Group - Research | School of Engineering | Vanderbilt...

MEMS IN THE MARKETTechnology Report

Group

25

M E M S I N T H E M A R K E T

Project Team

Name E-mail Backgrounds ResponsibilitiesRyan

DempseyRyan.d.dempsey@vanderb

ilt.eduBiomedical Engineering

Management of Technology

Business team leader Web site design

John Richardson

[email protected]

Biomedical EngineeringEconomicsBioMEMS

MEMS technology design team leader

Peter Shanahan

[email protected]

Biomedical EngineeringBioMEMS

Mathematics

MEMS technology design

Charles Bloom

[email protected]

Biomedical Engineering


Business team assistant Legal

Rachel Weaver

[email protected]

Biomedical Engineering


MEMS technology design assistant

Photography

Group 25 is composed of Ryan Dempsey, John Richardson, Peter Shanahan, Charles Bloom, and Rachel Weaver. The group was chosen based on a

combination of biomedical engineering and business backgrounds. Because the senior design project deals specifically with BioMEMS technology, it is our

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mailto:[email protected]










intention to assemble a group with MEMS experience and biomedical engineering majors. Furthermore, the project includes a business portion,

which develops a strategy to market the MEMS device to venture capitalists. Initially, the group entered a business competition called the MRS Challenge, but the group did not qualify for entrance due to a lack of graduate business

students in the group.

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M E M S I N T H E M A R K E T – T E C H N O L O G Y R E P O R T

Table of ContentsABSTRACT.......................................................................................................................................2

INTRODUCTION............................................................................................................................3

Biomems Background................................................................3Biomems market........................................................................3Consumer Demand.....................................................................4Primary objectives/Goals............................................................5Performance criteria .................................................................5

METHODOLOGY...........................................................................................................................6

Device Design.............................................................................6Device Fabrication.....................................................................7Flow Calibration.........................................................................9Device Testing..........................................................................10Equipment ...............................................................................10

RESULTS.......................................................................................................................................11

Device Creation and Testing....................................................11Economics................................................................................13Safety, health, and Risk...........................................................13

CONCLUSION...............................................................................................................................14

Informal Observations..............................................................14RECOMMENDATIONS...............................................................................................................15

Changes....................................................................................15Future Work.............................................................................15Ethical Issues...........................................................................15Acknowledgements..................................................................16

APPENDIX A; NANOPHYSIOMETER PROPOSAL..............................................................17

APPENDIX B: EQUIPMENT......................................................................................................20

APPENDIX C: QFD DIAGRAM.................................................................................................21

APPENDIX D: INNOVATION WORKBENCH (IWB)............................................................22

APPENDIX E: CONCEPT DIAGRAM......................................................................................27

APPENDIX F: DESIGN SAFE.....................................................................................................28

APPENDIX G: PROJECT NOTEBOOK........................................................34 REFERENCES36

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Abstract

In the proposal stage of our project, it was our intention to develop a tangible product to present in the Materials Research Society’s (MRS) Entrepeneurship Challenge. This is a competition that was designed to help members of MRS develop the entrepreneurial skill of placing laboratory technology in the market.

The MRS website1 states, “Through the Entrepreneurship Challenge, scientists and business students will form “virtual teams” to develop a 12-slide PowerPoint presentation that will present a startup technology to a panel of venture capitalist judges.” We decided upon BioMEMs Nanophysiometer devices as our startup technology. Unfortunately, we discovered that in order to be eligible for the Challenge, at least two graduate business students had to participate in our group. We decided to continue with the idea of the challenge and develop upon the idea of BioMEMs Nanophysiometer devices both technically and economically.

