Modular Hardware Interface for
Nanoporous Membrane
Filtration Experiments
Vanderbilt University
Team Members:
Jacob Bumpus, BME/EE 2014
Casey Fitzgerald, BME 2014
Michael Schultis, BME/EE 2014
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Abstract
The primary objective of this project is to be able to interface with different hardware
devices, such as a pressure sensor, an air regulator, and a fluid pump in order to implement a
feedback control system for regulation of air pressure and flow rate for filtration experiments.
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Another objective of this project is to implement a control system that is expandable by
allowing a user defined hardware setup so that numerous different experiments can be run
from the same system and is modular so that the system can be transported and connected to
different devices.
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Finally an intuitive graphical user interface (GUI) will be developed in order to allow the
user to control the system in an effective and efficient manner so that setting the experiment
parameters is secondary to deciding what the parameters should be.
Introduction
In 2010, nearly 600,000 patients were treated for end stage renal disease (ESRD) in the United
States alone.6 The consequences of this disease are quite severe, and “patients with renal failure
or renal insufficiency have a catastrophically reduced lifespan compared to age-matched healthy
peers”. 2 Standard treatment procedures for ESRD include kidney transplant and routine
dialysis. Current dialysis procedures are both disproportionately costly, averaging approximately
$65,000 annually, and time consuming, in many cases requiring thrice weekly treatment, and a
significant shortage of donor organs for transplant means that many patients are left with no
options other than years of routine dialysis.
Dr. William Fissell has been working to improve hemofiltration technologies, hoping to one day
develop an implantable artificial kidney for those who are unable to receive a live organ
transplant. His lab is currently investigating ultrathin porous membranes for their potential
hemofiltration applications. Our group is working in conjunction with the Fissell Lab to
automate the experimental protocol for these filtration studies, which require tightly-regulated
pressures, flow rates as well as mass and volume measurements. The Lab’s initial design was
successfully able to regulate pressure within the system by adjusting the output of an air pressure
regulator based on readings from two pressure sensors. This system, however, is limited to one
very specific application, and would need to be completely redesigned if the experimental setup
were to be altered.
The inability to expand the current feedback control system to other applications poses a problem
to the Fissell lab, as there are various different types of filtration experiments that require unique
pressure and flow rate specifications. Thus, we set out to design a new modular system that can
easily be expanded to incorporate a various combinations of pressure and flow conditions. Our
vision is to design one central hub into which all sensory input will go, and out of which all
control signals will go. All necessary circuitry will be contained within the hub, allowing for
quick and easy setup of the sensors, regulators, and pumps. This hub will be connected to a
desktop or laptop computer, on which a graphical user interface will allow the user to select
which input and output components will be used and the requirements associated with each
component.
The benefit of this new modular approach is that it provides a tremendous potential to expand
and evolve along with the dynamic experimental setup. This self-contained system will allow
the user to quickly change from one experimental design to another without having to worry
about the technical aspects behind the control system. Not only does this increase efficiency for
current experiments, but also encourages new experimental design that otherwise been too
difficult to implement.
History and Context:
The development of a bioartificial, implantable kidney has seen a variety of key advances over
the last several years, and the Fissell group is currently working to develop and test the
technological components which will reduce the physical dimensions of the device and while
permitting an increased production scale that can take the device to clinical functionality. The
project builds on the success of the large-scale version of the device, developed by Dr. H. David
Humes and associates at the University of Michigan, which completed Phase II clinical trials in
acute renal failure complicating sepsis.1,2,3 In their 2009 “Proceedings from the Cleveland Clinic
Workshop,”2 Fissell and Roy further discuss the technical details regarding two of the essential
components of the bioartificial implantable kidney: a high-permeability hemofilter and a cellular
bioreactor. Bolstered by selection for the FDA’s fast-track approval program, the project leaders
feel that the bioreactor technology present in the larger Humes device will permit the “smoothest
path to device development”2 in meeting that side of the project’s technical requirements.
To the end of an appropriate hemofiltration membrane, various fabrication methods have been
suggested, and these are outlined in their 2009 Seminars in Dialysis entry. Among them is one
first proposed by Streimer et al. (University of Rochester), which allows for production of
“ultrathin membranes by depositing a thin layer of silicon on a substrate and then thermally
annealing it.” Fissell and Roy state that, for the bioartificial kidney project, this method “is
attractive as it results in an ultrathin membrane with well-controlled (albeit not monodisperse)
pore sizes”. The weak mechanical strength of the membrane presents a strong disadvantage,
however, in that it requires the addition of a supporting microporous filter, thereby increasing its
minimum thickness and limiting its porosity. In their May 2006 patent, “Ultrafiltration
Membrane, Device, Bioartificial Organ, and Methods” (US 7,048,856 B2), the authors give a
brief overview of this fabrication process (shown below as Figure 1; appears as Figure 1 in the
patent). The ability of the membrane fabrication process to meet strict specifications is essential
to the ultimate hemofilter efficacy. Such specifications include the hydraulic permeability, which
must meet a minimum threshold in order to sufficiently generate ultrafiltrate at capillary
pressures in an implantable package size. Since hydraulic permeability is influenced by pore size
(Figure 2), this must also be tightly regulated, in addition to the need for sufficient restriction of
albumin passage and permission of middle molecules.2 The ability to increase the hydraulic
permeability of the hemofiltration membrane by increasing the pore size may also be used in
conjunction with the alternate approach of decreasing the membrane thickness, although this
results in lower mechanical strength and resistance to pressure transients.2
In light of this, as the design for the bioartificial implantable kidney continues to progress
through the pre-clinical and eventually clinical stages of its testing, the Fissell Nephrology
Laboratory will require a method of efficient, reliable and safe verification of the silicon
nanoporous membranes it receives from its research partners at UCSF. From our initial needs
assessment, we determined that this method must permit accurate, precise process execution and
must be performed with minimal extrinsic variation, allowing tasks to be readily synchronized.
