Self-propelled oil-droplet

Development of light activated motility of an oil droplet

It has been shown as a proof of principle experiment that an oil droplet composed of alkanes and metal catalyst can move upon light activation when placed into a solution containing a surfactant.

  • Chemical characterization
  • What are the essential components of the system? How do they interact chemically and physically? What are the chemical products of the system?
  • Controlled movement, FRAP
  • Preliminary evidence has shown that movement may be directional (i.e. away from the light source). Techniques such as FRAP and laser analysis are needed to understand and confirm phototactic behavior.
  • Movement with variation and selection (i. e. purposeful behavior) If there is phototaxis in this system, then oil droplet variants may be produced and selected for motility in a competition.

Contact: Martin Hanczyc

Characterization of oleic anhydride oil droplet system

The best studied and understood system of oil droplet self-movement is the oleic anhydride system. Here the hydrolysis of the anhydride precursor is coupled to the autonomous movement of the oil droplet. The movement appears to be governed by a pH gradient that affects the interfacial tension around the droplet and triggers a Marangoni instability and convective flow.

  • Chemistry (products, rates)
  • What is the rate of hydrolysis? How is this correlated with size of droplet?
  • Movement (direction, velocity, time)
  • How variable is the droplet movement? How does direction, velocity change with time?

Contact: Martin Hanczyc

Development of droplet-droplet interactions and higher order structures

If droplet movement is based on differences in interfacial tension around the droplet, then diffusible signals such as surfactants and pH gradients may affect neighboring droplets. In addition linking together droplets with vesicles, beads, surfaces may lead to the engineering of microscale soft robots.

  • Characterization of chemical messengers
  • Which types of chemical messengers can be used to effect chemical communication between neighboring droplets?
  • Linking tags and vesicles and beads to droplet surface
  • Use specific linkers that are embedded into the interface to build up more complex structures that may be capable of movement. Use the oil droplet as a motor to create micro-scale soft robots.
  • Characterization of spontaneous formation of droplet assemblies
  • Can groups of droplets self-assemble into multi-droplet structures that function as a whole? Preliminary evidence shows that groups of droplets may move together convectively. What is the physical basis for this collective behavior?

Contact: Martin Hanczyc

Development of polymer-fueled motility

A polymer may be substituted for the oleic anhydride fuel and this substitution results in self movement and chemotaxis.

  • Characterization of hydrolysis products
  • What are the main products of polymer hydrolysis?
  • Development of simple chemical model
  • Create a simplified chemical model for the polymer system consisting of known quantities of simpler subunits.
  • Detection of oil/water specific sequestration of products
  • Determine if any of the hydrolysis products are specifically sequestered within the oil or water phase.

Contact: Martin Hanczyc

Motility with ruthenium-based chemical system

The protocell being developed at FLinT relies on a ruthenium based catalysis of an amphiphilic precursor to produce fatty acids. This system may be useful to drive photo-activated movement of oil droplets when localized to the oil - water interface.

  • Produce oil droplet with Ru-complex anchored at interface
  • Test various oils with the photo-active chemistry
  • Test for movement in response to light.

Contact: Martin Hanczyc

Development of oil droplet replication cycle

Oil droplets that possess both chemistry and self-movement may be well suited in development of a new kind of protocell model. If systems that contain both variation and selection are successful (see section a iii above) then a methodology for droplet replication is required. This can be done on a microfluidics platform.

  • Induced fusion
  • Explore protocols that can induce droplet-droplet fusion or growth.
  • Induced fission
  • Explore protocols that can induce droplet fission.

Contact: Martin Hanczyc

Theory and simulations

As we move towards developing new and more complex systems and applications, this field of experimentation will benefits from careful modeling and simulation

  • Computational fluid dynamics and droplet movement
  • How the chemical processes and the physical processes are linked? How does symmetry breaking occur?
  • Chemical networks and droplet movement
  • How can droplet movement and behavior be affected by an embedded chemistry that is not just simply a one-step hydrolysis reaction. Can behavioral complexity arise from embedded chemical network complexity?
  • Droplet-droplet communication and higher order structures
  • How can higher order structures arise spontaneously or by design? How can potential chemical signal affect this organization and dynamic?

Contact: Martin Hanczyc