1. Towards a Bioartificial Kidney: Validating Nanoporous Filtration Membranes
Jacob Bumpus, BME/EE 2014
Casey Fitzgerald, BME 2014
Michael Schultis, BME/EE 2014

2. Background
600,000 patients were treated for end stage renal disease (ESRD) in the US alone in 2010
Current treatment procedures include kidney transplant and routine dialysis
Dialysis: COSTLY
$$: ~$65,000/patient/yr.
TIME: often requiring 3 treatments /wk.
Significant shortage of donor organs for transplant means that many patients are left with no options other than years of routine dialysis
Development of an implantable bioartificial kidney (BAK) would revolutionize treatment of end stage renal disease (ESRD).
Improve patient outcomes
Reduce economic burden of treatment
Concept illustration of an implantable bioartificial kidney. Courtesy of Shuvo Roy
Image Citation:
Fissell, William H., Shuvo Roy, and Andrew Davenport. "Achieving more frequent and longer dialysis for the majority: wearable dialysis and implantable artificial kidney devices." Kidney international 84.2 (2013):

3. Background
Dr. Fissell is working to develop an implantable bioartificial kidney using nanoporous silicon membranes as biological filters
These chips feature nanometer- scale pore arrays, invisible to optical characterization methods
Screenshots courtesy UCSF School of Pharmacy

4. Problem Statement
In order to verify the silicon chips received from their collaborators, the Fissell Lab uses a set of experiments to measure the chips’ filtration performance under a variety of conditions and correlate this to their pore sizes
The Fissell lab must manually configure these filtration experiments, monitor them continuously throughout their duration (sometimes days to weeks long), and collect data by hand
Current experiments are unable to simulate physiologically relevant fluid flow profiles, and are limited to constant flow rates
No failsafes exist in order to protect the silicon membranes from being damaged in the event of deviations from preset conditions

5. Clinical Relevance Our design:
Increase
Experimental Relevance
Control
Efficiency
Reduce
Man hours
Disorder
Lost $
Lost time
Our design:
Increases efficiency of experimentation by fully automating a variety of test protocols, allowing the group to characterize more chips
Reduces project risk of lost time and money by adding failsafes against chip fracture ($1000’s/chip)
Maximizes experimental control by tightly coupling pressure monitoring to hardware output and adjusting for temporal drift
Adds greater experimental relevance by allowing an adaptable physiological input platform, including simulation of pathophysiologic pressure conditions (hypertension)

6. Needs Statement
To design an integrated hardware/software suite that will streamline verification of these silicon membranes while maximizing experimental control and precision and minimizing user involvement

7. Goals
Experimental setups should be fully automated, permitting the lab technician to begin the experiments and then cease involvement except for occasional system monitoring
Allow user-defined hardware setup so that numerous different experiments can be run from the same system that is modular and expandable
An intuitive graphical user interface (GUI) should be developed in order to allow the user to control multiple experiments in an effective and efficient manner so that setting the experiment parameters is secondary to deciding what the parameters should be.
Add flow rate control and dialysate measurement to the current pressure control feedback system.

8. Factors Software Platform Software concurrency Hardware connections
LabVIEW more $ / much less development time
Software concurrency
More fewer programs running but internals are more complex
Hardware connections
Fewer cheaper in size and $ but more technically challenging

9. Experiments The solution must automate three modes of experimentation
Hydraulic Permeability Mode
Measures convective flow across membrane at various pressures (uL/min/psi)
Filtration Mode
Collect filtrate samples at various pressures for further analysis
Dialysis Mode
Sets and Measures diffusive flow across membrane with no pressure differential
Filtration and Dialysis Mode should include an option to run with constant flow or a periodic waveform

10. System and Environment

11. Experimental Setup – Dialysis Mode
Filtration Membrane
Peristaltic Pump
Peristaltic Pump
Pressure Transducer
Pressure Transducer
Air
Air
Air Regulator
Syringe Pump
PSI
Dialysate Side
Blood Side
To House Air
To House Air

12. Feedback Control Diagram
Voltage
Signal 1
Pressure Transducer 1
Pressure
(Blood)
ADC
Arduino/LabVIEW
Setpoint Flows or Waveforms
Peristaltic Pumps
RS-232
Signals
Flow Rate Σ
Pump VI HP ΔP
PID Loop ΔV Σ Σ
Error
Voltage
Pressure Regulator 1
Pressure
(Blood)
Voltage
Setpoint Pressure
Voltage
Pressure Regulator 2
Pressure
(Dialysate) Σ
Conversion VI
ADC
Pressure Transducer 2
Voltage
Signal 2
Pressure
(Dialysate)

