Ferromagnetic soft continuum robots

Abstract

Small-scale soft continuum robots capable of active steering and navigation in a remotely controllable manner hold great promise in diverse areas, particularly in medical applications. Existing continuum robots, however, are often limited to millimeter or centimeter scales due to miniaturization challenges inherent in conventional actuation mechanisms, such as pulling mechanical wires, inflating pneumatic or hydraulic chambers, or embedding rigid magnets for manipulation. In addition, the friction experienced by the continuum robots during navigation poses another challenge for their applications. Here, we present a submillimeter-scale, self-lubricating soft continuum robot with omnidirectional steering and navigating capabilities based on magnetic actuation, which are enabled by programming ferromagnetic domains in its soft body while growing hydrogel skin on its surface. The robot’s body, composed of a homogeneous continuum of a soft polymer matrix with uniformly dispersed ferromagnetic microparticles, can be miniaturized below a few hundreds of micrometers in diameter, and the hydrogel skin reduces the friction by more than 10 times. We demonstrate the capability of navigating through complex and constrained environments, such as a tortuous cerebrovascular phantom with multiple aneurysms. We further demonstrate additional functionalities, such as steerable laser delivery through a functional core incorporated in the robot’s body. Given their compact, self-contained actuation and intuitive manipulation, our ferromagnetic soft continuum robots may open avenues to minimally invasive robotic surgery for previously inaccessible lesions, thereby addressing challenges and unmet needs in healthcare.

Magnetic Actuation Systems for Miniature Robots: A Review

“…Mounting the ferromagnetic sphere is another option, and this type of catheter is often actuated by the applied magnetic gradient . Recently, a catheter fabricated from magnetized ink composed of hard magnetic particles and soft polymer was devised, and its diameter can be miniaturized below hundreds of micrometers . Catheters with controllable magnetization have also been proposed.…”

“…Because of their small scale, these robots can access complex and narrow regions of the human body in a minimally invasive manner, for example, in the gastrointestinal (GI) tract, vasculature, brain, and eye . Moreover, they have the potential to perform various tasks, such as targeted delivery, precise surgery, and medical examination . In addition, microsized robots have prospects for in vitro applications, such as cell manipulation and tissue engineering, because of their capability to manipulate down to subcellular entities with high precision and repeatability …”

Magnetic Resonance Imaging System–Driven Medical Robotics

“…Due to such a magnetic field constraint inside an MRI device, conventional magnetic untethered robot designs that rely on temporal change of magnetic fields, i.e., those with a nonuniform magnetization profile, cannot be used in MRI devices. Therefore, locomotion and functionalities based on rotation, spinning, and undulation types of motions cannot be realized through magnetic robots inside MRI devices . In addition, the very high constant magnetic field of an MRI device (e.g., 7 T) is typically strong enough to saturate the magnetic objects inside the bore.…”

A Unidirectional Soft Dielectric Elastomer Actuator Enabled by Built-In Honeycomb Metastructures

“…Soft robotics, an emerging multidisciplinary field, has been receiving increasing attention in the past decade, due to the flexibility and adaptability offered by soft materials to interact with unstructured environments [1][2][3][4][5][6]. Soft actuators, typically made of compliant materials that are responsive to external physical stimuli, play a key role in enabling the functionalities of soft robots.…”