Micro-scale aerosol jet printing of superparamagnetic Fe3O4 nanoparticle patterns.

The opportunity to create different patterns of magnetic nanoparticles on surfaces is highly desirable across many technological and biomedical applications. In this paper, this ability is demonstrated for the first time using a computer-controlled aerosol jet printing (AJP) technology. AJP is an emerging digitally driven, non-contact and mask-less printing process which has distinguishing advantages over other patterning technologies as it offers high-resolution and versatile direct-write deposition of a wide range of materials onto a variety of substrates. This research demonstrates the ability of AJP to reliably print large-area, fine-feature patterns of superparamagnetic iron oxide nanoparticles (SPIONs) onto both rigid material (glass) and soft and flexible materials (polydimethylsiloxane (PDMS) films and poly-L-lactic acid (PLLA) nanofilms). Investigation identified and controlled influential process variables which permitted feature sizes in the region of 20 µm to be realised. This method could be employed for a wide range of applications that require a flexible and responsive process that permits high yield and rapid patterning of magnetic material over large areas. As a first proof of concept, we present patterned magnetic nanofilms with enhanced manipulability under external magnetic field gradient control and which are capable of performing complex movements such as rotation and bending, with applicability to soft robotics and biomedical engineering applications.

Patient-Specific Magnetic Catheters for Atraumatic Autonomous Endoscopy.

Despite increasing interest in minimally invasive surgical techniques and related developments in flexible endoscopes and catheters, follow-the-leader motion remains elusive. Following the path of least resistance through a tortuous and potentially delicate environment without relying on interaction with the surrounding anatomy requires the control of many degrees of freedom. This typically results in large-diameter instruments. One viable solution to obtain dexterity without increasing size is via multiple-point magnetic actuation over the length of the catheter. The main challenge of this approach is planning magnetic interaction to allow the catheter to adapt to the surrounding anatomy during navigation. We design and manufacture a fully shape-forming, soft magnetic catheter of 80 mm length and 2 mm diameter, capable of navigating a human anatomy in a follow-the-leader fashion. Although this system could be exploited for a range of endoscopic or intravascular applications, here we demonstrate its efficacy for navigational bronchoscopy. From a patient-specific preoperative scan, we optimize the catheters' magnetization profiles and the shape-forming actuating field. To generate the required transient magnetic fields, a dual-robot arm system is employed. We fabricate three separate prototypes to demonstrate minimal contact navigation through a three-dimensional bronchial tree phantom under precomputed robotic control. We also compare a further four separate optimally designed catheters against mechanically equivalent designs with axial magnetization profiles along their length and only at the tip. Using our follow-the-leader approach, we demonstrate up to 50% more accurate tracking, 50% reduction in obstacle contact time during navigation over the state of the art, and an improvement in targeting error of 90%.