Because our group is larger than others, we found it necessary to go above and beyond the requirements of smaller groups. This report is made up of two sub-reports. The first of the two is the “Technology Report.” Our primary objective for the “Technology Report” is to create a bioMEMs lab-on-chip dual cell culture device at the pico-liter volume scale. The future objective for the “Technology Report” is for the dual-chamber device to allow for automated cell culturing and sensing for the testing of drugs and other perfused substances (also known as a nano-bioreactor). The second of the two is the “Business Strategy Report”. In it, we create a business proposal in order to market our technology to venture capitalists. Our long-term objective is to launch a start-up company based on our bioMEMs device. In order to do so, we must analyze the market for the device and the current demands for it. Also, we must analyze the corporate environment already in place for bioMEMs devices and the financing behind such ventures.

The development and results of our nano-bioreactor fabrication can be found in the “Technology Report”. The results entail the fabrication of an original dual-chamber nano-bioreactor. Included in the fabrication are two cell culture areas (600 μm x 600 μm x 15 μm),

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an input and output channel for experimental solutions and medium, and an input and output channel for the cells to be tested with

pneumatic pressure values that allow for the cells to be trapped in the cell cultures during experimentation. The development and results of the business proposal are detailed in the “Business Strategy Report.” The market was found to be made up of two related industries: 1) major drug manufacturers and 2) drug delivery research. It was found that the bioMEMs drug delivery market will increase from 14.4 billion dollar industry to a 28 billion dollar industry between the years 2002 and 2005. It was estimated that our device will save $1 million per year in reagent, labor and disposal costs for over 10 assays. Furthermore, the Net Present Value (explained further in the “Business Strategy Report”) was estimated near $7 million, an indication for profitability.

With the results from both reports, it is seen that the development of such a technology described in the “Technology Report” has great potential in the drug development industry. Implementing the suggested design updates presented in this lab could change the drug development industry all together.

IntroductionA lab-on-chip (LOC) device is a micro-scale laboratory utilizing a network of micro-channels, electrodes, sensors, and electronic circuits. 2 BioMEMS, a type of LOC, are bio-functionalized microelectromechanical systems (MEMS) that are designed for usage in biomedicine and bioengineering. The term MEMS was created in the late 1980s to develop sensors and actuators out of the basic integrated circuitry micro-fabrication technologies, utilizing silicon as the primary substrate and structure material. The term bioMEMS first appeared in the early 1990s as MEMS was applied in medicine and bioinstrumentation.

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BioMEMS can be divided into two main categories: (1) in vitro bioMEMS, and (2) in vivo bioMEMS. In vitro bioMEMS deals primarily with samples from the body. For example, blood, tissue, serum, urine, and saliva are among the most common body fluids studied. In vivo bioMEMS deals with the living host anatomy. Applications include long term medical implants, surgical tools, artificial organs, and drug delivery.3

In order to understand the market for BioMEMs devices, several areas of the market must be analyzed. First, the market must be defined. The primary market for our BioMEMS device includes companies involved in one of two related industries: (1) major drug manufacturing, or pharmaceuticals, and (2) drug delivery. The pharmaceutical industry comprises companies primarily engaged in one or more of the following:

manufacturing biological and medicinal products; processing botanical drugs and herbs; isolating active medicinal principals from botanical drugs and

herbs; and manufacturing pharmaceutical products intended for internal

and external consumption in such forms as tablets, capsules, vials, ointments, powders, or solutions.

The drug delivery industry comprises companies developing systems by which therapeutic agents are introduced into the body, and directed in a controlled way towards a target organ or site of action. Conventional drug delivery forms are simple oral, topical, inhaled or injection formulations.

Currently, the top three drug manufacturing companies, by market capitalization, include Pfizer Inc., Johnson and Johnson, and GlaxoSmithKline. The top three drug delivery companies, by market capitalization, include Hospira Inc., Elan Corporation, and Biovail Corporation4 Figure 1 displays all potential market applications for our microfluidic device. The primary applications for our BioMEMS device include high-throughput drug screening, clinical diagnostics,

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Figure 1: Market for MEMs devices


and genetic analysis. Our device will assist scientists by evaluating the effectiveness of a given drug to living cells.

In order to get a grasp on the market potential of our device, we must realize the market size with which we are dealing. Our dual-chamber MEMS device has enormous market potential. BioMEMS is predicted to have the fastest growth rate within the entire MEMS market, particularly biomedical applications such as drug discovery and delivery. BioMEMS applications will consist of approximately 16% of the entire $10.9 billion MEMS market. Research firm UBS Warburg estimates that the BioMEMS drug delivery market in the U.S. alone will go from $14.4 billion in 2002 to $28 billion in 2005. 5

The cause for this high demand is the increase in research and development (R&D) costs incurred by the drug companies. Currently, billions of dollars are spent finding “blockbuster” drugs by major pharmaceutical companies. Because of large amount of money that can be earned in the global healthcare market, these companies are spending more and more money on research and development (R&D) of new drugs. Despite rapid growth in outsourcing R&D activities over the last few decades, pharmaceutical companies have significantly expanded the number of their own employees devoted to the R&D of the company. Applying a real growth rate of 1.76% per year for compensation to a growth rate of 7.4% per year in employment yields a growth rate of 9.3% per year in labor costs for pharmaceutical companies. Given these labor costs, it would be in the best interests of a pharmaceutical company to save money on labor costs by utilizing new, more efficient technologies. Major pharmaceutical companies spend an average of $802 million and 10 to 15 years researching and developing a drug to come to the market9. Comparing this to the 1987 average of $231 million and the 1976 average of $54 million, it is quite obvious that developing new drugs has gotten extremely expensive6.

Lastly, we need to analyze the demand for such a device. In order for our bioMEMS device to have market success, a particular emphasis and effort should be placed on identifying the needs of our customers (i.e. pharmaceutical companies) and offering appropriate solutions. Among the most current demands given by major pharmaceuticals include7:

Cost efficiency Development of detection technologies (i.e. on-chip sensors) Interfacing micro and macro scales Reliable bonding metal electrodes onto polymer substrates.

Further market analysis can be found in the “Business Strategy Report.” In order to capture the market potential for such a device, the consumer demands must be met. Our goal is to offer a dual-chamber LOC nano-bioreactor. A dual-chamber bioMEMS device allows double the experiments to be performed on fewer chips, thus saving time and money. Also, the cell-to-volume ratio of our MEMs

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device is much greater than the Petri dish or T flask. This means two things: 1) the MEMs device is closer to in vivo cell-to-volume ratios, and 2) more accurate measurements of the cell medium can be obtained. Furthermore, our device will also decrease labor costs and reagent costs, thus promoting cost efficiency. In order to analyze the efficacy of drugs on the cell culture, sensors that enable the user to analyze the consistency of the cell culture medium must be fabricated into the device. This would allow one to detect cell metabolism in response to a drug.

The primary goal of the project was to create a bioMEMs lab-on-chip dual-chamber cell culture device at the pico-liter volume scale and discuss its marketability. The first step in accomplishing this goal was to create design parameters for such a device. The following are the device specs that we wished to accomplish:

Create a dual-chamber LOC cell culture device with each culture chamber at the pico-liter scale

Create separate perfusion channel inputs and outputs that allow for the cell cultures to be independent of one another

Create a pneumatic valve system to both shutoff cell input and prevent cell’s from leaving the cell chamber

Design a mixing system to use diffusion to mix substances Circular perfusion inlets to allow user-friendly cell and fluid

insertion Design the cell culture chamber so that the cell resides below

the perfusion inputs from a cross sectional perspective to contain cells

Addition of Clark oxygen sensor to measure cell metabolism Addition of a carbon dioxide, lactate, and glucose sensor Improve the perfusion system

Because of time restraints, we knew that accomplishing all of these design parameters would be difficult. We listed the parameters in order of importance and tangibility in order to accomplish as much as possible in such a little time period. Thus, our primary goal became the creation of a dual-chamber device and to show perfusion and cell input capabilities. Our secondary/future goals are to fabricate a plethora of sensors onto the LOC in order to analyze the metabolism of the cells in culture.

