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.
Highlights
Medical catheters are flexible tubes with different tip shapes used by surgeons to access a target location inside the human body [1]
Surgeons are required to be highly skilled in guiding the catheters manually, and they need to use different catheters with different tip shapes to navigate through complex branch bifurcations to reach a target site [6,7,8,9]
Branch angles of the human coronary arteries can vary from 32◦ to 124◦ [10,11], making catheter navigation challenging. The use of these devices can injure the inner walls of the vessel because of the friction produced by forcing a fixed tip to bend at a branch bifurcation and steer it in an intended direction [4,11]
Summary
Medical catheters are flexible tubes with different tip shapes used by surgeons to access a target location inside the human body [1]. One advantageous feature available with these hydrogels, including PNIPAM, is that they can be photo-patterned [42] to shape their structures in a manner compatible with planar lithographic processing [43,44,45] Due to this feature, they have been actively studied for micro-electro-mechanical systems (MEMS) applications [46,47,48,49,50,51,52,53]. The active-tip device provides the catheter with a steering ability for a wide range of bending angles, enabling the controlled maneuvering of the catheter to a target vessel branch (Figure 1b) This active functionality is aimed to mitigate or eliminate the need for multiple fixed-tip catheters during a catheterization procedure. FiFgiugruere 22..2D.DeveDviceievcediceesdigednseisgshnigonwsihnsoghwtohiwneigflnegxtihbtelheeafcltefixlveiebxsliebtrliepaicnatitcvetiegvreastetrdsitpwripitihnaitnepgteorgalyrte(aNdte-diswopiwtrhoitphyalaacpryopllayom(lyNi(d-Ne-) iso(iPspoNrpoIrpPoAyplMaycl)arychrlyaydmlarmoidgieed)le(l)Pa(yNPeINrPaIAPnMAd M)a hm)yhidcyrdorpgoeagltetlelarylnaeeyrdearpnaldanndaamra hmiceriaoctrpeoraptatatettrhenreendferedpelpaenlnaadnraohrfehtaheteartsetarrtiaptth. tehferefreeeenednd ofotfhtehsetrsitpri.p
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