Browsing by Author "Pinçe, Erçağ"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
Item Open Access Active matter alters the growth dynamics of coffee rings(OSA, 2018) Callegari, Agnese; Andaç, Tuğba; Weigmann, Pascal; Velu, Sabareesh K. P.; Pinçe, Erçağ; Volpe, G.; Volpe, GiovanniWe show that bacterial mobility starts playing a major role in determining the growth dynamics of the edge of drying droplets, as the droplet evaporation rate slows down.Item Open Access Active matter alters the growth dynamics of coffee rings(Royal Society of Chemistry, 2019) Andaç, Tuğba; Weigmann, Pascal; Velu, Sabareesh K. P.; Pinçe, Erçağ; Volpe, G.; Volpe, Giovanni; Callegar, AgneseHow particles are deposited at the edge of evaporating droplets, i.e. the coffee ring effect, plays a crucial role in phenomena as diverse as thin-film deposition, self-assembly, and biofilm formation. Recently, microorganisms have been shown to passively exploit and alter these deposition dynamics to increase their survival chances under harshening conditions. Here, we show that, as the droplet evaporation rate slows down, bacterial mobility starts playing a major role in determining the growth dynamics of the edge of drying droplets. Such motility-induced dynamics can influence several biophysical phenomena, from the formation of biofilms to the spreading of pathogens in humid environments and on surfaces subject to periodic drying. Analogous dynamics in other active matter systems can be exploited for technological applications in printing, coating, and self-assembly, where the standard coffee-ring effect is often a nuisance.Item Open Access Controlling active brownian particles in complex settings(OSA, 2017) Velu, Sabareesh K. P.; Pinçe, Erçağ; Callegari, Agnese; Elahi, Parviz; Gigan, S.; Volpe, Giovanni; Volpe, G.We show active Brownian particles (passive Brownian particles in a bacterial bath) switches between two long-term behaviors, i.e. gathering and dispersal of individuals, in response to the statistical properties of the underlying optical potential.Item Open Access Graphene based high frequency electronics(Bilkent University, 2010) Pinçe, ErçağRecent advances in chemical vapor deposition of graphene on large area substrates stimulate a significant research effort in order to search for new applications of graphene in the field of unusual electronics such as macroelectronics. The primary aim of this work is to use single layer of graphene for applications of high frequency electronics. This thesis consists of both theoretical and experimental studies of graphene transistors for the use of radio frequency electronics. We have grown graphene layer using chemical vapor deposition technique on large area copper substrates. The grown graphene layers are then transferred onto dielectric substrates for the fabrication of graphene transistors. The theoretical part of the thesis is focused on the understanding the performance limits of the graphene transistor for high frequency operation. We investigate the intrinsic high frequency performance of graphene field effect transistors using a self consistent transport model. The self-consistent transport model is based on a nonuniversal diffusive transport that is governed by the charged impurity scattering. The output and transfer characteristics of graphene field effect transistors are characterized as a function of impurity concentration and dielectric constant of the gate insulator. These experimental and theoretical studies shape the basis of our research on the graphene based radio frequency electronics.Item Open Access Manipulation and control of collective behavior in active matter systems(Bilkent University, 2016-10) Pinçe, ErçağActive matter systems consist of active constituents that transform energy into directed motion in a non-equilibrium setting. The interaction of active agents with each other and with their environment results in collective motion and emergence of long-range ordering. Examples to such dynamic behaviors in living active matter systems are pattern formation in bacterial colonies, ocking of birds and clustering of pedestrian crowds. All these phenomena stem from far-from-equilibrium interactions. The governing dynamics of these phenomena are not yet fully understood and extensively studied. In this thesis, we studied the role that spatial disorder can play to alter collective dynamics in a colloidal living active matter system. We showed that the level of heterogeneity in the environment in uences the long-range order in a colloidal ensemble coupled to a bacterial bath where the non-equilibrium forces imposed by the bacteria become pivotal to control switching between gathering and dispersal of colloids. Apart from studying environmental factors in a complex active matter system, we also focused on a new class of active particles, \bionic microswimmers", and their clustering behavior. We demonstrated that spherical bionic microswimmers which are fabricated by attaching motile E. coli bacteria on melamine particles can agglomerate in large colloidal structures. Finally, we observed the emergence of swimming clusters as a result of the collective motion of bionic microswimmers. Our results provide insights about statistical behavior and far-from-equilibrium interactions in an active matter system.