Poster/Flash Talk Abstracts

1-  Atomic Dunes: Pattern Formation in Xe Adsorption on Ag(110)

     Abdullah Bin Aamir

Depositing a monolayer of Xenon gas on a pristine Ag(110) surface at cryogenic temperatures (15-65K) and ultra-high vacuum conditions gives rise to a height modulated atomic pattern resembling the patterns observed on sand dunes. We investigate the formation of these patterns using a MATLAB based simulator that we have developed. The Xenon atoms are modeled as spherical particles that interact with each other and the underlying substrate via the Lennard Jones potential. The Ag(110) substrate is modeled as a sinusoidally modulated surface along one dimension. The simulations reveal that the Xenon atoms form hexagonal lattices while simultaneously traversing a modulated landscape, eventually resulting in an imperfect Moire modulation in line with the experimental observations. We follow the growth of the patterns from initial island formation towards monolayer coverage of the substrate. In real time, we analyze various properties of the pattern including, the dynamics of the individual particle potentials, island orientations, vacancy dynamics, and the competition between domains, etc. These analyses provide valuable insights into the mechanisms of atomic scale pattern formation.

2- Explicit Symmetry Breaking Unlocks Functional Laser-Nanopatterning and a Simpler Genesis of Homochirality

     Özgün Yavuz

Homochirality is the phenomenon in which the building blocks of living organisms possess distinct chiral properties. For example, most proteins are left-handed, while sugars are right-handed chiral. There is no reason impeding the other chirality from being selected as the seed in the prebiotic ages. In the literature, two ingredients are considered essential for homochirality: an initial chiral imbalance and a mechanism to amplify towards global dominance. We argue and demonstrate that both can be unified into a single condition, specifically, a single control parameter. This insight stems from Nonlinear Laser Lithography (NLL), a nanoscale, ultrafast laser-driven patterning technique involving two competing processes where one is oxidation and the other is material removal. A simplified mathematical analysis reveals a direct analogy with homochirality. NLL also enables precise fabrication of functional surfaces such as superhydrophilic/superhydrophobic coatings, temperature sensors, and structural colouration on metals and semiconductors.

3-  Parameter Space Diversity as a Measure of Robustness in Self-Organized Systems

      Orçun Okur

Robustness, the ability of  a system to preserve its desired state under environmental fluctuations, is encountered across various self-organized complex systems [1]. The robustness of these systems are usually quantified  through its correlates, stability and resilience, in the system’s phase space [2, 3, 4]. However, such analyses depend on parameters whose absolute value cannot be known or measured for some systems. Here we present the metric, parameter space diversity, for robustness assessment based on the system’s parameter space and validate it experimentally on a model self-organized system, a mode-locked fiber laser.  Our approach is statistical and grounded in the probability of remaining in the same state, which is shown mathematically equivalent to the Simpson diversity index. [5]. We further demonstrate, both theoretically and practically, that our methodology holds even under the random subsampling without the requirement of exhaustive measurements. In addition to pointing out to the development of better lasers, our framework is broadly applicable to other similar systems.

References: 

1. Carlson, J.M., Doyle J.: Complexity and robustness. Proc. Natl. Acad. Sci. USA 99, 2538-2545  (2002)

2.  Lyapunov, A. M.: The general problem of the stability of motion. Int. J. Control 55, 531-524 (1992)

3. Menck, P.J., et al.: How basin stability complements the linear-stability paradigm. Nature Physics 9, 89–92 (2013)

4. Gao, J., Barzel, B., Barabási A.: Universal resilience patterns in complex networks. Nature 530, 307-312 (2016)

5. Simpson, E. H.: Measurement of diversity. Nature 163, 688 (1949) 

4-  Towards Measuring Spatial Thermal Gradients with Nanothermometers During Ultrafast Laser-Driven Dissipative Self-Assembly

