The Chip Design Process (What You Will Turn In)

Chip Requirements

The Chip Design Process (what you will turn in)

Initial Sketch Requirements for the 1st Chip—this is part of your first lab memo

The initial design sketches can be a hand-drawn representation of your team’s ideas for your 1st chip design. Preparation for this design include reading the introduction, project objectives, and chip requirements section.
The sketch should be a two-dimensional representation of the chip design with proportional representation of the location and size of all features, i.e. wells, channels, team letter.
Consider shape and size in all features, wells and channels that will encourage the flow of fluids in the direction desired.

Preliminary 1st Chip Design (4 hole chipholder)

The 1st Chip Design should be created using Solidworks.
It must follow the LOC Design Requirements (see below).
You will meet with the GTA to discuss the design and any necessary corrections (see section “Two Phase GTA Meetings” for details)

1st Chip Design and Operational Design (4 hole chipholder)

After meeting with the GTA, you will incorporate any necessary corrections
The 1st Chip Design should be revised using Solidworks
You will also include sample calculations for all well volumes, flow lengths, etc (see below for the requirements)
You will also turn in an operation process describing how the chip will be used (see below for more information)

2nd Chip Design and Operational Process (3 hole chipholder)

The 2nd chip design should be created using Solidworks.
Students are encouraged to exercise originality in this design vs the first design (i.e. students are encouraged to try a different design for their second chip, rather than simply replicating their first chip design)
You will meet again with the GTA to review your design.
The 2nd chip design and operational process should incorporate review and corrections made by the instructional team.
You will also include sample calculations for all well volumes, flow lengths, etc
Operational process specifically indicating how the chip will be used and the sequence of operations. This can be done with an ordered list such as an outline, or by flowchart.

The operational designs may continue to evolve up to the Final System Test. All changes must be documented in the Final Report.

You will submit a fully-dimensioned drawing of your chip (see section V below)

Operational Process:

An operational process should be documented and submitted with the chip design. This is a list that explains all the steps performed when using the chip,as well as the tools and equipment used (syringes, plugs, DAD, etc), and can be done with an ordered list such as an outline, or by flowchart. It should be suitably detailed such that another engineering student could use your chip—much like an instruction manual.

Sample operational process (yours should be more detailed and specific to your chip):

Well1 – pump with sample using syringe, stop, test,
Well1 – flush with DI waterusing syringe
Well2—pump with sample using syringe…etc.
Etc…

[Note: This document must be typed]

Sample Calculations:

Provide sample calculations, footnotes, explanations, etc. as necessary to describe unique features, how feature sizes or shapes based on volume or flow or sealing requirements were determined, etc., in addition to:

Well volumes (ALL wells: staging, detection and waste, etc.)

Channel flow lengths (All)

Volumes along each flow length

Shortest distance from outermost edge of any feature to outside edge of chip

Shortest distance from innermost edge of any feature to edge of detection well

Any provisions made to ensure proper flow, prevent features fromcollapsing, leaking, etc.

[Note: This document must be typed and equation editor must be used]

LOC Design Requirements

Lab-on-a-Chip Design and Operational Design Requirements and Constraints

Chip Design Constraints and Requirements

Each team will create two chip designs - one will be designed to be accommodated in the 3-hole chip holder; the other will be designed to function in the 4-hole chip holder.

The entire layout of both chips must fit within a 5.08 cm circle. Solidworks seed files will be provided to help create accurate designs.

Figure 1: Sample chip with all required features

Chip Design Requirements:

The depth of all features (wells and channels) in the chip will be 200 microns. A flat PDMS lid will enclose the features.

Flow-through detection well, located in the exact center of the chip, in which the sample will be deposited.

Detection well should be designed to store exactly 3 μl of fluorescein solution sample.

Confirm the necessary size by noting the 200 micron depth and the volume of fluid to be placed in the detection well. From this volume and depth, determine the necessary size (determine diameter if circular). It would be best to err a bit on the larger side to be sure that the detection well can accommodate its intended contents.

CAUTION: Circular detection wells will most likely collapse owing to lack of support around the center. Other shapes should be considered.

At least one staging well to introduce the fluorescein solution into the chip.

Channels that connect the wells must be between 300 to 400μm (micrometers or microns) in width.

Intersections of channels with wells may create sharp inside corners which cannot be manufactured. For any sharp internal corners add a curved lined with a radius of curvature of 200 microns. This applies to sharp corners on any features including the team letter. See figure 2 below.

