Pietro Valdastri

Continuum robots offer inherent compliance and dexterity for operation in confined and unstructured environments; however, achieving hybrid multi-segment functionality typically requires application-specific redesign and tightly coupled architectures. To address this limitation, this study proposes a reconfigurable hybrid continuum robot architecture based around a multi-lumen central integration backbone that supports multiple actuation modalities and robot configurations. The proposed design combines external tendon-driven disk modules for proximal actuation with a pneumatically actuated distal tip, while internal lumens allow routing of pneumatic lines and the insertion of optional stiffening elements without structural interference. The reconfigurability of the architecture is demonstrated through two configurations: Concept-1, a two-segment hybrid system, and Concept-2, a miniaturized three-segment configuration achieved by reducing the disk diameter and extending tendon actuation to the backbone. Experimental evaluations are conducted to characterize segment-wise actuation, coupled deformation behavior, and workspace capabilities, hysteresis response, tip contact force, and phantom-based target reachability. Results show that the integration of tendon-driven and pneumatic actuation significantly expands and reorients the reachable workspace. Additional functional tests showed repeatable loading–unloading behaviour of the tendon-driven segment, a maximum pneumatic tip contact force of approximately 0.45 N, and successful access to five representative targets within a stomach-like phantom using Concept-2. A kinematic model based on a constant-curvature formulation is validated against experimental data, yielding root-mean-square errors (RMSE) of 5.44 mm and 6.12 mm for Concept-1 and Concept-2, respectively. These results demonstrate consistent model accuracy across different configurations and scales. Overall, the proposed architecture enables modular, scalable, and reconfigurable hybrid continuum robots, providing a flexible framework for applications ranging from large-scale manipulation to gastroscopy-inspired minimally invasive procedures.

We demonstrate a near-field terahertz (THz) imaging modality based on asynchronous optical sampling of on-chip THz sensors, and apply it to the sub-wavelength imaging of silicone soft-tissue phantoms. The sensor consists of a planar Goubau-line waveguide that incorporates a quarter-wavelength stub band-stop resonator, with photoconductive switches integrated into the waveguide for broadband THz signal generation and detection. By raster-scanning soft-tissue phantoms through the evanescent electric field above the resonator using a robotic manipulator, we reconstruct two-dimensional THz images with spatial resolution down to 50 μm - more than one order of magnitude below the free-space wavelength at the operating frequency (355 GHz) - and with pixel acquisition times down to 100 ms. Image contrast is obtained using both frequency shifts of the resonator and changes in power transmission through the device, enabled by the broadband nature of the on-chip system. These results simultaneously establish the potential of on-chip near-field THz sensors as a platform for high-resolution imaging of soft tissue analogues, while also highlighting their potential for future applications in biomedical imaging and real-time sensing.

Access to the small bowel remains challenging due to its length, diameter, and curvature, making conventional push endoscopes insufficient for deep exploration. Improved tools that can travel throughout the small bowel without risking mucosal trauma, maintain stable visualization, and offer fine distal manipulation are needed for diagnosis and targeted treatment of small-bowel diseases. This work presents the Inchiscope, a miniaturized modular self-propelled soft robotic endoscope developed to meet the challenges associated with small-bowel access. The presented configuration combines nine independent actuation units to deliver three anchoring balloons and two parallel bellows actuator (PBA) segments for extension/contraction and steering. The modular approach facilitates a minimized diameter (13 mm) while enabling three operation modes including full-body inchworm-inspired locomotion, independent distal segment control for traversing tight bends, and proximal anchoring for stabilized inspection. Characterization highlights stable anchoring at forces up to 12 N, a PBA elongation ratio of 300% and controlled omnidirectional bending to 110$^\circ$. Experiments in rigid and compliant phantoms demonstrate self-propelled locomotion at up to 11.4 mm/s and within tubular environments $< $25 mm in diameter and with bending radii between 30–45 mm, while the independently actuated distal tip delivered continuous 3-D control for observation and positioning in complex geometries.

Continuum robots have gained significant attention for endoluminal deployment due to their ability to operate in constrained environments. However, the complexity of many continuum robotic design approaches creates challenges in adapting robot geometry, dexterity, stiffness distribution, and functional integration to the requirements of specific medical procedures and/or patient-specific anatomy. This article presents a modular and adaptable design approach for the development of compact, multisegment tendon-driven continuum robots. The design strategy employs a compliant helical spring backbone with inner and outer self-anchoring spacer disks, enabling simple reconfiguration of segments and actuation tendons without increased manufacturing complexity. A design framework is introduced to formalize disk–spring integration, and a two-segment, seven-tendon example is presented for robotically assisted bronchoscopy. The design achieves a minimum diameter of 4.2 mm with a 2.4-mm working channel housing a camera and biopsy tool. An adapted piecewise constant curvature model is presented to predict shape and tip pose, with a mean tip error of 4.0 mm. Navigation trials within a bronchial phantom reached predefined targets for biopsy needle deployment with an average positioning error and navigation time of 2.4 mm and 75 s, respectively. The presented approach offers a versatile strategy for developing compact continuum robots for endoluminal interventions.

