WebZine
2017. 11
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Snakelike Robot Could Image, Operate on Intestines
by Mollie Bloudoff-Indelicato
As the small, snakelike robot oscillates, it slithers back and forth across the lab table. One day it might make the same journey through your intestines.
Researchers at Ben-Gurion University of the Negev in Be’er Sheva, Israel, have created a robot that may one day replace expensive colonoscopies and inefficient pill cameras. The device is about the size of an AA battery (2.6 cm wide and 5 cm long). Its developers believe it is the first robot to move by sine wave motion using only a single motor. They dubbed it SAW for its single actuator wave mode of transport.
“In the near future, I want to see a robot crawling deep inside a human intestine doing procedures,” said Nir Dgani, a mechanical engineering student working on the bot.
That starts with taking pictures. Today, if you want to film the small intestine the only options available are camera pills or colonoscopies. A camera pill is the simplest route, though it requires up to 12 hours to pass through the intestine. Camera pills also have limitations. They cannot stop to take more photos of problem areas. Instead, as the intestines push them along, they may get stuck in some places or move too quickly in others. And since camera pills are passive, they cannot perform biopsies or cauterizations or release medicine where needed.
The smaller, waterproof version of SAW. Image: Ben Gurion University of the Negrev.
A colonoscopy offers more flexibility, but procedures are expensive and usually require the patient to go under anesthesia and take the day off from work.
Though it’s still in prototype form, SAW aims to solve these issues with its combination of controlled motion, compact size, and ability to carry diverse payloads, said David Zarrouk, a roboticist at the university and head of the project.
Helical Motion
Zarrouk has been working on this project for the past 10 years, but came up with the idea for a wave-propelled robot just two years ago while teaching a class in mechanical design. “I was looking at a mechanical spring and, for a second, I thought, ‘What happens if you rotate the mechanical spring?’” he recalled.
Zarrouk modeled his idea and discovered that designing a helix-like spring with a very large pitch creates a sine wave that moves the robot forward like a snake, eel, or crocodile.
Zarrouk and his team attached dozens of links onto the helix, binding them to each other with a circular joint. He added a small brushed motor that was easy to control and required only a small battery for energy. When the helix rotated, it creates an advancing wave that propelled the robot forward.
Using a wave-like motion improves the ability of the device to work in the unstable small intestines, with its high compliance and very slippery walls.
“For very small devices, a millimeter and below, it’s like swimming in honey—you won’t go forward,” Moshe Shaham, a roboticist at the Technion Institute of Technology in Israel and an ASME fellow, said. “You have to swim by waving the tail.”
Building SAWs
Wave locomotion enables SAW to travel the entire 8-meter length of the intestine in about 2 hours—and it would still have enough battery life to move back and forth with the intestine for another 100 meters or more or keep the camera running for 10 hours. While it drains the battery to do both at the same time, even the prototype should have no problem lasting for the few hours needed to complete the procedure, Shaham said. Then, when done, the robot will be small enough to exit the body naturally.
This is much more convenient than undergoing anesthesia for a colonoscopy or waiting 12 hours for a pill camera to pass. Plus, SAW’s simplicity of design keeps costs down. The researchers 3-D print SAW robots using photopolymer, which should be able to survive in the body without degrading, though researchers said they may switch materials to be FDA compliant. It also has very few moving parts. “The simplicity is what makes this robot,” Zarrouk said. “If the robot was complex or made of too many parts, this would make it more expensive.”
The next challenge is to shrink the robot and start testing it in dead animals.
“We hope by the end of the year we’ll be able to have it small enough to make experiments inside the intestines of a pig,” Zarrouk said.
Mollie Bloudoff-Indelicato is a science and health writer based in Washington, DC.
Magnetic Field Controls Drug Delivery
By Emily Waltz
Posted 20 Nov 2017 | 16:00 GMT
Researchers have developed a new way to control the delivery of drugs to the body using nanoparticles and a weak magnetic field. The inventors, at the University of Georgia in Athens, GA tested their system with a chemotherapy drug, and published the results today in the journal Nature Catalysis.
Patients undergoing treatments for cancer and other diseases often must take drugs that affect the whole body, when they really only need the medicine in a small area. Chemotherapy drugs typically “act on all cells, killing cancer cells and also healthy cells,” says Sergiy Minko, a professor at the University of Georgia and an author of the report. As a result, “a big number of patients die because of complications” from the drugs, he says.
To address the problem, scientists have proposed all sorts of tiny gadgets that can selectively deliver drugs in the body, including organic electronic ion pumps, silicon nanowires, amoeba-like molecular robots, squishy micromachines, and robots controlled by magnetic fields.
In the new design, Minko uses nanoparticles that carry either a drug or a catalyst, and release the substances when exposed to a magnetic field. One difference between Minko’s tool and previous concepts is that the drug isn’t encapsulated inside a device, so the release is easy. And it doesn’t rely on a mechanical action or heat or salinity or light to do its job.
Minko’s nanoparticles are composed of an iron oxide core encased in a silica shell. The shell is coated with a polymer layer consisting of polyacrylic acid (PPA), and a second polymer layer of poly(ethylene glyco) methyl ether acrylate macromer (PPEGMA). The two layers form a brush-like structure that holds and shields substances from the external environment.
The brush-like structure is then loaded with the substances of interest. Half of the particles get an enzyme and the other half get a substrate that reacts with the enzyme, along with the drug of interest.
The particles would then be released into the body to drift to the area of interest, either naturally or guided by magnets or other substances. When they reach their destination, a weak external magnetic field is applied. That forces the nanoparticles together, compressing the brush-like polymer layers. When the polymer layers intertwine, the enzymes and substrates they are carrying interact, which allows the release of the therapeutic drug.
