Micromotors push around single cells and particles

October 25, 2019

A new type of micromotor--powered by ultrasound and steered by magnets--can move around individual cells and microscopic particles in crowded environments without damaging them. The technology could open up new possibilities for targeted drug delivery, nanomedicine, tissue engineering, regenerative medicine and other biomedical applications.

"These microswimmers provide a new way to manipulate single particles with precise control and in three dimensions, without having to do special sample preparation, labeling, surface modification," said Joseph Wang, a professor of nanoengineering at the University of California San Diego.

Wang, with Thomas Mallouk, a professor of chemistry at University of Pennsylvania, and Wei Wang, a professor of materials science and engineering at Harbin Institute of Technology in China, are senior authors of a paper describing the micromotors, published Oct. 25 in Science Advances.

Researchers used the micromotors to push around individual silica particles and HeLa cells in aqueous media without disturbing neighboring particles and cells. In one demonstration, they pushed around particles to spell out letters. Researchers also controlled the micromotors to climb up microsized blocks and stairs, demonstrating their ability to move over three dimensional obstacles.

The micromotors are hollow, half capsule-shaped polymer structures coated with gold. They contain a small piece of magnetic nickel in their bodies, which allows them to be steered with magnets. The inner surface is chemically treated to repel water so that when it is submerged in water, an air bubble spontaneously forms inside the micromotor.

This trapped bubble allows the micromotor to respond to ultrasound. When ultrasound waves hit, the bubble oscillates inside the micromotor, creating forces that propel its initial movement. To keep the micromotor moving, researchers apply an external magnetic field. By changing the direction of the magnetic field, researchers can steer the micromotor in different directions and alter its speed.

"We have a lot of control over the motion, unlike a chemically fueled micromotor that relies on random motion to reach its target," said Fernando Soto, a nanoengineering Ph.D. student at UC San Diego. "Also, ultrasound and magnets are biocompatible, making this micromotor system attractive for use in biological applications."

Future improvements to the micromotors include making them more biocompatible, such as building them from biodegradable polymers and replacing nickel with a less toxic magnetic material such as iron oxide, researchers said.
Paper title: "3D steerable, acoustically powered microswimmers for single-particle manipulation." Co-authors include Liqiang Ren, Zhifei Yan and Wu Liu, Pennsylvania State University; Nitesh Nama, University of Michigan; and Jeffrey M. McNeill, Pennsylvania State University.

University of California - San Diego

Related Magnetic Field Articles from Brightsurf:

Investigating optical activity under an external magnetic field
A new study published in EPJ B by Chengping Yin, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, South China, aims to derive an analytical model of optical activity in black phosphorous under an external magnetic field.

Magnetic field and hydrogels could be used to grow new cartilage
Instead of using synthetic materials, Penn Medicine study shows magnets could be used to arrange cells to grow new tissues

Magnetic field with the edge!
This study overturns a dominant six-decade old notion that the giant magnetic field in a high intensity laser produced plasma evolves from the nanometre scale.

Global magnetic field of the solar corona measured for the first time
An international team led by Professor Tian Hui from Peking University has recently measured the global magnetic field of the solar corona for the first time.

Magnetic field of a spiral galaxy
A new image from the VLA dramatically reveals the extended magnetic field of a spiral galaxy seen edge-on from Earth.

How does Earth sustain its magnetic field?
Life as we know it could not exist without Earth's magnetic field and its ability to deflect dangerous ionizing particles.

Scholes finds novel magnetic field effect in diamagnetic molecules
The Princeton University Department of Chemistry publishes research this week proving that an applied magnetic field will interact with the electronic structure of weakly magnetic, or diamagnetic, molecules to induce a magnetic-field effect that, to their knowledge, has never before been documented.

Origins of Earth's magnetic field remain a mystery
The existence of a magnetic field beyond 3.5 billion years ago is still up for debate.

New research provides evidence of strong early magnetic field around Earth
New research from the University of Rochester provides evidence that the magnetic field that first formed around Earth was even stronger than scientists previously believed.

Massive photons in an artificial magnetic field
An international research collaboration from Poland, the UK and Russia has created a two-dimensional system -- a thin optical cavity filled with liquid crystal -- in which they trapped photons.

Read More: Magnetic Field News and Magnetic Field Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.