Complex System Laboratory

Professor Lin I

lini_00.jpg

Chair Professor

Department of Physics, National Central University, Jhongli, Taiwan

Tel: 886-3-425-4649   E-mail: lini@phy.ncu.edu.tw

Academician, Academia Sinica

APS Fellow

 

The complex system laboratory at NCU was established in 1983 by professor Lin I. Base on the concepts of nonlinear dynamics, complex systems, and statistical mechanics developed in the past few decades, we investigate the fundamental physics and applications in various areas such as weakly ionized plasmas and think film processing, micro-structure and motion of strongly coupled dusty plasmas liquids, wave-particle dynamics in ordered wave to turbulent dusty plasma waves, fluid and soft matter systems, and bio-systems. The main researches in the pass two decades are summarized below.

 

(A)  Micro-structure and motion of strongly coupled dusty plasmas
Dusty plasma can be formed by suspending micro-meter sized dust particles in low pressure weakly ionized discharges. Through the strong Coulomb coupling of the large charges on dust particles (∼ 10,000 electron/particle), the suspended dust particles can be self-organized into highly order crystal or liquid state. The formation of dusty plasma crystals was predicted theoretically by Ikezi in 1986. In 1993, we demonstrated the first direct experimental observations of dusty plasma crystals, liquids, and gases in a weakly ionized rf discharge. The capability of direct visualizing particle motion at the kinetic level make the system a good platform to understand the micro-motion and structure of the above various states. In the past two decades, we have conducted the following leading researches.

1)      The first experimental observation of Wigner crystals with bcc, fcc, hcp and hexagonal cylinder structures in rf dusty plasma discharges, which could be melted to the liquid and gas states by increasing rf power.
[Physica A, 205, 183 (1994); Phys. Rev. Lett. 72, 4009 (1994); Science, 272, 1626 (1996)]

2)      The first direct microscopic observation of the interaction of free-dislocation defects associated with the thermal induced stick-slip type excitation of cooperative hopping vortices in cold dusty plasma liquid. The dynamics were found to be governed by the creation, annihilation, dissociation, recombination, and propagating of free dislocations.
[Phys. Rev. Lett. 77, 647 (1996); Phys. Rev. Lett. 3073 (1998)]

3)      The first experimental observation and investigation of dynamical heterogeneity with non-Gaussian dynamics, anomalous diffusion, power law distribution of hopping clusters and defect clusters, defect turbulence in cold 2D dusty plasma liquids.
[Phys. Rev. E 64, 015601 (2001); Phys. Rev. Lett. 89, 155002 (2002); Phys. Rev. Lett. 93, 065003 (2004), Phys. Rev. E 76, 016403 (2007), Contrib. Plasma Phys. 49, 4-5, 215 (2009)]

4)       The first laboratory observation of 2D Coulomb clusters of a few to a few tens or hundreds of charged fine particles suspended in a circular dusty plasma trap, exhibiting the same packing rules same as the raisin model proposed by JJ Thomson in 1904 for the “classical atom”, composed by a small number of electrons in neutralizing charged background. The micro-motion and defect dynamics for the nonuniform melting transition in the Coulomb clusters were also investigated numerically.
[Phys. Rev. E. 58 R6947 (1998), Phys. Rev. E, 60, 4743 (1999), Phys. Rev. E 64, 015601 (2001)]

5)    The first experimental study of the structure and motion of mesoscopic liquids confined in narrow gaps at about a few interparticle spacing. The transition to confinement induced layering and the slow dynamics with high viscosity as the gap width down to about six interparticle distance were demonstrated.
[Phys. Rev. E. 64, 016402 (2001), Phys. Rev. Lett. 93, 065003 (2004)] Lett. 93, 065003 (2004)]

6)    The first investigation of anomalous transport and structural rearrangement of the dusty plasma liquid at the discrete kinetic level by shearing the dusty plasma liquid through the radiation pressure of laser beams. Shear enhanced stick-slip hopping vortex and enhanced diffusion rate, shear banding and thinning (decreasing viscosity with increasing stress) were demonstrated.
[Phys. Rev. E. 64, 016402 (2001), Phys. Rev. Lett. 93, 065003 (2004)]

7)      By shearing the liquid with two counter parallel laser beams along the two opposite boundaries, shear banding and its origin through the multi-scale energy transfers from the boundary to the center and from the slow scale to the fast scale motion were observed and identified respectively. Further periodically chopping the two laser beams, the micro-origin of the visco-elastic response of the thin liquid at the discrete limit was identified. The packing and melting of mesoscopically con?ned two-dimensional Coulomb crystals in straight narrow channels were also investigated numerically.
[Phys. Rev. Lett. 90, 245004 (2003); Phys. Rev. Lett. 93, 220602 (2004), Phys. Rev. Lett. 98, 105002 (2007), Phys. Rev. E. 80, 036401 (2009), Phys. Rev. E, 82 (2010) 041504]