      Simon Spelthann

Driven dissipative colloidal systems are practical experimental platforms to study emergent phenomena ubiquitous in nature, such as the formation of complex structures and dynamic adaptive behaviour, unavailable in equilibrium conditions. We have established such a system, driven far from equilibrium by the continuous input of energy from ultrafast laser pulses [1,2]. A garden variety of simple and complex patterns emerge from this system, which dynamically transitions from one to another reacting to external changing conditions. The system’s purely physical dynamics (passive polystyrene (PS) microspheres suspended in water and confined between two glass slides) has provided first evidence of universality in driven dissipative self-assembly (DSA) from quantum dots to human cells [3]. The next major goal is to develop a theoretical understanding of our models’ internal dynamics, which could lay the foundation for a more general theory applicable to a wide range of driven dissipative systems. A key challenge is accurately measuring the spatially varying temperature profile in situ and in operando, as driven systems often exhibit non-uniform temperature distributions. In our system, the particles’ Brownian motion and diffusive character differ across solid-, liquid-, and gas-like regions. Since thermochromic dyes are not sensitive enough, the temperature can, so far, only be calculated as an effective temperature from the mean square displacement of particles. To solve this problem, we add upconverting β-NaYF4:Er3+,Yb3+ nanoparticles to the particle suspension. Such particles are excellent ratiometric luminescence nanothermometers [4]. We image their luminescence ratio during DSA experiments and compare it to effective temperature calculations. In the future, our thermal imaging approach will be applicable to other samples used in biology and elsewhere.

References: 

[1] S. Ilday et al. Nat. Commun. 8, 14942 (2017). 

[2] S. Galioglu et al. Adv. Mater. 2025, 2415562.

[3] G. Makey et al. Nat. Phys. 16, 795–801 (2020). 

[4] M. Suta, Nanoscale, 2025, 17, 7091-7099.

5-  Self-assembled Photo-arrested Nanoparticle Superlattices (SaPhire)

      Haniyeh Ataei

Ultrafast laser driven self-assembly offers a purely physical route to forming complex architectures and high performance materials. Our group has recently demonstrated ultrafast bottom up laser synthesis of nanometer scale zeolites [1]. In the present work, we extend this concept to the nanoscale assembly of gold nano-spheres functionalized with photopolymerizable ligands (PNIPAM-co-AmBp-SH and PNIPAM-co-AmBp-C12) to enable light-driven assembly. The ligand exchanged gold nanoparticles were dispersed in water and irradiated with an ultrafast laser (1034 nm, 189 fs, 1 MHz) focused through a 60 mm lens. Dynamic Light Scattering (DLS) and UV–Vis spectroscopy were used to monitor structural and optical changes. The surface plasmon resonance shifted from 519 nm to 524 nm after ligand exchange, confirming surface modification. DLS results showed an increase in mean size from 15 nm to 44 nm after ligand exchange, and to 140 nm after laser exposure, with a narrower size distribution. These observations suggest that laser irradiation influences the aggregation behavior of the polymer-coated gold nanoparticles and provide a basis for further investigation of laser-induced self-assembly mechanisms.

[1] S. Galioglu et al. Adv. Mater. 2025, 2415562.

6-  Point Cloud Data Analysis Using Persistence Homology 

 Joneyd Moradi

In confined driven colloidal bilayers, particles self-organize into complex Moiré patterns whose emergence and morphology vary with the driving force and fluctuations. Characterizing these structures requires methods that capture both geometric and topological features. Here, we apply persistent homology to simulation data of N-particle systems to quantify the organization of Moiré aggregates. Using filtration-based analysis, we extract persistence diagrams, Betti curves, and persistence entropy in both 2D and 3D to identify topological signatures of different pattern types. By utilizing these topological summaries, two new scalar quantities have been introduced for further topological signature identification. Principal component analysis (PCA) is used to explore correlations among these topological measures under varying potential and noise conditions. This approach provides a systematic way to link particle-level configurations to global topological organization in non-equilibrium colloidal systems, and propose a parameter for the system's evolution.