Figure 2: Internal corners of features need to be rounded with a minimum radius of 200 microns

Staging wells and detection wells and the waste well must be accessible via the access points on the chip holder. Chip design can be drawn over chip holder design (as a stencil) to accommodate this requirement.

A Waste well to accept unused fluorescein solution sample from the detection well along with flushing fluid. The waste well should be sized to hold at least the volume of all the other wells combined.

NOTE: Large unsupported cavities in the design are more difficult to properly seal and fill in the finished product.

[Please see Section V for information about seed files, drawing files, submitting your chip designs]

To carry out the analysis here are someadditional considerations:

To reduce undesired flow between wells, the transfer line in and out of each well may contain a capillary check valve if deemed necessary. This can be accomplished by adding a very small circular well with a diameter approximately 3-5 times the width of the transfer line. The small well should be placed approximately 0.5 mm (500 μm) from the entrance or exit of the larger well but not touching that well. Figure 3 shows an example of a check valve. Check valves increase the pressure required for flow during a dry or unprimed state. Experimentation with non-traditional (i.e., non-circular and/or multistage, such as “fishbone” capillary check valves) capillary check valves is encouraged. Figure 4 depicts an alternate check valve design. Remember: NO SHARP CORNERS!

Different well shapes and channel entrance and exit shapes affect resistance to fluid flow. Tapered transitions, in contrast to sharp edges, can be used to diffuse flow.

In order to avoid the edges of the chip where possible trimming and sealing issues may arise, keep the design as far as possible from the edge of the chip, while still utilizing the access points provided by the chip holder.

The detection well must be offset from the other wells by at least 1 cm in order to allow the photosensitive detector to focus only on that well. The photosensitive detector will be an electronic circuit and detection device built by the student team.

The chip must fulfill the following operational requirements:

Must be able to pass samples of varying concentrations of fluorescein solution for testing without contamination to samples (i.e., raising or lowering concentration due to presence of residual water or fluorescein solution from a previous trial).
Must be able to clean chip without removing from chip holder.

HINTS for converting units:

Your calculations will have to show conversions from linear dimensions (microns) to volumetric dimensions (microliters). Below are the conversion factor information you should use.

HOW BIG IS A MICRON??? - One thousand microns or micrometers (µm) are in one millimeter (mm).

SO HOW BIG IS A MICROLITER??? - One thousand microliters (µl) are in one milliliter (ml). One milliliter (ml) is also one cubic centimeter (cc or cm3).

HOW ARE CUBIC MICRONS OR CUBIC MICROMETERS CONVERTED TO MICROLITERS, AND VICE VERSA? - The answers to the first two questions can be used to determine this.

There are many useful websites for units conversions such as

Solidworks Design, Seed files, Drawings, and Submission Procedures

For the Solidworks submissions, note the following:

Chip Design Drawings should be fully dimensioned on OSU title block using Solidworks for both the 1st chip and 2nd chip design submissions
The drawings should only include the top view of the chip
Units of dimension for the drawings should be in microns.
The drawings must be in scale 3:1
The part file to be turned in for (.SLDPRT) each design should be properly extruded, with correct dimensions.

Procedure for creatingyour design

You will start the Solidworks design of your chip using the appropriate Seed File (3-hole or 4-hole).

Features of the seed file:

SI units (microns) by default
Grid: Minor Axis -100 microns (100 x 10-6 meters); Major Axis – 1000 microns
Snap: 10 microns
The boundary of the circular chip, has a diameter of 2 inches = 5.08 cm = 50.8 mm = 50800 micron.
XY plane, center point, X axis and Y axis are visible.
The design of the chip holder is available by turning on visibility.

Using Seed File for your designs:

Keep all rough design and design requirement and constraint documentation handy for reference.
The staging wellsand waste well(s) will be aligned with the access holes of the chipholder. The seed file includes a sketch of the chipholder. To locate where to place your staging wells and waste well(s), turn on the visibility of the chip holder sketch and use this overlayto help position these wells.
Open the seed file and extrude the given circle to a thickness of 5mm in the opposite direction of the chip holder sketch (i.e., do not extrude upwards through the chip holder sketch).
Start a new sketch on the same plane as the top of the extruded 2” circle and draw the detection well first, at the exact center of the chip design.

