image: (a) Milli-SRs perform biomedical tasks in narrow human cavities—like navigating complex orifices, removing foreign objects, and entering tiny vessels. (b) Bubble casting struggles with milli-SRs due to bubble fragments. (c) Mini bubble casting fixes this: The enhanced silicone resists interfacial tension, keeps bubbles stable, and enables reliable milli-SR fabrication.
Credit: ©Science China Press
Picture this: a clinician threads a noodle-thin scope into a patient’s airway. The tip, dexterous as a fingertip, slips left, right, downward until it reaches the deepest targeted area, tunnels too narrow for a grain of rice. There it snaps high-resolution images or gently hooks out a clot. Movie magic? Nope. It’s the latest demonstration from Prof. Guoying Gu’s team at Shanghai Jiao Tong University, unveiled today.
The pain point :
A major challenge in minimally invasive surgery has long been navigating and operating within the body’s narrow orifices. Soft robots—with their flexible, body-friendly design—are now emerging as promising tools for next-generation medical procedures. However, building soft robots that are just a few millimeters in size (and powered by fluid) remains a key hurdle:
Traditional “bubble casting” is a simple process, similar to making cotton candy: you inject a long bubble into liquid silicone, let the silicone harden, and you’re left with a hollow tube. But when scaling down to millimeter sizes, surface tension becomes a problem. It acts like a “bully”—tearing the fragile bubbles apart and causing the silicone structure to collapse into messy, uneven clumps (think lumpy “mountain ranges”) before it can fully set.
To solve the problem, researchers modified silicone liquid under high-stability conditions by inserting accelerator and thickener. The modified silicone liquid is like frozen toothpaste: soft when flowing, instantly stiff when it meets air. A bubble is injected through the “magic” silicone liquid and a flawless millimeter-scale inner void of soft robot is ready.
[Figure1]
In just 30 minutes and with a single syringe, researchers make soft robots no wider than a pin—1–3 mm, with mirror-smooth skin at 11 nm roughness, ten times slimmer than any bubble-cast forebear. No clean room, no doctorate: a bench, a hand, and the recipe are enough.
Show-off time:
[Video1]
[Video2]
“We aren’t just making robots smaller—we’re making surgery gentler too.” — Guoying Gu, corresponding author of the study. The next step in development is clear: first, equipping the robots with built-in sensors that can monitor temperature, pressure, and pH levels; second, adding a hydrogel drug coating that dissolves precisely when needed. The goal for this “Soft Robot 2.0” is to create non-invasive, smart “in-body pharmacies.”
Journal
National Science Review