Harnessing ultrafast optical pulses for 3D microfabrication by selective tweezing and immobilization of colloidal particles in an integrated system

Microfabrication using nano- to micron-sized building blocks holds great potential for applications in next-generation electronics, optoelectronics, and advanced materials. However, traditional methods like chemical vapor deposition and molecular beam epitaxy require highly controlled environments and specialized equipment, limiting scalability and precision. To address these challenges, we present a single-laser platform for selective tweezing and immobilization of colloids (STIC) that integrates particle manipulation, assembly, and stabilization in one system. STIC utilizes a femtosecond laser at ultra-low power for precise, contact-free optical manipulation of colloids without material damage. At higher power, the same laser enables two-photon polymerization (TPP) to immobilize colloids securely in their intended positions. Using STIC, we demonstrate the assembly of 3D structures from dielectric beads to patterned arrangements of transition metal dichalcogenides (TMD e.g., MoS2). We also incorporate a TPP-fabricated handle as an intermediate support, significantly enhancing the optical tweezing efficiency of TMDs. The single-laser design eliminates the need for dual-laser systems, simplifying optical alignment, reducing heating damage, and improving efficiency. Additionally, we show that STIC supports direct multiphoton imaging for in situ inspection during fabrication. This work establishes a versatile, scalable optical platform for high-precision microstructure fabrication, offering a pathway to overcome current limitations in micro- and nanomanufacturing.