Structural and Drug Diffusion Models of Conventional and Auxetic Drug-Eluting Stents

Abstract

Most balloon angioplasty procedures include the insertion of tiny cylindrical wire mesh structures, called cardiovascular stents, into the artery to prevent the elastic recoil that follows arterial dilatation. The scaffolding characteristics of the stent provide strength to the artery wall. However, vascular injury during stent deployment and∕or recognition of the stent as a foreign material triggers neointimal hyperplasia, causing re-closure, or restenosis, of the artery. A recent advancement to counteract restenosis is to employ drug-eluting stents to locally deliver immunosuppressant and antiproliferative drugs. In this project, Fick’s law of diffusion was used to model drug diffusion from the stent matrix into the adjacent arterial tissue. An analytical procedure was also developed to estimate the circumferential and the flexural stiffnesses of stents. Furthermore, a unique auxetic (negative Poisson’s ratio) stent structure was proposed that exhibits high circumferential strength in its expanded configuration and low flexural rigidity in its crimped configuration. Results generated with the analytical diffusion model, developed in this project, compare favorably with previously published clinical and experimental data. The circumferential and flexural stiffnesses estimated using the analytical procedure developed in this project compare favorably with the results from rigorous finite element analyses and previously published experimental data.

Buckling and Vibration of Circular Auxetic Plates

“…Auxetic materials have been initially observed in ferromagnetic films [1], face centered cubic crystals [2], hard cyclic hexamers [3,4], and foams [5][6][7][8]. Due to their counter-intuitive properties, auxetic materials have been investigated as smart materials for potential applications including cushion materials [9], stents [10,11], pressure vessels [12], sensors [13], morphing airfoils [14,15], smart folding structures [16], smart metamaterials [17], aeroengine fan blades [18], and vibration dampers [19], to name a few. Arising from their unique properties, the mechanical performance of auxetic solids has been investigated [20][21][22][23][24][25][26][27][28][29][30][31][32][33], including their elastic stabilities [34][35][36].…”

Analysis of Auxetic Beams as Resonant Frequency Biosensors

“…So far, materials that have been used for microcantilever sensors are conventional, i.e., they possess positive Poisson's ratio. Auxetic materials are solids that possess negative Poisson's ratio, and have been investigated for practical applications including fasteners, 25 arterial prostheses, 26 intervertebral disc, 27 drug releasing stents 28 and other prostheses, 29 cushions, 30,31 molecular lters, 32À35 antivibration glove, 36 novel textiles, 37 shoes for diabetic patients, 38 pressure vessels 39 and other thin-walled structures, 40 and shock absorbers. 41,42 It is of interest to note that although carbon nanotubes have been used as nanocantilever T.-C. Lim sensors and that auxetic nanotubes been investigated in recent years by Scarpa et al, 43 Yao et al; 44 and Coluci et al; 45 auxetic nanotubes have so far not being adopted as nanocantilevers for sensors.…”

Shear Deformation in Rectangular Auxetic Plates

“…After successful processing and analysis of such mate rials in the late 1980s [1][2][3], auxetic materials and structures have been investigated for a number of mechanical properties [4][5][6][7][8][9], and for possible applications as aircraft structures [10,11], implants [12,13] and smart structures [14], to name a few. After successful processing and analysis of such mate rials in the late 1980s [1][2][3], auxetic materials and structures have been investigated for a number of mechanical properties [4][5][6][7][8][9], and for possible applications as aircraft structures [10,11], implants [12,13] and smart structures [14], to name a few.…”