Researchers have developed a new fabrication strategy for microrotors with controllable bubble ejection sites, opening up potential possibilities for advanced mechanical and biological applications.

Close-up of iridescent bubbles floating in the air with a softly blurred background, showcasing a spectrum of colors.

Micromachines are tiny devices that convert energy into mechanical motion, often powered by external forces like magnetic, electrical, optical, or ultrasonic fields. However, these methods can be complex and often require substantial energy input. Researchers have been working to identify simpler, self-propelled modes of operation; one such method involves using bubble ejection, but controlling the bubble ejection sites to build micromachines with programmable actuation has been a challenge.

A team of researchers in China have recently proposed a new strategy for fabricating micromechanical systems with complex geometry and controllable bubble ejection sites. This involves a two-step process using a multimaterial femtosecond laser processing method. First, the team printed the polymer frame of the microsystems using direct laser writing (DLW). Then, they deposited catalytic platinum into the microsystems' desired local site via selective laser metal reduction (SLMR). This method allowed the researchers to successfully create microrotors that could rotate steadily in a fuel liquid by bubble ejection force.

They found that the rotation speed of the microrotors could be flexibly controlled by selectively controlling the catalyst deposition site. The microrotors demonstrated an independent rotation direction and high robustness in opaque media and dark environments. Furthermore, the microrotors could be integrated into various multicomponent mechanical transmission systems such as a microcoupling, crank slider, and crank rocker system.

This study, published in Nano Letters, opens up exciting possibilities in the field of microrobotics, microfluidics, and microsensors. The microrotors could one day be used as a stable, cost-effective power source for the transmission of various micromechanical systems, capable of tasks such as opening and closing microvalves and allowing for the flow control and transport of particles and cells.

The authors also note the potential for material substitution in their design, including the use of magnetic materials such as iron, ferric oxide, and nickel. These could potentially enable a magnetic driving mechanism, opening up possibilities for biological applications such as cell transport, mixing, and sorting.

The findings present a significant step forward in the development of micromachines and could pave the way for more advanced systems in the future. The authors are optimistic that their approach could be applied to modify other micromachines with sophisticated geometry, from single driving components to intricate 3D multicomponent architectures.

Watch a Headline Science short of the bubble-powered microrotors in action, created by the ACS Science Communications team:

Want More From This Journal?
Nano Letters journal cover

Stay Connected

Sign up now for email updates on future calls for papers, the latest issues, and other content from Nano Letters.

Want the latest stories delivered to your inbox each month?