Laser direct writing of micro- and nano-scale medical devices

Abstract

Laser-based direct writing of materials has undergone significant development in recent years. The ability to modify a variety of materials at small length scales and using short production times provides laser direct writing with unique capabilities for fabrication of medical devices. In many laser-based rapid prototyping methods, microscale and submicroscale structuring of materials is controlled by computer-generated models. Various laser-based direct write methods, including selective laser sintering/melting, laser machining, matrix-assisted pulsed-laser evaporation direct write, stereolithography and two-photon polymerization, are described. Their use in fabrication of microstructured and nanostructured medical devices is discussed. Laser direct writing may be used for processing a wide variety of advanced medical devices, including patient-specific prostheses, drug delivery devices, biosensors, stents and tissue-engineering scaffolds.

Figure 1. Selective laser sintering process

(A) Schematic of selective laser sintering process. (B) Poly(caprolactone) tissue-engineering scaffold in the shape of a human condyle; this structure was fabricated using selective laser sintering. (A) Reprinted from [21] with permission from Elsevier © 1999. (B) Reprinted from [39] with permission from ASME.

Figure 2. Laser machining process

(A) Poly(l-lactide) stent machined using a continuous wave CO₂ laser. (B) Poly(l-lactide) stent machined using a femtosecond laser. (C) Glass microfluidic device containing a nano-scale channel machined on the interior of the structure using a femtosecond laser. (A) Reprinted from [64] with permission from ASME. (B) Reprinted from [55] with kind permission of Springer, Science+Business Media © 1999. (C) Reprinted with permission from [1]. © 2005 American Chemical Society.

Figure 3. Matrix-assisted pulsed-laser evaporation direct write process

(A) Schematic of the matrix-assisted pulsed-laser evaporation direct write process. (B) Patterns of hydroxyapatite on borosilicate glass deposited by matrix-assisted pulsed-laser evaporation direct write. (C) Line of B35 neuroblast cells deposited by matrix-assisted pulsed-laser evaporation direct write. (A) Reprinted from [3], with permission from Elsevier © 2008. (B) Reprinted from [85] with permission from John Wiley and Sons. (C) Reprinted from [83] with permission from Elsevier © 2006.

Figure 4. Stereolithography process

(A) Composite PPF/DEF-hydroxyapatite tissue-engineering scaffold fabricated by stereolithography. (B) Reconstruction of a human skull defect produced by stereolithography of an epoxy thermosetting polymer. The model was then used to mold a hydroxyapatite prosthesis. (A) Reprinted from [90] with permission from Elsevier © 2009. (B) Reprinted from [99] with kind permission of Springer © 2007.

Figure 5. Two-photon polymerization process

(A) Schematic of a two-photon polymerization system. (B) Ormocer^® microneedle fabricated by two-photon polymerization. (C) Micrometer-scale Ormocer^® tissue-engineering scaffold with varying pore sizes on different axes. ADM: Acousto–optical modulator; CCD: Charge coupled device; TiSa: Titanium sapphire. (A) & (B) Reprinted from [101] with permission from Elsevier © 2006. (C) Reprinted from [110] with permission from Elsevier © 2007.