Nature Inspired Materials

Thought LeadersDr. Lauren ZarzarAssistant Professor of ChemistryPenn State University

In this interview, Dr. Lauren Zarzar, Assistant Professor of Chemistry, Materials Science, and Engineering talks to News-Medical and Life Sciences about how exploring the natural world can serve as both inspiration and model for the invention of dynamic materials.

Can you begin by telling us what nature-inspired materials are and how have they advanced our understanding of science?

Nature-inspired materials are materials that have some component that has been inspired or derived from living organisms, in their form, 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 and different forms and functions.

We can benefit from that as scientists by looking at how nature has solved its problems and that can provide some potential solutions to our engineering and design challenges. That’s the motivation behind looking at nature: Learning from how living organisms design their materials, then taking those lessons and applying them to our own design engineered materials.

How essential is research into materials, specifically nature-inspired, to the science and engineering industries?

I think it is very important. In terms of solving problems, both in the chemistry of materials and the mechanical properties of materials, nature has come up with some really fantastic solutions, whether that is an adhesive that works underwater that is inspired by slugs as one example, or even learning how bones are designed to be resilient.

This idea of creating materials that are adaptive and can respond to stress from their surroundings and environment, such as as self-healing or repairing themselves, is revolutionary for synthetic materials but commonplace in nature. These are a lot of the capabilities that living materials have that we're not very good at designing into synthetic materials. Living organisms in nature are really critical inspiration for our future development of more advanced materials.

Why are the observation and use of the natural world important for study into materials science?

Nature teaches us many lessons, both in terms of designing materials and inspiring  new applications or approaches.

Especially in our work that is interested in making materials that are lifelike in the sense that they are adaptive, responsive to their surroundings, looking to living organisms is key because we can see how living organisms have evolved to solve a lot of these problems in materials complexity.

We can try to learn from those design principles and then engineer similar approaches into our synthetic materials.

Image Credit: Digital Images Studio / Shutterstock.com

This year at Pittcon, you are presenting a talk titled ‘Nature-Inspired Materials Science.’ What's the key takeaway message from your work?

Our work is largely inspired by living organisms in that they are adaptive, responsive and can interact with their surroundings in different functional ways. My research is broadly related to adaptive and responsive materials.

The talk that I will be giving at Pittcon is more specifically related to how we control color in materials and make color that is responsive and adaptive. Nature is fantastic at controlling light, whether this is in lenses or structures that give beautiful iridescent colors, such as see in beetles, bird feathers or butterflies.

These color-shifting effects that you often see in nature are from tiny structures on the surface of the organism that direct light in unique ways. As scientists, we have learned a lot from looking at living organisms and how they control light and color and we try to adapt some of those approaches for synthetic materials.

In some sense, the work that I will be describing is inspired by nature and uses structures to control the color of materials. However, in other ways, we have taken it a step further and designed properties into the material that we do not know to exist in nature. We are using structures and materials and approaches to control color in ways that nature has not yet employed.

I would say this is a nice example of where we took some inspiration from nature in terms of our initial approach and then dosed in a little bit of our own creativity and science to take it a step further.

You have just discussed what you are going to be talking about at Pittcon. Can you also tell us a little bit more about your research into nature-inspired materials at Penn State's Department of Materials, Science and Engineering?

Our research at Penn State is largely focused on dynamic and responsive materials, thinking about how we can combine materials such that the sum of the parts is greater than the individual components. Just as living organisms are not made of just one chemical or one material, their functions result from cooperativity between many moving parts.

We have to think like chemists and material scientists. How can we take the materials available to us and combine them so that they can communicate and cooperate and work together?

Our research centers on mostly soft materials such as polymers, liquids, and gels that are deformable or movable and can exchange chemical components. We look at ways of combining different chemistries and different materials such that we can give rise to materials that are more responsive or adaptive.

Some platforms that we work in, for example, are droplets that move and talk to each other and assemble. We work with gels that might change shape or color depending on the temperature or the lighting conditions or the pH.

Again, a lot of this comes inspired by living systems and how they are very adaptive, taking those lessons and exploiting them in materials that have a more applied focus. For instance, taking a color-changing system and exploring whether you can use this for security applications or as a sensor to read out something about the chemical environment.

Image Credit:Shutterstock/AnnaOm

Your research lab not only explores soft materials but also a variety of different platforms that include hard materials. What does the exploration of each type of material contribute to your research and your research questions?

