“Disassemble after use” Challenge and possibility of dream plastic April 4, 18:40

The "plastic waste problem" is a common issue for all humankind.

If you walk along the beach, you will often see plastic trash such as shopping bags and PET bottles.

Because plastic is durable, it does not decompose in the environment and eventually flows out into the sea.

There are also concerns about health effects such as eating fish that mistakenly eat it.

Under these circumstances, Professor Tadahisa Iwata of the University of Tokyo has succeeded in developing a magical plastic that "is sturdy while in use and" disassembles "when it has finished its role."

And the beliefs of scientists are not only trying to solve the plastic waste problem, but also changing the future of various fields such as medical care and agriculture.

(Megumi Uchida, Director, Mito Broadcasting Station)

The trump card is "enzyme"

In the laboratory of Professor Tadahisa Iwata of the University of Tokyo in Bunkyo-ku, Tokyo, research on decomposing plastics using substances such as "white powder" is ongoing.

The true identity of this white powder is "enzyme".

Discovered from a mold, it is a trump card that breaks down plastic.

Nowadays, various "degradable plastics" (biodegradable plastics) are being developed in the world.

In the case of biodegradable plastics using "polylactic acid", which is widely distributed in Japan, the conditions of "temperature 60 degrees and humidity 60%" are required for decomposition.

However, such an environment does not exist in the natural world, and if it flows out into a river or the sea, it is extremely unlikely to be decomposed.

Therefore, Mr. Iwata came up with the idea of ​​enclosing the enzyme in plastic in advance.

When plastic flows into rivers and the sea and breaks, water enters the inside.

Then, the enzyme that was sleeping inside reacts with water and begins to decompose.

Mr. Iwata thought that it should work in theory.

Actually, when I cut a plastic film containing the enzyme with scissors and soak it in seawater ...

Over time, the disassembly began brilliantly.

It was also confirmed that the finer the film, the faster the disassembly speed.

Professor Tadahisa Iwata of the University of Tokyo

"I thought it would work in my head, but when the student did the experiment and heard a voice saying," Teacher, it worked! " I grabbed it and felt "OK"

It's durable when you're using it.

However, "dream plastic" was born, which begins to disassemble when the switch is turned on after finishing its role.

"Study in the sun" Continued days

Since the 1970s, plastic waste has become a social problem for "biodegradable plastics," which are decomposed in the environment, and many research institutes and companies, including universities, have begun to develop them as a technology to solve the problem.

However, the easier it is to disassemble, the more difficult it is to maintain the original strength of the plastic.

There are cases where it is not very resistant to heat and it melts when left in a warehouse, so the people concerned are leaning toward the evaluation that "biodegradable plastic has excellent functions but cannot be used as an actual material". rice field.

Originally, Mr. Iwata, who belonged to the Faculty of Agriculture at the university, was researching plastics using wood components.

However, he met Yoshiharu Doi, who is active in the front lines of biodegradable plastic research, and entered a new field.

Mr. Iwata chose the steep path of "decomposable plastic," which was thought to be far from practical use at that time, from the Faculty of Agriculture to the world of Engineering.

Some of his friend's researchers were worried.

However, Mr. Iwata has continued his research with conviction.

Professor Tadahisa Iwata of the University of Tokyo

"The important thing as a scientist in charge of basic research is to continue doing what you think is important, no matter how society makes decisions."

The result is about to blossom.

Development of plastic Originally "to protect animals"

As I continued my research, what supported Mr. Iwata's heart was the idea that the plastic problem is a "human problem" dealing with plastic.

This is symbolized by the history of the birth of plastic, which was originally developed to "protect animals."

A billiard ball originally made of ivory.

Humans have killed many elephants for production.

It is said that the beginning of plastic was developed by scientists to stop it.

Professor Tadahisa Iwata of the University of Tokyo

"I think that plastic was developed to protect animals and the environment."

