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Samuel Charles Sklare, et. al.

The receiving substrate is mounted on 3D stages threading and a signal/slot system that keeps the GUI
and positioned 500 to 2,000 µm below the ribbon [14] . responsive while handling control requests in different
The receiving side of the substrate is coated in a low threads, all of which are accomplished without excessive
viscosity biopolymer or gelatin. Coatings are chosen to layers of semaphores empirically adjusted for every
mitigate cell impact and promote desired cell behavior different piece of hardware.
by maintaining a moist/humid cellular environment The current implementation of GUI application links
++
and by mixing culture medium with the coating, to C programming resources provided by Aerotech,
[15]
preferentially promoting cell adhesion . Alternatively, Basler, Thor Labs, and Arduino to interface with, and to
substrates can be machined with the laser to create a control, equipment. Python programs are integrated into
customized cellular environment by moving the ribbon the control system for analysis and plotting in real time,
out of the way and refocusing the camera and laser. generating motion-control scripts, and acting as visual
With a prepared ribbon and receiving substrate in guides to help keep track of the printing process, even
place, single laser beam pulses are focused at the ribbon- though the GUI components and equipment controls
++
material interface. Methods that use interstitial metallic are written in C . The Python programming language is
layers (such as gold) or dynamic release layers (such as great for fast development of analysis tools and works
++
triazene and hydrogel) as energy-absorbing layers rely well with both Qt and C .
on the localized, rapid evaporation of these layers to This software is written to be useful to as many re-
produce a vapor bubble. The resulting force from this search groups as possible that use laser direct-write
cavitation bubble ejects a volume of material from the bioprinting and/or micromachining. Different motorized
cell suspension layer. stages, cameras, temperature and humidity probes,
humidifiers, heaters, coolers, lasers, and lasers triggers
3. Laser-assisted printing control software can easily be integrated due to an interstitial layer
The general user interface (GUI) control application is between the linked libraries and control program. This
composed of three main modules, one for each of the layer is used to abstract the control program from the
main functions of this laser setup: 1) MAPLE-DW, 2) hardware libraries. To add new hardware, it is only ne-
Micromachining, and 3) Microbead fabrication. These cessary to copy a hardware’s category skeleton file
modules are written in C using the Qt application and provide the new hardware API’s commands for
++
framework (https://www.qt.io/). With the Qt framework, basic functions listed in the skeleton file. For example,
we were able to create highly customized and detailed incorporating a new motor would involve identifying the
user interfaces that controlled our hardware via functions in the new API that provide position feedback
++
manufacturer-supplied C programming libraries. and motion control, and then creating a new version
Matlab (https://www.mathworks.com/) and LabVIEW of the skeleton file with those commands. The source
(http://www.ni.com/labview/) were considered in code, not including any hardware-specific libraries, and
building the application platforms; however, in contrast detailed documentation are being prepared for release on
++
to the way C development files are handled, hardware GitHub (https://github.com/) for use in other labs.
manufacturers do not provide Matlab-specific libraries 3.1. GUI Modules
or LabVIEW virtual instruments (VIs) for free. Buying
additional Matlab or LabVIEW programming libraries 3.1.1. Printing Module
quickly adds up to several thousand dollars for only
a few pieces of hardware. Furthermore, when new The MAPLE-DW Printing Module is designed to
hardware is added, one would have to check for an increase print speed, reproducibility and enable single-
available proprietary Matlab or LabVIEW library prior cell resolution. Print speed is a barrier to scaling up
to the equipment purchase. construct size and to performing many sets of parallel
In addition to cost considerations, Matlab is not well experiments, and it is also a critical experimental para-
suited for creating complicated GUIs that manage meter. Prepared ribbons and receiving substrates tend
different simultaneous hardware events in different to dry out, and this increases the inhomogeneity in
threads. Similarly, while LabVIEW is designed to the absorbing layer material properties and changes
quickly make control GUIs, there is no standardization the range of acceptable incident fluence for successful
across hardware interface VIs. The lack of standard transfer. Meanwhile, the receiving substrate’s amen-
interfacing can lead to problems with timing that requires ability to transferred cells can change with its stiffness
implementing semaphore time-management loops for and wettability. Reproducibility is improved by the
each communicating piece of hardware. A hard-coded integration and automation of all available sensors. For
time management system like this leads to unresponsive each initiated transfer, a multitude of data is collected:
GUIs. The Qt framework has several strategies for multi- laser energy, temperature, humidity, images of the ribbon

International Journal of Bioprinting (2017)–Volume 3, Issue 2 103