Draw the other wells (waste and staging) according to the guidelines in this section after you have drawn the detection well. Be sure to allow for enough space between wells as there has to be an adequate seal between each area to avoid leakage, contamination, etc. The chip design must fit the corresponding chip holder design provided in the seed file.

Next draw the channels to connect the staging wells to the detection well and the detection well to the waste well.
Be sure to join all entities carefully using constraints and/or Solidworks drawing indicators wherever possible.
There should be no breaks where a channel bends, meets a capillary valve, meets a well, or at any other type of junction, i.e., the entire design should be a closed loop.
The wafer manufacturing process uses computer-controlled milling machines with a circular bit, which cannot create sharp internal corners. For such features, round the corners with a radius of curvature of at least 200 microns.
Even though the channels are very small you should draw them as open channels and not a single line.

Now that all the wells and channels have been drawn, it is time to create some capillary valves (optional). These are small well-like areas immediately before a channel joins a well. To prevent unintended movement of the fluids due to capillary flow, capillary valves may be included in the design as described in the previous appendix.
Capillary valves may be small and not much greater than 1 mm in diameter, depending on the size of the channels and wells.
These need to be centered over the center of each channel while simultaneously being the proper distance from the well.
Next, in order to place the edge of the capillary valve 500 microns from the well, the center of the circle representing the capillary valve must be placed a distance of 500 microns plus the radius of the circle from the edge of the well.
Next create the circular capillary valve using the point on the line as the edge.
Now a great deal of trimming is necessary.
Trim the curved areas between the channel walls that intersect the wells and capillary valves. Then delete the small curved segment between the ends of the channel walls, leaving the remainder of the circle intact.
Trim the channel wall ends that extend into the capillary valves and wells.
Trim channel walls that pass completely through capillary valves.
If a rectangular shape was used for the waste well, the middle piece between the channel ends for the channel that terminates there should be trimmed.
Etc… (keep trimming as necessary)
Draw your team letter a significant distance from any design features.
Extrude (CUT into the chip) all the above to create a profile to a depth of 200 microns. Be sure to delete the words “Top Left” as well.

Instructions for submission of part files (.SLDPRT files)

Ensure that you turn in the properly extruded part files of both of your designs.
The files need to be named appropriately—include your team letter and chip type (i.e. 4 hole or 3 hole)
You will send these files to your GTA, who will use the files for the manufacture of your chips.

Creating and submitting the dimensioned drawings (see sample drawings below):

Follow the steps below to make the layout for your electronic or hardcopy submission.

If not already open, open your part file for your design—you will only be submitting the part file for the chip itself.
Select “Drawing” from the upper left-hand new file icon.
Click on Model View on the Drawing Toolbar
In the property manager, under Part/Assembly to Insert, select the file. Click next. Under orientation, click “front” under standard views. The view should resemble the samples below. Only the top view of the chip should be included (your chip may be in a different position depending on what axis you drew the chip—the main point is that it should look like the samples below).
Under Scale, select custom scale, User Defined, and set to 3:1.
DO NOT include the chip holder in this layout.
Under Annotate, choose Smart Dimension to dimension each feature of the drawing (dimensions must be in microns—see below for help). Place and format appropriately as per the step below.
Choose the standard OSU title block. Fill out the title block.
Resize and format the text in the view for proper visibility as necessary.
Save using the file naming conventions(i.e. include your team letter and chip type—4 hole or 3 hole) and save as type “Drawing Files (*.SLDDRW)”.

This file should be submitted on the due date given in the class schedule, along with all other required items (Operational Design, Calculations, etc. – see the earlier section concerning the “Chip Design and Operational Design” in the Project Description Document for details).

Tips for Dimensioning:

Dimension the chip design in one view: the top view.
Indicate the linear units of measure utilized.
Provide a center line for the chip boundary and dimension the chip boundary.
Dimension the detection well, staging wells, and waste well. Indicate size and location of these features.
Dimension the channels. Indicate channel width. Indicate channel angles where appropriate or if channels are diagonal. Indicate channel lengths.
Dimension the capillary check valves. Indicate size and location along the channel of each of these relative to the well to which they are closest.
Dimension the team letter (it is part of the design!). Do not bother with the intricacies of the lettering, just indicate overall size and location of the letter as a whole.
Use notes for repetitive dimensions (if channel widths, well sizes, capillary valve sizes, etc. are the same).
Save and submit this dimensioned design with the rest of your Chip Design and Operational Design documentation.

Changing dimensions to microns: