Current Microfluidic designs lack multiple cell growth chambers. Concentration gradients have been explored and developed but there has not been a fusion of multiple cell chambers combined with a concentration gradient. Our objective: To create a microfluidic device with 10 Tesla Diodes, cell growth ports, with an easily controllable concentration gradient

2. Parallelization of Yeast Diode and Implementation of a Concentration Gradient BENG 129A: Design Development in Cell Systems Bioengineering Jeff M. Hasty PH.D. Group #6: Douglas Cohen, Hirak Desai, Lawrence Hui, Robert Langsner, Rushang Patel

4. Microfluidic Theory Design principles: Laminar Flow = Linear Design Ohm’s law Poiseuille (Laminar) flow Circular Channel Rectangular Channel For water flow at 1mm/s through a channel 100µm wide, N Re = 0.01

10. Parallel: The parallel chip design is modeled after a parallel electric circuit. Originally used for a cell culture array for mammalian cells, we tried to expand on this design to include a chemical gradient. Each cell chamber is independent from the rest, therefore it increases the ease of fabrication and analysis of flow rates. Serial Dilution: This design capitalizes on constant media/buffer dilution to create discrete concentration levels. The media is diluted after each successive chamber. This design decreases the amount of work to analyze and model the circuit significantly. However, with this design the gradient is no longer linear, rather it becomes logarithmic as the M (media) mixes with B (buffer) at each successive port. Tree Dilution: This design allows us to create linear gradient with 3 media inputs and 5 ports overall. The was a novel design drawn by Group 6. Alternative Designs

11. Parallel Slant Resistors Fluid Rectifiers Serial Tree Dilution Square Resistors Slant Resistors Fluid Rectifiers Square Resistors Serial Dilution Basic Concept Design Thought Process

12. Features 0 = inadequate; 1 = weak; 2 = sufficient; 3 = good; 4 = excellent 231 164 174 217 Total 2 2 2 2 2 Industrial Application 3 3 3 3 3 Ease of Design 4 4 4 4 4 Cost 3 2 2 4 4 Modification Aptitude 4 4 4 4 5 Media gradient efficiency 4 2 2 3 6 Spatial Flexibility 4 4 4 4 6 Ease of Fabrication 4 3 3 4 7 # of inputs 3 0 0 4 8 Flow Analysis 4 2 3 4 10 Media mixing efficiency 3 3 3 1 10 Cell Loading Complications Serial Dilution w/ square resistors Tree Dilution w/ fluid rectifiers Tree Design w/ slant resistors Parallel Design Weight Parameters

13. 3) Flow Analysis for General Design MATLAB scripts facilitate chip design process by calculating pressures/flows throughout device Identify a Need Design Flow Analysis Finalize Design Fabrication Testing

14. Matlab: MOCA Microfluidic Open Circuit Analyzer Our system is modeled to the right, with hypothetical inputs (power sources) and arbitrary segment lengths (resistances). With 4 unknown inputs and 35 segment lengths, it becomes nearly impossible to solve this system by hand. On the right is an example of a circuit in which the currents at each joining section do not match and the power inputs are off so that a back-flow occurs on the far right.

15. Flow Analysis (correct)

17. Final Design: Cell Loading Final Design Final Design: Media Running

19. Microfluidic Overview Microfluidic device fabrication can be broken down into 3 steps:

23. Alternative Designs Parallel: The parallel chip design is modeled after a parallel electric circuit. Originally used for a cell culture array for mammalian cells, we tried to expand on this design to include a chemical gradient. Each cell chamber is on an independent channel from the rest, therefore it increases the ease of fabrication and analysis of flow rates. Design 4: The newest design is a simplified version of Design 2 with the use of only 4 inputs as opposed to the original design using 5 inputs. This design decreases the amount of work to analyze and model the circuit significantly. However, with this design the gradient is no longer linear, rather it becomes logarithmic as the M (media) mixes with B (buffer) at each successive port. Design 1 (Tree Design w/ slant resistors): The resistors in design were taken off a known resistor design commonly used to increase resistances and length of channels to provide adequate length for diffusion 1 . This serial design was designed with a linear gradient in mind. Design 2 (Tree Design w/ triangular mixers): This design uses the ‘Tree design’ that we previously designed. In a paper by Alex Groisman, a use of a microfluidic rectifier was used to induce mixing using triangular mixers 2 . Further mixers were added on the Cell line on the bottom to induce mixing once the chemicals had reached the chamber line.

24. Alternative Designs

25. Matlab: MOCA Microfluidic Open Circuit Analyzer Since we know that microfluidic channels can be modeled like an electric circuit, we can utilize the similarity in concept to model our system in matlab to understand flow and resistance analysis.

26. Groisman, A., and Quake, S. R., 2004, "A Microfluidic Rectifier: Anisotropic Flow Resistance at Low Reynolds Numbers," Phys. Rev. Lett., 92(9), pp. 094501 Alternative Designs

27. Features

28. Gradient Curves Tree Design Serial Design w/ 9 channels Serial Design w/ 5 channels