13. Control Box Concept Power Supply Control Box: Front View
AC Power Line H
Pressure Transducers N
Power Supply G 1 2 4 3 6 5 8 7 24
Pressure Regulators 12 1 2 3 4 5 6 7 8 5
-12
General Purpose USB 1 2 3 4 5 6 7 14 13 12 11 10 9 8
Through Hole Board R C
Control Box: Front View
USB Hubs and Female Connector Ports
Control Box: Top View

14. Ultrasound Blood Velocity Reading

15. Estimated Waveform
Velocity (cm/s)
Time (s)

16. Generated Pressure Waveform

17. Comparison

18. Software Architecture Diagram
Top Level Menu
Quadrant 1
Quadrant 2
Quadrant 3
Quadrant 4
Hydraulic Permeability
Filtration
Dialysis

19. Experimental Runtime GUI
Hardware select
(Pump, Transducer/Regulator, Balance)
Hardware select
(Pump, Transducer/Regulator, Balance)
Hardware select
(2x Pump, 2x Transducer/Regulator, Balance, Syringe Pump)
Experimental Runtime GUI
Peristaltic Pump
Mass Balance
Pressure Transducer
Syringe Pump
Experiment Overview
Air Regulator
Calibration

20. Top Level Menu

21. Hardware Select

22. Experimental Runtime GUI
Experiment Overview
Pressure Transducer
Transducer Calibration

23. Experimental Runtime GUI
Mass Balance
Peristaltic Pump
Syringe Pump In
Progress

24. Hydraulic Permeability Experiment
Load from File

25. Hydraulic Permeability Results
Experiment Results
Data Log

26. Error Handling Demo gif
Fail Safes
Set point = 0
Overrides the PID controller
Record Max/Min Pressure
Alert user of potential errors
Next: Automatic shut-down
Error Handling
What to do if something goes wrong?
Error Handling Demo gif

27. Recent Progress LabVIEW Control of
Pressure transducer (COMPLETE)
Pressure Regulator (COMPLETE)
Peristaltic Pump (COMPLETE)
Mass balance (COMPLETE)
Syringe Pump (IN PROGRESS)
LabVIEW PID feedback loop for pressure setup
Improved/updated circuitry
Initial iterations of pulsatile flow
Abstract submission to American Society for Artificial Internal Organs (ASAIO) Student Design Competition
Fully Automated Hydraulic Permeability Experiment
Initial Fail-safes and Error handling

28. Next Steps
Continue to iterate towards more physiologically relevant pulsatility
Develop Dialysate Mode Automation
Incorporate syringe pump control into complete system
Finalize power supply and order all components
Develop a 1st iteration CAD model of our hardware container

29. Gantt Chart

30. Special Thanks To: Vanderbilt University Medical Center
Vanderbilt School of Engineering
Vanderbilt Renal Nanotechnology Lab
Dr. William Fissell
Joey Groszek
Dr. Amanda Buck
Dr. Tim Holman
Dr. Matthew Walker III
JustMyPACE Peer Senior Design Group

31. Questions?

32. Hydraulic Permeability Mode
Fissell, William H., et al. "High-performance silicon nanopore hemofiltration membranes." Journal of membrane science 326.1 (2009):

33. Filtration/Dialysis Mode
Ideal Filtration
Example 1 psi Pressure
Example 2 psi Pressure
Filtrate Mass/ Original Mass (θ)
Size (arbitrary units)

34. Previous System

35. Previous Interface

36. Appendix: Feedback Control Simplified
Arduino/LabVIEW Σ
Pressure Regulator 1
PID Loop
Pressure Regulator 2
Pressure Transducer 2
Pressure Transducer 1
Conversion VI
Setpoint Pressure
Pressure
(Dialysate)
Voltage
Signal 1
ADC
Signal 2 ΔV
Error
(Blood)

37. Appendix: Feedback Control Diagram
Voltage
Signal 1
Pressure Transducer 1
Pressure
(Blood)
ADC
Arduino/LabVIEW
Setpoint Flow or Waveform
Peristaltic Pump
RS-232
Signal
Flow Rate Σ
Pump VI
PID Loop ΔV Σ Σ
Error
Voltage
Pressure Regulator 1
Pressure
(Blood)
Voltage
Setpoint Pressure
Voltage
Pressure Regulator 2
Conversion VI
ADC
Pressure Transducer 2
Voltage
Signal 2
Pressure
(Dialysate)