RESUMO
Nanoarchitected materials represent a class of structural meta-materials that utilze nanoscale features to achieve unconventional material properties such as ultralow density and high energy absorption. A dearth of fabrication methods capable of producing architected materials with sub-micrometer resolution over large areas in a scalable manner exists. A fabrication technique is presented that employs holographic patterns generated by laser exposure of phase metasurface masks in negative-tone photoresists to produce 30-40 µm-thick nanoarchitected sheets with 2.1 × 2.4 cm2 lateral dimensions and ≈500 nm-wide struts organized in layered 3D brick-and-mortar-like patterns to result in ≈50-70% porosity. Nanoindentation arrays over the entire sample area reveal the out-of-plane elastic modulus to vary between 300 MPa and 4 GPa, with irrecoverable post-elastic material deformation commencing via individual nanostrut buckling, densification within layers, shearing along perturbation perimeter, and tensile cracking. Laser induced particle impact tests (LIPIT) indicate specific inelastic energy dissipation of 0.51-2.61 MJ kg-1 , which is comparable to other high impact energy absorbing composites and nanomaterials, such as Kevlar/poly(vinyl butyral) (PVB) composite, polystyrene, and pyrolized carbon nanolattices with 23% relative density. These results demonstrate that holographic lithography offers a promising platform for scalable manufacturing of nanoarchitected materials with impact resistant capabilities.
RESUMO
PURPOSE: This study presents a series of organ transplant patients who developed problems that affected their upper extremities, related to the organ transplant operation itself, to the patient's underlying systemic disease, to long-term immunosuppression, or to subsequent hand injury after the organ transplant surgery. METHODS: A retrospective chart review of 40 organ transplant patients with upper extremity problems at 3 major organ transplant centers was performed. RESULTS: Six general problems were identified that affected the hand and upper extremity in these transplant patients: inflammatory conditions (16), nerve compression syndromes (18), infections (6), neoplasms (6), vascular problems (4), and trauma (14). Thirty-eight patients had 72 separate hand procedures. No problems were encountered with postoperative infections, and skin and bony healing occurred uneventfully. CONCLUSIONS: Organ transplant patients are prone to developing atypical infections, skin malignancies, ischemia, and various nerve compression syndromes that affect the hand. These patients with upper-extremity problems should be treated in a manner similar to any patient without prior organ transplant.
