This waffled, greyish thing may not look like much but scientists are hopeful that it can be useful as a health sensor in athletic shoes and elsewhere. A March 6, 2020 news item on Nanowerk describes the work in more detail (Note: Links have been removed),
Researchers have utilized 3D printing and nanotechnology to create a durable, flexible sensor for wearable devices to monitor everything from vital signs to athletic performance (ACS Nano, “3D-Printed Ultra-Robust Surface-Doped Porous Silicone Sensors for Wearable Biomonitoring”).
The new technology, developed by engineers at the University of Waterloo [Ontario, Canada], combines silicone rubber with ultra-thin layers of graphene in a material ideal for making wristbands or insoles in running shoes.
Fabricating a silicone rubber structure with such complex internal features is only possible using state-of-the-art 3D printing – also known as additive manufacturing – equipment and processes.
The rubber-graphene material is extremely flexible and durable in addition to highly conductive.
“It can be used in the harshest environments, in extreme temperatures and humidity,” said Elham Davoodi, an engineering PhD student at Waterloo who led the project. “It could even withstand being washed with your laundry.”
The material and the 3D printing process enable custom-made devices to precisely fit the body shapes of users, while also improving comfort compared to existing wearable devices and reducing manufacturing costs due to simplicity.
Toyserkani, a professor of mechanical and mechatronics engineering, said the rubber-graphene sensor can be paired with electronic components to make wearable devices that record heart and breathing rates, register the forces exerted when athletes run, allow doctors to remotely monitor patients and numerous other potential applications.
Researchers from the University of California, Los Angeles and the University of British Columbia collaborated on the project.
One of my favourite kinds of science story is the one where scientists turn to a children’s toy for their research. In this case, it’s silly putty. Before launching into the science part of this story, here’s more about silly putty from its Wikipedia entry (Note: A ll links have been removed),
During World War II, Japan invaded rubber-producing countries as they expanded their sphere of influence in the Pacific Rim. Rubber was vital for the production of rafts, tires, vehicle and aircraft parts, gas masks, and boots. In the U.S., all rubber products were rationed; citizens were encouraged to make their rubber products last until the end of the war and to donate spare tires, boots, and coats. Meanwhile, the government funded research into synthetic rubber compounds to attempt to solve this shortage.
Credit for the invention of Silly Putty is disputed and has been attributed variously to Earl Warrick, of the then newly formed Dow Corning; Harvey Chin; and James Wright, a Scottish-born inventor working for General Electric in New Haven, Connecticut. Throughout his life, Warrick insisted that he and his colleague, Rob Roy McGregor, received the patent for Silly Putty before Wright did; but Crayola’s history of Silly Putty states that Wright first invented it in 1943. Both researchers independently discovered that reacting boric acid with silicone oil would produce a gooey, bouncy material with several unique properties. The non-toxic putty would bounce when dropped, could stretch farther than regular rubber, would not go moldy, and had a very high melting temperature. However, the substance did not have all the properties needed to replace rubber.
In 1949 toy store owner Ruth Fallgatter came across the putty. She contacted marketing consultant Peter C.L. Hodgson (1912-1976). The two decided to market the bouncing putty by selling it in a clear case. Although it sold well, Fallgatter did not pursue it further. However, Hodgson saw its potential.
Already US$12,000 in debt, Hodgson borrowed US$147 to buy a batch of the putty to pack 1 oz (28 g) portions into plastic eggs for US$1, calling it Silly Putty. Initially, sales were poor, but after a New Yorker article mentioned it, Hodgson sold over 250,000 eggs of silly putty in three days. However, Hodgson was almost put out of business in 1951 by the Korean War. Silicone, the main ingredient in silly putty, was put on ration, harming his business. A year later the restriction on silicone was lifted and the production of Silly Putty resumed. Initially, it was primarily targeted towards adults. However, by 1955 the majority of its customers were aged 6 to 12. In 1957, Hodgson produced the first televised commercial for Silly Putty, which aired during the Howdy Doody Show.
In 1961 Silly Putty went worldwide, becoming a hit in the Soviet Union and Europe. In 1968 it was taken into lunar orbit by the Apollo 8 astronauts.
Peter Hodgson died in 1976. A year later, Binney & Smith, the makers of Crayola products, acquired the rights to Silly Putty. As of 2005, annual Silly Putty sales exceeded six million eggs.
Silly Putty was inducted into the National Toy Hall of Fame on May 28, 2001. 
I had no idea silly putty had its origins in World War II era research. At any rate, it’s made its way back to the research lab to be united with graphene according to a Dec. 8, 2016 news item on Nanowerk,
Researchers in AMBER, the Science Foundation Ireland-funded materials science research centre, hosted in Trinity College Dublin, have used graphene to make the novelty children’s material silly putty® (polysilicone) conduct electricity, creating extremely sensitive sensors. This world first research, led by Professor Jonathan Coleman from TCD and in collaboration with Prof Robert Young of the University of Manchester, potentially offers exciting possibilities for applications in new, inexpensive devices and diagnostics in medicine and other sectors.
