DOC

Thermal Cycler Project Plan

By Mario Arnold,2014-01-20 04:23
15 views 0
Thermal Cycler Project Plan

    JGI THERMAL CYCLER PROJECT

    DesignWorks team members:

    Ken Chow

    Lisa Gullo

     1

TABLE OF CONTENTS

    PROJECT SUMMARY KEY ISSUES ................................................................ 4 THERMAL CYCLER PROJECT PLAN ................................................................ 5 FIRST MEETING SUMMARY 4/30/01 .................................................................. 6 KEY POINTS ................................................................................................................ 6 BRAINSTORMING SESSION RESULTS ............................................................. 6 CONCEPT SUMMARY FOR CONCEPT 1: STRAIN GAGE SYSTEM ................. 6 DESCRIPTION OF CONCEPT .................................................................................. 6

    CONCEPT SUMMARY FOR CONCEPT 2: PRESSURE SENSITIVE FILM

    SYSTEM ........................................................................................................................ 7 DESCRIPTION OF CONCEPT .................................................................................. 7

    RESOURCES FOR PRESSURE SENSITIVE FILM.................................................. 8 CONCEPT SUMMARY FOR CONCEPT 3: TEKSCAN FORCE & PRESSURE

    SENSORS ...................................................................................................................... 8 DESCRIPTION OF CONCEPT .................................................................................. 8

    CIRCUIT DIAGRAM FOR PRESSURE SENSORS .................................................. 9 RESOURCES FOR SENSOR VENDORS ................................................................. 10 CLIENT BRAINSTORMING FOLLOW-UP MEETING - SUMMARY .................. 10 TEST PLAN TO CALIBRATE PRESSURE INDICATING FILM......................... 11 MICRO ........................................................................................................................ 11 ULTRA LOW .............................................................................................................. 11 SUPER LOW ............................................................................................................... 12 CALCULATION OF MICROPLATE SEALING SURFACE AREA ...................... 13 JGI MICRO PRESSURE TEST REPORT .......................................................... 13

     2

CONCLUSION 1: MEASUREMENTS ARE HIGHLY REPEATABLE (we can

    draw conclusions from one measurement reading because if we take multiple

    readings with everythingthe same, we will get the same pressure signatures). ......... 14 CONCLUSION 2: PRESSURE VARIATION IS PRIMARILY DUE TO

    DIFFERENT MICROPLATES. ................................................................................. 14 CONCLUSION 3: POOR SEALING OCCURS ON THE LEFT AND RIGHT

    SIDES OF THE DIFFERENT MICROPLATES. ..................................................... 15 CONCLUSION 4: THE DESIGNWORKS MICROPLATE SEALS MORE

    UNIFORMLY. ............................................................................................................. 15 CONCLUSION 5: THE GREINER MICROPLATE SEALS POORLY IN THE

    CENTER. ..................................................................................................................... 15 CONCLUSION 6: ADDING MORE TURNS TO THE THUMBWHEEL SCREW

    IMPROVES THE SEAL, BUT DOESN’T COMPLETELY SEAL THE SURFACE

     ...................................................................................................................................... 15 CONCLUSION 7: THICKER PAPER DOES NOT CHANGE OUR RESULTS ... 16 THERMAL CYCLER TEST PROCEDURE............................................................. 16 THERMAL CYCLER TEST CONDITIONS ............................................................ 17 TEST SAMPLES ................................................................................................ 18 SAMPLES 1-4 ............................................................................................................. 18 SAMPLES 5-8 ............................................................................................................. 19 SAMPLES 9-12............................................................................................................ 20 SAMPLES 13-15 .......................................................................................................... 21 SAMPLES 17-20 .......................................................................................................... 22 SAMPLES 21-24 .......................................................................................................... 23 INVENTORY ....................................................................................................... 24 WHAT’S NEXT? ................................................................................................. 24 FOLLOW UP LETTER ....................................................................................... 25

     3

PROJECT SUMMARY KEY ISSUES

The JGI thermal cycler project began 4/30/01 and ended 06/15/01.

    JGI thermal cycled biological test samples showed signs of evaporation around the sides of microplate test samples, causing lost data. A second order issue was that lab technicians were frustrated with the thermal cycler biological test process. They were tightening the bonnet of the thermal cycler without instrument feedback indicating when the seal was tight. Repetition of this process wore their fingers raw.

    JGI requested that DesignWorks confirm the evaporation and then identify the cause of the evaporation and based on that determination assess possible solutions. If practical, the solution would address the second order issues.

    Pressure tests were performed using pressure sensitive carbon paper. The tests indicated that at very low pressures there was leakage between the platen and the microplate. However, above a certain PSI, the results showed that there was fairly uniform pressure. DesignWorks analyzed the test results in detail and also determined that the uniformity of the seal between the platen and the microplate was dependent on the batch of microplates. Test results varied greatly between microplate types.

    DesignWorks presented findings to JGI and recommended possible options. (See sections JGI MICRO Pressure Test Report and What’s Next? for more detail).

    JGI chose to perform pressure tests using Pressurex Micro rated carbon paper on each batch of microplates. This would give them immediate feedback regarding the sealing properties of a specific plate. In addition, technicians will modify the test procedure by consistently setting the thumbscrew pressure as high as possible.

