Feeling the pressure: materials for a more sustainable world

Good afternoon, ladies and gentlemen.

We start a new academic year full of possibilities, but also full of goals to reach and targets to meet. I guess we all feel the pressure to achieve more every year. But about such type of pressure I am not going to talk in this festive occasion. Instead, I am going to give you a taste of what inspires me in my research and that has to do with a different kind of pressure.

Developing materials for a more sustainable world is my aspiration, as it is of several of my colleagues. The inspiration comes from looking to the future and being convinced that, as materials scientists, we can play a role in shaping that future. With our research we can contribute significantly to make a more sustainable world. Let me illustrate this with an example: as it seems now, one new aspect of this future is going to be the “Internet of Things”.

You have probably heard of it. The Internet of Things promises to change the world. The idea is that not only the people will be fully connected, like now, but also the objects will be part of a global network. We will be able to access their state and position and they will be able to communicate among themselves. The town hall will receive a notification when a particular trash bin is full, your computer will tell you when the meat in your fridge goes wrong; supermarkets will never be out of stock. Your car will be able to drive autonomously. The Internet of Things includes what is called the Smart Grid, which will allow better management of the energy supply according to demand, and efficient global use of renewable energy produced locally. This is an active field of research at our University.

All this can only happen provided our daily life objects are equipped with sensors to allow them to communicate. Sensors consume very little power but, still, they need to be powered, typically, with batteries. Now, imagine that, as the experts forecast, in 2020 50 billion objects will be connected. If nothing changes, this means 50 billion new batteries and billions of batteries that need periodic replacement… That is not sustainable… As a materials scientist, I feel the pressure and the responsibility of working towards the solution of this problem. One way is to help harnessing the energy that we waste overall in large amounts and use it to power devices: what we call energy harvesting.

The wasted energy to be harvested can have different origins and forms. The best known one is solar energy. Interestingly, we need the help of special materials with specific properties to harvest this energy. Light can be harvested using photovoltaic materials. Our University is among the best in the world in solar cell research, as you probably know. Other forms of harvesting are less known because the relevant scientific and technical understanding is under development. We can also harvest heat, thermal energy. To harvest thermal energy we use thermoelectric materials. And we could also harvest vibrations.

Vibrations , this annoying source of noise that exists overall, is indeed wasted mechanical energy. To harvest vibrations we can use the so-called piezoelectric materials. In the three fields that I have just mentioned, are the Materials Institutes of the RUG (Zernike and Stratingh) active. These three ways of harvesting energy are complementary and which one to use depends on several factors including what form of energy is mostly available in that particular location. Here I will focus on what I know best, piezo-electric energy harvesting.

‘Piezo’ comes from the Greek word for ‘pressure’. If a piezoelectric crystal connected to two wires is deformed or squeezed, its internal electrical charges at the level of atoms are reorganized. This results in an electrical current through the wires. Piezoelectrics can thus transform mechanical energy into electrical energy. In this way they can function as generators and as sensors of movement or vibrations.

Piezoelectrics are part of our daily lives. They are in lighters, in inkjet printers, crash sensors for airbags or in ultrasound generators in sonars. In vending machines, the impact sensors that detect the type of coin that has been inserted, are made of piezoelectrics. It is not only the airbag, in modern cars there are about 20 different piezoelectric devices, like the fuel injectors, the pressure sensors in the tires and the vibration dampers. Our hospitals would not be the same without piezos: blood sensors, ultrasound devices to make sure that IV fluids are being delivered at the correct rate and free from air bubbles; ultrasound cleaners, lithotripters for pulverization of kidney stones or nebulizers, that use ultrasonic waves produced by piezoelectric materials to break up solutions into aerosols.

So, piezoelectrics can transform vibrations or movement into electricity. Strong vibrations from trains, cars, machinery, but also weaker ones from humans. This can allow people to power small devices with their own motion. In remote places where people have no access to electrical power, powering devices using environmental energy may be life changing. But actually for many of us too: we are slaves of our batteries. The consciousness of the ending of the battery life and the possibility to be left disconnected changes our behaviour. The most wanted table in the restaurant is not any more the most romantic one, but the one close to the socket. You can also take a look at some airports, where all the action happens around the power plugs.

To harvest human motion is an old idea. You may have seen Zomergasten last night. Coincidentally, the designer Daan Roosegaarde was involved in the design of the first floor that could collect energy from people walking and dancing. The Sustainable Dancing Floor is a Dutch invention and was installed in a disco in Rotterdam about 5 years ago. Why is that not yet a reality at a larger scale?

The main reason is that one cannot get very large amounts of energy immediately, of course, so only in recent years when the power consumption of our devices has decreased substantially, one can start thinking of energy harvesting as a solution for self-powering devices. To mention some numbers. One of these tiles produces about 5W per step. One needs to run about ½ hour or walk normally for 1 h to charge the phone battery. Needless to say, that will be improved as devices becomes more efficient.

A second issue is that we need a portable power source or the size of a battery, or the smaller the better, that does not cost us extra energy. That is why piezoelectrics are far better than dynamos to harvest mechanical energy. The problem is that the best piezoelectric materials contain lead atoms. Lead is toxic in powder form and it is not desirable to cover kms of asphalt with lead.

So, my ultimate goal is to synthesize a material that is to the piezoelectricity industry what Silicon is to the semiconductor industry. That is, a light, abundant, cheap and harmless material that is at the same time a good piezoelectric. A material that can be installed everywhere where there is motion and vibrations with minimum environmental impact. How do I plan to go about doing this? By artificially creating new materials that have never existed before, that cannot be found in Nature, making them one atomic layer at a time. We can make at the Zernike Institute, something we are very proud of.

I would not like to finish without mentioning that the first funds that I have obtained to embark on this adventure have come, from the Zernike Institute, from which I have gotten support in all possible ways, and from the Ubbo Emmius funds of the RUG. More precisely, from the Aduarderkring, the alumni of the RUG living in the province of Groningen, who are personally contributing financially to see this idea materialize. Among the alumni there are a couple of scientists but they are mainly lawyers, economists, entrepreneurs and politicians supporting and project at the boundary between physics and chemistry. I have had the luxury to meet them personally in several occasions and it strikes me that their generosity, their vision and open mentality perfectly reflect the qualities of this University: open to the world and brave to start adventurous initiatives. This is a University that welcomes staff and students from all over the world and patiently accepts our struggles with the Dutch language, even allowing us to use English in official ceremonies; a University that understands that the small details matter to make you feel at home.

This event gathers us and welcomes us home after the summer holidays. Let’s show our colleagues and our students how much we enjoy our jobs…and let the materials feel the pressure.