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Real-time visual localization of needles is necessary for various surgical applications, including surgical automation and visual feedback. In this study we investigate localization and autonomous robotic control of needles in the context of our magneto-suturing system. Our system holds the potential for surgical manipulation with the benefit of minimal invasiveness and reduced patient side effects. However, the non-linear magnetic fields produce unintuitive forces and demand delicate position-based control that exceeds the capabilities of direct human manipulation. This makes automatic needle localization a necessity. Our localization method combines neural network-based segmentation and classical techniques, and we are able to consistently locate our needle with 0.73 mm RMS error in clean environments and 2.72 mm RMS error in challenging environments with blood and occlusion. The average localization RMS error is 2.16 mm for all environments we used in the experiments. We combine this localization method with our closed-loop feedback control system to demonstrate the further applicability of localization to autonomous control. Our needle is able to follow a running suture path in (1) no blood, no tissue; (2) heavy blood, no tissue; (3) no blood, with tissue; and (4) heavy blood, with tissue environments. The tip position tracking error ranges from 2.6 mm to 3.7 mm RMS, opening the door towards autonomous suturing tasks.

Reciprocity is one of the fundamental properties in the field of wave propagation. In acoustics, this property helps in various practical applications. But, breaking this reciprocity also has useful applications. As a result of which, many researchers have tried to break the reciprocity in acoustics, which is comparatively difficult, unlike in fields such as electro-magnetics. Majority of these proposed methods to break the reciprocity are hard-wired systems, which work for a very limited frequency range. Thus, we have introduced a non-reciprocal metamaterial having boundary control with the help of piezoelectric sensors and actuators. A theoretical model is introduced to induce the nonreciprocal behavior, and it is backed up by providing experimental evidence. Our setup consists of a cylindrical cell made up of acrylic, filled with water, having four piezo sensors/actuators, two on each end. The idea is to excite the piezo cell through an actuator on one side, collect the resulting signal from the piezo sensor on the other side, and perform appropriate mathematical operations on this signal to produce a feedback/control signal via a specially designed dynamic control action. This control signal affects the propagation of pressure waves through the water medium inside the cell as it introduces a virtual gyroscopic effect of controlled magnitude and direction. Thus, this is how non-reciprocity is introduced and controlled into the metamaterial cell. The obtained theoretical and experimental results demonstrate the effectiveness of the dynamic controller in breaking the acoustic reciprocity. Extension of this work to multi-cell metamaterial configuration is natural extension to be pursued.