The problem with LOC is that there are several design issues or criteria that must be addressed in order to achieve proper results. First, the liquid filling of the device must avoid entrapment (presence of air bubbles). Three steps must be done carefully in order to avoid entrapment: 1) careful design of the device, 2) proper control of the filling process, and 3) proper selection of materials. In our case, our channels are large enough that entrapment should not be a problem. Secondly, the filling process will be done strictly by gravity, thus avoiding the creation of bubbles due to turbulent flow. Lastly, the

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device will be made up of a silicon-type material (PDMS) and glass, both of which will not have significant adhesion problems. Also, the nano-bioreactor must allow for cells to be injected into the cell culture area. To achieve this, the cell input and output channels must be large enough to allow for cells to pass through (15 μm x 15 μm). Second, the user must be able to capture the cells in the cell culture volume in order to conduct experiments. To achieve this, we will implement pneumatic pressure values for the cell input and output channels. Third, the perfusion input must mix thoroughly in order to achieve consistency when entering the cell culture area. One problem with microfluidic devices is that the fluid flow is strictly laminar with very low Reynold’s numbers (<10). Because of this, the mixing of the solutions is strictly based on diffusion. In order to mix via diffusion, a mixing pattern was designed into the device at the perfusion input and output. Lastly, the output or waste of the two cell culture volumes must remain separate in order to keep the two experiments independent of one another.2

The contents of this report are broken down into two parts. The first part, “Technology Report”, details the design and development of a dual-chamber bioMEMs nano-bioreactor. It details the design steps, the fabrication steps and the testing of the device. The second part, “Business Strategy Report”, details the marketability of such a device. The first section of the “Business Strategy Report” defines the market of bioMEMs by characterizing the market size, strategic positioning, consumer pricing, and market drivers and barriers. Later sections of the “Business Strategy Report” include the technological environment of the device, the corporate environment of bioMEMs, the economic and government policies for such a device and a project valuation.

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Methodology

The proposed goal for this project was to create a theoretical device and present its market potential to venture capitalists through the Materials Research Society’s (MRS) Entrepreneurial Challenge. This is a competition that was designed to help members of MRS develop the entrepreneurial skill of placing laboratory technology in the market.

The MRS website1 states, “Through the Entrepreneurship Challenge, scientists and business students will form “virtual teams” to develop a 12-slide PowerPoint presentation that will present a startup technology to a panel of venture capitalist judges..” We decided upon BioMEMs Nanophysiometer devices as our startup technology. Unfortunately, we discovered that in order to be eligible for the Challenge, at least two graduate business students had to participate in our group. We decided to continue with the idea of the challenge and develop upon the idea of BioMEMs Nanophysiometer devices both technically and economically.

Device DesignThe primary goal of the project was to create a bioMEMs lab-on-chip dual-chamber cell culture device at the pico-liter volume scale and discuss its marketability. The first step in accomplishing this goal was to create design parameters for such a device. There were several preliminary design goals that we wished to accomplish:

Create a dual-chamber LOC cell culture device with each culture chamber at the pico-liter scale

Create separate perfusion channel inputs and outputs that allow for the cell cultures to be independent of one another

Create a pneumatic valve system to both shutoff cell input and prevent cell’s from leaving the cell chamber

Design a mixing system to use diffusion to mix substances Circular perfusion inlets to allow user-friendly cell and fluid

insertion

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Section

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Design the cell culture chamber so that the cell resides below the perfusion inputs from a cross sectional perspective to contain cells

Addition of Clark oxygen sensor to measure cell metabolism Addition of a carbon dioxide sensor Addition of lactate sensor Improve the perfusion system Addition of glucose sensor

