Biohybrid semiconductor microrobots represent a cutting-edge convergence of materials science, nanotechnology, and biomedical engineering. These microscale devices integrate semiconductor components with biological elements to enable precise, controlled interactions within biological systems. Their applications in targeted drug delivery and minimally invasive surgery are particularly promising due to their unique capabilities in actuation, localization, and biodegradability.

Semiconductor materials provide the foundation for these microrobots, offering tunable electronic, optical, and magnetic properties. Silicon, silicon carbide, and gallium nitride are commonly used due to their biocompatibility and robust performance in physiological environments. These materials can be engineered at the nanoscale to achieve specific functionalities, such as responsive drug release or real-time sensing. The integration of biological components, such as cell membranes or proteins, further enhances biocompatibility and reduces immune responses.

Magnetic actuation is a widely employed method for controlling semiconductor microrobots. By embedding magnetic nanoparticles or coating microrobots with magnetic layers, external magnetic fields can guide their movement with high precision. Rotating or oscillating magnetic fields enable propulsion through viscous biological fluids, while static fields facilitate directional steering. Studies have demonstrated that microrobots with diameters between 1 and 10 micrometers can achieve speeds of up to 100 micrometers per second under controlled magnetic fields. This method is advantageous for deep-tissue applications where optical penetration is limited.

Optical actuation leverages the photoresponsive properties of semiconductor materials. Light absorption generates localized heat or electron-hole pairs, which can induce mechanical motion or trigger chemical reactions. For instance, gallium nitride microrobots exhibit photoelectrochemical propulsion when exposed to ultraviolet light, while silicon-based structures can be actuated via near-infrared irradiation due to their lower optical absorption in biological tissues. Optical control offers high spatial resolution but is typically limited to superficial tissues due to light scattering and absorption in deeper regions.

Localization of semiconductor microrobots is critical for ensuring accurate delivery and minimizing off-target effects. Imaging techniques such as fluorescence microscopy, magnetic particle imaging, and ultrasound are employed to track microrobots in real time. Semiconductor quantum dots embedded in microrobots provide strong fluorescence signals for high-resolution tracking, while magnetic nanoparticles enable detection via MRI or magnetic particle imaging. Some designs incorporate feedback systems where microrobots adjust their trajectory based on real-time sensor data, enhancing precision in dynamic biological environments.

Biodegradability is a key requirement for clinical translation, as non-degradable microrobots could pose long-term toxicity risks. Semiconductor materials like porous silicon and certain organic semiconductors are engineered to degrade into non-toxic byproducts under physiological conditions. The degradation rate can be tuned by adjusting material composition, porosity, or surface coatings. For example, porous silicon microrobots degrade within days to weeks, releasing encapsulated therapeutics while dissolving into silicic acid, a naturally occurring compound in the human body. Similarly, organic semiconductors based on conjugated polymers can break down into benign fragments under enzymatic or hydrolytic conditions.

In drug delivery applications, semiconductor microrobots enable spatiotemporal control over payload release. Stimuli such as pH changes, enzymatic activity, or external fields trigger the release of drugs from microrobot carriers. Silicon nanowires functionalized with thermoresponsive polymers release drugs upon localized heating induced by near-infrared light. In another approach, gallium arsenide microrobots degrade in response to specific enzymes, releasing anticancer agents directly within tumor microenvironments. Such systems enhance therapeutic efficacy while reducing systemic side effects.

Surgical applications benefit from the precision and miniaturization offered by semiconductor microrobots. They can navigate through narrow passages, such as blood vessels or the gastrointestinal tract, to perform tasks like clot removal, tissue ablation, or targeted biopsies. Magnetic steering allows surgeons to guide microrobots to specific sites, where optical or electrical stimuli activate their surgical functions. For example, silicon carbide microrobots equipped with sharp edges can mechanically disrupt pathological tissues when actuated by external fields, offering a less invasive alternative to conventional surgical tools.

Challenges remain in scaling up production, ensuring consistent performance in heterogeneous biological environments, and meeting regulatory standards for clinical use. However, advances in semiconductor fabrication, such as roll-to-roll processing and 3D printing, are addressing some of these limitations. Future developments may focus on integrating artificial intelligence for autonomous navigation or combining multiple actuation mechanisms for enhanced control.

Biohybrid semiconductor microrobots exemplify the potential of interdisciplinary research to revolutionize medicine. Their ability to merge the precision of semiconductor engineering with the adaptability of biological systems opens new avenues for personalized and minimally invasive therapies. As material synthesis and control technologies continue to evolve, these microrobots are poised to become indispensable tools in next-generation biomedical applications.