Nancy Sottos is an American

materials scientist Materials science is an interdisciplinary field of researching and discovering materials. Materials engineering is an engineering field of finding uses for materials in other fields and industries. The intellectual origins of materials scien ...

and professor of

engineering Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...

. She is the Swanlund Endowed Chair and the head of the Department of Materials Science and Engineering at the

University of Illinois at Urbana–Champaign The University of Illinois Urbana-Champaign (UIUC, U of I, Illinois, or University of Illinois) is a public land-grant research university in the Champaign–Urbana metropolitan area, Illinois, United States. Established in 1867, it is the f ...

. She is also a co-chair of the Molecular and Electronic Nanostructures Research Theme at the

Beckman Institute for Advanced Science and Technology The Beckman Institute for Advanced Science and Technology is a unit of the University of Illinois Urbana-Champaign dedicated to interdisciplinary research. A gift from scientist, businessman, and philanthropist Arnold O. Beckman (1900–2004) and ...

. She heads the Sottos Research Group. Sottos studies deformation and

failure Failure is the social concept of not meeting a desirable or intended objective, and is usually viewed as the opposite of success. The criteria for failure depends on context, and may be relative to a particular observer or belief system. On ...

of materials at mesoscale,

microscale The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...

, and

nanoscale Nanotechnology is the manipulation of matter with at least one dimension sized from 1 to 100 nanometers (nm). At this scale, commonly known as the nanoscale, surface area and quantum mechanical effects become important in describing propertie ...

levels, and has made significant contributions in

self-healing material Self-healing materials are artificial or synthetically created materials, substances that have the built-in ability to automatically repair damages to themselves without any external diagnosis of the problem or human intervention. Generally, mate ...

, advanced polymer matrix composites, and

thin films A thin film is a layer of materials ranging from fractions of a nanometer ( monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many ...

. She is a pioneer in the area of adaptive materials, creating the first self-healing

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

s with Jeffrey S. Moore, Scott R. White, and others as of 2000.

Education

Nancy Sottos studied

mechanical engineering Mechanical engineering is the study of physical machines and mechanism (engineering), mechanisms that may involve force and movement. It is an engineering branch that combines engineering physics and engineering mathematics, mathematics principl ...

at the

University of Delaware The University of Delaware (colloquially known as UD, UDel, or Delaware) is a Statutory college#Delaware, privately governed, state-assisted Land-grant university, land-grant research university in Newark, Delaware, United States. UD offers f ...

, receiving her B.S. in 1986 and her Ph.D. in 1991. She also participated in women's varsity track and field and was active on the Athletic Governing Board and the Commission on the Status of Women.

Career

Sottos accepted a faculty position in the

College of Engineering Engineering education is the activity of teaching knowledge and principles to the professional practice of engineering. It includes an initial education ( Dip.Eng.)and (B.Eng.) or ( M.Eng.), and any advanced education and specializations tha ...

at the

in 1991. She was a member of the Department of Theoretical and Applied Mechanics, eventually serving as its interim head. In 2006 she joined the Department of Materials Science and Engineering. She was named the Donald B. Willet Professor of Engineering of the Department of Materials Science and Engineering and a University Scholar. She was appointed co-chair of the Molecular and Electronic Nanostructures Research Theme at the

in 2004, succeeding Jeffrey Moore. Sottos has been active on the editorial boards of ''

Experimental Mechanics ''Experimental Mechanics'' is a peer-reviewed scientific journal covering all areas of experimental mechanics. It is an official journal of the Society for Experimental Mechanics and was established in 1961, being published monthly. From 1983 to 20 ...

'' (1999–2006) and '' Composites Science and Technology'' (2002–present). She is a Fellow of the

Society of Engineering Science A society () is a group of individuals involved in persistent social interaction or a large social group sharing the same spatial or social territory, typically subject to the same political authority and dominant cultural expectations. Soc ...

(2007) and Fellow of the Society for Experimental Mechanics (2012). She was the president of the

Society for Experimental Mechanics Society for Experimental Mechanics (SEM) is a professional organization for engineers and scientists studying the design and implementation of experiments to characterize materials, structures, and systems. Formed in 1943 as the Society for Experim ...

for 2014–2015. She was elected a member of the

National Academy of Engineering The National Academy of Engineering (NAE) is an American Nonprofit organization, nonprofit, NGO, non-governmental organization. It is part of the National Academies of Sciences, Engineering, and Medicine (NASEM), along with the National Academ ...

in 2020 for contributions to the design and applications of self-healing and multifunctional materials.