The list above was ranked in order of importance. Because of time restraints, we knew that it might not be possible to accomplish all of our preliminary goals. The cross section of our very first design sketch is shown in Figure 2. The aerial view of the first design sketch is shown in Figure 3. This design includes a dual-chamber cell culture fitted with pneumatic pressure valves, perfusion and cell inputs and outputs that allow for independent testing, a “ditched” cell culture chamber, a “mixer” design for input channels and circular perfusion inlets. We also had to calculate the necessary dimensions for the system. The basic requirement was to allow cells to move through the channels. We knew that most fibroblasts that would be used are around 10 μm in diameter. Considering that this diameter was an average, we decided upon using 15 μm as the minimum size of the channels and chamber to allow for the cells to pass easily. Next, we decided upon a 600 μm x 600 μm cell culture area. This large area would allow for sensor fabrication in later steps. Each branch seen entering the cell culture area has a cross-sectional area of 100 μm x 15 μm. The larger input and output branches seen toward the exterior of the view are 200 μm x 15 μm. These cross-sectional areas are ample space for the cells and solution mixtures to pass through to the cell culture chamber. The cell culture chamber was calculated to have a volume of 5.4 pL. The next step was to move from design into development.

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Device FabricationThe term for MEMs development is fabrication. To fabricate our device, we use soft-lithographic BioMEMS fabrication techniques to create inexpensive silicone-based PDMS (Poly-Dimethylsiloxane)) elastomeric devices. An outline of the soft-lithographic technique is seen in Figure 4. First, a 3” silicon wafer substrate is cleaned with pressurized nitrogen gas. Then, the silicon wafer is coated with SU-8 (seen in Figure 4A), a negative photoresist, at a speed of 500 rpm for 10s then 3000 rpm for 30s using a spincoder (seen in Parts A&B of Appendix B). The SU-8 we used is SU-8 2015, which when spun onto the silicon wafer, has a depth of approximately 15 μm. Because a bead layer forms around the circumference of the wafer from the adhesion properties of the SU-8, we had to spin the wafer at 500 rpm and apply acetone around the edge of the wafer to remove this edge. This SU-8-covered silicon wafer is then baked at 65˚C for 1 minute and then 90˚C for 3 minutes on a hotplate (seen in Part D of Appendix B) in order to remove the solution. This is known as the soft bake. Next, the SU-8-covered silicon wafer is exposed to UV light through a mask

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Figure 2: Cross-sectional image of first design sketch

Figure 3: Aerial view of first design sketch


filter for 30 seconds. This process, seen in Figure 4B, hardens the SU-8 that is exposed to the UV light. The SU-8 that is exposed to the UV light creates strong cross-linkages. In other words, the transparent pattern on the mask will be transferred to the photoresist layer, as seen in Figure 4C. The UV light apparatus can be seen in Part C of Appendix B.

The development of the mask is the most time consuming part of the fabrication process. The first step is to create a design layout using AutoCad 9.0. Unfortunately, several changes had to be made to our sketch from Figures 2 and 3. The new design can be seen in Figure 5 from an aerial perspective. Part 5 of the mask is actually a separate mask used to make the pneumatic control channels. They are put into this image to conserve space. The first change that had to be made to the preliminary sketch was the perfusion output channels. The sharp turn in the perfusion output channel may have created problems with reverse flow and fabrication detail. In order to prevent these errors, a more rounded output channel was designed, as seen in Figure 5. The mixing design that was first drawn up was changed as well. It is very difficult to fabricate such a branching pattern at a micrometer scale. The mixing pattern that is seen in Figure 5 for the mask is not as efficient, but will allow for some diffusion-powered mixing to occur. Unfortunately, the “ditched” cell culture chamber concept was also eliminated. The fabrication process to develop such a multi-leveled device is too difficult for us to develop. With all of these changes, it is hard to see what it is we were able to keep. The new design still includes a dual-chamber cell culture fitted with pneumatic pressure valves, perfusion and cell inputs and outputs that allow for independent testing, a “mixer” design for input channels, and circular perfusion inlets. The image in Figure 5 is actually the AutoCad image

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Figure 4: Soft-lithography fabrication process16


of the mask design. The mask itself is seen in Figure 6. The AutoCad design is printed onto a 35mm film, seen in Figure 6.

