Electrothermally Driven Hydrogel-on-Flex-Circuit Actuator for Smart Steerable Catheters

Abstract

This paper reports an active catheter-tip device functionalized by integrating a temperature-responsive smart polymer onto a microfabricated flexible heater strip, targeting at enabling the controlled steering of catheters through complex vascular networks. A bimorph-like strip structure is enabled by photo-polymerizing a layer of poly(N-isopropylacrylamide) hydrogel (PNIPAM), on top of a 20 × 3.5 mm2 flexible polyimide film that embeds a micropatterned heater fabricated using a low-cost flex-circuit manufacturing process. The heater activation stimulates the PNIPAM layer to shrink and bend the tip structure. The bending angle is shown to be adjustable with the amount of power fed to the device, proving the device’s feasibility to provide the integrated catheter with a controlled steering ability for a wide range of navigation angles. The powered device exhibits uniform heat distribution across the entire PNIPAM layer, with a temperature variation of <2 °C. The operation of fabricated prototypes assembled on commercial catheter tubes demonstrates their bending angles of up to 200°, significantly larger than those reported with other smart-material-based steerable catheters. The temporal responses and bending forces of their actuations are also characterized to reveal consistent and reproducible behaviors. This proof-of-concept study verifies the promising features of the prototyped approach to the targeted application area.

Functional Hydrogel Interface Materials for Advanced Bioelectronic Devices

“…Combining compliant electrode arrays in open, serpentine mesh layouts with PNIPAM hydrogels yields a class of soft actuators, capable of complex and programmable threedimensional shape transformation. 48 Use of PNIPAM applied onto the tip of a medical catheter with a thin-film metal heater 49 enables active, steering across a wide range of bending angles for maneuvering through complex vascular networks to target regions of interest. Another class of thermal functionality involves evaporative cooling.…”

“…b, Uniform layer of a thermoresponsive hydrogel as the basis for bimorph thermal actuators in catheters that can be maneuvered to a target vessel branch. Reproduced with permission from ref . Copyright 2020 Molecular Diversity Preservation International.…”

Sequential Oxidation Strategy for the Fabrication of Liquid Metal Electrothermal Thin Film with Desired Printing and Functional Property

“…The electrothermal effect is an energy conversion process that converts electrical energy into thermal energy, which has many potential applications in aerospace, biomedical, and industrial applications [25,26]. The heating devices prepared by the traditional metal wire have the problems of local overheating and low flexibility.…”

An Electrically Actuated Soft Artificial Muscle Based on a High-Performance Flexible Electrothermal Film and Liquid-Crystal Elastomer

“…Artificial muscles, also referred to as soft actuators, generate mechanical responses to external stimuli, such as an electric field, magnetic field, light, and heat, in the form of stresses or strains. Various smart materials and diverse fabricating approaches have been widely explored, as well as their potential application in soft robotics, − surgical assist systems, , organ assist devices, − etc. For instance, Kim et al proposed 3D-printed soft materials with programmed ferromagnetic domains, which could achieve complex shape changes under applied magnetic fields and widely used in reconfigurable soft electronics and soft robots .…”