Selective Tweezing and Immobilization of Colloids for Dexterous Manipulation of Biological Materials

The assembly of arbitrary 3D structures using nano- to micron-scale colloidal building blocks has broad applications in photonics, electronics, and biology. Combining optical tweezers (OT) with two-photon polymerization (TPP) enables 3D selective tweezing and immobilization of colloids (STIC) without requiring specialized particle functionalization. Unlike traditional approaches, we demonstrate that high-repetition-rate femtosecond laser pulses, rather than continuous-wave lasers, allow optical tweezing at intensities below the TPP threshold. This dual functionality enables both OT and TPP using a single laser source. This platform was applied on S. aureus cells into desired configurations, highlighting its potential for advanced cell patterning. TPP was further used to fabricate intricate 3D microstructures, including microgrooves and cylindrical constructs, facilitating spatially resolved studies of single-cell dynamics and interactions. This work highlights the potential of STIC as a versatile tool for advanced biological applications, including tissue engineering and microbial research.