Dr Loren Picco
Nanophysics and Soft Matter Group
My research interests are focused on exceeding current limitations on the rate and sensitivity of scanning probe microscopy measurements. To this end I am involved in the following projects: the fastest contact mode AFM in the world (over 1,200 frames per second); the development of a video-rate non-contact technique, unique to Bristol called Transverse Dynamic Force Microscopy (TDFM); as well as the creation of cantilever arrays for mass sensing, capable of femto-gram measurements.
Current grants: SARTRE - Diagnostic probe arrays; EPSRC - Optical atomic force microscopy; EPSRC Pathways to Impact grant.
Research keywords: High-Speed AFM, Mass Sensing, High-Sensitivity Force Probes, Multitouch Instrumentation, Transverse Dynamic Force Microscopy
Tel. No.: +44 (0)117 331 7083
Featured research: HSAFM | Multitouch control | Cantilever modelling | TDFM
This video demonstrates millisecond time resolution over large, soft structures such as human chromosomes. Example video footage of the HSAFM in use from the Group's YouTube channel: http://www.youtube.com/user/BristolNanoPhysics#p/u.
High speed AFM
Atomic force microscope (AFM) images are produced by raster scanning the surface (line-by-line, pixel-by-pixel), a time consuming method and one which conventional, commercial AFMs accomplish in timescales of tens of seconds to multiple minutes. This means that biological processes, available to us as the material is active, can only be imaged in time lapse. We have developed a high-speed AFM (HSAFM), which captures images at video-rate and unlocks the potential of the AFM as a practical tool for the observation of nanoscale processes occurring at the millisecond timescale. The HSAFM works equally well in liquid conditions as it does in the ambient environment.
Additionally, one of the reasons that the AFM has become such a popular tool is that it is a mechanical microscope, meaning that it is not only capable of imaging surfaces, but also of interacting with them. AFMs are useful tools within the field of nanocharacterisation and nanofabrication and the HSAFM enables the production of nanostructures in much faster timescales.
This video demonstrates multitouch control of the HS-AFM, imaging a calibartion grid. The panel on the left is the current image frame while the panel on the right stitches the frames together.
Multitouch Control of the High-Speed AFM
Our HSAFM collects images at video rate and beyond. This thousand-fold increase in imaging speeds has enabled us to interact with the instrument and our samples in real-time, rather than the time-lapse format of commercial AFM imaging. The functionality of the HSAFM was limited initially because controls were updated one scan parameter at a time in the same manner as a standard AFM. To take advantage of the capabilities and responsiveness of the HSAFM, it is necessary to implement a user interface which allows the operator to interact with multiple controls simultaneously. The result is much closer to how a conventional optical or even scanning electron microscope can be operated, which enables even non-skilled operators to control the instrument effectively. We believe that the combination of LabVIEW and multitouch interfaces unlocks the full potential of the software by providing users with more intuitive and responsive methods of control.
The system was recently published on the NI website as a case study (http://sine.ni.com/cs/app/doc/p/id/cs-13097)
The movie above shows the motion of a triangular cantilever over a 1 um pitch, 200 nm high silicon calibration grid as it is scanned with a 1 kHz line rate (equal to a tip velocity of 6 mm/s). The movie displays 1 in every 100 frames and provides nanosecond temporal resolution of the dynamics of the cantilever.
Further Developments to the High-Speed AFM with Ollie Payton
When using the High speed AFM the cantilever acts in contact mode. In this mode of operation the sharp tip of the cantilever is in contact with the surface which is being imaged. In order to achieve such high frame rates tip velocities above 1 mm/s are required. It is therefore surprising that neither the tip nor the sample seem to be affected by these very high speeds at the length scales involved.
