Deformation of flexible robots can be practically assessed using extension/compression, shear, curvature, and torsion. Sensing based on one or more of the above characteristics enables closed-loop control for delicate tasks that require precision and dexterity. Due to the increasing popularity of flexible robotics in recent years, significant research effort has been directed to this burgeoning field. Although numerous studies have addressed soft sensing technologies, their successful integration into flexible robotic systems remains limited. This article provides a comprehensive review of sensing methods, from multidimensional deformation to the underlying principles of deriving hard-to-measure deformation from surrogate parameters. It focuses on sensing modalities such as strain measurement via piezoelectric, capacitive, resistive, and optical techniques. The applications of deformation sensing in industrial and service robotics are described. Future challenges and potential research issues including resolution, conformability, multifunctionality, crosstalk, and miniaturization are discussed. The need for a synergistic approach across disciplines is highlighted, emphasizing the integration of new materials, microstructures, advanced manufacturing technologies, and state-of-the-art signal processing techniques.

Percutaneous coronary intervention (PCI) involves the delivery of a flexible submillimeter guidewire and existing x- ray based approaches impose significant ironing radiation. The use of magnetic resonance imaging (MRI) for intraoperative guidance has the advantages of not only being safe but also having high positioning accuracy and excellent tissue contrast. This paper develops a pneumatically driven MR-conditional delivery mechanism for the ease of manipulation of the guidewire in vivo. It incorporates newly developed rotary pneumatic step motors and a pneumatic slip ring for actuation and decoupling of translational and rotational motions. An effective clamping mechanism for the locking and releasing of the guidewire is also incorporated. The proposed pneumatic slip ring mechanism decouples six gas lines, where four are used to supply a pneumatic step motor for translational motion and two for the clamping mechanism. High friction sil sleeve is used to hold the guidewire firmly. The rotary pneumatic motor has excellent sealing and stability, providing an output torque of 15.75 Nm/MPa. Experiments show that the average error of translational motion is 0.37 mm. Real-time MRI-guided endovascular intervention is performed in a vascular phantom with pulsatile flows to validate its potential clinical use. The imaging artifact test under MRI shows no noticeable distortion and the loss of Signal-to-Noise Ratio (SNR) is less than 2%.

MRI-guided robotic systems are emerging platforms for minimally invasive intervention because of high positioning accuracy and excellent tissue contrast. MR safe encoders are critical components for closed-loop robotic control. This paper develops an MR safe absolute rotary encoder based on eccentric sheave and FBG sensors. The eccentric sheave transforms the rotational motion of the shaft to the bending deflection of the beam on which FBG sensors are integrated. A model is built by establishing the relationship of the kinematics of the sheave, the mechanical properties of the beam with unknown length, and the strain model of two Fiber Bragg Grating (FBG) sensors. A Pseudo-Rigid Body (PRB) 3R model is used to solve a set of constrained equations for accurate rotary encoding. A prototype is built to calibrate the parameters and validate the accuracy of the encoder and its MR compatibility. Results show that the maximum angular error is 1.6°, and the RMS error is 0.46°. MRI shows that no noticeable artifacts are observed, and the Signal to Noise Ratio (SNR) is not affected. The results demonstrate the potential of the proposed method for it to be integrated with MR safe robots with easy fabrication, compact structures, and continuous measurement.

Electrospinning has exhibited excellent benefits to treat the trauma for tissue engineering due to its produced micro/nano fibrous structure. It can effectively adhere to the tissue surface for long-term continuous therapy. This paper develops a robotic electrospinning platform for endoluminal therapy. The platform consists of a continuum manipulator, the electrospinning device, and the actuation unit. The continuum manipulator has two bending sections to facilitate the steering of the tip needle for a controllable spinning direction. Non-circular joint profile is carefully designed to enable a constant length of the centreline of a continuum manipulator for stable fluid transmission inside it. Experiments are performed on a bronchus phantom, and the steering ability and bending limitation in each direction are also investigated. The endoluminal electrospinning is also fulfilled by a trajectory following and points targeting experiments. The effective adhesive area of the produced fibre is also illustrated. The proposed robotic electrospinning shows its feasibility to precisely spread more therapeutic drug to construct fibrous structure for potential endoluminal treatments.

Continuum robots composed of elastic backbones have a broad application prospect in the narrow and restricted environment because they overcome the disadvantages of traditional articulated robots, such as being bulky and inflexible. Statics plays an important role in the planning and control of the continuum robot composed of the elastic backbone. Pseudo-Rigid Body (PRB) theory has shown great potential in the description of flexible body statics. The PRB 3R model accurately describes the large deformation of the flexible body and has high computational efficiency. However, PRB 3R models mostly focus on the planar static modeling, and there are few applications in three-dimensional (3D) statics. In this paper, a 3D static modeling method of cable-driven continuum robot based on PRB 3R theory is proposed. By introducing the equilibrium constraint equations of resultant force/moment and bending plane normal of the elastic backbone, the state of the continuum robot is determined. The 3D static equations established by the proposed method take into account the comprehensive effects of the elastic force, external force, gravity and friction. A static verification experiment system of the cable-driven continuum robot is designed to verify the proposed method. The accuracy of the proposed method is verified by comparison with experimental data. The maximum position error between simulation and experimental results is 7.6%.