Morphing, composites and structural muscle: thoughts from an Advanced Composites postgraduate researcher

We asked Eric Eckstein, the recipient of the prestigious Jefferson Goblet award for ‘overall best student paper’ at the 57th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, about his work with ‘morphing’ composites. The following is a guest post about his journey to Bristol and with his composites research as an Advanced Composites postgraduate researcher with the ACCIS CDT

A composite laminate made from carbon fiber and aluminum alloy, heated in an oven to 150°C. Aluminum wants to expand under heat, but carbon fiber doesn't. When you stick the two materials together, the whole laminate curls as each layer tries to have its own way.
A composite laminate made from carbon fiber and aluminum alloy, heated in an oven to 150°C. Aluminum wants to expand under heat, but carbon fiber doesn’t. When you stick the two materials together, the whole laminate curls as each layer tries to have its own way.

Bristol has been my home for the past four years, having originally been born and raised in the USA.  Our university is one of the most well-known in the field of composites research, and was really a perfect fit for my interests in morphing structures.  The big idea behind morphing is to open up new ways of changing the shape of an object.  Traditionally, engineers get things to move about using a collection of hinges and actuators, but in many situations, it’s better to facilitate movement using organic flexing and twisting motions.  Nature has been using these morphing techniques for millennia, we see it in action every time a flower pivots itself to track the sun, or a pine cone closes up in the rain.  Meanwhile, engineers aim to exploit the same principles in order to make everything from more efficient aircraft to haptic feedback touch screens.  This is all great, but what really turned me onto the subject was an opportunity to achieve morphing in a simple, elegant manner.

Most moving structures have actuators separate from the structure, just like how our muscles are separate from our bones.  Morphing structures, like those sun-tracking flowers, have their muscle and structure built into one.  For cases where engineers can take the same approach, their moving structures won’t need hinges, pistons, or any other steampunk-like hardware, thus they can be made beautifully simple.

Ceramix matrix composite morphing structure at room temperature.
When heated to 1000°C, the structure bends upwards by about 6mm, driven by the thermal expansion of a stainless steel strut.

One of the biggest challenges we face is finding a good structural muscle.  The perfect material for the job would be able to expand and contract on command, much like our own muscles, yet be stiff and strong enough to bear great loads.  A great deal of progress has been made on this front using metals and polymers which respond to heat by expanding or contracting, but composite materials open up a whole new world of possibilities.  Because their expansion and stiffness properties can be accurately tailored by the designer, they can allow for a rich variety of movements, everything from bending, twisting, to snapping shut like a venus fly-trap.  I think that working with composite materials is akin to an artist swapping out his charcoal pencil for a whole pallet of rich colours.

The simplicity of a thermally-driven morphing structure can give them a natural durability in adverse environments, such as salty seas or hot jet exhausts.  The right materials need to be found, of course, and that’s one of our main focuses.  Metal-matrix and ceramic matrix composites have given us promising results, however these materials are still very much adolescent developments, compared to mankind’s established metallics knowledge.

We hope of course that our technology is picked up by the aerospace industry, but the real icing on the cake would be to find other, much broader applications.  I’ve read about an idea where morphing micro-capsules of a virus-fighting drug could be injected into your body, lying in wait for months until you get a fever.  That increase in body temperature triggers the thermally-driven morphing capsule to release the drug automatically.  Who knows what other applications exist?

The Why and The How

Madeline_BurkeMadeline Burke is a third-year postgraduate researcher in the department of Cellular and Molecular Medicine.  Madeline did her undergraduate degree in Mechanical Engineering before switching disciplines when she started a PhD with the Bristol Centre for Functional Nanomaterials (BCFN). She is currently building a 3D bio-printer that can create human tissue by printing stem cells. Madeline’s research is interdisciplinary, using concepts from chemistry, cell biology and engineering, to design matrices for stem cells that not only support the cells, but cause them to grow into desired tissue such as cartilage. Most of her time is spent in the lab, designing new experiments and building her 3D printer.


What are the differences between sciences and engineering? Not an earth shattering, life changing question, I’ll admit, but one I have been pondering recently after my foray into nanoscience. Having previously defined myself as an engineer, a PhD in nanoscience has made me challenge my views and definition of science as a subject. Cheesy I know, but seriously, the differences between my engineering student university experience and that of my science graduate colleagues were astounding to me. So I decided to try and define these differences and where better to start answering my questions than the oracle of all things known (also known as Google or in this case my first hit, Wiki answers).

Wiki answers says “A scientist is a person who has scientific training or who works in the sciences. An engineer is someone who is trained as an engineer.” Somehow I don’t think it is that simple. As I’ve found out there is a huge amount of overlap between science and engineering, especially nanoscience. Let me explain – engineering is essentially applying scientific principles to real world problems, a product or solution is created and the problem is solved (or so engineers like to think). Science looks at the world around us and tries to find answers to its mysteries. The difference is not about the knowledge needed to study or practise these disciplines, but in the questions you ask.

In essence, a scientist looks at something and wants to understand “why?” Why is the sky blue? Why do things behave differently on the macro and micro scale? Why do stem cells proliferate and other cells do not? Essentially, it is about understanding and acquiring new knowledge. Engineering is more about “how?” As an engineer, I ask how I can make other cells differentiate. How can I sequence DNA cheaply and accurately? How can I make computers better, smaller and cheaper? Engineering is about invention and solving real-world problems rather than acquiring new knowledge.

This is where the hot new subject of nanoscience comes in, bridging the proverbial gap between science and engineering. Nanoscientists ask both types of questions: why do things behave differently at the nanoscale, and how can I apply this to a real world problem?

But I suppose the big question is who cares? Should there be a distinction between science and engineering? I highlight the well-known case of the chicken and the egg: in school, we were taught that science came first and engineering was the application of science, but now important advances in nanoscience are usually the result of a new tool becoming available. You could say that nanoscience is driven by engineering advances.

Nanoscience is starting to address the distinctions between engineering and science, and also within science itself. Coming from an engineering background the “why?” of science was a shock to me, but I’ve come to see it as an advantage. Engineering is often money and product focused, but without the why of science it wouldn’t exist. I still have the odd “how are you ever going to apply that to anything useful?” moment but in general nanoscience is perfect for me. I get the why and the how!