Light-Driven Gears: Building the Smallest Motors for Medicine

The trend of miniaturization has permeated a wide range of industries.

In particular, efforts are ongoing to create smaller, more efficient, and more powerful devices across various fields, including electronics, artificial intelligence, space, and medicine.

The concept of miniaturization simply involves the manufacturing of smaller products and devices. This results in lighter, more compact, and portable products with enhanced performance and lower costs, leading to greater accessibility and innovation.

The miniaturization of mechanical machines is actually key to advancing nanotechnology and reducing the environmental impact of the device. However, it is more complex due to the way the structural properties of mechanical parts change as they are scaled down.

In mechatronics, researchers have been working on downsizing key machine components like gears and micromotors for the past few decades. However, these engineered efforts have faced limitations at around 0.1 millimeters (mm).

That is because of the complexities regarding constructing drive trains and coupling systems at such a small scale.

But a team of researchers from the University of Gothenburg has finally found an alternative to achieve this. Published in Nature, the study titled ‘Microscopic geared metamachines’¹ details their approach that involves using optical metasurfaces (OM) to locally drive the tiny machines.

The new approach can actually be fabricated using standard lithography methods and seamlessly integrated on the chip, allowing the researchers to achieve sizes down to tens of micrometers (μm) with movements precise to the sub-micrometer scale. 

In their proof of concept, the team demonstrated the construction of microscopic gear trains powered by a single driving gear, with a metasurface activated by a plane light wave. They also developed a “versatile pinion and rack micromachine,” capable of performing periodic motion, transducing rotational motion, and controlling tiny mirrors for light deflection.

The on-chip fabrication process enables straightforward integration. Meanwhile, the use of light as an easily controllable energy source allows miniaturized metamachines to offer precise movement and control, thus unlocking new possibilities for micro- and nanoscale systems, noted the study.

Downsizing Mechanical Systems for Advanced Miniaturization

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From ancient mills to modern robotics and simple clocks to complex cars, gears are everywhere, reflecting the advancement of human technology. 

These geared mechanisms are systems where interlocking gears transfer motion, force, and power to perform tasks efficiently. Crucial for automotive, aerospace, robotics, and other applications, these systems offer precise control by changing speed and increasing mechanical advantage.

Current gear advances focus on miniaturizing them to micrometer scales, which will reduce waste and enhance material efficiency. 

This will also open novel possibilities for mechanizing and exploring a length scale that so far remains out of reach. For instance, downsizing the system will provide us with a deeper understanding into friction and surface interactions, while enabling innovations like high-performance microfluidic devices and reconfigurable optical technologies.

Currently, efforts in this regard have been centred on creating individual micromotors, which are tiny objects capable of rotation. And to power them, mechanisms like static and AC electric fields, light fields, and magnetic fields have been explored.

However, the problem has been integrating micromotors into small, geared mechanisms that actually work, which has created a need for a scalable approach.

The latest research breakthrough provides a solution by creating tiny gears that can be powered directly by light, thus enabling the construction of the smallest motors ever for on-chip applications. 

As the study noted, recent advances in active matter have used unfocused light to move tiny vehicles using metasurfaces that produce lateral optical forces via directional light scattering. 

Microvehicles with these nanostructures arranged in a parallel pattern have been shown to propel forward under the linearly polarized light. They can also be controlled using polarized light via spin angular momentum transfer.

Moreover, laying out the scatterers in a circular pattern has been shown to allow rotation under linearly polarized light. Even more advanced designs use four individually addressable chiral plasmonic nanoantennas, which enable full 2D motion control by applying dual-wavelength light.

Building on these advances, the team has created a geared mechanism that’s driven by optical metasurfaces that work under steady illumination.

Metasurfaces are specifically engineered, ultra-thin 2D materials that are made of subwavelength structures that control electromagnetic waves by manipulating their phase, amplitude, and polarization. By precisely shaping these waves, metasurfaces enable applications like lenses, holographic displays, advanced sensors, efficient energy harvesting, and improved wireless communication systems.

Optical metasurfaces (OMs) here offer promising candidates to solve the bottleneck of bulky optical elements. They provide a new way to manipulate light based on scattering from resonant nanostructures, thus offering efficient phase, polarization, and emission control.

In order to embed the optical metamaterial into the gears right on a microchip, the team used standard photolithography.

Photolithography is a microfabrication process that uses light to transfer a geometric pattern from a photomask onto a light-sensitive material (photoresist) on a substrate, such as a silicon wafer. This process is key to creating the intricate patterns found in semiconductors.

As for the material used for gears, each of which is only about a few tens of micrometers (0.016 μm specifically) in diameter, the team used silicon.

Silicon (Si) is a crucial element for modern technology that serves as the essential semiconductor material in microchips and transistors. The team used it as their primary material for its compatibility with photolithography, thus facilitating large-scale manufacturing.

