PhD studentship available

A PhD studentship is available to start in September 2014 on a project entitled Membrane engineering of artificial lipid vesicles. The goal of this project is to use optical tweezers to probe the mehanical properties of biomimetic vesicles undergoing temperature or light-induced phase or structural transformation, and to use the results of these studies to engineer membrane materials with properties optimised for applications including controlled drug release and microreactors.

Experimental work will be carried out in the Optical Tweezers Group in the Department of Physics & Astronomy at UCL and in the Biological Soft Matter Group in the School of Materials Science at the Japan Advanced Institute of Science & Technology (JAIST).  The project is jointly supervised by Dr Phil Jones (UCL) and Dr Tsutomu Hamada (JAIST).

The studentship will pay a stipend and fees at the rate applicable for UK/EU students for three years.  The student will be registered for a PhD at UCL where they will spend the first and third years.  The second year of the PhD will be spent at JAIST.

Please contact Dr Phil Jones for further details or to express an interest.

AMOP Physics Open Day

The Atomic Molecular Optical and Positron Physics group will be holding an Open Day on Wednesday December 4th 2013 at 13:00.  The Open Day will be held in rooms A1 and E7 located on the Physics building on UCL's main Gower Street Campus. 

The agenda of the day is: 

13:00 - 15:00  Short research presentations by AMOPP faculty (A1)

15:00 - 18:00  Poster presentations by research groups (E7)

15:00 - 17:00 Lab tours

Please see here for further details of how to get to us.

Review paper in Nature Nanotechnology

Our paper 'Optical trapping and manipulation of nanostructures' has been published in Nature Nanotechnology 8 807-819 (2013).

From the abstract:  Optical trapping and manipulation of micrometre-sized particles was first reported in 1970. Since then, it has been successfully implemented in two size ranges: the subnanometre scale, where light–matter mechanical coupling enables cooling of atoms, ions and molecules, and the micrometre scale, where the momentum transfer resulting from light scattering allows manipulation of microscopic objects such as cells. But it has been difficult to apply these techniques to the intermediate — nanoscale — range that includes structures such as quantum dots, nanowires, nanotubes, graphene and two-dimensional crystals, all of crucial importance for nanomaterials-based applications. Recently, however, several new approaches have been developed and demonstrated for trapping plasmonic nanoparticles, semiconductor nanowires and carbon nanostructures. Here we review the state-of-the-art in optical trapping at the nanoscale, with an emphasis on some of the most promising advances, such as controlled manipulation and assembly of individual and multiple nanostructures, force measurement with femtonewton resolution, and biosensors.

Bragg Lecture 2013 by Prof Paul Chaikin

The 2013 Bragg Lecture will take place on Wed 30 October, and will be given by Prof Paul Chaikin (New York University) on Some small steps towards artificial life.

Abstract: The properties we often associate with living things are motility, metabolism, self-replication and evolution. According to the Nobel Laureate Richard Feynman: “What I can’t create, I don’t understand”. We thought we’d give it a shot - understanding life - and in the process we’ve made two different systems, one that exhibits both autonomous motility and metabolism and another which is the first artificial system that can replicate arbitrarily designed motifs. The first system, artificial swimmers, provides insight into many natural phenomena such as a flocking of birds and schooling of fish. The second system uses diurnal cycles of temperature and light and at present is doubling each cycle, growing exponentially. It provides a new way of producing many, many copies of nanoscale devices and may give insights into the origin of conventional life on earth.  We even have initiated an elementary form of evolution.

Marios Sergides PhD viva

Congratulations to Optical Tweezers PhD student Marios Sergides who has successfully defended his PhD thesis on Optical manipulation of micro-and nanoparticles using evansecent fields.  Marios will be leaving the group to start a postdoc with a Japan Sciety for the Promotion of Science (JSPS) Postdoctoral Fellowship at the Okinawa Institute of Science and Technology (OIST), Japan, in the Light-Matter Interactions Unit under the supervision of Dr Sile Nic Chormaic.  Many thanks to Dr Mark Ellerby (UCL) and Dr Valeria Garbin (Imperial College) for acting as examiners.

Well done Dr Sergides, and good luck in Japan!

SPIE Conference Proceedings

Proceedings from the SPIE Optics + Photonics 2013 conference have been published.  These include a paper containing calculations by Stephen Simpson (Bristol University) based on our optical binding experiments: S. H. Simpson, P. H. Jones, O. M. Maragò, S. Hanna & M. J. Miles. 'Optical binding of nanowires in counter-propagating beams’, Proc SPIE 8810 Optical Trapping and Optical Micromanipulation X, 881026, doi: 10.1117/12.2024466 (2013).

