Title

Traveling Faster in Traffic: Disorder Induced Transport

Poster Number

4

Lead Author Affiliation

Mechanical Engineering

Lead Author Status

Faculty

Introduction

Transport of particles is of critical importance in a multitude of fields ranging from electrons in solids to classical particles in fluid environments. It is typically believed that disordered environments or obstacles in a material will inhibit transport and may even lead to localization. Such phenomena has been directly observed in the transport of light in disordered photonic crystals.

Purpose

Here we ask if the same principle applies to active soft materials, where there is a continuous input of energy at the particle level. Active entities play a key role in many vital biological processes that depend on the active transport of molecules inside cells and organisms ranging from molecular motors to cellular transport. Furthermore, the organization of such complex environments is not perfectly ordered and understanding the effect of disorder on the motion of active matter can shed light on the principles behind transport in living systems. In particular, it is important to know whether disorder leads to the inhibition of transport and localization, or enhances transport. The former scenario might prove catastrophic for living organisms, and in fact, one would expect living systems to be robust against disorder. In this respect, here we demonstrate that transport of actively rotating systems undergo a disorder-induced delocalization transition that leads to anomalous super diffusive transport.

Method

Our active system consists of ferromagnetic spinning particles, or spinners, in a 2D array of fixed non-magnetic particles (obstacles). The ferromagnetic particles are made active via the actuation of an externally applied rotating magnetic field. This array of fixed particles corresponds to the ordered/disordered substrate. In the absence of obstacles the spinning particles do not exhibit any motion beyond Brownian transport, a rather slow mechanism at this length scale. This work can in principle probe how such systems navigate through a disordered medium, like a cell moving through the ECM. The active particles were rotated using a rotating homogeneous magnetic field at different frequencies: 1, 5, and 20 Hz. Thus, the activity is modified by more than an order of magnitude. The non-magnetic obstacles were silica particles fixed to an indium-tin oxide coated glass substrate using electrochemistry. The particles were tracked using custom written code and the trajectories were analyzed, particularly the mean squared displacement.

Results

We observed that in locally ordered environments the spinners became trapped and localized with the mean square displacement showing sub-diffusive behavior. However, when spinners encountered a disordered environment the spinners became de-localized and exhibited super-diffusive behavior. Thus we observed a disorder-induced transition and emergent translation motion.

Significance

In summary we have demonstrated that active spinning matter exhibits a disorder-induced delocalization transition as well as anomalous super diffusive transport in such disorder substrates. This mechanism is robust and might be important to regulate transport in different systems that display vorticity. Additionally, this delocalization of active particles in disordered environments can have serious implications for understanding how active component navigate complex biological environments.

Location

DeRosa University Center

Format

Poster Presentation

Poster Session

Afternoon

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Apr 27th, 12:30 PM Apr 27th, 2:30 PM

Traveling Faster in Traffic: Disorder Induced Transport

DeRosa University Center

Transport of particles is of critical importance in a multitude of fields ranging from electrons in solids to classical particles in fluid environments. It is typically believed that disordered environments or obstacles in a material will inhibit transport and may even lead to localization. Such phenomena has been directly observed in the transport of light in disordered photonic crystals.