Network for Computational Nanotechnology

'Nanocantilevers' yield surprises critical for designing new detectors

Today's pathological tests are relatively inefficient and require millions of copies of virus/bacteria present in a milli-liter of blood for diagnosis of a disease. In contrast, the emerging electronic nanobio sensors promise that one day, in not so distant future, one would be able to detect single virus, bacteria, or pathogen in simple, inexpensive, and ubiquitous tests - allowing earlier detection and more effective prevention. This could forever change environmental-health monitoring in hospitals and homeland security and could pave the way for "lab-on-a-chip" technologies.

This rendition depicts an array of tiny, diving-boardlike devices called nanocantilevers. The devices are coated with antibodies to capture viruses, which are represented as red spheres. New findings about the behavior of the cantilevers could be crucial in designing a new class of ultra-small sensors for detecting viruses, bacteria and other pathogens. (Image generated by Seyet, LLC).

One such sensor — the nanocantilever — detects biomolecules by monitoring the reduction of frequency of vibration after the molecule is attached. The smaller the cantilever, the more sensitive is the detection - or so says the classical theory - and hence the worldwide effort to reduce the dimensions of the cantilever to nanometer range. Now a member of the NCN Nanobio group — M. A. Alam — in collaboration with Prof. Bashir of ECE/BME have shown that the physics of sensors nanoscale is more complex/counterintuitive than previously believed. Indeed, as the molecules attach to sensors, its frequency may either increase (!) or decrease depending on sensor dimensions. This is because at nanoscale the larger cantilevers catch more antibody than smaller ones. And since the protein thickness is comparable to thickness of the cantilever, these biomolecules not only increase the mass (expected) but also changes the spring constant (surprise) of the cantilever. In short, when sensor size becomes comparable to the molecules being sensed, classical intuitions are no longer effective guides and design of sensors require dramatically new approach.

These results were recently published in Proceedings of National Academy of Sciences. The research was supported by NCN and NIH. A. Gupta from Prof. Bashir's group did the key experiments and P. Nair from Prof. Alam's lab developed the mathematical models. See more on Alam at http://www.nanohub.org/contributors/2624/ and Bashir at http://www.nanohub.org/contributors/4202/