From the abstrast:  We present a computational model for the simulation of optically interacting nano-structures immersed in a viscous fluid. In this scheme, nanostructures are represented by aggregates of small spheres. All optical and hydrodynamic interactions, including thermal fluctuations, are included. As an example, we consider optical binding of dielectric nanowires in counterpropagating plane waves. In particular, the formation of stable, ladder like structures, is demonstrated. In these arrangements, each nanowire lies parallel to the polarization direction of the beams, with their centres of mass colinear.

New Group Members

At the start of the new academic year we are welcoming several new members to the Optical Tweezers Group.  Chris Richards and Tom Smart are new PhD students who will both be working on the project Exploring Stochastic Thermodynamics with Optical Traps.  Chris is a UCL Physics graduate, and worked in the group last year for his MSci project.  Tom comes to us from Leeds University via IoP publishing where he worked for 12 months in the editorial office.

Alessandro Magazzu has also joined us as a visiting student for one month under the EU COST Action MP1205 on Optofluidics.  Alessandro is in the second year of his PhD at Università degli Studi di Messina, Sicily, and is supervised by Dr Onofrio Marago at the NanoSoft Lab, IPCF-CNR.

Finally Adam Plowman is joining us for his MSci project to investigate the dynamics of artificial micoswimmers. 

Entry in Encyclopedia of Optical Engineering

The article on Optical Tweezers has now been published in the Taylor & Francis Encyclopedia of Optical Engineering.

From the abstract: Optical tweezers are devices that use a single, strongly focused laser beam for the remote, non-contact trapping and manipulation of microscopic objects. Since the first demonstration of optical tweezers in 1986, they have become commonly used across physics, chemistry, and biology for experiments as diverse as measuring the step size of motor proteins to a demonstration of fluctuations in entropy production in microscopic systems. In this entry, the mechanism behind optical tweezers is introduced, followed by a discussion of practical aspects in the use of optical tweezers, such as data collection and analysis for quantitative measurements, and the use of holographic optical traps. Also, a review of one of the many applications of optical tweezers is presented, namely, the optical trapping of nanoparticles and nanostructures and their use for imaging and force sensing.

Susan Skelton wins Carey Foster Prize

Congratulations to former Optical Tweezers PhD student Dr Susan Skelton who has won the Carey Foster Prize for 2013 for her thesis Applications of cylindrical vector beams to optical micromanipulation  The Carey Foster Prize is awarded annually for outstanding postgraduate research in Atomic, Molecular, Optical and Positron Physics to a PhD student who has submitted their thesis in the past year.

Susan gained her PhD in February 2013, and is presently a postdoctoral research associate at the Laboratory for Scientific Instrumentation and Engineering (LaSIE) at the University of Osaka, Japan.

Theoretical Characterisation of Microbubbles Paper

As part of the NPL/UCL/Oxford microbubble trapping collaborative project a paper Theoretical characterisation of the radial and translational motion of coated microbubbles under acoustic excitation has been published as C. J. Harfield et al, J. Phys.: Conf. Ser 457 012001 (2013).

From the abstract: Ultrasound contrast agents, in the form of coated microbubbles, are a powerful tool in current diagnostic imaging. Given their sensitive dynamic response they also have the potential to be used for quantitative measurements of the properties of the surrounding tissue (e.g. percentage perfusion or blood pressure). For this potential to be realised, however, the theoretical descriptions of bubble behaviour, in particular the constitutive equations for the microbubble shell, need to be improved and a method needs to be developed for the accurate characterisation of individual bubbles. In this paper the first steps are taken towards deriving a complete model for the coupled radial and translational motion of a coated bubble. It is then shown that with this model the bubble can be characterised by a unique set of parameters describing the bubble shell corresponding to its viscous and elastic response. This uniqueness will enable the model to be used to interpret experimental data and quantify these parameters for which accurate values are currently lacking but which are critical to predicting bubble response and hence enabling advanced diagnostic applications.

Visit by Prof Jixiong Pu

We are pleased to welcome Prof Jixiong Pu (Huaqiao University) to the group as a distinguished visiting scholar.  Prof Pu is Professor of Physics and Dean of the College of Information Science and Engineering, Huaqiao University.  He has been awarded a visiting scholarship to come to UCL and will be staying with us from 25 July - 08 September 2013,  His research interests include the generation of partially coherent light beams and their focusing and propagation, vortex beams, tight focusing of stochastic electromagnetic beams, applications of surface plasmon polaritons (SPP), and optical manipulation

Konnect: The smart lecture experience

UCL Physics students Adam & Nat have entered their idea Konnect - The smart lecture experience into the JISC Summer of Student Innovation competition. 

Learning works best with participation. However, lectures are typically highly passive experiences. For the students, lectures are more akin to watching a performance than expanding their knowledge and understanding of a particular topic. This is especially true for students in their first year of university who have become accustomed to relatively small classes at school and college.

