A Hybrid Tendon-Pneumatic Continuum Robot with Pressure-Driven Length Modulation and Tool-Channel Locking

Continuum robots capable of modulating both their geometry and stiffness are well-suited to the demands of minimally invasive interventions within confined anatomical environments. Existing designs typically achieve either bending through tendon actuation or axial extension via pneumatic chambers, but rarely integrate both functions in a compact architecture. This paper presents a hybrid tendon-pneumatic continuum robot that integrates pressure-driven length modulation and tendon-based steering within a soft thermoplastic elastomer (TPE) body. The tubular robot has a diameter of 14 mm and houses a $\mathbf{4 ~ m m}$ central tool channel. Pressurization enables continuous extension and contraction and reversible toolchannel locking, while three peripheral tendons provide precise directional control. Experimental evaluation demonstrates a pressure-dependent deployment rate up to 70 mm, and a defined 3D workspace. Model validation shows $\lt 2 \%$ relative error between predicted and measured shapes in different backbone configurations. Phantom demonstrations confirm the robot’s suitability for confined endoluminal environments, while multirobot configurations demonstrate the possibility for collaborative, adaptable grasping. The compact geometry, integrated hybrid actuation, and pressure-responsive locking capability represent a promising step toward multifunctional continuum manipulators for medical and industrial applications.