Semi-Autonomous 2.5D Control of Untethered Magnetic Suture Needle

Untethered miniature surgical tools could significantly reduce invasiveness and enhance patient outcomes in robot-assisted laparoscopic surgical procedures. This paper demonstrates the feasibility of performing semi-autonomous suturing tasks using an untethered magnetic needle controlled by an external electromagnetic manipulator. The electromagnetic manipulator can generate magnetic torques and gradient-based pulling forces to actuate the magnetic needle. Here, we develop and implement a semi-autonomous 2.5D control method for controlling the in-plane position and both in-plane and out-of-plane orientations of a magnetic needle for suturing on tissue-mimicking agar gel phantoms. The method includes recognizing needles and incisions, planning trajectory, and performing suturing with visual feedback control. We conduct two mock suturing tasks using both continuous and interrupted techniques on 1% agar gel phantoms with 2 cm and 3 cm incision sizes. The results demonstrate precise needle control, with an average root-mean-square position error of 1.01 mm and 1.12 mm across tasks. The system also achieved submillimeter-level suture spacing accuracy, comparable to surgeons using state-of-the-art surgical robots. These findings highlight the feasibility of using untethered magnetic suture needles for minimally invasive suturing procedures.