A comparison of open-loop and closed-loop strategies in colloidal self-assembly

Tang, Xiangdong; Zhang, Jianli; Bevan, Michael A.; Grover, Martha A.

doi:10.1016/j.jprocont.2017.06.003

Cited by 20 publications

(12 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The MDP framework is general and can be employed to develop optimal control policies for different equations of motion and actuation mechanisms ( e.g. , see examples of tunable depletion and electric-field-mediated − colloidal assembly). Uncertainty in particle states in experiments from imaging limitations can be considered within the MDP framework using signal processing strategies ( e.g.…”

Section: Results and Discussionmentioning

confidence: 99%

Optimal Navigation of Self-Propelled Colloids

Yang

Bevan

2018

ACS Nano

Self Cite

View full text Add to dashboard Cite

Controlling the navigation of self-propelled, Brownian colloids in complex microstructured environments (e.g., porous media and tumor vasculature) is important to emerging applications (e.g., enhanced oil recovery and drug delivery). Here, we report a feedback control strategy by which to navigate self-propelled colloids through free space and increasingly complex mazes. Colloid rod position and orientation within mazes is sensed in real time, and instantaneous propulsion along the rod long axis can be actuated via light intensity. However, because uncontrolled rod rotational diffusion determines the propulsion direction, feedback control based on a policy is required to decide how to actuate propulsion magnitude versus colloid position and orientation within mazes. By considering stochastic rod dynamics including self-propulsion, translational−rotational diffusion, and rod−maze interactions, a Markov decision process framework is used to determine optimal control policies to navigate between start and end points in minimal time. The free-space navigation optimal policy effectively reduces to a simple heuristic in which propulsion is actuated only when particles point toward the target. The emergent structure of optimal control policies in mazes is based on the practice of globally following the shortest geometric paths; however, locally, propulsion is actuated to either follow paths toward the target or to produce collisions with maze features as part of generating morefavorable positions and orientations. Findings show how the coupled effects of maze size, propulsion speed, control update time, and relative particle translational and rotational diffusivities influence navigation performance.

show abstract

Section: Results and Discussionmentioning

confidence: 99%

Optimal Navigation of Self-Propelled Colloids

Yang

Bevan

2018

ACS Nano

Self Cite

View full text Add to dashboard Cite

show abstract

“…While the stimulus is off, thermal motion helps anneal defective, arrested configurations that persist otherwise. Promislow and Gast first demonstrated this enhanced self-assembly with paramagnetic colloids that rapidly crystallized in strong, toggled magnetic fields yet arrested in steady fields. , Further work by Swan, Furst, and co-workers showed that the assembled structures and their dynamics could be controlled with the toggle parameters. − Tang, Grover, Bevan, and co-workers designed a feedback control scheme for the toggle parameters to efficiently crystallize colloids in toggled electric fields. , A variety of simulations extended toggled self-assembly to other types of particle interactions and structures, including those that are not observed with steady interactions. ,,− …”

mentioning

confidence: 99%

“…24−28 Tang, Grover, Bevan, and coworkers designed a feedback control scheme for the toggle parameters to efficiently crystallize colloids in toggled electric fields. 29,30 A variety of simulations extended toggled selfassembly to other types of particle interactions and structures, including those that are not observed with steady interactions. 10,11,31−37 These works demonstrate that toggling particle interactions can overcome the engineering challenges inherent to passive self-assembly, at the expense of continually injecting energy into the assembling system.…”

mentioning

confidence: 99%

Transmutable Colloidal Crystals and Active Phase Separation via Dynamic, Directed Self-Assembly with Toggled External Fields

Sherman

Swan

2019

ACS Nano

View full text Add to dashboard Cite

A diverse set of functional materials can be fabricated by assembling dispersions of colloids and nanoparticles. Two principal engineering challenges prevent efficient production of these materials: first, scalable synthesis of particles with carefully tailored interactions required to generate complex structures, and second, the propensity of such materials to arrest in undesirable metastable states. Active assembly processes, such as dynamic, directed self-assembly in which the interactions among particles are externally controlled and vary over time, offer a promising method to address these challenges. For dispersions of polarizable dielectric or paramagnetic nanoparticles, an effective mode of active assembly can be achieved by toggling an external electric or magnetic field, which induces attractive particle interactions, on and off cyclically over time. Here, we develop computational and theoretical models for such active assembly processes and find that cyclically toggling the external field leads to growth of colloidal crystals at significantly faster rates and with many fewer defects than for assembly in a steady field. The active process stabilizes phases that are only metastable in steady fields, including a dense fluid phase and body-centered orthorhombic crystals. The growth mechanism and terminal structure of the dispersion are easily controlled by the toggling protocol, and the toggle parameters can be used to continuously transmute between crystal structures with different lattice parameters. Finally, we show how results from linear irreversible thermodynamics can be used to predict the dissipative terminal states of the active assembly process in terms of parameters of the toggling protocol.

show abstract

“…A particularly promising feature of induced interactions is the ability to vary them over time. For example, these approaches show promise for enhancing crystallization rates while reducing defects 87,[143][144][145] as well as assembling structures not stable at equilibrium. 140 ods are challenging to realize experimentally.…”

Section: B Engineering Assembly Protocols With External Controlsmentioning

confidence: 99%

Inverse methods for design of soft materials

Sherman

Howard

Lindquist

et al. 2020

The Journal of Chemical Physics

View full text Add to dashboard Cite

Functional soft materials, comprising colloidal and molecular building blocks that self-organize into complex structures as a result of their tunable interactions, enable a wide array of technological applications. Inverse methods provide systematic means for navigating their inherently high-dimensional design spaces to create materials with targeted properties. While multiple physically motivated inverse strategies have been successfully implemented in silico, their translation to guiding experimental materials discovery has thus far been limited to a handful of proof-of-concept studies. In this Perspective, we discuss recent advances in inverse methods for design of soft materials that address two challenges: (1) methodological limitations that prevent such approaches from satisfying design constraints and (2) computational challenges that limit the size and complexity of systems that can be addressed. Strategies that leverage machine learning have proven particularly effective, including methods to discover order parameters that characterize complex structural motifs and schemes to efficiently compute macroscopic properties from the underlying structure. We also highlight promising opportunities to improve the experimental realizability of materials designed computationally, including discovery of materials with functionality at multiple thermodynamic states, design of externally directed assembly protocols that are simple to implement in experiments, and strategies to improve the accuracy and computational efficiency of experimentally relevant models. arXiv:2004.00181v1 [cond-mat.soft] 1 Apr 2020

show abstract

A comparison of open-loop and closed-loop strategies in colloidal self-assembly

Cited by 20 publications

References 46 publications

Optimal Navigation of Self-Propelled Colloids

Optimal Navigation of Self-Propelled Colloids

Transmutable Colloidal Crystals and Active Phase Separation via Dynamic, Directed Self-Assembly with Toggled External Fields

Inverse methods for design of soft materials

Contact Info

Product

Resources

About