8)      The first laboratory demonstration of the 2+1 D chain bundle dusty plasma liquid with long flexible chain bundles, formed through the dipole like forces under the strong vertical ion flow. Its stereo micro-structure and motion, and the long distance projectile channeling along the chain bundle were also demonstrated and investigated.
[Phys. Plasmas, 17, 053073 (2010), Phys. Plasmas 18, 033704 (2011), Phys. Rev. E. 85, 026467 (2012)]

 

9)     The microdynamics and basic collective excitations of cold dusty plasma liquid around freezing. including: The first experimental observation of power law dynamical slow down relaxation of supercooled dusty plasma liquid after quenching. The first experimental identification of the crystalline ordered domain rupture through thermal or stress induced domain co-rotation, trailed by ruptured domain reconnection as the basic cooperative excitation process for cooperative particle motion and structural rearrangement in cold liquids with and without external stress, and domain boundary migration for crystallization after quenching.
[Physical Review E. 86, 016405 (2012); Phys. Rev. Lett, 109, 225003 (2012) and Physical Review Focus at http://physics.aps.org/articles/v5/133; Phys. Rev. Lett. 109, 195002 (2012); Phys. Rev. E (Rapid Communication), 90, 050401(R) (2014); Phys. Rev. E (Rapid Communication) 89, 041102(R) (2014)]

10)   The first laboratory observation of self-organized dust density waves and turbulence in weakly ionized dusty plasmas.
[J. Phys. D. 27, 296 (1993); Physica A, 205, 443 (1994); Science, 272, 1626 (1996); Phys. Rev. E, 62, 5667 (2000); Phys. Rev. E. 62, 5571 (2000)]

11)   The first experimental investigations of Lagrangian-Eulerian micro-dynamics in the coordinate-velocity phase space of self-excited dust acoustic waves, and the search for the micro-origin of its wave breaking with the transition from ordered particle cyclic motion to the chaotic oscillation.
[Phys. Rev. Lett. 100, 185004 (2008); [Phys. Rev. Letts. 103, 245005 (2009)]

12)   The first experimental observation of self-excited defect mediated dust acoustic wave turbulence, associated with the pair generation and annihilation of fluctuating low amplitude hole filaments coinciding defect trajectories. The observation of pair generation of acoustic vortices with helical waveforms oppositely winding around the defect filament pair through the finite length rupturing and reconnection of sequential wave crest surface, as basic collect excitations in unstable dust acoustic waves, was also experimentally demonstrated for the first time.
[Phys. Plasmas, 20, 083703 (2013); Phys. Rev. E. 90, 013106 (2014)]

13)  The first experimental observation of a traveling plasma bubble (cavity with dust depletion) generated by the expanding ablation plume from a pulsed laser on suspended particles. The bubble maintains its shape and travels downward with a trailing dust acoustic solitary wave. The dynamics of the bubble in the initial forming stage, and bubble-dust acoustic wave interaction have also been studied.
[Phys. Rev. Lett. 90, 075004 (2003); Appl. Phys. Lett. 89, 101503 (2006), Phys. Plasmas, 16, 063702 (2009)]

(B)   Dynamics of soft matter and bio-systems
Based on the fundamental physics concepts of nonlinear strongly coupled complex systems and collective excitations, and the established techniques such as digital video microscopy and analysis, and micro-ablation techniques, we further built up the dissection and invitro cell incubation systems, micro-ablation systems, confocal microscopy, etc., and study the micro-dynamics of bio- and soft matter systems in the past decades.

1)     The first experimental study on the interaction and fragmentation between two laser bubbles generated by two focused intense laser beams, for the thin liquid confined by two glass slices. The push-pull formation of two opposite laser jets were identified to be the main cause leading to the complicated and entangled fragmentation patterns.
[Phys. Rev. Lett. 96, 034505 (2006), Phys. Rev. E 77, 026304] (2008)]

2)      The experimental study of synchronous firing of calcium florescent signals of rat cortical neuron networks in vitro. At high neuron density, clusterized networks were observed in the late maturation stage. Each calcium spike corresponds to a burst of electric firings. The clusterized network exhibits slow modulation on the synchronous calcium spikes, which corresponds to the super-burst, i.e. the burst of electrical bursts with increasing day in-vitro. The modulation can be changed and tuned off by changing Mg and K ion concentrations. Whether there are pacemakers in the synchronous firing of clusterized neuronal networks were also checked.
[Chinese J. Phys, 46, 217 (2008), J. Phys. Soc. Jpn. 77, 084803 (2008)]

3)     The first experimental manifestation of multi-fractal dynamics of turbulence flow of the self-propelling dense E-Coli, and the experimental and numerical demonstration of suppression turbulence of self-propelling cells by low concentration strongly coupled passive particle additive.
[Phys. Rev. E.86, 011924 (2012); Phys. Rev. E, 88, 033004 (2013); Phys. Rev. E 91, 030302(R) (2015)]