Additionally, the modification of process variables should be simple but versatile from the user’s
perspective. Finally, all corresponding data-logging must confer consistent and reliable archiving
of input parameters, monitor data, and allow for real-time verification. From here, the
engineering team took inventory of the current technology which has been utilized up to this
point, simultaneously collecting relevant documentation. Coupling this with user interviews to
enhance our understanding of the protocols for which the system may be used, we then
proceeded to research the availability and appropriateness of alternative hardware and software
components. Additional details of our project progress are described below in “Work plan and
outcomes”.
The direct customer for our design will be the Fissell Laboratory Manager, Joey Groszek, as it
will be designed specifically to address the needs of their filtration experiments. Our design will
streamline the verification process for the aforementioned silicon membranes, making it easier
and more efficient for the Fissel Laboratory to analyze the filtration membranes. As a result of
these experiments, the Lab hopes to one day improve hemofiltration technologies and develop an
implantable artificial kidney that can improve the lives of millions of ESRD patients around the
world.
Team:
Dr. William Fissell - Dr. Fissell is the Principal Investigator for the laboratory that the control
system is being developed for.
This team member is the Principal Investigator (PI) for this project.
Joseph Groszek - Joey is the main administrative contact for the aforementioned team members
that are developing this system. Joey is the end-user of the system that is in development and
will play a key role in determining what the necessary requirements are for this project.
This team member is an advisor on this project and will act as the Administrative Contact
(AC).
Jake Bumpus – Jake will work to develop a system level design to ensure that the proper
hardware is in place in order to communicate with the transducers and feedback devices within
the system. Jake will play a role in determining what connections and parts are necessary for this
project.
This team member is a student on the project that will see this project through to market.
This team member will also lead business model development and co-lead on technical
model development.
Casey Fitzgerald – Casey, with developed skills in software development, will be instrumental in
the architecture of the high-level software design. He will also play a role in ensuring that the
high-level code interacts with the graphical user interface to provide a seamless user experience.
This team member is a student on the project that will see this project through to market.
This team member will co-lead technical model development.
Michael Schultis – Michael will play a role in developing the software necessary for hardware
integration. He will also play a role, in conjunction with Casey Fitzgerald, in developing the
graphical user interface to allow for customized user control of hardware.
This team member is a student on the project that will see this project through to market.
This team member will co-lead technical model development.
Work Plan and Outcomes:
Our ultimate goal for this project is to develop a feedback control system for use with
filtration experiments in the Fissell Lab; however, we do not plan on generalizing our product in
order to market it to the general public. In order to achieve our desired goals we have followed,
and will continue to follow, our plan that is laid out in the Gantt chart (The Gantt chart is
attached as another document below this document on the website). By the end of the grant
period we desire to have a control box, potential design attached below, built in order to interface
with all the necessary hardware for these filtration experiments and this will likely be the end to
the project. We believe that, as a team, we have the necessary skills to be able complete the
project and have it be successful by the end of the grant period.
The figures above display the proposed design for the control box that will be implemented by
the end of the grant period.
Evaluation and Sustainability Plan
Our design will have succeeded if, when it is completed, the Fissel Lab can more efficiently and
accurately carry out the nanoporous membrane filtration experiments that it is currently
undertaking. Furthermore, our successful design would be easily expandable and adaptable,
allowing for increased innovation as the group moves forward with the goal of improving
treatment for the millions of people who suffer from ESRD around the world.
Appendix A: Budget Template
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RS232-to-USB Cables for interfacing with devices
Discrete electronic components for sensors’ analog front end (Instrumentation amplifiers,
capacitors, resistors)
Electronic communication connections (RS232-to-TTL connectors, USB hubs, ribbon cables)
Microcontroller Unit (likely Arduino MEGA)
3D printed container parts
Total estimated budget should not exceed $300
Appendix B: Resumes
In order to maintain each resume’s specific formatting, the resumes are uploaded as
separate PDF files which should be found on the same webpage that this file was found.
Appendix C: Supporting Documents
1. http://news.vanderbilt.edu/2013/07/project-seeks-to-create-bioartificial-kidney/
2. Fissell, William H., and Shuvo Roy. "Innovation in the Treatment of Uremia: Proceedings
from the Cleveland Clinic Workshop: The Implantable Artificial Kidney." Seminars in
Dialysis. Vol. 22. No. 6. Blackwell Publishing Ltd, 2009
3. Lysaght, Michael J. "Maintenance dialysis population dynamics: current trends and longterm implications." Journal of the American Society of Nephrology13.suppl 1 (2002): S37S40.
4. Tumlin, James, et al. "Efficacy and safety of renal tubule cell therapy for acute renal
failure." Journal of the American Society of Nephrology 19.5 (2008): 1034-1040.
5. Fissell IV, William H., et al. "Ultrafiltration membrane, device, bioartificial organ, and
methods." U.S. Patent No. 7,048,856. 23 May 2006.
6. “Atlas of End-Stage Renal Disease in the United States.” 2012 USRDS Annual Data Report,
vol. 2. National Institute of Health. http://www.usrds.org/2012/pdf/v2_00intro_12.pdf