The Invention of Dynamic Materials
Nature-inspired materials are materials that have some component that has been inspired or derived from living organisms in their function or design. The idea behind bioinspired or nature-inspired materials is that living organisms and nature have had billions of years to evolve and test different materials. Thus, we can benefit from that as scientists by looking at how nature has solved its problems. This can provide some potential solutions to the engineering and design challenges that we face today [1].
There are many capabilities that living materials have that are generally found to be difficult to incorporate into synthetic systems. Self-healing and repair, efficient response to external stimuli and the ability to adapt quickly and potently are commonplace features in nature and could be revolutionary in the field of engineering. Taking inspiration from the living organisms in nature, Dr. Lauren Zarzar of Pennsylvania State University works toward the creation of what she calls “life-like materials.” Essentially, these substances try to emulate the evolutionary feature that is characteristic of most living creatures. Just as an organism responds to the gradual adversity it faces in its external space over a period of time, our systems may also be designed in a manner that allows them to cope with change without requiring new additions or corrections.
Thus, most materials that we interact with in our daily lives are static in character. They are engineered to function in a specific, predetermined set of circumstances. However, the continuously changing nature of the environment around them poses a challenge to their long-term use and sustainability. Through her research and its application, Dr. Zarzar aims to craft materials that are “dynamic” and adaptive. These systems would ideally develop modifications in accordance with the stimulus they face (such as light or heat). These changes may be in terms of colour, surface properties or movement – and this would grant them greater use in a much wider range of conditions [3].
Liquids: Magic Materials
Dr. Zarzar believes liquids to be the most dynamic and responsive materials to work with as a material scientist. Unlike solids, they change shape easily, and two liquids in contact can essentially communicate by passing molecules between each other.
Specifically, she works to develop ways to control the shapes and compositions of tiny droplets of complex emulsions (Figure 1). These droplets are made of liquids that don’t mix, such as a droplet containing fluorocarbon oil inside a hydrocarbon oil floating in water.
Figure 1: Microscopic image showing an example of a complex emulsion.
Through her studies, Dr. Zarzar developed an easy way to build these droplets and then change their structure. For example, she could pick which oil was on the inside of the droplet and which was on the outside. She started with oils that didn’t mix at room temperature, but could when heated. By then cooling these heated mixtures with surfactants*, she could control the structure of the emulsions since the oils stopped mixing. By adding different surfactants to a solution containing the emulsions, she could change the droplets’ structure again [2].
Adding surfactants and changing surface tension of these liquid droplets essentially allowed Dr. Zarzar to change their curvature, having a profound impact on their optical properties (i.e., the way in which these droplets interact with or deflect the light incident on their surface). This has opened the field of material chemistry to an abundance of new applications.
* A surfactant is a substance such as a detergent that, when added to a liquid, reduces its surface tension. This increases its spreading and wetting properties, and influences the droplets’ structure by controlling the surface tension of the different liquids in the emulsions.
The Zarzar Lab and the Future of Material Chemistry
With her extensive work on life-like materials with dynamic and adaptive properties, Dr. Zarzar hopes to make a meaningful contribution to the development of more sustainable systems. We can actively learn from and emulate the common phenomena observed in our environment and can create materials that remain unfazed by sudden changes in their surroundings. This allows them to coordinate better with more contemporary applications. This development also proves to be more cost-efficient in the long run, as it saves resources that would otherwise have to be spent on repair or replacement of some of these systems.
Her work on liquids as materials, in fact, already proves to have wide-ranging applications in daily life. Researchers could use the droplets as lenses and tune them as they would microscope. Even more broadly, they could also capitalise on the aforementioned change in the liquid’s optical properties to create reflective displays and colourful coating for cars, clothing, in makeup, etc. This works by controlling the curvature of the droplet, causing interference of light inside it and resulting in a change in its iridescence. Dr. Zarzar describes this effect as a tunable version of structural colour, which is colour that arises not from dyes but from how light interacts with the structure of a material [2].
Learn More
If you’d like to hear more about the fascinating world of material chemistry, visit us on Spotify to listen to our ChemTalk podcast with Dr. Lauren Zarzar of Pennsylvania State University to learn more about what sparked her interest in chemistry, her thoughts on “oobleck”, and what she believes is the most important aspect in research.
Find the ChemTalk podcast here.
Works Cited
[1] Pittcon. “Nature Inspired Materials.” Medical News. 10 February 2021.
[2] Torrice, Michael. “Lauren Zarzar.” Chemical and Engineering News. 25 August 2019.
[3] Zarzar, Lauren. Personal Interview. Conducted by Olivia Lambertson and Nafeesa Mahmood. 15 June 2021.