Accessible Microfluidic Mold Fabrication Using 3D Printing
Aaron Heuckroth, Cassie Huang, Ryan Silva, Sonya Iverson, Traci Haddock, Alan Pacheco, Douglas Densmore
Electrical and Computer Engineering Dept., Boston University
Introduction
Flexible microfluidic devices offer biologists the ability to
analyze and affect biological systems in controlled,
repeatable ways.
Fabrication Process
Usage Example
A transposer element has
the ability to selectively
swap the contents of two
channels, allowing the user
to route fluids through the
chip dynamically while
maintaining continuous
flow.
1. Design your device
These devices are commonly fabricated by designing,
ordering, and casting from photolithographic molds, a
process that requires a significant investment in time,
specialized equipment, and personnel training.
Python scripts are used to place
primitive features and configure
device layers. “Flipped” layers
will be automatically inverted, to
be printed upside-down.
We present an alternative fabrication process which uses
inexpensive Fused Deposition Modeling (FDM) 3D printers
A
to produce molds in minutes and at minimal cost, in which
we use free, open-source software to design and produce
molds with complex internal geometry from simple,
parameterized components.
This process removes significant barriers of cost, time, and
expertise from the fabrication of microfluidic devices. This
makes it easier for researchers to adopt and experiment
with this technology, and facilitates the rapid prototyping,
refinement, and sharing of device designs within the
synthetic biology community.
To demonstrate the use of this system, we
designed and fabricated molds for a theoretical
microfluidic transposer element.
hello_device.py
This design requires that one channel “jump” over another by traversing
between the flow and control layers. While difficult to fabricate using
conventional photolithography techniques, our molding process allows
these transverse features to be cast easily in a single step.
These scripts generate OpenSCAD files
for each layer of the device, as well as
an overall structural mockup.
Subsequent steps require only minimal,
“drag-and-drop” software interaction.
An initial prototype was designed and fabricated using our process. We then
refined the design over the course of a week to dramatically reduce both
individual feature size and the device’s overall footprint.
2. Compile 3D geometry
hello_device_MOCKUP.scad
hello_device_flow.scad
Hello_device_control.scad
An OpenSCAD library creates
printable 3D models for each layer.
Each OpenSCAD file contains a list of primitives
and parameters that determine the structure
and placement of features in that layer.
Materials and Software
Size: 61 x 36 x 4 mm
Volume: 1 cm3
Footprint: 22 cm2
Channel Width: 2mm
Channel Height: .5mm
Size: 19 x 12 x 1.2 mm
Volume: 30 mm3
Footprint: 2.27 cm2
Channel Width: .2 mm
Channel Height: .1 mm
Size: 14 x 14 x 1.2 mm
Volume: 30 mm3
Footprint: 1.86 cm2
Channel Width: .2 mm
Channel Height: .1 mm
3. Slice layer models into G-code
This process will work with nearly
all G-code compatible FDM
printers, since feature sizes can be
optimized for the capabilities of
the target printer during initial
device design.
Slic3r is used to slice each 3D
model into G-code instructions
based on nozzle size, minimum
layer height, and other printerspecific factors.
You need...
We used…
An FDM 3D Printer
Filament
Hairspray
2x3” Glass Slides
Printrbot Simple Metal
Gizmodorks White PLA
Consort (Extra Hold)
C&A Sci. 6101
Price at
$600*
$25/kg
$5/can
$.10/per
4. Print separate layers onto glass slides
• Instructional guides and videos on our process and workflow
• Easy and inexpensive procedures for casting PDMS devices from 3D printed molds
• Interlocking features that aid in XYZ alignment during PDMS casting
OpenSCAD is a procedural solid-body modeler. We
use it to create the models for our device designs
because it lets us turn code into 3D-printable objects.
Get it at openscad.org
Octoprint
Octoprint is a host application that provides a web
interface for remotely controlling and monitoring a
3D printer. We use it to run all of CIDAR’s 3D printers
because of its convenience and compatibility with
almost all FDM printers.
Get it at octoprint.org
Source code is publicly available for this
project and all examples shown on this
poster. If you try it out, please let us know!
Get it at github.com/CIDARLAB/3DuF
*We upgraded our printer with
a heated bed, an ATX power
supply, and a .2mm nozzle
from printrbot.com. ($200)
Control
We are currently working on…
Python is an object-oriented programming language.
We use it to create designs for microfluidic device
molds because it’s powerful and easy to use.
Get it at python.org
Slic3r
Flow
Future Work
All software used in our fabrication process is
free, open-source, and totally awesome.
Slic3r is a G-code generator for 3D printers. We use it
to convert our 3D mold models into the instructions
that run our printer because it handles tiny features
well and will work with almost all FDM printers.
Get it at slic3r.org
The result is a parametric
transposer module that can
be easily customized and
adapted for fabrication at a
wide range of feature sizes.
• Printable chip-to-world interfaces that can be generated in tandem with devices
Slide holders are printed in
situ, ensuring proper X/Y
feature positioning.
Once the holders are
finished, the print pauses
automatically and glass
slides are inserted.
Hairspray is applied at 65°C,
improving slide surface
adhesion and mitigating
imperfect z-axis calibration.
The print is resumed, and
mold features are printed
directly onto the surface of
each slide.
5. Assemble layers for PDMS casting
The standardized slide shape provides X/Y
alignment. “Standoff” primitives can be used to
fix the Z distance between layers, such as for
preserving the thickness of valve membranes.
• Electronics, software, and hardware for automated microfluidic device control.
• Improved process automation, removing manual OpenSCAD and Slic3r interaction.
• Integration with Fluigi (cidarlab.org/fluigi/) for initial device design and routing
Copyright ©Aaron Heuckroth, 2015
This mold was
fabricated in
less than 15
minutes at a
cost of $0.25.
Special thanks to Carlo Quinonez, PhD and
the Bio/Nano/Programmable Matter
group at Autodesk, Inc. for advice and
inspiration regarding 3D-printable
bioelectronic devices.