Click here to learn about maskless lithography, a game changer for chip manufacturers

Revolutionizing Medicine with Tiny Machines

Instead of employing traditional mechanics, the research team at the University of Gothenburg used laser light to build microscopic gears that can not only spin but also change direction and even power microscopic machines.

The motor is so tiny that it can fit nicely inside a strand of hair. These advancements are hoped to lead to futuristic medical tools that will only be the size of human cells.

With this breakthrough, the researchers have overcome the limitation of building smaller drive trains that move micro-engines, which stalled their progress to 0.1 mm, by simply ditching the drive trains altogether.

The microscopic machines are instead set in motion by laser light. For that, the team used optical metamaterials, the small, intricately patterned structures that can capture as well as control light with great precision and at a very small scale.

By shining a laser on the metamaterial, the researchers make the gear wheel spin, and by controlling the intensity of the laser light, they control the speed. What’s more is that they can shift the direction of the gear wheel by adjusting the light polarization. 

“We have built a gear train in which a light-driven gear sets the entire chain in motion. The gears can also convert rotation into linear motion, perform periodic movements, and control microscopic mirrors to deflect light.”

– Gan Wang, the study’s first author & researcher in soft matter physics at the University

This ability to integrate microscopic machines directly onto a chip and propel them with light opens exciting new possibilities. 

For starters, the researchers are another step closer to building micromotors, which can be scaled up to complex microsystems, as laser light is easy to control and doesn’t need to have a fixed contact with the machine.

“This is a fundamentally new way of thinking about mechanics on a microscale. By replacing bulky couplings with light ones, we can finally overcome the size barrier.”

– Wang

Another possibility is the use of micromachines and nanomachines, which can manipulate small particles or be incorporated into lab-on-a-chip systems, enabling the assessment of biological systems.

Using light as a widely available and biocompatible energy source makes the micromotor well-suited for manipulating cells, bacteria, and other biological matter. 

The system used a standard 1064 nm laser, which has low absorption by water and tissues, and as a result, diminishes any damage to biological samples. Also, the light operates at a low power requirement, only a few mW, and is within the safe thresholds for biological systems. 

Notably, the light can be selectively directed to the driving gear, which prevents the need to directly expose biological samples to the light source. This indirect, non-harmful mechanism to deliver energy expands the applications of light-driven metachines and micromotors in biomedical environments.

More specifically, microscopic gears can help regulate fluid flows or control drug delivery systems.

With gear wheels measuring 16 to 20 μm, the size of certain human cells, the new micromotors could be used as pumps inside the human body to regulate various flows, and they may also function as valves that open and close.

On top of it all, the intricate, multi-step process of on-chip fabrication used here is compatible with the widely used Complementary Metal-Oxide-Semiconductor (CMOS) lithography, which can facilitate its smooth integration with other CMOS components like plasmonic sensors and metalenses.

With its light-powered gears of micrometer scale, the study promises groundbreaking capabilities in micro- and nanoscale mechanical systems. However, there is still a limitation in relying on pre-designed metasurfaces, which restricts dynamic motion adjustability.

To address this, the researchers recommended integrating phase-transition materials like vanadium dioxide (VO2) into the metasurface design. This will enable real-time reconfiguration of optical properties in response to external stimuli such as light, temperature, or electric fields. 

They also suggested alternative metasurface materials like TiO2 for extending the operational wavelength into the visible light region, which will simplify optical calibration and potentially improve the system’s adaptability, performance, and applicability across diverse environments.

Miniaturization’s Leap into Medicine

Miniaturization has been revolutionizing electronics for decades now. The fabrication of smaller, more energy-efficient, and high-performance devices has enabled advancements in smartphones, wearables, and communication systems.

This, however, is equally important in medicine, where miniature machines can allow for greater precision. Such tools can not only improve diagnostics but also enable new therapies at the cellular level and make healthcare more accessible.

Hence, researchers are exploring expanding miniaturization to medicine.

As we saw with Gothenburg metasurface gears, they solved actuation bottlenecks by eliminating drive trains. Another team has solved it by embedding sensing directly into their machines and is paving the way for real-world applications of intelligent miniature devices.

The team of researchers from the School of Integrated Circuits and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, China, has developed miniature magneto-ultrasonic machines² for wireless robotic sensing and manipulation.

This study addresses the issue of sensing-actuation incompatibility at microscopic scales that obstruct the development of intelligent miniature systems that can significantly advance biomedical applications. 

As a solution, the researchers proposed a new approach that incorporates embedded ultrasonic soft sensors (EUSSs) with magnetic actuators. The EUSS is soft, compact, and lightweight in design. With a weight of just 4.6 milligrams and dimensions of 1.3 mm x 1.3 mm x 1.6 mm, it is compatible with both soft and rigid components in both size and deformability. 

Moreover, the team designed onboard transducers and, in addition to external magnetic fields, used passive ultrasound communication, which allowed them to wirelessly detect and regulate force, vibration, temperature, and viscosity.

