Microscopically tiny nanomachines which move like submarines with their own propulsion—for example in the human body, where they transport active agents and release them at a target: What sounds like science fiction has, over the past 20 years, become an ever more rapidly growing field of research. However, most of the particles developed so far only function in the laboratory. Propulsion, for example, is a hurdle. Some particles have to be supplied with energy in the form of light, others use chemical propulsions which release toxic substances. Neither of these can be considered for any application in the body. A solution to the problem could be acoustically propelled particles. Johannes Voß and Prof. Raphael Wittkowski from the Institute of Theoretical Physics and the Center for Soft Nanoscience at the University of Münster (Germany) have now found answers to central questions which had previously stood in the way of applying acoustic propulsion. The results have been published in the journal ACS Nano.
Ultrasound is used in acoustically propelled nanomachines as it is quite safe for applications in the body. Lead author Johannes Voß sums up the research carried out so far as follows: “There are many publications describing experiments. However, the particles in these experiments were almost always exposed to a standing ultrasound wave. This does admittedly make the experiments considerably simpler, but at the same time it makes the results less meaningful as regards possible applications—because in that case traveling ultrasound waves would be used.” This is due to the fact that standing waves are produced when waves traveling in opposite directions overlap one another.
What researchers also did not previously take into account is that in applications the particles can move in any direction. Thus, they left aside the question of whether propulsion depends on the orientation of the particles. Instead, they only looked at particles aligned perpendicular to the ultrasound wave. Now, for the first time, the team of researchers in Münster studied the effects of orientation using elaborate computer simulations.
They came to the conclusion that the propulsion of the nanoparticles depends on their orientation. At the same time, the acoustic propulsion mechanism in traveling ultrasound waves functions so well for all orientations of the particles—i.e. not only exactly perpendicular to the ultrasound wave—that these particles really can be used for biomedical applications. Another aspect the Münster physicists examined was the propulsion the particles exhibited when they were exposed to ultrasound coming from all directions (i.e. “isotropic ultrasound”).
A basis for the step towards application
“Our results showed how the particles will behave in applications and that the propulsion has the right properties for the particles to actually be used in these applications,” Johannes Voß concludes. As Raphael Wittkowski adds, “We have revealed important properties of acoustically propelled nanoparticles which had not previously been studied, but which need to be understood to enable the step to be made from basic research to the planned applications involving the particles.”
The two Münster researchers examined conical particles, as they can move fast even at a low intensity of ultrasound—i.e. they have efficient propulsion—and also they can easily be produced in large numbers. The particles are almost one micrometer in size—almost a thousand nanometres. In comparison, a red blood cell has a diameter of around 7.7 micrometers. This means that the nanoparticles could move through the bloodstream without blocking up the finest blood vessels. “The particle size can be selected in line with what is needed in the particular application intended, and the propulsion mechanism also functions in the case of smaller and larger particles,” Johannes Voß explains. “We simulated the particles in water, but the propulsion is also suitable for other fluids and for tissue.”
By means of computer simulations, the team investigated systems and their properties which could not be studied in the many preceding experiments. Looking into the future, Raphael Wittkowski says, “An important step would be for experiment-based research to move on to looking at these systems.”

News
Johns Hopkins Researchers Uncover a New Way To Kill Cancer Cells
A new study reveals that blocking ribosomal RNA production rewires cancer cell behavior and could help treat genetically unstable tumors. Researchers at the Johns Hopkins Kimmel Cancer Center and the Department of Radiation Oncology and Molecular [...]
AI matches doctors in mapping lung tumors for radiation therapy
In radiation therapy, precision can save lives. Oncologists must carefully map the size and location of a tumor before delivering high-dose radiation to destroy cancer cells while sparing healthy tissue. But this process, called [...]
Scientists Finally “See” Key Protein That Controls Inflammation
Researchers used advanced microscopy to uncover important protein structures. For the first time, two important protein structures in the human body are being visualized, thanks in part to cutting-edge technology at the University of [...]
AI tool detects 9 types of dementia from a single brain scan
Mayo Clinic researchers have developed a new artificial intelligence (AI) tool that helps clinicians identify brain activity patterns linked to nine types of dementia, including Alzheimer's disease, using a single, widely available scan—a transformative [...]
Is plastic packaging putting more than just food on your plate?
New research reveals that common food packaging and utensils can shed microscopic plastics into our food, prompting urgent calls for stricter testing and updated regulations to protect public health. Beyond microplastics: The analysis intentionally [...]
Aging Spreads Through the Bloodstream
Summary: New research reveals that aging isn’t just a local cellular process—it can spread throughout the body via the bloodstream. A redox-sensitive protein called ReHMGB1, secreted by senescent cells, was found to trigger aging features [...]
AI and nanomedicine find rare biomarkers for prostrate cancer and atherosclerosis
Imagine a stadium packed with 75,000 fans, all wearing green and white jerseys—except one person in a solid green shirt. Finding that person would be tough. That's how hard it is for scientists to [...]
Are Pesticides Breeding the Next Pandemic? Experts Warn of Fungal Superbugs
Fungicides used in agriculture have been linked to an increase in resistance to antifungal drugs in both humans and animals. Fungal infections are on the rise, and two UC Davis infectious disease experts, Dr. George Thompson [...]
Scientists Crack the 500-Million-Year-Old Code That Controls Your Immune System
A collaborative team from Penn Medicine and Penn Engineering has uncovered the mathematical principles behind a 500-million-year-old protein network that determines whether foreign materials are recognized as friend or foe. How does your body [...]
Team discovers how tiny parts of cells stay organized, new insights for blocking cancer growth
A team of international researchers led by scientists at City of Hope provides the most thorough account yet of an elusive target for cancer treatment. Published in Science Advances, the study suggests a complex signaling [...]
Nanomaterials in Ophthalmology: A Review
Eye diseases are becoming more common. In 2020, over 250 million people had mild vision problems, and 295 million experienced moderate to severe ocular conditions. In response, researchers are turning to nanotechnology and nanomaterials—tools that are transforming [...]
Natural Plant Extract Removes up to 90% of Microplastics From Water
Researchers found that natural polymers derived from okra and fenugreek are highly effective at removing microplastics from water. The same sticky substances that make okra slimy and give fenugreek its gel-like texture could help [...]
Instant coffee may damage your eyes, genetic study finds
A new genetic study shows that just one extra cup of instant coffee a day could significantly increase your risk of developing dry AMD, shedding fresh light on how our daily beverage choices may [...]
Nanoneedle patch offers painless alternative to traditional cancer biopsies
A patch containing tens of millions of microscopic nanoneedles could soon replace traditional biopsies, scientists have found. The patch offers a painless and less invasive alternative for millions of patients worldwide who undergo biopsies [...]
Small antibodies provide broad protection against SARS coronaviruses
Scientists have discovered a unique class of small antibodies that are strongly protective against a wide range of SARS coronaviruses, including SARS-CoV-1 and numerous early and recent SARS-CoV-2 variants. The unique antibodies target an [...]
Controlling This One Molecule Could Halt Alzheimer’s in Its Tracks
New research identifies the immune molecule STING as a driver of brain damage in Alzheimer’s. A new approach to Alzheimer’s disease has led to an exciting discovery that could help stop the devastating cognitive decline [...]