After the SU-8-covered silicon wafer is exposed to the UV light with the mask pattern, it must then be baked at 65˚C for 1 minute and 90˚C for 5 minutes using the hotplate. This allows the cross-linking of the exposed photoresist. This is known as the “Post-exposure bake.” The hardened SU-8 is then developed with acetone, removing the soft SU-8 that was not exposed to the UV light, leaving a form represented by the image in Figure 4C. Methanol creates a white film when in contact with unexposed SU-8. With this bit of knowledge, the development progress can be checked to see if any unexposed SU-8 remains. After developing, the wafer is then spun at 3000 rpm to dry it. It is then placed on the hotplate and baked until the plate reaches 200˚C in order to melt and seal cracks in the SU-8. This is known as the hard bake. The “master” has now been created (seen in Figure 6B). The master is basically the silicon wafer with 15 μm of hardened SU-8 protruding from it where it was exposed to UV light. There were two separate masters in our project: one was the cell culture layer and the other was the pneumatic control layer.

The last step uses polydimethylsiloxane (PDMS) to create the bioMEMs device. PDMS is a elastomer and its base is a monomer. It is usally mixed with a curing agent in a 15:1 mass ratio. A portion of PDMS is then placed in a mixer/degasser where it is mixed for 2 mintues and degassed for 3. A very thin layer of 20:1 PDMS (softer) is then poured onto the cell culture master, creating impressions in the PDMS where the master is elevated with hardened SU-8 (seen in Figure 4D). A thick layer of 10:1 PDMS (harder) is poured onto the pneumatic control master. The master/PDMS forms are placed into a vacuum chamber to eliminate air bubbles and heated at 80˚C for about 12 minutes to partially cure the PDMS (device seen in Part G of Appendix B). The pneumatic layer is then placed on top of the cell culture layer and the two are cured together for the remaining 3 hours that is required for complete curing. The cured PDMS is then cut from the master, creating objects like that in Figure 4E. The blocks are then punched with 19 gauge needles to create flow channels for the channels on the device. It is then cleaned with nitrogen gas. This formed PDMS and a glass substrate are then placed in a plasma cleaner (seen in Part F of Appendix B) for 20 seconds, both with their bonding surfaces exposed. The two are then sealed together, forming channels between the PDMS and the glass. This process has created our actual device which we will test later.

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Flow calibrationBefore any testing of the device could take place, the flow parameters for the device had to be defined. The flow of this device is important for two reasons. First, it is essential to have proper flow to avoid entrapment (discussed in the Introduction). Second, in order for this device to be used with cell cultures, the media of the culture must be changed. To do this, the culture volume must be exchanged at proper flow rates. Dr. Franz Baudenbacher, our advisor, wished for us to achieve a flow rate of 10nL/s. This flow rate will allow for the medium to be exchanged without disrupting the cells in culture. Initially, we spoke about using two different ways to feed the medium and cells into the device. The first was to connect a 1 mL syringe to a 508 μm tube protruding from the input channels and use gravity to insert the solutions into the device. The second was to use a peristaltic pump in the device to seemingly pull the solution into the device. After testing a peristaltic pump last semester in BME 274, we found that the pumping mechanism was inconsistent in its flow rate and caused entrapment. Because of this, we decided to use gravity to feed our device. In order to determine the flow rate via gravity, we attempted to track beads across the cell culture area by using the “Q-Imaging Micropublisher” and a Zeiss microscope provided by the BME department. Unfortunately, we were unable to get an exact flow rate. On the positive side, we successfully created a device that allowed for solution flow into each of its orifices.

