Atomic Architecture: Nanotechnology and Sustainable Design

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1 Atomic Architecture: Nanotechnology and Sustainable Design Michelle Stanard Editor Werner Lang Aurora McClain csd Center for Sustainable Development

2 II-Strategies Technology 2

3 2.13 Nanotechnology and Sustainable Design Atomic Architecture: Nanotechnology and Sustainable Design Michelle Stanard Based on a presentation by Dr. Rod Ruoff Figure 1: The Atomium in Brussels Introduction Nanotechnology focuses on the engineering of functional systems at the atomic level. When working with materials at the nanoscale, physical, chemical, and biological properties can emerge that differ from the properties of materials examined at a larger scale. 1 At the nanoscale, materials can prove better at conducting heat or electricity, have different magnetic properties, reflect light differently, or prove stronger than the same materials analyzed on a larger scale. In principle this means that nanotechnologists could alter materials on the most basic level to increase certain material properties such as strength, flexibility, heat absorption, heat conduction, etc. Such practices have actually been part of the building profession for centuries. For example, the introduction of fly ash, a material that possesses great strength at the nanoscale, to concrete mixtures provides a perfect example of the way that the nanoscale properties of one material can be used to alter the performance of a larger system. Another more recent example (not yet implemented in the building profession) includes the formation of nanoscale carbon tubes, some of which are incredibly strong and that can in principle be used in combination with polymers to make strong, lightweight materials. These applications to materials apply to the field of sustainability because they give engineers the opportunity to custom design stronger and lighter materials on the atomic level, thereby saving fuel and decreasing the environmental footprint of buildings. Graphene and its use in building materials The research that Dr. Rod Ruoff has been conducting focuses specifically on the nanotechnology of graphene, and its application in a wide variety of areas such as nanoelectronics, polymer matrix composites, paper-like materials, electrical energy storage, thermal management, and as a transparent but electrical conductor. 2 Graphene has the potential to enhance the specific strength, specific stiffness, thermal conductivity, and barrier resistance of materials including polymers and thin films. Like many nanoscale materials, graphene also has a larger surface area than similar volumes of larger scale materials, meaning that it has more surface area available for interactions with other surrounding materials. This nanoscale material attribute, along with its good electrical conductivity, makes graphene particularly useful in ultracapacitors, a type of electrical energy storage system. Thus graphene and the broader field of nanotechnology have the capability to influence new materials possibilities for the field of sustainable design. Various applications for nanotechnology While nanotechnology certainly presents interesting possibilities in the field of sustainable 3

II-Strategies Technology Figure 2: Graphene Polymer Figure 4: Concrete Balloon with lightweight, polymer membrane Figure 3: Graphene sheets embedded in a polymer matrix design, scientists around the

3 In the field of medicine, nanoscale machines or particles have the potential to travel through the human body, targeting certain viruses or destructive cells in order to deliver medication directly

In the area of environmental science, nanotechnology has the ability to provide environmental monitors for pollution levels.

4 II-Strategies Technology Figure 2: Graphene Polymer Figure 4: Concrete Balloon with lightweight, polymer membrane Figure 3: Graphene sheets embedded in a polymer matrix design, scientists around the world are excited about its application in the fields of medicine, space technology, environmental science, and even weapons manufacturing. 3 In the field of medicine, nanoscale machines or particles have the potential to travel through the human body, targeting certain viruses or destructive cells in order to deliver medication directly to unhealthy areas. Nanotechnology is already being explored in the field of space technology, as a way to produce ultra-lightweight and durable materials for use in space vessels. In the area of environmental science, nanotechnology has the ability to provide environmental monitors for pollution levels. Tiny, machine-like probes could potentially remove the finest contaminants from water supplies and air as well as continously measure and mitigate pollutants in the environment. 4 However, it should be noted that these machines have not been made at this time. Although these applications of nanotechnology certainly represent progress in the fields of medicine, space travel, and environmental science, nanotechnology - like any other emerging technology - also poses certain risks to the environment and human health. 5 For example, if nanotechnology has the ability to invade the human body and destroy harmful cells, it seems reasonable to assume that it could also be used in weapon format to do the exact opposite. Furthermore, if we can now use nanotechnology to make virtually indestructable and lightweight building materials, then it is almost certain that those materials could also be applied to weapons manufacturing. With these realizations in mind, the U.S. Environmental Protection Agency and the National Nanotechnology Coordination Office have identified some basic research needs for the field of nanotechnology and have encouraged building a broader community of interdisciplinary scientists to foster better understand and manage this growing field. 6 Application of graphene Graphene sheets Graphene can be understood as a single layer of carbon atoms arranged in a chicken-wire like lattice, which can be embedded into other materials in order to alter certain material attributes (Figures 2 and 3). If embedded in materials like plastics, graphene sheets might impart remarkable local stiffness and strength (graphene sheets are stronger than steel and as stiff as diamonds) due to the bonds between the carbon atoms. While the stiffness, strength, toughness, and barrier properties of graphene make it an attractive material to work with, there are a variety of challenges that still 4

