Perspective on the Next Generation of Injectable Probes Inspired by the History of Catheters’ Development

Catheters have evolved from rigid 19th-century tubes to sophisticated actuation-capable systems, driven by clinical demands for precise navigation through tortuous vasculature, robust infection control in long-term use, and multifunctionality across organ-specific applications. Key reinforcements include magnetic actuation for enhanced steerability in neurointerventions, antimicrobial coatings like rifampin-minocycline reducing bacteremia risks, and biocompatible soft polymers for improved flexibility and durability under physiological stresses. These advancements address challenges like sub-millimeter accuracy (<1 mm diameters) in humans, minimizing trauma, and enabling high-flow procedures. Such catheter-inspired innovations have catalyzed the development of injectable probes featuring cellular-scale dimensions (<100 µm) and multifunctional capabilities for neural interfacing, real-time sensing, electrical stimulation, and targeted drug delivery in ultra-minimally invasive therapies. This perspective reviews historical evolutions from ancient rudimentary tools to modern smart systems, organ-specific classifications highlighting geometry adaptations, actuation mechanisms (tendon-driven, pneumatic, hydraulic, electromechanical/magnetic), and material innovations, including shape-memory alloys and hydrogel coatings for degradation mitigation. Future directions focus on AI (Artificial Intelligence)-enabled wireless actuation, nanomaterials for personalized device geometries with >100% strain recovery, hybrid mechanisms, and bioinspired designs to achieve omnidirectional control and enhanced biocompatibility, thereby transforming precision medicine through advanced neuromodulation, stroke thrombolysis, and minimally invasive interventions.