Materials that heal themselves are going bigtime. Scientists have cooked up a chemical concoction that can patch a 9-millimeter-wide hole in a sheet of plastic, a self-repair orders of magnitude larger than ever demonstrated before. The finding could lead to new kinds of airplane wings and spacecraft components that can repair themselves midflight.“It’s exciting; I think it’s a big step forward in being able to autonomously heal structures without intervention,” says University of Michigan, Ann Arbor, mechanical engineer Ellen Arruda. She calls the researchers’ scheme “the polymer equivalent of a blood clot.”Complex life could never have evolved without the ability to heal itself. When an animal suffers a puncture wound, for example, compounds flow from blood vessels to the wound site, where they feed the growth of new tissue to fill the damaged area. The process, however, requires a vascular system to deliver the needed components. 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In one such scheme, narrow channels similar to animal blood vessels deliver compounds that seal small fissures in a material made of fiberglass and polymer resins. So far, such systems have only repaired fractures so small that opposite sides of the wound nearly touch. When the damage site is larger—say, the size of a bullet hole—liquid compounds tend to leak out before they can form a seal.Now, scientists and engineers from the University of Illinois, Urbana-Champaign, report a two-part solution to fill such big voids. In the first step, the researchers filled two parallel 330-micrometer-diameter channels with two mixtures of organic molecules known to combine to form solid and semisolid structures; the mixtures were dyed red and blue. The researchers then embedded the channels in a 3-millimeter-thick plastic sheet, laid the sheet flat and punctured it, causing the red and blue mixtures to flow into the nearly circular hole and mingle with each other. A catalyst joined the two compounds into cross-linked fibers, resulting in a semisolid gel that filled the hole from the outside in.The gel’s fibers formed a netlike scaffold that set the stage for the second step in the healing by supporting a third compound that flowed in from the channels. This compound reacted to form solid crisscrossing polymers, which filled in the hole and surrounding cracks with a cloudy, purplish substance. The polymer made a seal with the original clear plastic and restored most of the material’s strength.“What we did here was what I like to call repair by regrowth,” says chemist Jeffrey Moore, a research team member. He says the critical insight was choosing chemicals that react at different rates, so the net could form before polymerization started. “Timing is everything here,” Moore says.Moore and his colleagues report online today in Science that their scheme can repair a hole nearly 1 centimeter in diameter, with cracks radiating over an area 3.5 centimeters in diameter. This is about 100 times larger than any previously self-repaired defect in a nonliving material, Moore says. A system like theirs could someday be part of self-healing airplane wings or spaceship components that include composite materials made of multiple constituents. Humans cannot easily repair such components during flight.But Arruda says that unlike in a human wound, which is eventually repaired with the same kind of tissue that was originally lost, the makeup of Moore’s team’s polymer differs from that of the original plastic. As a result, the repaired material is somewhat weaker than an intact sheet; in tests, it can absorb only about 62% as much energy from an impact. The researchers will also need to show that their repairs hold up under a range of real-world conditions like varying humidity and extreme temperatures, she says.
Go back to the enewsletterA group of 60 guests were treated to lunch with the team from Dream Cruises and internationally-acclaimed Australian chef Mark Best this week. Sydney harbour provided a sparkling backdrop for the lunch event held at the Quayside Room of the Museum of Contemporary Art Australia.Vice President Brigita Devries shared images of the newest member of the Dream Cruises fleet, Explorer Dream, along with plans for the upcoming Australian and New Zealand deployment.Chef Mark BestExplorer Dream will commence of a series of itineraries north from Sydney to the Sunshine Coast in Queensland before crossing the Tasman Sea where she will cruise from Auckland taking in ports on the North and South Islands. The relocation cruises between Sydney and Auckland have proved very popular for both Australian and New Zealand markets. In the new year, Explorer Dream will head back to Sydney to commence a brief series of Tasmanian itineraries, before returning to Asia via Indonesia, Singapore, Kota Kinabalu, the Philippines, Hong Kong and finishing in Keelung – Taiwan.Regarding the onboard ambience, Devries said, “the onboard lifestyle and culture will resonate with the Australian way of life…Relaxed and casual, yet offering the highest level of service standards.”Dining onboard Explorer Dream will be a treat for any ‘foodie’, with a broad offering of international flavours. Among them is Chef Mark Best’s Seafood Grill – the third such restaurant at sea for Chef Best who has partnered with Dream Cruises since the brand’s inception almost three years ago. His signature restaurants feature on both Genting Dream and World Dream.Chef Best’s Beetroot Salad with Goat Cheese, Cherry and Native Pepper BerryBest aims to “revolutionise ocean dining by bringing the extraordinary produce of Australia to a unique outdoor setting – Seafood Grill by Mark Best – on Explorer Dream”.Guests can enjoy uniquely styled dishes with Australian influences, while enjoying the relaxing ambient surrounds and dining under the southern stars.Also on offer at Seafood Grill will be a Champagne Brunch menu designed by Chef Best, where guests can choose from Sourdough toast with Vegemite to a full Aussie Breakfast. Each dish will be accompanied by a glass of Champagne or beer, along with coffee, tea & chilled juices.During Explorer Dream’s local deployment, Chef Best will also host a series of Market to Table experiences, whereby guests will have the opportunity to join Best in visiting local markets, meet resident farmers face to face and source local produce at various ports. From there guests will then be treated to an exclusive and immersive cooking class and lunch where Chef Best will create and demonstrate a selection of dishes from the produce sourced at the markets.Chef Best’s Red Braised Wagyu Short Rib with Mustard Cabbage and Olive“This is an extraordinary experience for our guests to be able to connect with their inner ‘foodie passion’, learn about local produce and take away some expert cooking tips,” says Devries.Guests at the event were treated to a four-course culinary preview created by Chef Best, starting with Beetroot Salad with Goat Cheese, Cherry and Native Pepper Berry, followed by Hot and Sour Soup with Native Australian Freshwater Crayfish and Red Braised Wagyu Short Rib with Mustard Cabbage and Olive. Dessert was Sauternes Custard with Osmanthus Biscuits.Lead image: Dream Cruises team from left: Aaron Eilers, Inside Sales Manager; Leonie Fraser, Marketing Manager; Chef Mark Best; Brigita Devries, Vice President and Andrew Loving, Sales Manager – NSW & ACT.Go back to the enewsletter