graphene oxide - may provide scaled up alternatives.

5 2.13 Nanotechnology and Sustainable Design need to be addressed. While graphene has potentially useful properties, it remains an open question as to whether it can be produced on a large scale, although working with chemically modified forms of graphene - like graphene oxide - may provide scaled up alternatives. 5 Like all new material technologies, further research on the topic and better communication between professions can certainly increase the understanding and potential use of nanotechnology and materials like graphene - especially in the field of sustainable design. Figure 5: Solar Panels with Thin Film Figure 6: Sheet of Synthentic Graphite Figure 7: Microscopic image of Graphene Sheets O OH O O OH O OH O OH Figure 8: Graphene Oxide molecular structure. Currently, about eight hundred million tons of graphite is available on earth per the United States Geological Survey. Manipulating graphite into graphene sheets would afford the ability to significantly alter our building materials and shape the way we build. Recently, Dr. Ruoff and his team produced composite materials, including graphene-polystyrenes, which showed excellent dispersion of the individual platelets and suggested improved mechanical properties. By introducing graphene sheets into materials like polystyrene and various polymers, is is in principle possible to create strong, stiff, lightweight building materials. These have the potential to reduce the amount of energy needed in construction and material production, therefore helping architects achieve the goals of sustainable development (Figure 4). Graphene sheets can also be inserted into other materials such as paint or glass. In thin films graphene can enhance certain material attributes and increase building performance (Figure 7). Since graphene sheets are good electrical conductors, they can potentially be inserted into different exterior building materials such as windows, paints, or other surfaces in order to create a new kind of solar cell coating. Due to the fact that a monolayer of graphene absorbs about 2.5% of visible light, graphene-embedded thin films would essentially act as thicker thin films that would offer about 90% light transmittance, overcoming the problem of porosity that traditional thin films face (Figure 5). Graphene-based thin films would therefore increase the solar transmittance of thin films, allowing more natural light to filter into the building space, decreasing the amount of artificial light needed and thereby increasing building performance. These new graphene-based thin films would mitigate the use of indium tin oxide, an expensive and scarce material used in traditional thin films, and further support the goals of sustainability by conserving a waning global resource. The same kind of graphene-embedded technology could potentially be applied to windows: a thin film of graphene coating glass panes could essentially turn a regular window or wall 5