Robotic deformable object manipulation (DOM) faces critical challenges in industrial and medical applications due to under-actuation, unpredictable deformation, and partial observability. Model-free methods often suffer from unstable Jacobians arising from ill-conditioned observations, while physics-based models typically depend on precise parameters and volumetric meshing, limiting their real-time practicality. We propose a wavelet-boundary element method (BEM) framework that leverages multiscale wavelet descriptors to control 3D deformations directly from efficient feedback modalities, such as contours and curves. By coupling wavelets with BEM, we derive an analytical deformation Jacobian that functions independently of material stiffness (e.g., Young’s modulus), relying solely on an online-calibrated Poisson’s ratio. This mesh-free formulation significantly enhances real-time performance and robustness against sensor occlusion. Validated in simulation and on the da Vinci Research Kit (dVRK) with phantom and ex vivo animal tissue, our method achieves millimetre-level accuracy. Comparative studies against Fourier-based, model-free, and online finite element method (FEM) approaches demonstrate superior stability and computational efficiency. Notably, our framework achieves convergence speeds significantly faster than online FEM by avoiding volumetric computations, while resolving ill-conditioning through spatial–frequency localization. This work advances deformable object manipulation in unstructured environments, particularly in surgical robotics, where stability under partial observability is essential. Project page: https://junleihu.github.io/projects/dwtbem/ .

Terahertz (THz) light’s sensitivity to water, nonionizing nature, and sub-millimeter resolution make it ideal for medical imaging, particularly for diagnosing and managing skin conditions such as eczema, psoriasis, and skin cancer. Traditional handheld THz probes suffer from positional errors, tremors, and inconsistent contact pressure, which worsen with prolonged use. To address this, robotic THz acquisition systems can be leveraged to segment regions of interest on the skin surface and compute the appropriate probe pose for scanning. This paper proposes a markerless method for automatic identification and estimation of the pose for the placement of the THz probe over high-curvature facial regions. An RGB-D camera is utilized to select, recognize, and track the scanning targets on the patient using an end-to-end network-based model for 3D human face mesh prediction. We then solve for the landing pose to position the probe at normal incidence to the tissue surface at the target scan regions. We evaluated scanning area localization accuracy, motion execution accuracy, and THz acquisition capability using a mannequin head and human volunteers. Results demonstrated target registration error of 1.71 mm, scan target localization accuracy of less than 3 mm and probe landing pose estimation accuracy of 2.769 ±3.02 mm in X, 6.62 ± 0.6 mm in Y and 4.792 ± 2.18 in Z and orientation error of 1.6±0.8 degrees.

Ultrasonic bone scalpels are known to offer benefits of low cutting force, high precision, low microdamage around the cut site, and tissue selectivity in surgical procedures. However, all current commercial devices are too large to be integrated with the flexible endo-wrist of a surgical robot, and therefore, there is a significant gap for innovation in miniature devices. Ultrasonic bone scalpels in use in clinical settings are all based on a bolted Langevin transducer (BLT), which consists of a pre-stressed piezoceramic ring stack, two end masses, and a cutting blade. The BLT-based device must operate in resonance to achieve sufficient displacement amplitude at the surgical tip to cut through bone, and this dictates its size. Flextensional transducers have emerged as an alternative, but these transducers generally contain a low volume of piezoelectric driving material, and hence cannot excite the required displacement amplitude, and their reliance on adhesive bonds in their fabrication means they fail at the excitation levels required for a bone surgery device. We present a flextensional configuration that forms an ultrasonic surgical device, where the vibration-amplifying metal caps are excited by a pre-stressed piezoelectric stack. In vitro ultrasonic bone cutting tests facilitated with a Kuka robot are performed for a range of cutting speeds and penetration rates. The results demonstrate effective integration with a Kuka robot and that bone cutting can be achieved with an extremely low cutting force ( < 1 N) and high precision (the width of the bone cut presents under 6% deviation from the thickness of the blade). The flextensional device overcomes both the large size of conventional ultrasonic osteotomy devices and the displacement amplitude limitations of other miniaturisation approaches. Integration with an articulated robotic endo-wrist is enabled, establishing a foundation for low-force and high-precision ultrasonic bone cutting in minimally invasive, anatomically constrained robotic surgical environments.

The introduction and development of soft continuum robots (SCRs) for minimally invasive surgery and endoluminal intervention offers a promising option for navigating delicate, convoluted human anatomy across various procedures. However, successful translation of SCRs from research prototypes through to clinically viable tools relies on overcoming the challenge of functionalization for targeted diagnostic and therapeutic intervention. Functionalization demands specialized design and fabrication strategies to ensure practical integration of operational components, such as stimuli-responsive materials and tip-mounted transducers, with soft bioinspired geometry and actuation mechanisms. This review aims to highlight the state of the art in the development of functionalized SCRs for minimally invasive and endoluminal applications. Drawing on advances over the past twenty-five years, we provide a comprehensive discussion of the innovations to date and of the pivotal clinical and developmental challenges to be overcome for the functionalization, therapeutic benefit and therefore, clinical translation of SCRs. Through developing coherence between the fields of bio-inspired soft robotic design, digitally driven fabrication, materials engineering and intra-operative control, further clinically significant advances may be realized in the domain of functionalized SCRs.