Device TestingIn order to test our device, we did two things. First, we inserted red and blue food coloring into the device to show the mixing ability in the cell culture chamber. Second, we used beads 10 μm in diameter, similar in size to cells, to show that cell-like objects can be inserted into the device. We planned to show cell-viability over a given period of time using calein and mercury lamps, but our time parameters and inability to get on the mercury lamps restricted us from doing so. The results of the tests on the device can be found in the results section.

EquipmentPhotos and details of the equipment used can be found in Appendix B.

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Results

Like the rest of the project, the results of this report are split between the “Technology Report” and the “Business Strategy Report”. In the “Technology Report”, we were able to create a preliminary sketch, develop a mask using AutoCad 9.0, fabricate our device and test the device to see if it met our goals. In the “Business Strategy Report”, we were able to define the bioMEMs market in terms of size, demands, drivers and barriers. We also analyzed the existing corporate environment of bioMEMs. Furthermore, government and economic policies of our device were reviewed and a patent search was performed to asses the competition. It was then concluded that the project was profitable for venture capitalists due to the positive NPV and profit predictions. This part of the report will detail the results of the “Technology Report”. For detailed results of the business aspect, please see the parallel “Business Strategy Report.”

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Device creation and testing

As stated above, we were able to create a preliminary sketch, develop a mask using AutoCad 9.0, and fabricate our device. After learning the limitations of bioMEMs, we were able to reconstruct our design to the form seen in Figure 5. The new design still includes a dual-chamber cell culture fitted with shutoff valves, perfusion and cell inputs and outputs that allow for independent testing, a “mixer” design for input channels, and circular perfusion inlets. The image in Figure 5 is actually the AutoCad image of the mask design. The mask itself is seen in Figure 6A. The AutoCad design is printed onto a 35mm film seen in Figure 6. The master can be seen in Figure 6B. We created 10 devices using the procedure described in the methodology section.

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Figure 5: AutoCad drawing of mask

Figure 7: Shows the pneumatic valve system open (A) and closed (B).


After creation, we then tested the device. The food coloring experiment described in the methodology section was conducted, but a problem existed: the food coloring was not dense enough at such small volumes to show color on the image taken with the “Q-Imaging Micropublisher.” Because of this, the images were not used due to their inability to show any results. Fortunately, we were able to use beads 10 μm in diameter, similar in size to cells, to show that cell-like objects can be inserted into the device. The imaging from these experiments can be seen in Figure 6C. We were also able to incorporate pneumatic valves (pressure-controlled shutoff valves) on our device. As stated in the methodology section, we used the mask (seen in Figure 5) for the pneumatic valves (Part 5). The valves on the device were also tested. Figure 7 shows the input channel for the cells running vertically and the pneumatic valve (pressure-controlled shutoff valve) running horizontally. Figure 7A shows the valve open, meaning that there is no external pressure being applied through the valve channel. Figure 7B shows that the valve closes when external pressure is applied to the pressure channel. As explained in the methodology section, the valve channel is actually above the input channel in this case. When the valve channel constricts due to the pressure gradient placed across it, it squeezes the channel below it, thus closing it. When the pressure gradient is released, it returns to the normal, open position. The device can be seen in Figure 8.

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EconomicsAs explained earlier in this report, our project was split into two sections: “Technology Report” and “Business Strategy Report”. Please see parallel “Business Strategy Report” for economic analysis of product..

Safety, Health, and RiskPlease see Appendix F: Design Safe

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Figure 6: A) Mask made of 35 mm film taped to glass in preparation for UV exposure. B) Master consisting of elevated/hardened SU-8 on a silicon wafer. C) Results of bead test shows the successful perfusion of beads into the device. The beads are seen in the red circles. The larger bubbles seen in input channel 1 are a result of entrapment. The channel numbering matches that of the mask design in Figure 5.

