3D-printed machines that manipulate microscopic objects using capillary forces

Area of Science:

• Soft Matter Physics
• Micro-robotics
• Materials Science

Background:

• Capillary forces are crucial for assembling objects at liquid interfaces, but assembled structures are typically static.
• Existing micromanipulation techniques are often complex, costly, or limited in programmability.

Purpose of the Study:

• To dynamically modulate capillary forces for programmable two-dimensional movement of floating objects.
• To develop a novel class of 'capillary machines' that convert vertical motion into programmable lateral object manipulation.
• To demonstrate the assembly of complex microstructures using these machines.

Main Methods:

• 3D-printed devices with height-varying channels were used to trap and guide floating objects via repulsive capillary forces.
• Vertical movement of the devices in a water bath steered trapped microscopic objects in two dimensions.
• Elementary capillary machines were combined to create centimeter-scale compound machines for braiding filaments.

Main Results:

• Demonstrated programmable translation, rotation, and separation of multiple floating objects.
• Showcased the ability to perform work on submerged objects through cyclic vertical motion.
• Successfully braided microscopic filaments into prescribed, including non-repeating, topologies.

Conclusions:

• Capillary machines offer a distinct, meniscus-linked approach to micromanipulation, simplifying control requirements to the capillary length scale.
• The method allows for rapid, inexpensive fabrication of machines capable of manipulating microscopic particles and braiding microwires.
• This technology holds potential for applications in micro-assembly, high-frequency electronics, and advanced materials fabrication.