Inductively Heated Shape Memory Polymer for the Magnetic Actuation of Medical Devices

TLDR

Shape memory polymers are being explored for expandable stents and microactuators, but achieving safe, effective in‑vivo thermal actuation remains a key challenge. This study introduces a Curie‑thermoregulated inductive heating scheme to actuate such devices. SMPs loaded with nickel‑zinc ferrite particles were actuated in air by an alternating magnetic field, while dynamic mechanical analysis and calorimetry assessed how particle size and loading affect heating and mechanical properties. The tests confirm that inductive heating can rapidly and uniformly actuate the SMP, with up to 10 % ferrite loading not impairing shape recovery.

Abstract

Presently, there is interest in making medical devices such as expandable stents and intravascular microactuators from shape memory polymer (SMP). One of the key challenges in realizing SMP medical devices is the implementation of a safe and effective method of thermally actuating various device geometries in vivo. A novel scheme of actuation by Curie-thermoregulated inductive heating is presented. Prototype medical devices made from SMP loaded with nickel zinc ferrite ferromagnetic particles were actuated in air by applying an alternating magnetic field to induce heating. Dynamic mechanical thermal analysis was performed on both the particle-loaded and neat SMP materials to assess the impact of the ferrite particles on the mechanical properties of the samples. Calorimetry was used to quantify the rate of heat generation as a function of particle size and volumetric loading of ferrite particles in the SMP. These tests demonstrated the feasibility of SMP actuation by inductive heating. Rapid and uniform heating was achieved in complex device geometries and particle loading up to 10% volume content did not interfere with the shape recovery of the SMP.