Industrial application of nanogel step closer
Bijels promising for super-efficient chemical separation, energy storage and catalysis
Bijels - pronounced "bye-gels" - are relatively new gels with unique properties. In her PhD research at the Debye Institute for Nanomaterials Science, Mariska de Ruiter has taken significant steps toward the industrial application of these promising materials, with potential uses in – among others - filters and batteries. Her work focuses on controlling the structure of bijels during the manufacturing process and scaling up their production. De Ruiter defended her PhD on 25 November at Utrecht University.
In 2007, scientists succeeded in producing bijels in a lab for the first time. Bijels are gel-like materials in which oil and water are intricately interwoven yet remain separated by a layer of nanoparticles. This unique structure creates two interlocking networks of oil and water channels, as illustrated in the image on the right, making bijels promising for various applications in chemical separation, energy storage, catalysis, and more.
The high surface area where oil and water meet, separated only by nanoparticles, gives bijels their versatility. For example, a bijel membrane could potentially desalinate seawater instantly, producing drinking water from saltwater without delay.
Tinkering with structure
In her PhD research, De Ruiter discovered ways to control the structure of bijels during their formation. She found that it’s possible to adjust the size of the channels in bijels and to connect these channels to reservoirs of different liquids, facilitating their interaction. Additionally, she developed a method to produce bijel films at a rate of several cubic centimeters per minute - a crucial advancement for scaling up bijel production for industrial use.
De Ruiter worked specifically with STrIPS bijels, a type developed by her supervisor, Martin Haase, in 2015. These bijels offer significant advantages over other types, such as the ability to use smaller nanoparticles for stabilization, resulting in much finer channels.
Crafting
One of the biggest challenges in De Ruiter's research was finding a way to connect the oil and water channels in bijels to corresponding reservoirs of oil and water - an essential step for practical applications. The PhD candidate ultimately succeeded by developing hollow fibers, allowing different liquids to flow past each other during the formation of the channels. To achieve this, she crafted a custom setup using a microscope slide fitted with several glass tubes carefully aligned. “I spent quite a few afternoons on that,” De Ruiter says.
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Stunning visuals
Throughout the manufacturing process of bijels, De Ruiter experimented with various parameters and then examined the results using two advanced microscopy techniques. With a confocal laser scanning microscope, she could observe the distribution of water, oil, and nanoparticles within the bijels. Using an electron microscope, she captured high-resolution images of the nanoparticle layers left behind after the bijels dried. Both techniques produced not only valuable insights but also stunning images, as shown here. For De Ruiter, this was one of the most enjoyable aspects of her research. “It’s amazing to see with your own eyes what you’ve created,” she says.
