FOR 5584: Transient Sieves

Transient sieves constitute a novel technological concept to separate species dissolved or suspended in a liquid. Until now, separation processes have largely been based on spatial exclusion: It depends on whether a component is small enough to pass through a pore or not. In this research group, we are investigating separation by temporal exclusion, i.e. the permeability of a sieve or pore as a function of time. The decisive factor is whether a species can pass through a pore in a certain time. The aim is to equip sieves with novel and useful properties, e.g. increased selectivity or lower energy consumption.

Permeability as a function of time

Principle of a transient sieve: The passage of a mixture of species at the entrance of a pore is enabled for a specific opening time (centre image), during which predominantly one of the species is able to penetrate the pore (e.g. via diffusion).
Principle of a transient sieve: The passage of a mixture of species at the entrance of a pore is enabled for a specific opening time (centre image), during which predominantly one of the species is able to penetrate the pore (e.g. via diffusion).

What we want to find out

A fundamental objective will be to understand the key phenomena in the passage of species through transient sieves. Further objectives are the experimental realization of transient properties of sieves, the optimization of the spatial structure of transient sieves and the temporal structure of the permeability, and the demonstration of the advantages of transient sieves compared to standard separation methods.

Our approach

The research group Transieves comprises three different lead experiments that represent specific realizations of transient sieves:

  • In experiments with ping-pong droplets, transient liquid pores emerge when a droplet is driven towards a liquid-liquid interface by a DC electric field. For strong enough fields, the droplet bounces back. During the rebound process, a narrow liquid pore forms between the droplet and the liquid on the other side of the interface.
  • Transient sieves can also be implemented via light-controlled barriers. In that case, microparticles with different hemispheres are driven by the interaction with a light field. Switching the light field on an off establishes a transient sieve.
  • Last but not least, the passage of charged molecules or particles through a nanopore can be controlled by a gate electrode covering the pore walls, therefore enabling electrically modulatable nanopores. Applying a time-dependent voltage to the gate electrode makes such a setup a transient sieve.

Funding:

Transieves is funded by the German Research Foundation (DFG) – Project number 509491635.
Transieves is funded by the German Research Foundation (DFG) – Project number 509491635.

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