A mixture of experimental and theoretical experiments are helping us to understand the tip-sample interaction and dynamics of the cantilever as it moves across a surface. Using this information we are designing methods to reduce image noise, artifacts and the pressure that the tip places on the surface. This is enabling us to create new detection systems and real time image analysis that will provide cleaner images at a higher temporal and spatial resolution. We are also working on novel ways to present the 3D surface information so that the instruments we build are more user friendly.
The following movie file shows the high-speed TDFM scanning along several strands of lambda DNA deposited on muscovite mica. The imaging is performed at 2 frames per second with scan size that moves from 5 um to 90 nm during the movie.
Transverse Dynamic Force Microscope with Rob Harniman
Over the past fifteen years, we have developed a range of shear-force or transverse dynamic force microscopes (TDFM). This technique senses the sample surface before contact through the changes in complex mechanical properties of the molecular water layers confined in the gap (<1 nm) between the probe tip and the sample. We are developing a high-speed version of the TDFM through the use of bespoke, highly-sensitive and high-resonant frequency probes to shift to shorter timeframes. The system utilizes a custom-made high-speed scanning stage, a Scattered Evanescent Wave (SEW) detection system, and high-sensitivity, high-resonance probes. Its ability to scan at sub-second temporal resolutions in a non contact regime enables samples to be investigated with a minimum of applied force.
In developing the HSTDFM we have simultaneously addressed the two major challenges present in force microscopy; low tip-sample interaction forces and high imaging rate.
- Hired Guns - a collective of Certified LabVIEW Associate Developers (CLAD) based in Bristol.
- Spyglass - an award-winning entrepreneurial start-up, Spyglass hopes to develope and produce affordable, easy-to-use scanning probe microscopes.
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| Author | Title | Year | Reftype | DOI/URL |
|---|---|---|---|---|
| Bowman, R., Gibson, G., Carberry, D., Picco, L., Miles, M.J & Padgett, M. | iTweezers: optical micromanipulation controlled by an Apple iPad | 2011 | Journal of Optics 13(4), 044002 |
DOI URL |
| Payton, O., Champneys, A., Homer, M., Picco, L. & Miles, M.J. | Feedback-induced instability in tapping mode atomic force microscopy: theory and experiment | 2011 | Proceedings - Royal Society. Mathematical, Physical and Engineering Sciences 467(2130), 1801 -1822 |
DOI URL |
| Payton, O.D., Picco, L., Champneys, A.R., Homer, M.E., Miles, M.J. & Raman, A. | Experimental observation of contact mode cantilever dynamics with nanosecond resolution | 2011 | Review of Scientific Instruments 82(4), 043704 |
DOI URL |
| Carberry, D.M., Picco, L., Dunton, P.G. & Miles, M.J. | Mapping real-time images of high-speed AFM using multitouch control | 2009 | Nanotechnology 20(43), 434018 |
DOI |
| Pyne, A., Marks, W., Picco, L., Dunton, P., Ulcinas, A., Barbour, M., Jones, S., Gimzewski, J. & Miles, M.J. | High-speed atomic force microscopy of dental enamel dissolution in citric acid | 2009 | Archives of Histology and Cytology 72(4-5), 209-215 |
DOI URL |
| Antognozzi, M., Ulcinas, A., Picco, L., Simpson, S.H., Heard, P.J., Szczelkun, M.D., Brenner, B. & Miles, M.J. | A new detection system for extremely small vertically mounted cantilevers | 2008 | Nanotechnology 19(38), 384002 |
DOI |
| Picco, L.M., Dunton, P.G., Ulcinas, A., Engledew, D.J., Hoshi, O., Ushiki, T. & Miles, M.J. | High-speed AFM of human chromosomes in liquid | 2008 | Nanotechnology 19(38), 384018 |
DOI |
| Picco, L.M., Bozec, L., Ulcinas, A., Engledew, D.J., Antognozzi, M., Horton, M.A. & Miles, M.J. | Breaking the speed limit with atomic force microscopy | 2007 | Nanotechnology 18(4), 044030 |
DOI |