6 II-Strategies Technology store an electrical charge by physically separating positive and negative ions. The surface areas of the materials inside an ultracapacitor determine in part how much electricity can be stored, which is why graphene is so ideal for this application. Capacitors typically store a smaller amount of energy than a battery, yet have the advantage in that they can be charged and discharged nearly half a million times before the charge per cycle starts to significantly decline (Figure 10). Ultracapacitors share this characteristic long lifespan, but can also store more energy than a typical capacitor. Ultracapacitors can charge and discharge large amounts of stored electrical energy very quickly, unlike a battery, which releases a smaller amount of energy very slowly. This makes ultracapacitors extremely useful in starting items like electric vehicles and even some wind turbines, because they provide the initial burst of energy necessary to get things moving. Figure 9: Blobwall Pavillion with lightweight, polymer-infused bricks used as sustainable building materials of glass into the base structure for a solar cell, with other components such as photovoltaic material added. Although these types of material manipulations have yet to be fully tested, the possibility of turning something as low-tech as a coat of paint or a pane of glass into a solar collector reveals why designers should further explore the implications of nanotechnology in sustainable design. Graphene oxide In addition to using graphene as a sheet embedded within other materials, chemists have been exploring how to convert graphite into graphene oxide. Graphene oxide, a material that dissolves when suspended in water to become individual chemically modified graphene sheets, can be used to create a highly flexible, very strong paper-like material (Figure 8). After the water has been filtered out from the suspended graphite/water mix, the film is composed of stacked graphene oxide sheets that can then be peeled away from the filter, and stacked to create a new, paper-like material. This thin paper material provides versatility because of its ability to undergo further chemical modification and adjustment of its physical and chemical properties, thereby expanding the potential applications of graphene. 6 These types of graphene-based papers could eventually be used in a variety of applications that would help materials scientists and designers achieve sustainable goals. For example, these graphene-based papers could be used to create protective membranes and coatings, or used to create super lightweight, strong, and flexible materials for buildings and wind turbines (Figure 9). Providing designers with the ability to use durable, lightweight materials, and enabling the creation of more wind turbines through a less energy-intensive process, proves how the modification of graphite and graphene sheets by nanotechnology will be playing a significant role in the ongoing development of sustainable design. However, it will take time before designers will see building materials significantly altered by nanotechnology. Since nanoscale materials such as graphene oxide are still in the early stages of research and development, these graphenebased papers will most likely be used first in niche applications where cost is less a factor (such as aerospace engineering) before being applied to building materials. Graphene Ultracapacitors One of the earliest applications for graphene and graphene sheets will be their use in graphene-based ultracapacitors. Ultracapacitors, which are often compared to batteries, An ultracapacitor can be understood as the pairing of two porous electrodes that are suspended within an electrolyte (a salt dissolved in water or other solvents). Between the electrodes is a thin membrane known as a separator. The separator allows the ions in the electrolyte to flow directly between the electrodes, but blocks the flow of electrons. When a voltage is applied to the ultracapacitor, electrons flow from one electrode to the other electrode through the external circuit. To balance the electrical charge that builds up on the electrodes, negative ions in the electrolyte flow to the positively charged electrode and the positive ions flow to the negatively charged electrode. As a storage device, the ultracapacitor relies both on the surface area of the electrode material to capture as many ions as possible and on its conductivity to efficiently transport the electrons. Using layers of graphene as the electrode material of the ultracapacitor may provide an optimal storage solution because the surface area of graphene is extraordinarily high and its electrical conductivity is superb: the higher the surface area that is well contacted by the electrolyte, the more charge can be stored. 8 The potential to increase the performance of ultracapacitors with a high-surface area material like graphene could signify a major advance in the world of sustainable design. A current problem with many forms of clean energy is that they typically generate the highest amount of energy at times out of sync to the highest load. For example, wind turbines located in a hot climate produce more energy at night, when the wind typically blows harder, but less during the day when houses typically need more energy to run an HVAC system. Ultracapacitors would have the ability to store 6

2.13 Nanotechnology and Sustainable Design Figure 10: Comparison - Ultracapacitors and Batteries Figure 11: Composition of an Ultracapacitor Figure 12: Windfarm built with lightweight materials some

Similarly, solar panels perform more efficiently in relatively cooler conditions, when excessive heat from the sun does not impede operation of the photovoltaic cells.

performance by allowing electrical energy to be stored so that it can be used when most needed. Electrical Energy St

