Abstract
This paper presents a computational model and design optimization strategy for shape memory alloy (SMA) flexural actuators. These actuators consist of curved SMA wires embedded within elastic structures; one potential application is positioning microcatheters inside blood vessels during clinical treatments. Each SMA wire is shape-set to an initial curvature and inserted along the neutral axis of a straight elastic member (cast polydimethylsiloxane, PDMS). The elastic structure preloads the SMA, reducing the equilibrium curvature of the composite actuator. Temperature-induced phase transformations in the SMA are achieved via Joule heating, enabling strain recovery and increased bending (increased curvature) in the actuator. Actuator behavior is modeled using the homogenized energy framework, and the effects of two critical design parameters (initial SMA curvature and flexural rigidity of the elastic sleeve) on activation curvature are investigated. Finally, a multi-objective genetic algorithm is utilized to optimize actuator performance and generate a Pareto frontier, which is subsequently experimentally validated.
Highlights
Liver cancer is the second leading cause of cancer-related death worldwide [1]
Despite the large number of patients affected by these diseases, current treatment options are less than ideal, as 80–90% of patients are not good candidates for surgery [2], 50% of patients with solid tumors have full resistance to chemotherapy [2], and liver tissue is more sensitive to external radiation than the tumor itself [3]
The experimental evaluations frontier based on these models reveals inherent design tradeoffs between activated and deactivated of yd at low κ 0 (100, 125 m−1 ) were higher than predicted and high κ 0 (200, 250, 333 m−1 ) were less displacement
Summary
Selective internal radiation therapy (SIRT) is an emerging treatment for liver cancer during which the blood vessels supplying tumors are embolized with radioactive microspheres. These microspheres contain the radioactive isotope yttrium-90 (90 Y) which delivers high-energy, low-penetrating radiation that destroys tumor tissue while limiting adverse effects to surrounding healthy liver tissue [4]. SIRT uses a single-lumen microcatheter (1.0 mm diameter) and a manually operated syringe to deliver the 90 Y microspheres into the hepatic artery. Despite the documented advantages of SIRT, the inability to directly target tumor sites has limited its widespread adoption.
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