4D-Printed Microrobots with Synergistic Integration of Magnetic Actuation, Diffractive Optical Sensing, and pH-Adaptive Morphing

Abstract

Soft microrobots exhibit distinct advantages in biomedical applications, with their exceptional maneuverability in confined spaces and environmental adaptability offering innovative solutions for targeted theranostics. However, current systems are inherently constrained by the physical separation of sensing and actuation modules, leading to inadequate integration and operational efficiency that hinder practical implementation. To overcome this challenge, a micro-nano 4D printing design paradigm is proposed. Through spatial programming of multi-responsive materials and biomimetic microstructural engineering, a microrobotic system is fabricated with synergistic perception-actuation capabilities. By integrating gradient magnetic field-responsive composites and pH-sensitive hydrogels, a 150-µm-scale biomimetic fish-shaped microrobot is developed, innovatively integrating three functionalities: magnetic-actuation, pH-triggered joint actuation, and diffractive optical sensing. Specifically, its tail joint enables adaptive modulation of doxorubicin release kinetics via pH-mediated mechanical deformation, while the head-mounted diffractive spectral sensor provides dynamic optical feedback of pathological microenvironment pH (5.0–6.5). Proof-of-concept experiments demonstrate the system's precise drug release control and environmental monitoring capabilities in gastric cancer cell therapy. This work provides a 4D printing design approach for next-generation intelligent therapeutic microrobots capable of environmental perception, intelligent response, and precise execution.