by Serena Blacklow
A start-up launched late in 2014 from our own Wyss Institute for Biologically Inspired Engineering is working to commercialize ‘SLIPS’ technology. SLIPS Technologies’ mission is to customize super-repellent surfaces for whatever application under demand.
Slippery lubricant-infused porous surfaces (SLIPS) can be formulated to repel water, bacteria, and oil, among other “fouling agents”. They can prevent biofilm formation, reduce ice accumulation, and increase flow rates through tubing.1 Thus SLIPS can be applied to medical devices, such as catheters, outdoor heating installations subject to cold weather environments, and pipelines that transport fluids such as mud, cement, and oil. SLIPS Technologies works on translating a laboratory engineering development into a method for commercial use.
First inspired by the lotus leaf, Harvard Professor Joanna Aizenberg and her team sought to emulate the leaf’s superhydrophobic (water repellent) surface to create a novel liquid and ice-repellent surface. The idea behind these surfaces is to maintain the largest contact angle possible between the droplet and the surface it contacts. The more preserved the droplet structure after it hits the surface, the more easily the droplet will slide off.
The first surfaces created in the lab were micro- and nano-structured, so they relied on these small structures to prevent water droplets from breaking their shape and spreading over the surface upon contact. In high humidity conditions, however, water and ice crystals would accumulate in the air pockets between the micro- and nano-structures, and the surface would lose its superhydrophobic ability.
Currently, fabrication of SLIPS uses an additional liquid lubricant that is immiscible (does not mix) with the fluid it repels; this addition to the original structured surfaces eliminates the problems associated with high humidity conditions as long as there is lubricant infused in the surface because there are no air pockets in which that water or ice could accumulate. More specifically, there are two main approaches to manufacturing SLIPS:
- Lubricant-coated nanostructured surface
- Lubricant-infused polymer surface
The lubricant-coated nanostructured surfaces have been created with aluminum and a perfluorinated lubricant and have displayed anti-icing promise.2 This system can be applied to many surfaces, but one drawback is the depletion of lubricant leading to failure of the system again under high humidity conditions. The second approach aims to solve this problem by incorporating a vascular system that can replenish lubricant at the surface as it is depleted.3 This system, however, is a silicone oil-infused polymer-based system so it requires applying the additional layer of polymer to the surface of interest. Some combination of these approaches could be the next step towards creating a more robust superhydrophobic surface.
A superhydrophobic surface is just one example of a bio-inspired material. Hopefully, innovations around this technology will extend beyond nature’s ability so a durable superhydrophobic surface can revolutionize the anti-fouling and anti-ice industries.
Serena Blacklow ’17 is a junior in Leverett House, concentrating in Engineering Sciences.
- SLIPS Technologies. http://www.slipstechnologies.com/solutions.php (accessed Oct. 31, 2015).
- Kim, P., et al. ACS Nano. 2012, 6 (8), pp 6569–6577.
- MacCallum, N., et al. ACS Biomaterials. 2015, 1, pp 43−51.