In a groundbreaking leap for soft robotics and biomedical technology, researchers have unveiled a novel class of ultrasound-driven artificial muscles that boast rapid, programmable motion capabilities thanks to integrated microbubble arrays. These innovations, described in a recent Nature publication, showcase the power of ultrasound to remotely actuate soft devices, opening avenues for wireless interventions and smart biocompatible machines capable of delicate manipulation and targeted therapy inside living organisms. This technology marks a significant stride toward minimally invasive medical robotics that combine precision, adaptability, and safety.
The core advancement lies in the design of microbubble-array artificial muscles—miniaturized structures embedded with tens of thousands of microscopic bubbles that respond dynamically to ultrasonic waves. Unlike traditional actuators that require bulky electronics or wires, these microbubble arrays enable wireless control of soft grippers and contractile muscles submerged in fluid environments. When exposed to ultrasound at carefully tuned frequencies (around 95.5 kHz) and voltages (60 V_PP), these muscles undergo swift and reversible shape changes, providing sufficient force to grasp fragile biological specimens without damage.
Remarkably, the research team demonstrated a soft gripper composed of multiple artificial-muscle petals, each petal embedded with approximately 10,000 to 20,000 microbubbles precisely sized at 12 micrometers in diameter and 50 micrometers in depth. This gripper could gently trap a live zebrafish larva within just 100 milliseconds upon ultrasound stimulation. Once the stimulus ceased, the larva was able to swim away unharmed, highlighting the device’s gentle yet effective gripping capability. The absence of induced heat or toxicity after repeated cycling confirmed its biocompatibility and potential for delicate biological applications.
Extending beyond simple gripping, the researchers transformed the microbubble-array muscles into a conformable robotic skin that adheres to arbitrary three-dimensional surfaces. Employing this skin, they attached the actuator onto objects such as an almond and a blade of grass, demonstrating controlled rotation and bending motions respectively upon ultrasonic activation. This conformable property allows the artificial muscle to impart versatile mobilities to inanimate objects without significant weight or volume increase, illustrating its adaptability for a wide range of soft robotic applications.
Capitalizing on the skin’s flexibility and biocompatibility, the researchers took a crucial step towards medical usage by affixing the microbubble-array muscle onto the epicardial surface of an ex vivo porcine heart. The muscle maintained stable adhesion and functional actuation for over an hour under continuous ultrasound excitation, underscoring its potential for integration with living tissues. Through engineered bubble patterns and frequency tuning, the muscle generated selective localized mechanical forces enabling multimodal shape transitions, which could be harnessed for targeted drug delivery or precise mechanical stimulation in cardiac therapies.
The intelligent design also encompassed a biodegradable capsule for safe, minimally invasive delivery of the artificial muscle to internal organs. Injected into an excised porcine bladder, the capsule dissolved gradually over 3 to 5 minutes, releasing the muscle which then adhered securely to the inner bladder wall upon ultrasound activation. This breakthrough demonstrates practical wireless actuation and deployment of soft robotic devices within organ cavities, showcasing potential clinical applications such as localized drug delivery or tissue modulation without the need for surgical implantation.
Pushing the boundaries of bioinspired robotics, the team engineered an ultrasound-powered wireless stingraybot, mimicking the natural propulsion mechanisms of aquatic lifeforms. Equipped with two side-mounted artificial muscles patterned with microbubble arrays of differing sizes (12, 16, and 66 micrometers in diameter), this soft robot exhibits undulatory fin motions when subjected to a sweeping-frequency ultrasound signal spanning 30 to 90 kHz. The resultant locomotion propels the stingraybot at approximately 0.8 body lengths per second, exemplifying highly efficient, biomimetic swimming driven purely by external acoustic stimuli.
Importantly, the stingraybot and other artificial muscles can be pre-folded and encapsulated within edible hydroxypropyl methylcellulose capsules, enabling safe ingestion and deployment within gastrointestinal environments. In ex vivo experiments using porcine stomach tissue, ultrasound guided the release, attachment, and propulsion of these soft robots in fluid-filled, confined spaces—demonstrating precise navigation and actuation inside complex biological structures. This approach holds promise for future targeted therapies inside the digestive tract, offering new modalities for drug dissemination, tissue diagnostics, or minimally invasive surgeries.
The researchers also explored alternative geometries, folding a linear artificial muscle into a wheel-like configuration. Under ultrasonic sweeping-frequency stimulation, this structure demonstrated directional rolling movement across the stomach and intestinal mucosal surfaces, adapting to curved and complex terrains. Such adaptability positions these soft robots as potential tools for navigating tortuous lumens, providing access and actuation capabilities in areas unreachable by traditional rigid instruments, enhancing the scope of robotic medicine.
Further ex vivo studies utilized high-intensity focused ultrasound to drive precise locomotion and deformation of these artificial muscles within intestinal environments, underscoring their robustness and controllability in challenging physiological settings. The synergy of ultrasound stimulation with engineered microbubble patterns provides a rich palette for programming intricate actuation sequences, thrusting this technology into the spotlight for next-generation wireless soft robotics.
This pioneering work sets a foundation for the future development of wearable and implantable devices that leverage wireless, ultrasound-powered muscles to deliver dynamic mechanical responses and therapeutic payloads on demand. Tuned ultrasound frequencies paired with microbubble-array architectures enable selective, local actuation—crucial for applications such as anti-fibrotic treatments, gene delivery, and mRNA therapy targeting, areas of growing medical importance.
Moving forward, ongoing research aims to refine folding strategies, steering mechanisms, and the integration of these artificial muscles into multifunctional platforms capable of navigating the body’s complex biomechanical and fluidic environments. The challenges of in vivo stability, targeted control, and upscaling fabrication remain at the forefront, but the demonstrated feats herald a new era in minimally invasive, programmable soft robotic devices poised to revolutionize healthcare and biological research.
In sum, the innovative use of ultrasound-responsive microbubble arrays to induce rapid, reversible actuation in soft artificial muscles represents a significant breakthrough in wireless robotics. This technology extends capabilities from gentle biological manipulation to complex locomotion and internal navigation within organ systems. With biocompatibility and remote control at its core, it promises transformative applications ranging from precision biopsies and targeted therapeutics to post-surgical rehabilitation, ushering soft robotics into clinical realities with unprecedented finesse.
Subject of Research: Ultrasound-driven programmable artificial muscles for wireless soft robotics and biomedical applications.
Article Title: Ultrasound-driven programmable artificial muscles.
Article References: Shi, Z., Zhang, Z., Schnermann, J. et al. Ultrasound-driven programmable artificial muscles. Nature 646, 1096–1104 (2025). https://doi.org/10.1038/s41586-025-09650-3
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41586-025-09650-3
Keywords: Ultrasound actuation, microbubble array, soft robotics, artificial muscles, wireless control, biocompatibility, soft grippers, conformable robotic skin, bioinspired robots, minimally invasive devices, targeted drug delivery, biomedical navigation
Tags: advanced biomedical technologybiocompatible smart machinesfluid-environment compatible actuatorsmicrobubble array innovationsminimally invasive surgical devicesprogrammable soft robotics technologyrapid shape-changing materialssoft grippers for delicate manipulationtargeted therapy mechanismsultrasonic wave actuationultrasound-driven artificial muscleswireless medical robotics applications