Instead of turning used plastic into a bad guy called "garbage," he continued his research, thinking that "the human side may have the role of using it to the end."

Expected in the medical field "Biodegradable plastic"

Efforts have begun to utilize the characteristics of plastics that gradually decompose in the medical field.

The developer is Mitsuhiro Ebara, a researcher at the Materials Research Organization (Tsukuba, Ibaraki).

Mr. Ebara focused on a disease called "carpal tunnel syndrome," in which the nerves of the hand are pressed.

When symptoms worsen, surgery to remove the tissue around the nerves needs to be done.

Mr. Ebara developed a special sheet that contains the ingredients of the drug in biodegradable plastic for the administration of the drug to the affected area after surgery.

At the end of surgery, place the wound around the damaged nerve and close the wound.

After that, the medicine that has exuded from the sheet is delivered directly to the affected area, and the sheet itself is decomposed in the body as it is.

Eventually, it is excreted out of the body through urine.

The materials used in the sheets have been approved by the FDA = Food and Drug Administration in the United States and are already used as part of products to be implanted in the body.

In surgery, the wound is closed after applying a plastic sheet at the end.

It is said that the medicine will be delivered directly to the affected area for about half a year.

This epoch-making sheet, which applies biodegradable plastic technology, is currently undergoing clinical trials and is expected to be put into practical use.

Also for biodegradable plastic "cancer treatment"

These medical plastics are about to be applied to "cancer treatment".

By impregnating the sheet with an "anti-cancer drug" and attaching it to the affected area, the anti-cancer drug can be delivered directly to the cancer cells.

Furthermore, we are currently researching whether it is possible to kill cancer cells by making the sheet "fever".

Mitsuhiro Ebara, National Institute for Materials Science

"I want to save my life with plastic technology. For that purpose, I want to be" soft "so that it doesn't hurt when I put it in my body," take out medicine ", and finally" decompose ". It is necessary to adjust all of this in a timely manner. I think it is a combination of polymer chemistry. "

Sea, river.

Underground ... To turn on the "disassembly switch" everywhere

Plastic researchers, including Professor Tadahisa Iwata of the University of Tokyo, are taking on the challenge of developing various "decomposition switches" to solve the problem of plastic waste that remains in the environment.

It is an attempt to use environmental conditions such as water pressure, salinity, light, temperature, and pH as triggers to switch on.

For example, a "water pressure switch" is being considered for a broken "fishing net" that may sink to the bottom of the sea and become plastic waste.

Research is also underway to see if a structure can be created in which the decomposition switch is turned on when the water pressure exceeds a certain level when it sinks to the seabed and does not decompose under the water pressure at the depth of normal fishing.

The "Plastic Resource Recycling Law," which will come into effect this month, requires companies to reduce the number of plastic products.

Professor Tadahisa Iwata of the University

of Tokyo "Plastic is basically important to collect, collect, and recycle as much as possible. However, no matter how hard you try to collect it, it is absolutely necessary to collect it. It leaks. In such a place, biodegradable plastic that decomposes when it leaks into the environment is required. "

In the future, we would like to replace about 20% of all plastics with "biodegradable plastics" so that plastics do not remain in the natural environment.

Professor Tadahisa Iwata of the University of Tokyo

"Masks for dealing with the new coronavirus are also made of plastic such as polyethylene and polypropylene, and most medical instruments are made of plastic, so plastic is our society. It is absolutely necessary inside. The question of whether to make the material a "bad guy" or a "good one" that can be used properly is just how we humans face and process this plastic. There are still many issues to be solved, but I think that if researchers bring their knowledge and proceed with research experiments, they will surely find a solution. I think it's important to do what you need to do without being swept away. "

Mito Broadcasting Station Director

Megumi Uchida

Joined in 2019 Science ZERO "Change your life !? Forefront of" athlete science "" etc.

"Plastic that" decomposes "" For details, see NHK Plus

Instagram "Mirai of the Earth" (leaving the NHK site)