7 2.13 Nanotechnology and Sustainable Design Figure 10: Comparison - Ultracapacitors and Batteries Figure 11: Composition of an Ultracapacitor Figure 12: Windfarm built with lightweight materials some of the energy produced at night so that it could be used during the hotter part of the day. Similarly, solar panels perform more efficiently in relatively cooler conditions, when excessive heat from the sun does not impede operation of the photovoltaic cells. Although these methods of capturing clean energy are undoubtedly a significant part of sustainable design, the addition of ultracapacitors to wind and solar applications can increase their performance by allowing electrical energy to be stored so that it can be used when most needed. Electrical Energy Storage (EES) is currently targeted by the U.S. Department of Energy as the most critical area for technological advances for large scale implementation of renewable energy. 9 Graphene based ultracapacitors could be used in combination with fuel cell technology to increase the performance of the hybrid ultracapacitor system even further. Increasing the performance of ultracapacitors with graphene and using these ultracapacitors in application with other clean energy systems, gives nanotechnology a significant role to play in the development of sustainable design. Conclusion The potential for materials based on graphene, graphene oxide, and other chemically modified graphene sheets in the creation of new building materials, as well as the development of graphene ultracapacitors and energy storage systems has helped link the worlds of nanotechnology and sustainable design. Although much remains to be explored in the world of nanotechnology and the possible uses of graphene, many possible applications of new materials and nanotechnology in the fields of architecture and sustainable design are apparent. The U.S. Environmental Protection Agency predicts that, In 30 years, nanotechnology is likely to be pervasive and incorporated into all aspects of daily life. We believe that this emerging technology can be developed responsibly with a full appreciation of its health and environmental impacts. 10 While designers and scientists alike face the same critical issues of global warming and waning global resources, new findings in the world of materials science and nanotechnology offer possibilities for everything from medical advancesand weapons technology to building materials and energy storage (Figure 12). New materials and devices will eventually have a significant impact on the sustainable design of buildings, but that progress can only be made through a constant exchange between the fields of architecture, science, and engineering. Perhaps our greatest challenge to the field of sustainable design is therefore still something as simple as communication. Notes 1. Center for Responsible Nanotechnology. What is Nanotechnology. org/whatis.htm 2. The following information about graphene and the application of nanotechnology to sustainable design has been collected and transcribed from the following presentation: Rod Ruoff. Nano materials. Presentation addressed to the Seminar in Sustainability, October 15, School of Architecture, University of Texas at Austin. 3. U.S. Environmental Protection Agency and National Nanotechnology Coordination Office. Nanotechnology and the Environment. vii 4. Ibid. page 1 5. Rod Ruoff. News and Views: Calling all Chemists. Nature Nanotechnology. Vol 3. January U.S. Environmental Protection Agency and National Nanotechnology Coordination Office. Nanotechnology and the Environment. 7. University of Texas Cockrell School of Engineering. Carbon Materials Pioneer joins Mechanical Engineering Department. July 25, articles/ /index.cfm 8. Allen, Greg. How an Ultra Capacitor Works. October 23, Electrical Energy Storage as quoted in Rod Ruoff, Nano materials. Presentation addressed to the Seminar in Sustainability, October 15, School of Architecture, University of Texas at Austin. 10. U.S. Environmental Protection Agency and National Nanotechnology Coordination Office. Nanotechnology and the Environmental. viii 11. Biography from University of Texas at Austin Cockrell School of Engineering. engr.utexas.edu/faculty/bios/ruoff.cfm Figures Figure 1: The Atomium in Brussels. Builti in 1958 for an Industrial Exhibition. Graphene Polymer. com/2006/07/20/scientists-turn-graphite-intographene/ 7

8 II-Strategies Technology Figure 2: Graphene Embedded in Polymer Matrix. scientists-turn-graphite-into-graphene/ Figure 3: Concrete Balloon with Polymer Membrane. avb-core77 Figure 4: Solar Panels with traditionl Thin Film. Figure 5: Sheet of Synthetic Graphite. Photo by Rod Ruoff. Figure 6: TEM image of Graphene Sheets. Image by Rod Ruoff. Figure 7: Graphene Oxide. Image from Heyong He. Figure 8: Blobwall Pavillion with lightweight polymer-infused bricks. com/wp-content/uploads/2007/09/nanotechnology.jpg Figure 9: Technology Comparison. Adapted from Maxwell, January Figure 10: Composition of an Ultracapacitor. Figure 11: Clean Energy Wind Farm. wximagenew/m mikecarter/23.jpg Biography Dr. Rod Ruoff is a professor at the University of Texas at Austin Cockrell School of Engineering, and holds the Cockrell Family Regents Chair of Engineering #7. He earned his Pd.D. in chemical physics from the University of Illinois at Urbana-Champaign in 1988, and joined The University of Texas at Austin faculty in Dr. Ruoff is recognized as a leader in understanding the mechanical, chemical, and physical properties of carbon structures such as carbon nanotubes and graphene. His recent research includes developing graphenebased materials by chemically breaking down graphite to produce single layers ( graphene ). His research team has also produced a transparent, but electrically conductive, thin film consisting of glass with embedded graphene sheets. Other areas of interest to Dr. Ruoff include the global environment and energy, the chemical and physical properties of nanostructures, nanorobotics, and new tools for biomedical research. 11 8

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