This combination of hard and soft materials could be considered bio-inspired. Take the human, for example. You have a skeleton that provides the rigidity and the mechanical robustness so that you can stand up and walk around and move.

We need that rigid structure of the skeleton, but then, of course, we need our soft tissues, our organs and our cells, and the ability for liquids and chemicals to move through materials, which requires a soft material. We require something porous and deformable that can stretch and grow.

Humans are possible because of this combination of hard and soft materials and a lot of the materials that we might design in the future, as well as for dynamic materials, will largely take inspiration from this combination. Your hard materials might be providing the mechanical structure while your soft materials might be there for the chemical responsiveness.

In my graduate work, I did bio-inspired work on actuators that really utilized this concept. We had micro-structures that were rigid but could bend a little bit and put them into a responsive polymer that acted as a muscle, representing a muscle and bone analogy. We were creating responsive actuators in which we could move these micro-structures, the bones, with a responsive gel that could respond to temperature, light, or pH.

I think that exploring both hard and soft materials and then innovating on ways to combine them is going to lead to some really exciting, responsive materials in the future.

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Drawing from what you just said, your research at Penn State delves into dynamic materials and is intended to impact future technology. Can you tell us a little more about dynamic materials?

Dynamic materials are materials that, rather than being static, can actually sense when there are changes in their surroundings and respond in some functional way. Most of the materials that we have are not adaptive or dynamic. They are designed for use under a specific set of circumstances and when those circumstances change, you look for a new material.

However, we think the future of materials is in designing a material that is functional under many different circumstances and, depending on what the environment happens to be at the time, that material can actually adapt.

So, to give an example of how this might be useful in your day-to-day lives, I would say the tires on your car: what if the rubber on your car tire could change or the surface properties of your tire could change depending on if you are driving on dry pavement or wet pavement or ice? The same rubber surface is not necessarily the best material for all of these different circumstances. You could think of designing a new adaptive material instead.

There are many examples like this, where if we could design responsive or adaptive characteristics into our synthetic or engineered materials, they would be far more useful and far more functional. We think about how we can design that adaptiveness into soft materials primarily in order to give them more lifelike or bio-inspired properties.

What are some of the novel technology applications you envision for dynamic materials?

For our work specifically, one target application could be that of a sensor. If you have a material that can respond to its surroundings, you can use that material as a readout of what is happening around it.

For example, if you have a material that can sense when it has been stressed, for instance, if you stretch it or drop it, it could have color-changing properties to indicate the areas of high stress. Maybe you could engineer the material to even stiffen and actually get stronger in response to that stress. We are also looking at chemical sensors that change color under different chemical conditions.

Image Credit:  Andrew Berezovsky / Shutterstock.com

You have touched on this a little bit but your research is not just about nature-inspired materials, you also cover other topics like polymer chemistry. How do these different knowledge bases contribute to your work and to your research?

It is really important to draw on knowledge from many different fields of science and engineering, not just chemistry or material science. I would say this is especially important when thinking about designing adaptive and responsive materials or bio-inspired materials because they typically require so many different components where you are thinking about both the chemistry and the mechanical properties of the material as well as properties that span many different length scales.

I would say our next generation of adaptive and responsive materials are not going to just be one material, but rather composites or mixtures of multiple materials that work cooperatively. In order to achieve these goals, we really have to draw on the expertise of people from across different disciplines.

My training is primarily in chemistry, but we collaborate with physicists and materials scientists and theoreticians and mechanical engineers. I am very interested in learning about science and engineering in disciplines that are very different from my background.

I think that the most exciting discoveries are going to be those that come at the intersections of these more traditional fields and which can bridge those gaps and actually design new disciplines at the interfaces of these areas of science and engineering.

Just to follow up from that, what new disciplines do you envision these cross working with different researchers in different disciplines? What do you envision you can create?

I think there are going to be new areas of science that are going to evolve from these intersections between your more traditional areas of science and engineering. A couple of examples of newly emerging areas of research that really draw on many different disciplines are, for example, the fields of active matter, as well as something like mechanobiology.

For instance, the active matter field is looking at how we make objects move and communicate with each other to give rise to collective behavior, similar to schools of fish or flocks of birds. So, you not only need people like chemists to think about the reactions that are going to drive this motion, but you need physicists and you need theoreticians to model these interactions and the very complex behavior that emerges from these collections of active objects.