Research

Self-healing polymers

Sottos helped develop the first polymeric

with colleagues including Jeffrey Moore and Scott White. The work was completed in 2000, and published in ''Nature'' in 2001. They have shown that microencapsulated healing agents can polymerize to heal areas of damage such as cracks smaller than a human hair. Their approach was to develop a polymeric matrix which involved both a reactive liquid healing agent and a

catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

. While undamaged, these were kept structurally separate. The liquid agent was contained inside non-reactive reservoirs within the material, while the catalyst was dispersed throughout the polymer. Once the material was damaged and a crack occurred, the reservoirs broke open, and

capillary action Capillary action (sometimes called capillarity, capillary motion, capillary rise, capillary effect, or wicking) is the process of a liquid flowing in a narrow space without the assistance of external forces like Gravitation, gravity. The effe ...

caused the liquid agent to disperse into the damaged area, where it reacted with the catalyst and solidified to seal the crack. They have studied both the use of a contained healing agent and a dispersed catalyst, and the use of a dispersed healing agent and a contained catalyst. Using

dicyclopentadiene Dicyclopentadiene, abbreviated DCPD, is a chemical compound with formula . At room temperature, it is a white brittle wax, although lower purity samples can be straw coloured liquids. The pure material smells somewhat of soy wax or camphor, with ...

(DCPD) and

Grubbs' catalyst Grubbs catalysts are a series of transition metal carbene complexes used as catalysts for olefin metathesis. They are named after Robert H. Grubbs, the chemist who supervised their synthesis. Several generations of the catalyst have also been develo ...

in an

epoxy Epoxy is the family of basic components or Curing (chemistry), cured end products of epoxy Resin, resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide fun ...

matrix, polycyclopendiene was formed to seal cracks, recovering up to 75% of the original fracture toughness. They have since developed a catalyst-free self-healing system using

chlorobenzene Chlorobenzene (abbreviated PhCl) is an aryl chloride and the simplest of the chlorobenzenes, consisting of a benzene ring substituted with one chlorine atom. Its chemical formula is C6H5Cl. This colorless, flammable liquid is a common solvent a ...

microcapsules for the active solvent. Cracking releases the chlorobenzene solvent, which washes pockets of unreacted epoxy monomers into the crack. There polymerization occurs to fill the crack. Tests of the catalyst-free self-healing system have restored up to 82% of the fracture’s strength. Both approaches are examples of autonomous self-healing, in which the repair mechanism is triggered by the occurrence of damage. Materials that autonomously self-repair can retain their structural integrity under stress and last longer.

Microvascular networks

Sottos has also focused on the design of microvascular networks for the distribution of active fluids in autonomous materials systems. Such designs offer possibilities for "self-healing, regeneration, self-sensing, self-protection and self-cooling" properties, similar to those of biological systems. To create such a material, a three-dimensional pattern of organic inks is laid down, and the interstitial pores in the pattern are filled with epoxy resin. The polymer is left to cure, and then the ink is removed. The spaces it leaves form well-defined, three-dimensional microchannel networks, which can be filled with healing agents. With this design, a greater supply of self-healing agent can be incorporated into the created material. The process of constructing such a material is very complex. This approach has been used to support repeated self-healing in fiber-reinforced composite materials. An epoxy resin and a hardener can be stored in adjacent overlapping microchannel networks. Damage to the network structure causes the healing agents to autonomously mix and polymerize, effectively glueing together the damaged area. Healing was reported to occur at nearly 100 percent efficiency over multiple fracture cycles. This approach has potential applications in the design and use of fiberglass and other composite materials for structures including airplanes and wind turbines. It is reported that microvascular networks can support healing of larger-scale damage, up to 11.2 mm.

Self reporting materials

A team led by Sottos and Wenle Li has developed polymeric structural materials that can indicate the presence of damage by changing color. Such self-reporting materials can act as a color changing warning system. The researchers created a polymer that contained microcapsules of epoxy resin and PH-sensitive dye. Damage to the polymer causes the capsules to break open and the epoxy and dye to mix. The resulting reaction causes the color of the material to change from yellow to red. The deeper the damage, the more intense the color change. This autonomous visual indicator can enable engineers to detect mechanical damage and intervene before a structure is compromised.

Smart materials

Sottos is involved in the development of self-sensing, mechano- and thermo- chemically active polymeric materials. These

smart inorganic polymers Smart inorganic polymers (SIPs) are hybrid or fully inorganic polymers with tunable (Smart polymer, smart) properties such as stimuli responsive physical properties (shape, conductivity, rheology, bioactivity, self-repair, sensing etc.). While orga ...

belong to the class of

smart materials Smart materials, also called intelligent or responsive materials, are designed materials that have one or more properties that can be significantly changed in a controlled fashion by external stimuli, such as stress, moisture, electric or magnet ...

