Pietro Cicuta visit and seminar

Pietro Cicuta (Cambridge University) is visiting the lab on Wednesday 07 November, and giving the AMOPP/BioP seminar.  Pietro works on a variety of problems relevant to soft matter and biological physics, including colloidal systems, complex fluids and membranes.  His talk is titled Emergence of collective states in active colloids, and the abstract is below:

Title: Emergence of collective states in active colloids. Pietro Cicuta (Cambridge University)

Abstract:  Coupled oscillators can, under some conditions, synchronise. There are examples of this everywhere in natural phenomena, technology, and material properties.  A relatively unexplored area is the synchronisation of colloidal oscillators: these are micron-sized objects, coupled through hydrodynamic interaction.   There is reason to study these because physiologically similar structures are thought to enable fluid transport in various organs;   technologically it might be possible to construct very sensitive micro-resonators.
Over the last few years we have worked in this area by developing an experimental platform: optical tweezers are used to create phase oscillators. This talk will present various strategies for making oscillators (active colloids), and the resulting collective behaviour of two or more of these elements.

SPIE Conference Proceedings

Our contributions to the Optical Trapping and Optical Micromanipulation IX meeting at SPIE Optics + Photonics 2012 are now published in the conference proceedings as:

S. E. Skelton, M. Sergides, M. G. Donato, S. Vasi, R. Sayed, P. G. Gucciardi, R. Saija, M. A. Iatì, O. M. Maragò and P. H. Jones.  'Shaping the trapping volume in optical tweezers using cylindrical vector beams', Proc. SPIE 8458, Optical Trapping and Optical Micromanipulation IX, 84582Z, doi: 10.1117/12.929927 (2012)

S. E. Skelton, M. Sergides, G. Memoli, O. M. Maragò and P. H. Jones.  'Optical squeezing of microbubbles: Ray optics and Mie scattering calculations', Proc. SPIE 8458, Optical Trapping and Optical Micromanipulation IX, 84581F, doi: 10.1117/12.929900 (2012)

M. Sergides, S. E. Skelton, E. Karczewska, K. Thorneycroft, O. M. Maragò and P. H. Jones.  'Optically bound particle structures in evanescent wave traps', Proc. SPIE 8458, Optical Trapping and Optical Micromanipulation IX, 84583C, doi: 10.1117/12.929612 (2012)

New Group Members

This year we welcome two final year undergraduate students into the Optical Tweezers Group for their MSci projects.  Chris Richards will be working on light scattering calculations relevant to our optical trapping and optical binding experiments.  Zhi Wong will be investigating the optical and light scattering properties of metallic nanoparticles in his project on Plasmonics.

SPIE Optics + Photonics Conference

Marios and Susan are attending the Optical Trapping and Optical Micromanipulation IX conference, part of SPIE Optics + Photonics, in San Diego, CA, 12 - 16 August.  Susan will be giving a talk 'Optical squeezing of microbubbles: Ray optics and Mie scattering calculations' (Paper 8458-51) on Wed 16 Aug (Session 10: Combining optical traps with acoustics) and presenting a poster on 'Shaping of the trapping volume in optical tweezers using cylindrical vector beams' (Paper 8458-110).  Marios will be presenting a poster 'Optically bound particle structures in evanescent wave traps' (Paper 8458-124).

Paper published in Optics Letters

Our paper 'Optical trapping of single walled carbon nanotubes with cylindrical vector beams has been published as M. G. Donato et al, Opt. Lett. 37 3381-3383 (2012).  

From the abstract: We use laser beams with radial and azimuthal polarization to optically trap carbon nanotubes. We measure force constants and trap parameters as a function of power showing improved axial trapping efficiency with respect to linearly polarized beams. The analysis of the thermal fluctuations highlights a significant change in the optical trapping potential when using cylindrical vector beams. This enables the use of polarization states to shape optical traps according to the particle geometry, as well as paving the way to nanoprobe-based photonic force microscopy with increased performance compared to a standard linearly polarized configuration.

This paper has also been selected for inclusion in the Virtual Journal of Biomedical Optics 7 (2012)

Royal Society Summer Exhibition

This week we have been at the Royal Society Summer Exhibition 2012 with a display titled POP! The sound of bubbles.  Opposite you can see members of the team explaining the science of bubbles to guests at the soiree on Thu 05 Jul.

The exhibition and our display also featured on the BBC news, and in BBC R4's Material World programme on 05 July. The podcast of this show will be available to download for the next few weeks. 

Trapping and deformation of microbubbles in a dual-beam fibre-optic trap

  

Our paper Trapping and deformation of microbubbles in a dual-beam fibre-optic trap has been published as S E Skelton et al, Journal of Optics 14 075706 (2012).

From the abstract:  We present results of numerical calculations to evaluate the performance of a dual-beam fibre-optic trap for low refractive index particles such as ultrasound contrast agent microbubbles. Using a geometrical optics approach, we determine the range of parameters of microbubble size and beam dimensions over which the optical trap is stable and evaluate the trapping forces and spring constants. Additionally, we calculate the optically induced stress profile over the surface of the microbubble and evaluate the resulting deformation of the microbubble using elastic membrane theory. Our results suggest that such an experiment could be a useful tool for quantifying the mechanical properties (elastic modulus) of the shell material of an ultrasound contrast agent microbubble.

This paper has been included in the IoPscience collection of featured articles "chosen for their quality and recency".