Browsing by Author "Ghaffari, Roujin"

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Open Access
Dynamic adaptive colloidal crystals far from equilibrium
(2019-08) Ghaffari, Roujin
Self-assembly has been the center of attention of many researchers from all branches of science. Self-assembly of static structures such as crystals often forms through energy minimization, while dynamic ones need constant energy flow to maintain their state. Most of the studies on self-assembly are limited to static self-assembly, and despite its ubiquity in nature, our comprehensions of dynamic self-assembly are still in its infancy due to lack of experimental settings that can keep the system in its dynamical state. In 2017 a state-of-the-art dissipative (dynamic) self-assembly method was introduced by S. Ilday, and co-workers (Nature Commun., 2017). Here, using this method, we studied the formation of dynamic adaptive colloidal crystals far from equilibrium. We use a femtosecond laser as an energy source to drive a quasi-2D confined colloidal system far from thermodynamic equilibrium, and for the first time, we observed the formation of a rich set of dynamic adaptive colloidal crystals of tens to hundreds of units of polystyrene spheres, which interact through hydrodynamic and hard-sphere interactions. We report formation of periodic 2D Bravais lattices, Moiré patterns, honeycomb lattices and aperiodic quasicrystals. Furthermore, we identify, analyze, and verify some of the key experimental parameters, e.g., physical boundaries, thickness of the liquid film, and the average velocity of Brownian motion, affecting the formation of such a variety of colloidal crystals. We anticipate this study to be a starting point to uncover the physical principles behind the emergence of patterns from simple parts.
Open Access
Universality of dissipative self-assembly from quantum dots to human cells
(Nature Research, 2020) Makey, Ghaith; Galioğlu, Sezin; Ghaffari, Roujin; Engin, E. D.; Yıldırım, Gökhan; Yavuz, Özgün; Bektaş, O.; Nizam, Ü. S.; Akbulut, Özge; Şahin, Özgür; Güngör, Kıvanç; Dede, Didem; Demir, Hilmi Volkan; İlday, Fatih Ömer; İlday, Serim
An important goal of self-assembly research is to develop a general methodology applicable to almost any material, from the smallest to the largest scales, whereby qualitatively identical results are obtained independently of initial conditions, size, shape and function of the constituents. Here, we introduce a dissipative self-assembly methodology demonstrated on a diverse spectrum of materials, from simple, passive, identical quantum dots (a few hundred atoms) that experience extreme Brownian motion, to complex, active, non-identical human cells (~1017 atoms) with sophisticated internal dynamics. Autocatalytic growth curves of the self-assembled aggregates are shown to scale identically, and interface fluctuations of growing aggregates obey the universal Tracy–Widom law. Example applications for nanoscience and biotechnology are further provided.