, exhibiting stimuli-responsive functions. A specific input stimulus such as a change in force or temperature can trigger a desired change in one or more properties of the polymer.

Sensitivity to mechanical force

Mechanical force can provide a source of energy used by a desired chemical reaction. To create such materials, mechanically sensitive chemical groups called mechanophores are built into the chemical structure of the polymer. In one set of experiments, researchers used

spiropyran A spiropyran is a type of photochromic organic chemical compound, characterized by their ability to reversibly switch between two structural forms—spiropyran and merocyanine—upon exposure to light or other external stimuli. This reversible trans ...

molecules to detect mechanical stress. The spiropyran (SP) mechanophore was covalently bonded into a stretchy barbell-shaped polymer called polymethyl acrylate (PMA) and a small, glasslike bead-shaped polymer called polymethyl methacrylate (PMMA). SP transformed into a fluorescent merocyanine (MC) form in response to stress. The orientation of the MC subspecies relative to the tensile force could be characterized based on the anisotropy of the fluorescence polarization. Spiropyrans were normally colorless but turned vivid shades of red or purple when stressed. They also fluoresce. The researchers have also demonstrated that mechanical force can power a chemical response in the polymer, changing the covalent bonding. A next step in this research is to explore the potential to use mechanochemical reactions to activate chemical pathways in materials to respond to shock waves in positive ways, by altering or enhancing properties of the material.

Thermal sensitivity

Another area of research focuses on the prevention of

thermal runaway Thermal runaway describes a process that is accelerated by increased temperature, in turn releasing Thermal energy, energy that further increases temperature. Thermal runaway occurs in situations where an increase in temperature changes the cond ...

in batteries. The researchers coated the

anode An anode usually is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, which is usually an electrode of the device through which conventional current leaves the devic ...

or separator layer of the battery with microspheres sensitive to heat. An increase in temperature causes the microspheres to melt, blocking transmission of the lithium ions and causing the battery to shut down. Microspheres of both

polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bott ...

and

paraffin wax Paraffin wax (or petroleum wax) is a soft colorless solid derived from petroleum, coal, or oil shale that consists of a mixture of hydrocarbon molecules containing between 20 and 40 carbon atoms. It is solid at room temperature and melting poi ...

were tested with CR2032 Li-ion batteries and demonstrated both successful operation of the battery at normal temperatures and shutdown of the battery at temperatures below those at which the battery's separator would become damaged.

Thin films

Sottos has also been involved in research on

thin film A thin film is a layer of materials ranging from fractions of a nanometer ( monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many ...

s, and the measurement techniques for dynamic interfacial energy measurements of adhesion in multilayer thin films.

Awards

Sottos has received numerous awards for her teaching and research. These include: * The University of Delaware Presidential Citation for Outstanding Achievement (2002) * The Hetényi Award from the

(2004) for J. Wang, R. L. Weaver, N. R. Sottos “A parametric study of laser induced thin film spallation” ''Experimental Mechanics'' 42, no. 1 (2002): 74–83. * The Hetényi Award from the

(2016) for E.M.C. Jones, M.N. Silberstein, S.R. White, N.R. Sottos “In Situ Measurements of Strains in Composite Battery Electrodes during Electrochemical Cycling” ''Experimental Mechanics'' 54, no. 6 (2014): 971–985. * Scientific American's SciAm 50 Award (2008) * The M.M. Frocht and B.J. Lazan awards from the

(2011) *

Tau Beta Pi The Tau Beta Pi Association (commonly Tau Beta Pi, , or TBP) is the oldest engineering honor society and the second oldest collegiate honor society in the United States. It honors engineering students in American universities who have shown a ...

Daniel C. Drucker Eminent Faculty Award (2014) *The C.E. Taylor award from the

(2020) *

(2020) *The W.M. Murray award and lecture from the

(2021) *

American Academy of Arts and Sciences The American Academy of Arts and Sciences (The Academy) is one of the oldest learned societies in the United States. It was founded in 1780 during the American Revolution by John Adams, John Hancock, James Bowdoin, Andrew Oliver, and other ...

(2022) *

National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...

(2022)

Culture

Self-healing materials created by Sottos and others at the Beckman Institute were included in the exhibit ''Science Storms'' at the Museum of Science and Industry in

Chicago Chicago is the List of municipalities in Illinois, most populous city in the U.S. state of Illinois and in the Midwestern United States. With a population of 2,746,388, as of the 2020 United States census, 2020 census, it is the List of Unite ...

in 2010.

References

{{DEFAULTSORT:Sottos, Nancy 21st-century American chemists American materials scientists American women chemists Living people University of Illinois Urbana-Champaign faculty Year of birth missing (living people) Fellows of the Society for Experimental Mechanics 21st-century American women scientists