We propose a platform that provides a real time connection between students and their lecturer. We aim to make the lecture environment one that promotes engagement; students will start to question their understanding for themselves. Essentially, our platform is comprised of a website, which acts as the hub of the service, and a smart phone app for students. Using these, a connection can be formed between a lecturer and his/her students.

Vote for Adam & Nat's idea with the JISC Elevator Vote button opposite.

MSci Projects 2013

This year we have had two MSci students working in the group for their final year projects.  Chris Richards used Mie scattering theory to calculate optical forces experiences by microscopic particles in optical trapping experiments.  In particular he was interested in finding the range of parameters for which an optical pulling force or 'tractor beam' was possible. By finding the fields scattered by a dielectric sphere and evaluating the Maxwell Stress Tensor to find the distribution of optical stress over a sphere he was able to determine the combination of beam and particle properties that would lead to the strongest 'backward' directed scattering force.  Above you can see some of Chris' calculated stress distributions on the sphere surface in the forward- and backward scattering directions.

Zhi Hao Wong also worked with us to investigate the optical properties of metallic nanoparticles. Opposite you can see the calculated extinction spectra for gold and silver spherical nanoparticles as a function of size and optical wavelength which clearly show the enhancement of optical scattering arising from their plasmonic properties.  Zhi Hao then went on to investigate how these properties could be used to control the dynamics of metallic nanoparticles in optical fields.

More MSci projects will be available for Physics and Natural Science students in the year 2013-14.  Contact Dr Phil Jones for details of available projects.

PHOTOPTICS 2014

The 2nd International Conference on Photonics, Optics and Laser Technology (PHOTOPTICS2014) will be held in Lisbon, Portugal, 07-09 Jan 14.  The conference will feature three different tracks on Optics, Photonics and Lasers, covering both theoretical and practical aspects, and the Keynote Speaker is Prof David Andrews of the University of East Anglia.

Big Bang Science Fair

POP! The Sound of Bubbles was at the Big Bang Science Fair in the ExCeL Centre in Docklands 14 - 17 March.  Members of the NPL/UCL/Oxford microbubble project together with colleagues from NPL, Glasgow University and King's College demonstrated bubble science to over 63,000 visitors in four days.
Among the visitors to our stand was the Secretary of State for Business, Innovation and Skills, Vince Cable, here being shown our Kundt Tube demonstration of acoustic resonance by Ian Butterwoth of the NPL.

Susan Skelton PhD viva

Congratulations to Optical Tweezers PhD student Susan Skelton who has successfully defended her PhD thesis on Applications of cylindrical vector beams for optical micromanipulation.  Susan will be leaving the group to start a postdoc at the University of Osaka, Japan, in the Laboratory for Scientific Instrumentation and Engineering (LaSIE) under the supervision of Prof Satoshi Kawata.  Many thanks to Dr Stephen Hogan (UCL) and Dr David McGloin (Dundee University) for acting as examiners.

Well done Dr Skelton, and good luck in Japan!

AMOP Physics Open Day

On Wednesday 13 February the UCL AMOP Physics Group is holding an Open Day for students interested in studying for a PhD in the group.  The timetable for the day is:

13:00 - 13:30  Introductory talk by Dr Agapi Emmanouilidou and Prof Ferrucio Renzoni (A1)

13:30 - 13:45  Buffet Lunch (E7)

13:45 - 15:30 Poster presentations by research groups (E7)

14:00 - 16:00 Lab tours

A PhD studentship is available to work in the Optical Tweezers Group on the project Exploring stochastic thermodynamics with optical traps.

Simon Hanna visit and seminar

Simon Hanna (Bristol University) is visiting on Wed 30 Jan 2013 to give the AMOP Physics seminar.  Simon is a theoretician in the Nanophysics and Soft Matter Group at Bristol with wide-ranging interests including liquid crystals and polymer physics.  His talk, however, will be about modelling optical forces on specially shaped micoparticles in optical traps.

Title: Optimising forces and torques for optical micromanipulation, Simon Hanna (Bristol University)

Abstract: The motion of a colloidal particle in an optical field depends on a complex interplay between the structure of the field, and the geometry and composition of the particle. There are two complementary approaches to generating a particular force field. The first, involving sculpting of the optical field with e.g. a spatial light modulator, has been extensively developed.  A second method, highlighted recently, involves sculpting of the particles themselves, and has received much less attention. However, as modern two-photon polymerisation methods advance, this avenue becomes increasingly attractive for micromanipulation. In this talk I will show how computational methods may be used to optimise particle geometries in such a way as to produce desirable patterns of forces and torques.  These designs are then tested using particles fabricated using the two-photon method.  In particular, I will demonstrate the design of a constant force optical spring for use as a passive force clamp, a high efficiency optical wing, and a shape-optimised microtool.