Something like mechanobiology, which draws on the more traditional fields of biology or biochemistry but then incorporates mechanics and looks at how stress or deformations or forces on cells and tissues actually feedback and influence the chemistry and biology, is becoming a really important part of understanding living organisms. It combines two fields that you normally think of as very distinct, mechanics and biology, but it turns out you need both to really understand how living systems grow.

With regards to the talk you will give, the biological use of light matter interactions is prevalent in nature. What specific natural systems inspired you to work toward engineering light manipulation materials and optical technologies? In addition to biological light manipulation, what other sources of inspiration do you believe can come from nature’s interactions with biological systems?

Living organisms have developed many different ways of controlling light and harvesting light and we take a lot of inspiration from those approaches when we design artificial materials. Specifically, my lab looks at controlling color.

If you look to living organisms, biology has evolved many different ways of controlling and using color, whether this is using color to signal between organisms of a similar species or to signal to a predator using very bright colors to say, ‘Stay away, don't eat me.’ There are a lot of different ways that living systems have developed and used color.

Living organisms create color in two ways typically: either they use pigments such as dyes and chemicals, or they use what we call structural color.

Structural color can be seen on things like bird feathers, butterfly wings and beetles and often have color shifting or iridescent features. Structural color is actually due to tiny structures on the surface of the butterfly wing or the beetle or the feather that causes light that hits that surface to interfere. Nature has inspired many intricate, complex structures to manipulate light in different ways.

There is a field of research in bio-inspired optics that examines nature, sees a beautiful color, asks the question, ‘how did the organism create that optical effect?’ and then seeks to try to replicate that in man-made materials. However, we can also take inspiration from living systems in terms of the general design approach, but instead of replicating the exact materials we adapt the design to somethign more suitable for our applications or something that is more readily attainable. For example, living organisms are really excellent at controlling structures on the nanoscale. We as humans, are not quite so good at it. We function a little bit better on the micro-scale, so orders of magnitude larger than nanoscale. My lab has been asking questions about how we can control color in similar ways and create these beautiful iridescent effects but do so in materials on a slightly larger scale.

So athough the research is bio-inspired, we are making structures and creating these effects in materials like synthetic polymers that a living organism would not use. We take inspiration from nature, but we add our own twist to it and try to make it a little bit more functional for us in our day-to-day lives.

With the research that you just explained to us, did you encounter any obstacles or face any challenges?

We encounter obstacles and challenges every day. I mean, just doing science in and of itself is very challenging. A lot of the exciting discoveries that we have made have not been intentional. There have been many cases that are accidental where we try to do something, but we see a result that is unexpected and we dig a little bit deeper into those results and find something really exciting.

In many ways, some of our greatest successes have come from our greatest failures. Because of that, I try to take this mindset that we may not achieve what intended, but we are going to learn from our failures along the way and that is going to teach us something exciting and see where it takes us. We encounter challenges every day, but I see them as opportunities and take that mindset to the lab and try to get my students to see things in the same way.

While collaborating with and teaching students from multiple disciplines and backgrounds, how do you feel this has shaped your experience, work and research?

It has really been my pleasure to have students from very diverse backgrounds in our research group. We have a lot of chemistry students in my research group, which is my home department, but I also have students from materials science and chemical engineering backgrounds too.

Beyond that, we collaborate with researchers that are in fields such as electrical engineering, mechanical engineering, and physics. These collaborations between people from different backgrounds and different disciplines yields the best science because we are bringing together people that look at the world in different ways.

When I have a problem, I am looking at it more from the chemist's perspective, thinking about the molecules, while my colleague, who is a mechanical engineer, is going to look at the same problem in a totally different way. So, we really need teams of people that have this diverse training, expertise and experience to tackle the hardest problems and come up with solutions that span these different disciplines.

I keep coming back to this idea of bioinspired materials. The next generation of materials is going to be characterized by materials that adapt and respond to many different situations. You are going to need people with different backgrounds and expertise to solve these hard problems.

What does the future hold for you and your research on nature-inspired and dynamic materials and what innovations do you expect in the coming years?

We are doing a significant amount of work right now using liquid droplets. These are soft materials and we try to understand how to control liquids as a material. I am very excited by this idea. In some ways, even though it is a little bit removed, I like to think of it as:  how do we create order from disorder? How do we take very simple chemical systems and design a way for them to evolve and self-organize? Even though we are likely not using the chemicals that would exist in a prebiotic earth, we are asking similar questions, such as how do you create things that have lifelike characteristics – the ability to move, communicate, grow and organize? How do we create these systems with limited chemical complexity? What are the design principles for that? Liquids are an important materials platform in which to explore such questions.