Prof Coleman, Investigator in AMBER and Trinity’s School of Physics along with postdoctoral researcher Conor Boland, discovered that the electrical resistance of putty infused with graphene (“G-putty”) was extremely sensitive to the slightest deformation or impact. They mounted the G-putty onto the chest and neck of human subjects and used it to measure breathing, pulse and even blood pressure. It showed unprecedented sensitivity as a sensor for strain and pressure, hundreds of times more sensitive than normal sensors. The G-putty also works as a very sensitive impact sensor, able to detect the footsteps of small spiders. It is believed that this material will find applications in a range of medical devices.
Prof Coleman said, “What we are excited about is the unexpected behaviour we found when we added graphene to the polymer, a cross-linked polysilicone. This material as well known as the children’s toy silly putty. It is different from familiar materials in that it flows like a viscous liquid when deformed slowly but bounces like an elastic solid when thrown against a surface. When we added the graphene to the silly putty, it caused it to conduct electricity, but in a very unusual way. The electrical resistance of the G-putty was very sensitive to deformation with the resistance increasing sharply on even the slightest strain or impact. Unusually, the resistance slowly returned close to its original value as the putty self-healed over time.”
He continued, “While a common application has been to add graphene to plastics in order to improve the electrical, mechanical, thermal or barrier properties, the resultant composites have generally performed as expected without any great surprises. The behaviour we found with G-putty has not been found in any other composite material. This unique discovery will open up major possibilities in sensor manufacturing worldwide.”
Dexter Johnson in a Dec. 14, 2016 posting on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers]) puts this research into context,
For all the talk and research that has gone into exploiting graphene’s pliant properties for use in wearable and flexible electronics, most of the polymer composites it has been mixed with to date have been on the hard and inflexible side.
It took a team of researchers in Ireland to combine graphene with the children’s toy Silly Putty to set the nanomaterial community ablaze with excitement. The combination makes a new composite that promises to make a super-sensitive strain sensor with potential medical diagnostic applications.
“Ablaze with excitement,” eh? As Dexter rarely slips into hyperbole, this must be a big deal.
The researchers have made this video available,
For the very interested, here’s a link to and a citation for the paper,
The lettuce we eat was cultivated from prickly lettuce, which is now considered a weed. That status may change if scientists at Washington State University (WSU) are successful with their research into the plant’s ability to produce rubber. From an April 6, 2014 WSU news release by Sylvia Kantor (also on EurekAlert),
Prickly lettuce, a common weed that has long vexed farmers, has potential as a new cash crop providing raw material for rubber production, according to Washington State University scientists.
Writing in the Journal of Agricultural and Food Chemistry, they describe regions in the plant’s genetic code linked to rubber production. The findings open the way for breeding for desired traits and developing a new crop source for rubber in the Pacific Northwest.
“I think there’s interest in developing a temperate-climate source of natural rubber,” said Ian Burke, a weed scientist at WSU and a study author. “It would be really great if prickly lettuce could become one of those crops.”
Here’s what prickly lettuce looks like,
Prickly lettuce, the wild relative of cultivated lettuce, is a potential source for the production of natural rubber. (Photo by Flickr user Jim Kennedy)
Here’s a close-up of a prickly lettuce stem with sap,
The milky sap, or latex, of the plant could be used to produce rubber. (Photo by Jared Bell, WSU)
Getting back to the prickly lettuce news release,
When the lettuce we eat and grow in our gardens bolts, a milky white sap bleeds from the stem. In prickly lettuce, the wild relative and ancestor of cultivated lettuce, this same substance could prove to be an economically viable source of natural rubber and help alleviate a worldwide threat to rubber production.
Natural rubber is the main ingredient for many everyday products, from boots to condoms to surgical gloves. Roughly 70 percent of the global supply of rubber is used in tires.
But more than half of rubber products are made from synthetic rubber derived from petrochemical sources. And the largest source of natural rubber, the Brazilian rubber tree, is threatened by disease.
Burke has reviewed many studies of prickly lettuce and its cultivated cousins, but one in particular gave him an idea. A study published in 2006 found that the latex in prickly lettuce was very similar to the polymers found in natural rubber.
“It occurred to me that we could grow the heck out of prickly lettuce in eastern Washington,” he said.
Genetic markers for desired traits
He knew that to develop a viable new crop for rubber production, he had to start by understanding the genetics of rubber production in the plant.
Burke, doctoral student Jared Bell and molecular plant scientist Michael Neff began their studies with two distinct samples of prickly lettuce collected from eastern Washington. These differed in their rubber content, leaf shape and tendency to bolt. The scientists were able to identify genetic markers not only for rubber content but for the way the plants grow, including the number of stems produced and bolting.
Sought-after traits in cultivated lettuce – like abundant leaves, a single stem and delayed bolting – are the exact opposite of traits desired for rubber production. Early bolting plants with multiple stems would allow for multiple harvests over the season and potentially maximize rubber yields.
Burke said that selecting for other traits, like water use efficiency, could allow prickly lettuce to be grown with minimal rainfall, meaning it could be grown in rotation with other crops.