At some point, microvehicles that are small enough to navigate our blood vessels will allow physicians to insert biopsies, insert stents and deliver drugs accurately to hard-to-reach sites. , all from within the body. Scientists around the world are currently studying and developing suitable microvehicles. In most cases, they are powered and controlled by acoustic and magnetic fields or using light. However, so far, moving microvehicles against water flow has been a major challenge. This would be necessary in order for the micromachines to be able to float in blood vessels against the direction of blood flow. Researchers at ETH Zurich have now developed field-treated microvehicles that can swim against the current.
In their laboratory, the research team led by Daniel Ahmed and Bradley Nelson, professors at the Department of Mechanical and Process Engineering of ETH Zurich, used magnetic beads made of iron oxide and polymer with a diameter of 3 micrometres. A magnetic field causes these grains to accumulate in a sword with a diameter between 15 and 40 micrometres. The scientists studied the behavior of this arrow in a thin glass tube with liquid flowing through it. The glass tubes had a diameter of 150 to 300 micrometres, similar in size to the blood vessels in a tumor.
To move the microswarm against the current in the tube, the ETH researchers applied the same trick to canoeists on a river: they chew the banks of the river to paddle up the river, as anti- the collision of the bank makes the stream slower there than in the middle of the river. .
Using ultrasound at a specific frequency, the scientists first guided the collection of microbes near the wall of the tube. The researchers then turned to a magnetic rotating field to move them against the current.
As their next step, the researchers plan to study how the microvehicles respond in the blood vessels of animals. “Because both ultrasound waves and magnetic fields enter the tissue of the body, our technique is ideal for controlling microvehicles within the body,” says Professor ETH Ahmed.
Microsurgery, such as unclogging closed blood vessels, is one of the future applications the researchers hope this method will serve. In addition, the microvehicles could one day be used to deliver cancer drugs to tumors through the blood vessels and release them directly into the tumor mass. Finally, another area of application is the transfer of drugs from blood vessels into the tissues of the brain.
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