In an interview Dr Justin Weibel, a research assistant professor; Dr Xuemei Chen, a post-doctoral research associate and Dr Suresh Garimella, a Goodson distinguished professor, all at the school of mechanical engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, US with Chemical Today magazine talks about the simple solution they found for the hazardous problem (oil spills) which is endangering the world.
Explain the dynamics of your research.
Nature is an important source of inspiration for developing advanced materials. One area of our group’s current research focuses on bio-inspired micro/nano-structured superhydrophobic surfaces that enable fundamental investigation of interfacial wetting phenomenon, as well as the development of new material technologies that exploit these characteristics. These surfaces can be applied in drop wise condensation, water harvesting/reclamation, anti-icing, anti-fouling, biomedical and other various applications. We have most recently used these techniques to develop a functionalized sponge material that can collect large amounts of oil while preventing any water from being absorbed; the material has great potential for cleanup of oil spills and oil-water separation.
Elaborate on the advanced materials and technology that gave shape to your research.
Only two materials comprise this new technology, namely, melamine sponge and polydimethylsiloxane (PDMS). The melamine sponge acts as a skeleton material with a highly porous structure (over 99 percent open volume) onto which the PDMS is coated. The intrinsic hydrophobic nature of the PDMS, in combination with the microporous structure of the melamine sponge, renders the material super hydrophobic (robustly repels water). During the one-step solution-immersion fabrication process, hexane is used as a solvent to dissolve PDMS, but is not retained in the final material.
In what ways is this technology different from other similar research work?
We present a simple solution-immersion method for the fabrication of superhydrophobic and superoleophilic PDMS-functionalized melamine sponges. In order to functionalize the sponge, it is immersed in a homogeneous solution of PDMS and hexane. The sponge is removed from the solution, wrung out, and dried in an oven at an elevated temperature. This process leaves a thin layer of PDMS coated onto the underlying sponge microstructure. Previous functionalized polymer sponges (for oil-water separation) typically include both a nanostructured hydrophobic coating material and a separate adhesion medium for binding, which require more complex fabrication processes and limits their reusability. In the new technology that we developed, the melamine sponge does not need any secondary treatment, and only a single low-cost material (PDMS) is used as the coating. In combination with the simple fabrication process, these features make the final oil-water separation product cost-effective and scalable.
How will your research help in case of environment and industrial chemical leaks?
The as-fabricated functionalized sponge material exhibits robust superhydrophobic and superoleophilic properties, meaning it can strongly repel water while easily absorbing oils. The commercially available raw materials and scalable fabrication process ensure that this material can be adopted for the cleanup of oil spills and industrial chemical leaks of low-surface-tension contaminants that are immiscible with water.
What is the economic viability of this technology on a larger commercial scale?
The raw materials used in the technology are quite common: melamine sponges are found as household cleaning sponges; PDMS is a polymer commonly used for the fabrication of microfluidic devices, and hexane is used in a variety of industrial cleaning and degreasing processes. These materials can be readily obtained from large chemical suppliers. Also, to fabricate the oil-absorbent product, only a small amount of PMDS coating material is needed. Due to the facile fabrication approach and low-cost materials, we are certain that the material can be readily fabricated on a large scale.
Give us a sense of the longevity and re-usability properties of the material?
We have demonstrated in the laboratory that the sponges retain their properties after absorbing in oil and squeezing out oil tens of times for a single sample, without any degradation in performance. We have no reason to suspect that the coating would degrade over much more such operations. The coating is chemically stable and would not require retreatment, but can be cleaned to remove any residual oils left in the sponge.
What are the challenges you faced while carrying out your research?
Due to the excellent selectivity for absorption of oil by the sponge (and not water), during our oil-water separation experiments, it was quite difficult to quantify the infinitesimal amount of water that unintentionally captured along with the oil. Using a coulometer (a device that measures the water content in oils), the purity of the collected oils was over 99.98 percent, a near-perfect separation efficiency within the measurement accuracy.
Are you in talks with the industry for commercialising your technology?
We have applied for a patent on this material technology, which is receiving much attention and interest from potential industrial users. We are excited to see this product adopted for eventual use in large-scale systems.
Read Full Story: Tackling Major Oil Spills with Sponge
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