, QC, H3A 2T8, Canada
² Research Institute of the McGill University Health Centre, 2155 Guy Street, Montreal, QC, H3H 2R9, Canada
³ Department of Chemistry and FQRNT Centre for Self Assembled Chemical Structures, McGill University, 801 Sherbrooke Street West, Montreal, QC, H3A 2K6, Canada

^* e-mail: haagal@physics.mcgill.ca

Received: 18 June 2014
Accepted: 10 December 2014
Published online: 21 February 2015

Abstract

Cantilever based sensors are a promising tool for a very diverse spectrum of biological sensors. They have been used for the detection of proteins, DNA, antigens, bacteria viruses and many other biologically relevant targets. Although cantilever sensing has been described for over 20 years, there are still no viable commercial cantilever-based sensing products on the market. Several reasons can be found for this – a lack of detailed understanding of the origin of signals being an important one. As a consequence application-relevant issues such as shelf life and robust protocols distinguishing targets from false responses have received very little attention.

Here, we will discuss a cantilever sensing platform combined with an electrochemical system. The detected surface stress signal is modulated by applying a square wave potential to a gold coated cantilever. The square wave potential induces adsorption and desorption onto the gold electrode surface as well as possible structural changes of the target and probe molecules on the cantilever surface resulting in a measurable surface stress change. What sets this approach apart from regular cantilever sensing is that the quantification and identification of observed signals due to target-probe interactions are not only a function of stress value (i.e. amplitude), but also of the temporal evolution of the stress response as a function of the rate and magnitude of the applied potential change, and the limits of the potential change.

This paper will discuss three issues that play an important role in future successful applications of cantilever-based sensing. First, we will discuss what is required to achieve a large surface stress signal to improve sensitivity. Second, a mechanism to achieve an optimal probe density is described that improves the signal-to-noise ratio and response times of the sensor. Lastly, lifetime and long term measurements are discussed.