Figure 8: Picture shows two of our devices. A single device is the square block of PDMS seen.


ConclusionsThe primary goal of the “Technology Report” part of the project was to create a bioMEMs lab-on-chip dual-chamber cell culture device. Several goals were listed in the introduction section of this lab. Of them, we were able to create a device with: a dual-chamber cell culture LOC at 5.4 pL each, pneumatic shutoff valves for the input and output channels to prevent cells from leaving during experimentation, perfusion and cell inputs and outputs that allow for independent testing, a “mixer” design for input channels in order to mix the solutions with diffusion, and circular perfusion inlets for easier access. Although sensors and the multi-leveled cell culture chamber were not incorporated into the device, the prototype that was created seems to fit its intended use. Suggestions for the future can be found in the Recommendations section and errors that might have come into play are listed in the informal observations section. For the analysis of the market potential of this device, please see “Business Strategy Report.”

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Informal ObservationsIn designing and developing such a small device, a plethora of errors might arise. Of them, the most outstanding are found in the table below.

Step ErrorFabrication Cleaning the silicon wafer with nitrogen is essential

before starting fabrication. A dirty wafer will be useless to you.The bead from the circumference edge of the silicon wafer must be removed. If this is not done, the mask will not fit snuggly and the exposure will be skewed.If the wafer is not developed completely, the master will be forever ruined due to raised SU-8 that should not be present.PDMS must not contain bubbles. This will also ruin the device.The glass and PDMS may not seal properly, creating room for the PDMS to peel back from the glass. To avoid this, assure proper plasma cleaning.

Experimentation

Too high a flow rate will ultimately separate the PDMS from the glassWhen working with such small scales, uncontrollable factors might come in play

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Recommendations

The project as a whole was a success. We were able to create a LOC bioMEMs device with two cell cultures that allowed for fluid exchange. We were also able to analyze the market in a very detailed fashion, as seen in the “Business Strategy Report”. However, there is great potential for this type of device; therefore, it is essential to perfect this type of technology.

ChangesThe device we created was successful in its testing, but several things about the device need to be changed. First, without a multi-leveled approach to the cell culture chamber, the device is unable to retain the cells in the cell culture chamber even with the help of pneumatic controls. We suggested a checkerboard approach to the cell culture area which trapped cells into its valleys, but that too was very difficult to create. In hindsight, the cell culture “ditch” could be chiseled into the glass before it is attached to the PDMS membrane. This ditch should be at minimum 15 μm deep to retain the cells in the culture area. Another approach to retain the cells might be to create a filter that only allows medium to pass through. However, this approach has been found to be faulty due to the elasticity of some cells. Other than the inability of our device to retain the cells in the chamber, it worked to speculation. As stated above, this device has great potential and addition to its basic design are essential for its marketability.

Future WorkDr. Franz Baudenbacher helped us develop the preliminary idea of the dual-chamber LOC nano-bioreactor. This idea was the preliminary stage of his ongoing research with Vanderbilt. The future work on this device should be in parallel with Dr. Baudenbacher’s research. The first step in creating his proposed NanoPhysiometer is to “design and

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fabricate disposable cell culture cartridge with multiple cell chambers and integrated sensor arrays.”8 The first part of this step was accomplished in this project. Future direction would be to incorporate some of the sensors discussed in the introduction onto the device. Other directions may be to create an automated system that exchanges fluid within the device. Please refer to Dr. Baudenbacher’s NanoPhysiometer proposal in Appendix A for future integrations.

Ethical IssuesThere were no ethical issues associated with this device. Its sole purpose is to create a cell culture to test drug efficacy and safety.

AcknowledgementsWe would like to thank Dr. Franz Baudenbacher for his insight on this project and his continued participation. We would also like to cordially thank Raghav Venkataraman for his hard work and continued dedication in helping us with this project.

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Group - Research | School of Engineering | Vanderbilt...

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