ENGINEERING 2D AND 3D CELLULAR MICROENVIRONMENTS USING LASER DIRECT WRITE - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 106

FIGURE 5.2
Schematic of typical LDW setup for material or cell deposition. A laser beam passes through a laser-transparent
print ribbon to interact with material, partially volatalizing a sacrificial layer and forming a vapor pocket to eject
the transfer to a receiving substrate. Independent CAD/CAM control of the ribbon and receiving stages allows
programmatic deposition of material.
occurs at a much faster time scale than heat transfer ( Barron et al., 2004a ). Furthermore, heat shock
protein expression does not appear to be elevated with LDW ( Chen et al., 2006 ), meaning that ther-
mal damage to the transferred material is negligible. Moreover, the laser-material interaction occurs
at the surface of the material ( Barron et al., 2004a; Barron et al., 2004b ), so the bulk of the material
that is transferred using LDW never directly interacts with the laser. After deposition, the receiving
substrate is moved to the next programmed position, and a new spot is used for volatilization on
the ribbon; serial deposition creates a desired structure or pattern according to the programmed stage
positions. Typically, a receiving substrate is a Petri dish, cover slip, or glass slide, and is often coated
with a thin layer of material that serves as the matrix material.
5.2 MATERIALS IN LDW
5.2.1 MATERIAL PROPERTIES INFLUENCING CELLULAR MICROENVIRONMENTS
In this section, we will focus on how the materials used in LDW can affect cell response and thus be
used to engineer desired microenvironments. Functional and mechanical properties of the material
will determine not only how the cells interact with the substrate, but also how they interact with other
nearby cells.
Mechanical properties of a substrate play a critical role in the gene expression and determina-
tion of the functional role a cell performs. As cells adhere to a substrate, they form focal complexes
that become points of force transfer between the substrate and the cell. On a softer substrate, in
response to a stress initiated either externally or by the cell itself, the substrate-cell attachment region
deforms more than the cell. On stiffer surfaces, less deformation of the substrate interacting with