When tested in rabbits and porcines, the team found the device offered accurate drug dosing, physiological monitoring, and robotic feedback control.

In another instance, EPFL researchers developed³ a Miniaturized Brain-Machine Interface (MiBMI) that enhances the efficiency as well as scalability of BMIs, which offers a promising way to restore control and communication to individuals with severe motor impairments.

Being small and low-power, the system makes it suitable for implantable applications, while its minimal invasiveness ensures patient safety. It is a fully integrated system with the recording and processing done on two really small chips. 

“MiBMI allows us to convert intricate neural activity into readable text with high accuracy and low power consumption. This advancement brings us closer to practical, implantable solutions that can significantly enhance communication abilities for individuals with severe motor impairments.“

– Mahsa Shoaran, at whose Integrated Neurotechnologies Laboratory (INL) at EPFL the device was developed

Investing in the Future of Miniaturized Tech

While $122.6 bln market cap Medtronic (MDT -0.22%) boasts a broad portfolio in medical devices such as micro-sensors, actuators, and robotic assistive devices, and $12 bln market cap Lumentum Holdings (LITE -9.56%) is advancing the optical and photonic field. Today, we will cover the investing potential of SiTime Corporation (SITM -4.39%), which illustrates how MEMS (micro-electromechanical systems) scale and how their integration into chips is handled commercially.

SiTime Corporation (SITM -4.39%)

SiTime is an analog and semiconductor company whose products are used for precise timing in electronics.

Just this week, SiTime Corporation announced the launch of the Titan Platform, a family of MEMS resonators that is about four times smaller than the smallest legacy quartz alternatives. According to the company, this will enable “unprecedented miniaturization” as well as integration in small, battery-powered devices, powering the next wave of innovation in medical devices, wearables, and industrial IoT.

With a market capitalization of almost $8 billion, SiTime’s shares are currently trading at $306.5, up 42.3% year-to-date (YTD). Just last year in April, SITM shares were under $100 and have surged more than 323% since then. The stock is also up over 106% since this April low, in line with the broad stock market, which has climbed to record highs. 

Financially, the company reported a 58% increase in net revenue to $69.5 million for the second quarter of 2025.

Its GAAP gross profit was $36.1 million, GAAP operating expenses were $60.7 million, and GAAP net loss was $20.2 million, or $0.84 per diluted share. Meanwhile, non-GAAP gross profit was $40.5 million, non-GAAP operating expenses were $33.3 million, and non-GAAP net income was $11.6 million, or $0.47 per diluted share.

“SiTime’s continued momentum across our end markets demonstrates that our focus on high performance applications is working. Revenue from our Communications, Enterprise, and Data Center market (CED) grew 137% year over year, fueled by AI that created strong demand for our Precision Timing solutions.”

– CEO Rajesh Vashist

The company ended the quarter with $796.7 million in total cash, cash equivalents, and short-term investments.

Latest SiTime Corporation (SITM) Stock News and Developments

Conclusion

Micro-engineering stands to transform our mechanical approach to microscopic systems, and the latest breakthrough in the creation of gears on a micrometer scale makes that possible. The newly developed tiny light-powered gears promise to revolutionize medicine by powering machines only the size of human cells.

This reflects the transition of miniaturization from electronics to medicine, which shows that scaling down technology isn’t only about efficiency but also about unlocking entirely new possibilities.

Over time, these devices will continue to get smaller and more capable, paving the way for autonomous microsystems that could one day operate seamlessly inside the human body, where they’ll regulate flows, deliver drugs, and may even repair tissues at the cellular level.

Click here to learn about how 3D-printed microscopic particles could change medicine and electronics.

References:

<sup>1. Wang, G., Rey, M., Ciarlo, A., Shanei, M., Xiong, K., Pesce, G., Käll, M. & Volpe, G. (2025). Microscopic geared metamachines. Nature Communications, 16:7767. (Version of Record), published 20 August 2025. https://doi.org/10.1038/s41467-025-62869-6
2. Liu, X., Tang, H., Li, N., He, L., Tian, Y., Hao, B., Xue, J., Yang, C., Sung, J. J. Y., Zhang, L., & Zang, J. (2025). Miniature magneto-ultrasonic machines for wireless robotic sensing and manipulation. Science Robotics, 10(106). (Version of Record), published 17 September 2025. https://doi.org/10.1126/scirobotics.adu4851
3. Shaeri, M., Shin, U., Yadav, A., Caramellino, R., Rainer, G., & Shoaran, M. (2024). A 2.46-mm² miniaturized brain–machine interface (MiBMI) enabling 31-class brain-to-text decoding. IEEE Journal of Solid-State Circuits, 59(11), 3566–3579. (Version of Record), published November 2024. https://doi.org/10.1109/JSSC.2024.3443254</sup>