We study pore nucleation in a model membrane system, a freestanding polymer film. Nucleated pores smaller than a critical size close, while pores larger than the critical size grow. Holes of varying size were purposefully prepared in liquid polymer films, and their evolution in time was monitored using optical and atomic force microscopy to extract a critical radius. The critical radius scales linearly with film thickness for a homopolymer film. The results agree with a simple model which takes into account the energy cost due to surface area at the edge of the pore. The energy cost at the edge of the pore is experimentally varied by using a lamellar-forming diblock copolymer membrane. The underlying molecular architecture causes increased frustration at the pore edge resulting in an enhanced cost of pore formation.


We probe the viscous relaxation of structured liquid droplets in the partial wetting regime using a diblock copolymer system. The relaxation time of the droplets is measured after a step change in temperature as a function of three tunable parameters: droplet size, equilibrium contact angle, and the viscosity of the fluid. Contrary to what is typically observed, the late-stage relaxation time does not scale with the radius of the droplet-rather, relaxation scales with the radius squared. Thus, the energy dissipation depends on the contact area of the droplet, rather than the contact line.


We propose new searches that exploit the unique signatures of decaying sterile neutrinos with masses below MW at the LHC, where they can be produced in rare decays of Standard Model gauge bosons. We show that, for few-GeV-scale sterile neutrinos, the LHC experiments can probe mixing angles at the level of \( 10^{-4} \)–\( 10^{-3} \) through powerful searches that look for a prompt lepton in association with a displaced lepton jet. For higher-mass sterile neutrinos, i.e., \( M_N \overset{>}{\sim} 15 \, \mathrm{GeV} \), run II can explore similarly small mixing angles in prompt multilepton final states. This represents an improvement of up to 2 orders of magnitude in sensitivity to the sterile neutrino production rate.


We report on the design, construction, and characterisation of a new class of in-vacuo optical levitation trap optimised for use in high-intensity, high-energy laser interaction experiments. The system uses a focused, vertically propagating continuous wave laser beam to capture and manipulate micro-targets by photon momentum transfer at much longer working distances than commonly used by optical tweezer systems. A high speed (10 kHz) optical imaging and signal acquisition system was implemented for tracking the levitated droplets position and dynamic behaviour under atmospheric and vacuum conditions, with ±5 μm spatial resolution. Optical trapping of 10 ± 4 μm oil droplets in vacuum was demonstrated, over timescales of >1 h at extended distances of ~40 mm from the final focusing optic. The stability of the levitated droplet was such that it would stay in alignment with a ~7 μm irradiating beam focal spot for up to 5 min without the need for re-adjustment. The performance of the trap was assessed in a series of high-intensity (\(10^{17}\) W cm) laser experiments that measured the X-ray source size and inferred free-electron temperature of a single isolated droplet target, along with a measurement of the emitted radio-frequency pulse. These initial tests demonstrated the use of optically levitated microdroplets as a robust target platform for further high-intensity laser interaction and pointsourcestudies.


We report on how the relaxation of patterns prepared on a thin film can be controlled by manipulating the symmetry of the initial shape. The validity of a lubrication theory for the capillary-driven relaxation of surface profiles is verified by atomic force microscopy measurements, performed on films that were patterned using focused laser spike annealing. In particular, we observe that the shape of the surface profile at late times is entirely determined by the initial symmetry of the perturbation, in agreement with the theory. The results have relevance in the dynamical control of topographic perturbations for nanolithography and high density memory storage.


We investigate the dewetting of a disordered melt of diblock copolymer from an ordered residual wetting layer. In contrast to simple liquids where the wetting layer has a fixed thickness and the droplets exhibit a single unique contact angle with the substrate, we find that structured liquids of diblock copolymer exhibit a discrete series of wetting layer thicknesses each producing a different contact angle. These quantized contact angles arise because the substrate and air surfaces each induce a gradient of lamellar order in the wetting layer. The interaction between the two surface profiles creates an effective interface potential that oscillates with film thickness, thus, producing a sequence of local minimums. The wetting layer thicknesses and corresponding contact angles are a direct measure of the positions and depths of these minimums Self-consistent field theory is shown to provide qualitative agreement with the experiment.