7-  Hybrid Illumination with Machine Learning for Particle Tracking and Pattern Analysis in Ultrafast Laser-Driven Self-Assembly of Colloidal Particles

      Deniz Can Çağlar

Ultrafast laser-driven self-assembly of colloidal particles provides a unique and powerful platform for exploring structure formation in far-from-equilibrium conditions. In this project, we introduce a novel imaging approach that combines coherent (holographic) and incoherent (bright-field) illumination within a single optical microscope setup. This hybrid illumination improves particle visibility and is expected to enable effective three-dimensional localisation, particularly in dense or dynamic systems. To extract quantitative information from the images, we are developing a machine learning pipeline aimed at detecting, tracking, and analysing individual particles. As a first step, we demonstrate reliable particle detection using the You Only Look Once (YOLO12) object detection algorithm, trained on incoherent (bright-field) microscopy data. These results validate the detection pipeline and establish a foundation for integrating depth estimation, structural classification, and feedback-guided control. Further, preliminary experiments with the hybrid illumination setup indicate improved contrast and signal quality, laying the groundwork for integration into automated analysis pipelines.

8-  Dynamics of Pulsed-Laser Interaction with Janus Particles

 Elif Okumuş

Janus particles –with their flexible chemistry and multifunctionality– have broadened the scope of optical manipulation as an emerging class of materials. Laser-based manipulation is particularly promising for half– metal-coated particles, offering a platform to probe coupled optical and thermal effects. However, the dependence on the laser operating regime remains insufficiently understood. In this study, the interaction of nanosecond-pulsed light with 4.1 μm Au–Janus particles bearing a 100 nm gold cap was explored. We focused on the interaction: Three pulse-energy regimes were identified: (i) low influence (< 10 nJ), where motion is indistinguishable from Brownian diffusion; (ii) medium influence (up to 40 nJ), where the range of motion increases; and (iii) high influence (> 40 nJ), where trajectories become superdiffusive and particles establish a new equilibrium position. (2) During optical manipulation, a threshold pulse energy of 4 nJ (average power 40 μW) was sufficient to move Au–Janus particles against the laser spot. Translation velocities of 0.9 μm s⁻¹ to 5.1 μm s⁻¹  at 4 nJ to 50 nJ was achieved. (3) The gold cap is damaged at 20 nJ (fluence 0.7 J cm⁻²) when the laser is focused on the particle, consistent with theoretical predictions, and the ablation process generates micro-and submicrometer gold particles. These findings reveal the potential of pulsed lasers for precise, power-efficient manipulation of Janus particles, advancing our understanding of laser–particle interactions and opening new pathways for optical manipulation applications.

9-  Collective pulse amplification via burst-mode gain-managed nonlinear amplification

     Amirhossein Maghsoudi

Burst-mode pulsed lasers are increasingly employed in applications that demand both high pulse energies and ultrashort durations. Combining gain-managed nonlinear amplification (GMNA) with burst-mode operation enables the generation of sub-50 femtosecond pulse bursts. We demonstrate a GMNA burst-mode Yb-fiber amplifier delivering sub-50 femtosecond pulses and show that the amplificaiton process comes with two collective effects acting on different time scales. On fast, intra-burst scales, gain depletion coupled to the GMNA energy threshold produces leading–trailing asymmetry and compressed-duration variations that grow with pulse count. On slow, thermal scales, varying the pulse count and the pump power yields distinct spectral states at fixed per-pulse energy, indicating temperature-mediated collective amplification. We map these regimes and propose design strategies to extend the number of uniform GMNA pulses per burst, thereby broadening the applicability of this regime in burst-mode systems.

10-  Towards a 3D Atom Printer

      Çağrı Şenel

More than 30 years ago, the IBM logo was spelled using 35 xenon atoms, demonstrating unprecedented atomic control and inspiring visions of atom-by-atom manufacturing. Although 3D printers are now widespread, their resolution remains thousands of times too coarse for true atomic fabrication. Even the most advanced laser-based techniques achieve only about 100 nm precision.

This talk considers a long-term question: could a practical 3D atom printer ever be realized, operating at room temperature, producing macroscopic objects, and controlling every atom’s position? Three major challenges to direct laser writing will be outlined: the mismatch between laser wavelengths and atomic size, the exponential increase in processing steps as resolution improves, and the dominance of random fluctuations at atomic scales.

Self-organisation does not face these fundamental limits. By combining laser-driven self-organisation with direct writing, a potential path toward bridging atomic and mesoscopic fabrication will be proposed, bringing the concept of true atomic manufacturing closer to feasibility.