Then, once we understand those design rules, we can take those rules and build up more and more complex systems. We are starting to ask these questions within simple oil and water emulsions. Think of salad dressing: you have got oil, water and some surfactants, which is like a soap. These are very simple molecules that organize into much more complex materials that have interfaces that can exchange chemical components across those interfaces and communicate with each other.

Whereas the droplet work is very fundamental, we also have research that is taking a much more applied approach. The structural color work that I was describing earlier is an example. We learned some new ways fundamental ways of controlling color in materials and now we are trying to apply them and ask questions like, can we make a coating? Can we make a paint or a product that somebody would actually buy and use? Trying to translate our fundamental discoveries into products that someone might want to use it really challenging but quite fun!

 

It is very exciting that this upcoming event will be your first Pittcon. What you envision to gain from it. Also, why did you decide to present your work this year at Pittcon?

I am always excited to share our work with other academic scientists, but also to share our work with folks in the industry. I have talked a lot about working with people in different disciplines, but collaborating with scientists in industry is something that is newer to me which I am really excited about. I would love to make more connections with people.

There is a need for more collaboration between academia and industry, and how we can start to bridge that gap is by meeting each other and talking about our problems. The problems that I have in my lab in academia while working with emulsions are, I am sure, very different from the problems that somebody has working at, say, a company that is actually trying manufacture and formulate a paint. We both are making emulsions but they are used for totally different purposes. There may be connections there that we don't see unless we talk to each other.

I think conferences like Pittcon are a great way to build those connections with people who come from very diverse backgrounds and are solving very different kinds of problems. By learning about what we all do, what we are all thinking about and what we are excited about, we are going to draw those connections and maybe start some new collaborations that will lead to future products and solutions that are going to really benefit everyone.

In 2021, Pittcon is going virtual. Are you looking forward to this virtual Pittcon and what new trends do you think it will bring?

I will say I always love meeting people in person. There is definitely part of me that is very sad that we cannot gather in person. At the same time, virtual platforms do enable things that an in-person platform may not. For instance, I am hoping that people who potentially would not have the time or resources to be able to travel to a conference for several days may be able to attend virtually.

I think it could be also easier to arrange to meet people on a virtual platform rather than running around a conference hall trying to track down somebody. I think that there are definitely challenges that come with a virtual platform, but that we should try to embrace it. I am excited to see how the virtual platform of Pittcon is run and take advantage of the opportunities that it will provide.

 

Things are a lot different in 2020. Why do you feel events like Pittcon are important for the science community to come together now more than ever?

Because of the pandemic, I think a lot of us have felt very isolated. We're isolated from other people physically, you cannot walk down the hall and meet your colleagues and strike up a conversation anymore. Because so many events have been canceled, we are also isolated from learning about exciting research that is still in progress and not yet published. We have not had as many opportunities to connect with our friends and colleagues.

We have to take advantage of these virtual platforms in order to continue that dialogue, to continue sharing our work and learning from others and to build connections and start new collaborations.

The science does not stop, our work does not stop and so we want to make sure that we continue pushing forward and that we are sharing our exciting discoveries with other people and communicating that. When things go back to normal we will be setting up these new relationships and new directions for research.

When we can start to travel again and visit colleagues, we will have lots of new directions and things to do that we are looking forward to. I recently published a paper with someone that I met by chance at a poster session at a conference, which led to this fantastic collaboration. We cannot physically have a poster session anymore, but we can design something similar in a virtual platform so that these almost chance interactions can still happen and still trigger these new research directions. Attending conferences is a great way of finding new research, new science and new collaborators.

About Lauren Zarzar

Dynamic materials that sense and adapt to their surroundings are primnality. Therefore, in addition to the exploration of novel mechanisms coupling these chemical and mechanical cues, it will also be critical to develop prototyping approaches that facilitate the integration of a myriad of materials, especially at nano and micrometer length scales. In the Zarzar Lab, we explore a multitude of platforms including both hard and soft materials. For example, we study: direct laser writing of polymers, metals, and oxides for 2D and 3D nano/microscale patterning; dynamically reconfigurable soft materials, such as emulsions and polymers, with functions such as tunable lenses, sensors, and triggered release.

 

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