Baryogenesis through neutrino oscillations is an elegant mechanism that has found several realizations in the literature corresponding to different parts of the model parameter space. Its appeal stems from its minimality and dependence only on physics below the weak scale. In this paper we show that by focusing on the physical time scales of leptogenesis instead of the model parameters, a more comprehensive picture emerges. The different regimes previously identified can be understood as different relative orderings of these time scales. This approach also shows that all regimes require a coincidence of time scales and this in turn translates to a certain tuning of the parameters, whether in mass terms or Yukawa couplings. Indeed, we show that the amount of tuning involved in the minimal model is never less than one part in 105 according to a metric constructed from a combination of the sterile neutrino mass degeneracy and the Barbieri-Giudice tuning of the Yukawa coupling. Finally, we explore an extended model, where the tuning can be removed in exchange for the introduction of a new degree of freedom in the form of a leptophilic Higgs with a vacuum expectation value of the order of GeV.


We propose a practical scheme to use photons from causally disconnected cosmic sources to set the detectors in an experimental test of Bells inequality. In current experiments, with settings determined by quantum random number generators, only a small amount of correlation between detector settings and local hidden variables, established less than a millisecond before each experiment, would suffice to mimic the predictions of quantum mechanics. By setting the detectors using pairs of quasars or patches of the cosmic microwave background, observed violations of Bells inequality would require any such coordination to have existed for billions of yearsan improvement of 20 orders of magnitude.

Recent Publications

Student authorFaculty author


Mark Ilton, Christian DiMaria, and Kari Dalnoki-Veress

Direct Measurement of the Critical Pore Size in a Model Membrane

Physics Review Letters 117 (2016) .
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Mark Ilton, Oliver Baeumchen, and Kari Dalnoki-Veress

Onset of Area-Dependent Dissipation in Droplet Spreading

Physical Review Letters 115 (2015) .

Eder Izaguirre and Brian Shuve

Multilepton and Lepton Jet Probes of Sub-Weak-Scale Right-Handed Neutrinos

Physical Review D 91 (2015) 093010.
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C. J. Price, Thomas D. Donnelly, S. Giltrap, N. H. Stuart, S. Parker, S. Patankar, H. F. Lowe, D. Drew, E. T. Gumbrell, and R. A. Smith

An in-vacuo optical levitation trap for high-intensity laser interaction experiments with isolated microtargets

Review of Scientific Instruments 86 (2015) 033502.
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RSI Donnelly 2015

Michael Benzaquen, Mark Ilton, Michael V. Massa, Thomas Salez, Paul Fowler, Elie Raphael, and Kari Dalnoki-Veress

Symmetry plays a key role in the erasing of patterned surface features

Applied Physics Letters 107 (2015) .

Mark Ilton, Pawel Stasiak, Mark W. Matsen, and Kari Dalnoki-Veress

Quantized Contact Angles in the Dewetting of a Structured Liquid

Physical Review Letters 112 (2014) 068303.
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Brian Shuve and Itay Yavin

Baryogenesis Through Neutrino Oscillations: a Unified Perspective

Physical Review D 89 (2014) 32.
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Luke St. Marie, Fangzhao Alex An, Anthony L. Corso, John T. Grasel, and Richard C. Haskell

Robust, Real-time, Digital Focusing for FD-OCM using ISAM on a GPU

Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XVIII 8934 (2014) 89342V.

Alanna L. Weisberg, Nathaniel J. Bean, Theodore B. DuBose, Elizabeth Orwin, and Richard C. Haskell

Physical Attributes and Assembly of PEG-linked Immuno-labeled Gold Nanoparticles for OCM Image Contrast in Tissue Engineering and Developmental Biology

Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XVIII 8934 (2014) 89342V.

Jason Gallicchio, Andrew S. Friedman, and David I. Kaiser

Testing Bell’s Inequality with Cosmic Photons: Closing the Setting-Independence Loophole

Physical Review Letters 112 (2014) 195.
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