## Docente responsável: Prof. Dr. Douglas Soares Galvão

Área: Matéria Condensada

Grupo de Sólidos Orgânicos e Novos Materiais - Site do Grupo - Site do docente

## Bolsas disponíveis

**Tipo**: Doutorado

**Quantidade de Bolsas**: 2

**Agência Financiadora**: Fapesp/CEPID

**Valor**: R$ 3.010,80 / R$ 3.726,30

## Resumo do Projeto

Associate Researcher (Advisor): Prof. Douglas S. Galvão (Physics)

Level: DR

Smart surfaces with tunable wetting behavior under diverse conditions have attracted intense experimental and theoretical attention in recent years. They can be the basis for a large class of technological applications, such as; self-cleaning surfaces, adhesives, sensors, etc. In particular two effects are very important defining some of these properties: the so-called gecko and lotus effects [1]. Geckos are a family of lizards well spread over the world. Their ability to climb up on any vertical surface and hang from ceilings has intrigued researchers for decades. The molecular origin of this behavior is still an object of debates [2]. Theoretical works have indicated that this gecko-like behavior can be mimicked by a combination of diverse materials, including vertically aligned carbon nanotube forests [2]. The topology and optimal parameters to achieve this is an open and polemical question. In particular, how to tune the wettability of these structures and the behavior of their interactions with liquid droplets are poorly understood. One of the objectives of the present work is to investigate some of these phenomena from the atomistic point of view through fully atomistic molecular dynamics and finite elements modeling. The other closely related effect to these phenomena is the Lotus effect, which is a well-known example of super-hydrophobicity exhibited by Lotus leaves (thus, its name). Water in super-hydrophobic surfaces spreads or is absorbed very quickly and exhibits a water contact angle close to zero. In recent years, there is a great interest in studying these properties for nanomaterials [3], especially with the discovery of the unusual tribological behavior of graphene and water [4]. We intend to investigate some of these problems using fully atomistic molecular dynamics simulations and finite elements modeling.

### Methodology

In order to carry out these investigations we intend to use large-scale classical molecular dynamics simulations (LAMMPS code, CHARM and reactive force fields) and finite elements modeling.

### Objectives

- To build structural carbon nanotube-based models to mimic the gecko behavior
- To identify and optimize critical parameters to this effect
- To build structural liquid droplet models
- To investigate the tribological properties of liquid droplets and carbon-based materials, such as carbon nanotube forests and graphene-like membranes.
- To build macroscale models using finite elements approaches

These problems require a multi-disciplinary approach and demand high computational resources. Thus, they fit perfectly in the scope of the project we are proposing here. Also, it is important to mention that, besides the important basic science involved in these problems, they have the capability of potentially generate new and valuable patentable processes/products and are of great interest for the company patterns associated with this CEPID project.

### References

- The Geckos foot, by Peter Forbes, W. W. Norton & Company, New York (2005)
- L. Qu, L. Dai, M. Stone, Z. Xia, and Z. L. Wang, Science 322, 238 (2008)
- E. Ueda and P. Leukind, Adv. Mater, ASAP papers (2013)
- H. E. Nguesson et al., Nature Commun. 3, 1242 (2012)