THE POWER OF CAD/CAM LASER BIOPRINTING AT THE SINGLE-CELL LEVEL: EVOLUTION OF PRINTING - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 81

couple device cameras to observe and record the transfer process, and motorized stages to enhance
laser focusing and cell placement ( Hopp et al., 2010 ).
4.2.3 MAPLE-DW
MAPLE-DW facilitates forward transfer of biological materials in a controlled environment by utilizing
two 3D motorized computer-controlled stages and automated features. Additionally, MAPLE-DW is an
all-optical imaging and printing system, with environmental controls in the current version. These are
among the features that distinguish it from AFA-LIFT and other laser-assisted transfer systems. The cur-
rent system is the culmination of improvements from previous generations; the first-generation MAPLE-
DW system had no motorized stages, the second generation added motorized stages and incorporated
CAD/CAM features, and the contemporary third-generation system has subsequently added environmen-
tal control. Previously, during printing, it has been difficult to keep small volumes hydrated and trypsinized
cells alive for attachment. Environmental control, which includes control and monitoring of temperature
and relative humidity, mollifies this without disrupting the print pattern or changing other print parameters.
Screen captures from the graphical user interface (GUI) of the third-generation MAPLE-DW system
is shown in Figure 4.3 . This GUI enables researchers to control ribbon and substrate stage positioning,
laser fluence, pulse trigger, local temperature, and relative humidity. Live video feed of the print ribbon
allows researchers to inspect and select cell groups for printing. The live video feed is shown on the right
side of the first screen in Figure 4.3 . Geometric arrays, 2D patterns and 3D constructs can be printed in
a semi-autonomous way thanks to incorporated CAD and CAM tools. Cell selection, the rate-limiting
step, still needs to be done manually, significantly decreasing the process speed. In order to automate
single-cell printing, “machine vision” (MV) capability was incorporated into the latest generation of
MAPLE-DW. The MV image analysis algorithms identify and locate individual cells for transfer into
user-defined patterns, thereby increasing the fabrication rate and achieving fully automated printing.
MAPLE-DW print ribbons are coated with a thick ( ∼ 30 m m) sacrificial biopolymer layer, fre-
quently Matrigel ® or gelatin, to absorb laser energy instead of the metal layer used in AFA-LIFT.
Trypsinized cells are partially encapsulated into the hydrogel layer, leaving a sacrificial zone between
FIGURE 4.3
Dual screen GUI for MAPLE-DW. GUI Screen 1: (Left side top to bottom) Ribbon and substrate X and Y stage
position feedback and motion controls; temperature and humidity control; laser fire type controls. (Right side top to
bottom) Tabs to select display below (live feed, original image, processed image, humidity and temperature graph,
system parameters); system shutdown; display window (live feed pictured here). GUI Screen 2: Counter-clockwise
from top left: energy meter; ribbon and substrate Z stage position feedback, motion controls, and focus control;
automated iris control; laser control software.