Highlighted by Discovery Channel News MIT Technology Reviews

1. March 2010 • Highlighted by • Discovery Channel News • MIT Technology Reviews • Materials Research Society Bulletin (USA) • + several others

2. Why aroused broad interest • Nature shows stiff and strong nanocomposites • Nacre, silk, etc • Drastically exceed the properties of the present day synthetic polymeric nanocomposites • Problem: how to prepare them in technically relevant methods • Real bottleneck! • Biomimetics • Learn the essential aspects of natural materials and realize them in new ways that allow mass production • Not easy • Extensive efforts have been to mimic nacre • Work in the lab, too slow or expensive for “real life” • We show the first route for practical nacre-mimetic materials • Painting, paper-making, spraying, doctor-blading, etc…. • The innovation is conceptual, works for a large set of materials How?

3. What could be a daydream engineering material • High modulus • Stiff • High strength • Strong • Tough • Does not break eg. upon deformations • Cracks do not grow easily • Small density • Light weight construction • Easily processible at large scale • Economic • Safe • Porcellain • Stiff and strong • Not tough: cracks propagate easily • Rubber • Tough: elastic and cracks do not propagate • Not stiff and strong Difficult! Standard practice: Aim to combine properties by multicomponent composites

4. Examples of classic composites • Light weight metal alloys, such as aluminium and duralunium alloys • Eg. airplanes, telecommunication, … • Widely used • Polymer composites • Add reinforcing fibers and fillers to polymers • Glass fibers, carbon fibers, Kevlar fibers etc • Some improvement achieved • Polymer nanocomposites • Add reinforcing nanofibers or nanoplates to polymers • Carbon nanotubes, nanoclay, cellulose nanofibers • Some improvements achieved • Improvement observed, why worry ? However: Biological materials shows how to prepare drastically improved properties using nanocomposites

5. Mollusc Nacre as a model for daydream material • Stiff • Modulus 70 GPa • vs Aluminiun alloy • Strong • Strength 80-130 MPa • vs cast iron • Extremely tough • Lightweight • Synthesized under mild conditions • CaCO3 plates • Thickness 0.5 mm, width 20-30 mm • Polymer “glue” in between • Thin layers (only!) • Why • Thin reinforcing platelets reinforce • In deformation the cracks cannot easily propagate, deflect, consume energy crack

6. Nacre cannot be produced industrially: Can one mimic nacre ? • Sequential depositions of inorganic platelets and polymers • Feasible in the lab, but slow! • Can take a week to deposit • Not feasible in bulkproduction Kotov et al, Nature Mat 2003 2 413 Kotov et al, Science_2007 318 80 Studart et al Science_2008 319 1069 • Ice templating • Energy consuming • Feasible in the lab • Not feasible in production Deville et al Science 2006 311 515 Ritchie et al, Science 2008 322 1516

7. We found a simple scientific concept for self-assembly which opens the routes for production • Reinforcing units coated with soft polymers etc • Subsequent self-assembly • Simple and facile processing by technologically relevant ways Walther, Bjurhager, Malho, Ruokolainen, Pere, Berglund, Ikkala, Nano Letters, asap, (2010) Walther, Bjurhager, Malho, Ruokolainen, Pere, Berglund, Ikkala, submitted (2010) Walther, Laukkanen, Ikkala, patent pending .

8. Mechanical properties • Modulus Strength Density • (GPa) (Mpa) (g/cm3) • Our Nacre-mimetics 45 250 ca. 2.0 • Nacre 80 80-130 2.8 • Silk 10 1100 • (major ampullata) • Low density & good mechanical properties • Modulus Strength Density • (GPa) (Mpa) (g/cm3) • Steel 200 250-2000 7.8 • Al alloy 70 410 2.8 • Polypropylene 1.5-2 20-80 1.5 Walther, Bjurhager, Malho, Ruokolainen, Pere, Berglund, Ikkala, Nano Letters, asap, (2010) Walther, Bjurhager, Malho, Ruokolainen, Pere, Berglund, Ikkala, submitted (2010) Walther, Laukkanen, Ikkala, patent pending .

9. Lessons from the nature Classic approach Our biomimetic approach Reinforcement Polymer Modulus = 0.9 GPa Strength = 20 MPa Nanoclay composites were Introduced by Toyota Ltd for car bumpers Modulus = 45 GPa Strength = 250 MPa

10. High shielding capacity against fire • See a separate film • Protects against ca. 2000 oC

11. Very low gas permeability • Out nacre mimetic materials shows 0.325 cm3 mm/m2/day/atm for oxygen transport even at high humidity (80%RH) • Painted layers! • One of the lowest known

12. Next... • A general principle : has been extended/is being extended a large variety of reinforcing materials and polymers, also fibers! • Need • Improve still the toughness • Demonstrate bulk materials and laminates • Even if we are beginning to understand a glimpse how nanocomposites should be designed, we understand as yet very little still the practical applications • Search collaborations for product ideas and joint efforts for products • Lightweight construction: • Laptops, mobiles, airplanes, aerospace, • Low gas permeation • Organic electronics, packaging • Heat/fire shielding • Aerospace, fireproof clothes, smart textiles Walther, Bjurhager, Malho, Ruokolainen, Pere, Berglund, Ikkala, Nano Letters, asap, (2010) Walther, Bjurhager, Malho, Ruokolainen, Pere, Berglund, Ikkala, submitted (2010) Walther, Laukkanen, Ikkala, patent pending .