In March 2018, the Senate of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) established the Priority Programme “Dynamic Wetting of Flexible, Adaptive and Switchable Surfaces” (SPP 2171). The programme is designed to run for six years. The present call invites proposals for the second three-year funding period.

The dynamic process of liquids wetting or dewetting various substrates is ubiquitous in everyday life and of key importance in many technological applications and natural systems. Earlier work mostly focused on the influence of the topography and composition of rigid and inert substrates. Recent developments in areas like microelectronics and 3D printing have demonstrated a pressing need to also understand cases in which (de)wetting dynamics and substrate dynamics are strongly coupled. This holds true especially on microscopic and mesoscopic length scales, where (non)equilibrium surface phenomena dominate.

The Priority Programme aims at establishing a deeper understanding of the fundamental physics behind the dynamic (de)wetting of flexible, adaptive and switchable substrates combining experimental and theoretical perspectives. The focus lies on rather simple liquids that shall be employed to investigate the different cases of strong coupling between liquid hydrodynamics and (primarily reversible) substrate dynamics. The investigation will further develop the foundations for developing future technologies and for understanding biological systems that utilise and control such wetting phenomena.

• Flexible substrates experience deformations due to the traction that a (de)wetting liquid exerts on them, which in turn experiences an altered geometry. Thus, static and dynamic (de)wetting processes are governed by this two-way coupling between liquid and substrate. This holds true for elastomeric materials, hydrogels, or slippery liquid infused porous surfaces, and is even amplified for substrates that expose “hairy” structures.
• In contrast, adaptive substrates change their physico-chemical properties due to the presence of a liquid. This may be induced by direct contact like under a sessile droplet, or it may be mediated through an external phase like the ambient atmosphere or a second liquid. Typical modification agents are temperature or ambient humidity. The functional surfaces of many carnivorous plants belong to this category, as well as swellable polymer gels or surfaces with grafted polymer brushes.
• Finally, switchable substrates alter their physico-chemical properties upon exposure to an external influence. For instance, switching could be induced by electric or magnetic fields, as well as via changes of pH or temperature. For instance, nematic elastomers or coatings that contain photoswitchable azobenzenes fall into this category.

Often, real model systems cannot be clearly assigned to a single category, but exhibit features of several of them. The common base of all three categories is a strong coupling between (de)wetting hydrodynamics and substrate processes. This typically introduces additional time- and length scales that do not exist in the (de)wetting of inert and rigid substrates. Strong couplings also impact the mechanisms of energy dissipation, potentially altering the dynamics on a global scale. To allow for a clear identification of these coupling mechanisms, projects shall normally focus on relatively simple, low-molecular-weight liquids. This includes the mixtures of such liquids and dilute suspensions or tenside solutions that offer novel coupling mechanisms through their internal degrees of freedom.

This Priority Programme invites experimental, numerical, and theoretical contributions from all natural sciences and mathematics. Projects should aim at a fundamental understanding of the dynamics of three phase contact lines on flexible, adaptive or switchable substrates. To keep the programme coherent, it shall not support projects that exclusively aim at application development or biological systems. Also, the focus shall be on the coupling of liquid and substrate dynamics, for liquids that as such are already well understood. Furthermore, the substrate dynamics shall normally be reversible which, e.g., excludes processes based on irreversible chemical reactions or permanent mechanical change. The questions that are addressed in the programme are highly interdisciplinary, reaching from materials science to theoretical physics of liquids. Both, experimentalists and theoreticians, face the challenges of phenomena that are inherently multiscale, where physico-chemical processes at the microscale determine the evolution on the macroscopic scale.

Proposals must be written in English and submitted to the DFG by 15 January 2022. Please note that proposals can only be submitted via elan, the DFG’s electronic proposal processing system. In addition to submitting your proposal through elan, please send an electronic copy to the programme coordinator.

Applicants must be registered in elan prior to submitting a proposal to the DFG. If you have not yet registered, please note that you must do so by 7 January 2022 to submit a proposal under this call; registration requests received after this time cannot be considered. You will normally receive confirmation of your registration by the next working day. Note that you will be asked to select the appropriate Priority Programme call during both the registration and the proposal process.

If you would like to submit a proposal for a new project within the existing Priority Programme, please go to Proposal Submission – New Project – Priority Programmes and select “SPP 2171” from the current list of calls. Previous applicants can submit a proposal for the renewal of an existing project under Proposal Submission – Proposal Overview/Renewal Proposal.

In preparing your proposal, please review the programme guidelines (form 50.05, section B) and follow the proposal preparation instructions (form 54.01). These forms can either be downloaded from our website or accessed through the elan portal.

The review colloquium for the Priority Programme will probably be held on 31 March 2022 and 1 April 2022 in Mainz.

Further Information

More information on the Priority Programme is available under:

• www.uni-muenster.de/SPP2171

The elan system can be accessed at:

• https://elan.dfg.de/en

DFG forms 50.05 and 54.01 can be downloaded at:

• www.dfg.de/formulare/50_05
• www.dfg.de/formulare/54_01

For scientific enquiries please contact the Priority Programme coordinator:

• Professor Dr. Uwe Thiele
  Institut für Theoretische Physik
  Westfälische Wilhelms-Universität Münster
  Wilhelm-Klemm-Straße 9
  48149 Münster
  phone +49 251 83 34939
  u.thiele@uni-muenster.de

Questions on the DFG proposal process can be directed to:

• Programme contact: 
  Dr. Mario Bomers
  phone +49 228 885-2007
  mario.bomers@dfg.de
• Administrative contact: 
  Natalie Kaiser
  phone +49 228 885-2184
  natalie.kaiser@dfg.de