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Abstract Macrotextured silicone breast implants are associated with several complications, ranging from seromas and hematomas to the formation of a rare type of lymphoma, known as breast implant-associated anaplastic large cell lymphoma (BIA-ALCL). The presence of silicone wear debris has been detected within the peri-implant region and fibrotic capsule and histological analyses reveal inflammatory cells surrounding debris particles. However, it is unclear how these debris particles are generated and released from macrotextured implant surfaces, and whether wear debris generation is related to implant stiffness. In this study, we created an accelerated implant aging model to investigate the formation of silicone wear debris produced from self-mated (“shell-shell”) tribological interactions. We created implant-like silicone elastomers from polydimethylsiloxane (PDMS) using Sylgard 184 base:curing agent (10:1, 12:1, and 16:1) and quantified their mechanical properties (E* = 1141 ± 472, 336 ± 20, and 167 ± 53 kPa, respectively). We created macrotextured PDMS samples using the lost-salt technique and compared their self-mated friction coefficient (< µ > = 4.8 ± 3.2, 4.9 ± 1.8, and 6.0 ± 2.3, respectively) and frictional shear stress (τ = 3.1 ± 1.3, 3.2 ± 1.7, and 2.4 ± 1.4 MPa, respectively) to those of the recalled Allergan Biocell macrotextured implant shell (E* = 299 ± 8 kPa, < µ > = 2.2, andτ = 0.8 ± 0.1). Friction coefficient and frictional shear stress were largely insensitive to variations in elastic modulus for macrotextured PDMS samples and recalled implant shells. The stiffest 10:1 PDMS macrotextured sample and the recalled implant shell both generated similar area fractions of silicone wear debris. However, the recalled implant shell released far more particles (> 10×), mainly within the range of 5 to 20 µm2in area. Bone marrow-derived macrophages (BMDMs) were treated with several concentrations of tribologically generated silicone wear debris. We observed widespread phagocytosis of wear debris particles and increasing secretion of inflammatory cytokines with increasing concentration of wear debris particles. Our investigation highlights the importance of avoiding macrotextured surfaces and mitigating wear debris generation from silicone implants to reduce chronic inflammation.
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Real area of contact and tractions on the patterned surfaces generated by spinodal decomposition and amplified instability
Past decades featured significant advancements in additive and micromanufacturing that facilitated the creation of functional patterned surfaces with impressive spatial resolutions. However, these techniques are expensive and require a considerable amount of time and energy, and hence lack scalability to practical surfaces. Recent techniques employing spinodal decomposition and instabilities amplified via centrifugal acceleration offer viable and cheaper alternatives. The patterns created by those techniques, however, vary randomly in geometry. When interfacing those patterned surfaces with other components and under self-contact scenarios, geometric variations lead to stress concentration and abrupt failure around the contact. In this study, we investigate numerically real contact areas, contact tractions, and stress concentration. We generate patterned surfaces in congruence with actual surfaces created by those techniques. Then, we conduct normal-contact analyses of those surfaces boundary element method (BEM) under nominal mean pressures ranging from 0.001E* toE*, whereE* is the contact modulus. We record real contact areas and stress concentration as a function of nominal mean pressures. We compare these values with the analytical solutions from sinusoidally-patterned and randomly rough surfaces. Randomness in pattern geometry is primarily influenced by the processing parameters such as the degree of anisotropy in spinodal decomposition and acceleration in amplified instabilities. To understand the influence of the processing parameters, we perform a parametric study. We find isotropic spinodal decomposition creates patterns that deliver contact area and traction distributions similar to randomly rough surfaces, and lead to high-stress concentrations. Such high-stress concentrations are expected to occur under self-contact loading scenarios, and thus can explain the compromised resilience and strength in recently-proposed spinodal metamaterials. For patterned surfaces created by amplified instabilities, high-stress concentrations are obtained for the surfaces created at high accelerations. At high accelerations, increased elastic instabilities and stochastic growth result in a more skewed and broader distribution in heights. Therefore, high-stress concentrations are inevitable. To account for combined loading scenarios, we conduct additional simulations on the same surface patterns with frictional pre-sliding contacts. We find the frictional tractions play a secondary role in stress concentrations where the primary factor is the processing parameters determining the degree of randomness in pattern geometry.
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- Award ID(s):
- 2224380
- PAR ID:
- 10480168
- Publisher / Repository:
- Frontiers
- Date Published:
- Journal Name:
- Frontiers in Mechanical Engineering
- Volume:
- 9
- ISSN:
- 2297-3079
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/fmech.2023.1253207