     4

THERMAL CYCLER PROJECT PLAN

Project Description: JGI requested that DesignWorks modify an instrument that is

    used for thermal cycling of biology samples. The instrument does not equally seal across

    the top plate. Our goal is to modify the instrument so that it seals better as well as

    providing a psi readout so that all instruments are calibrated equally. An added bonus to

    JGI would be to modify the instrument in such as way that lab technicians don’t have to

    continuously adjust the pressure dial. This is inconvenient and wears on fingers.

    Scope: Initially one instrument will be modified and then the remaining instruments will be modified the same way. It is estimated that there are a minimum of 64 instruments

    that will need modification.

DesignWorks Process: We see the project going through all the stages of

    a "Gadget" project. For this project, the stages include the following

    design tasks:

    1. Specify the design problem

    2. Gain an understanding of relevant issues (how it is used, desired life, conditions

    used, who will use it, etc.)

    3. Perform concept generation to identify a variety of concepts

    4. Define constraints, requirements, desires, and prioritize values (e.g. do you want a

    low-cost fix that wears out, is it important for the solution to be easy to use?)

    5. Narrow concepts to a small number for further study and detailing

    6. Identify critical components of concept(s) (e.g. does the concept depend on strain

    gages? Does it depend on an operator who is well trained?)

    7. Validate critical components through prototyping, testing, or analysis (if we go

    with a strain-gage concept, we'll make a prototype with gages mounted on it)

    8. Incorporate changes, tweaks, and other details into final design (this task and

    numbers 6 and 7 will go through iterations)

    9. Procure and fabricate necessary items

    10. Assemble and test final product

    11. Write a "How to Use" document to deliver with the product

    12. Deliver and train users on its use

     5

FIRST MEETING SUMMARY 4/30/01

Marty Pollard, Ken Chow and Lisa Gullo met to discuss the Thermal Cycler Project Plan

    and the MJ thermal-cycler instrument that DesignWorks will be modifying for JGI.

KEY POINTS

    Requirement: DesignWorks shall design a device to calibrate pressure for the MJ thermal cycler’s platen seal. The device shall have read-out instrumentation and the seal

    shall be measured evenly (in approximately five different places).

Scope: DesignWorks first order goal is to design a calibration device. After developing

    the calibration device, the scope of the project may extend to the task of developing a

    plate that seals better as well as modifying the instrument in a way that the dial didn’t

    wear on fingers. The modifications may be applied to roughly sixty MJ instruments.

Instrument Operation: The instrument is cycled approximately 20 to thirty times per

    use and the temperature varies from 65? - 95? c. The plastic sampler is inserted once at

    room temperature.

    Summary: In response to some key questions regarding the project, Marty Pollard stressed that his highest priority is to develop a calibration device. Concept generation

    should be a part of the DesignWorks process, but only a small percentage our time should

    be dedicated to this. Marty will be the primary contact, however in a couple of week’s

    time, Karl Petermann may be available as a main contact. In the meantime, questions

    will be directed toward Marty. Marty provided a charge number, LWRAES, for parts, etc.

    Marty will be bringing DW another plate for DW to analyze and test. People who may

    be available to help on this project are Charlie Reiter, electronics assembly and test, B25,

    and Mario Cepeda, machining, B25.

BRAINSTORMING SESSION RESULTS

CONCEPT SUMMARY FOR CONCEPT 1: STRAIN GAGE SYSTEM

DESCRIPTION OF CONCEPT

    A calibration plate is used to provide data on pressure applied by the thermal cycler lid.

    Strain gages mounted at strategic locations on the lid are wired to a cable that connects to

    a meter that displays the results.

    Reliability: Fairly reliable. Strain gages are very mature technology and issues such as drift should not be a problem after the system is debugged and if the system is used properly.

    Accuracy: Highly accurate. Strain gage design must be properly conducted (placement, orientation, configuration). Strain readings must be carefully calibrated to provide accurate pressure values.

     6

    Ruggedness: Medium. Several items need to be handled properly (and inspected) to avoid misreads due to damage. These include strain gages, leads, and electronic components.

    Ease of use: Medium. Proper alignment is necessary. Features can be added to improve ease of use (conversion of voltages to pressure, strain relief, alignment pins, etc.)

    Area coverage: Minimal. One gage needed for each location. Reasonable number of gages is no more than six, therefore we would only get readings at these six points.

    Feedback time: Instantaneous. Readings can be displayed continuously as the pressure is adjusted.

    Development cost: Medium. Effort includes: analysis, detail design, selecting components, design of readout subsystem, and assembly of system components. Individual components are inexpensive but

    putting a system together that works takes development effort.

Development time: Medium. Associated with development time.

    Advanced functions: None.

    Long-term costs: Very low. No single-use items are needed to perform a reading.

    Versatility: Limited. System will probably need to be adapted for other applications.

Overall this concept will likely lead to a device that provides a reading that can be correlated to pressure,

    but a lot of effort is needed to ensure accuracy, reliability, ruggedness, and ease of use. The effort may

    include FEA to determine strain gage location and configuration. Testing is likely needed to calibrate

    readings to pressure.

The main drawbacks to this concept are the limited number of pressure points and the amount of

    development needed.

The main advantages to this concept are the use of mature technologies and the very low long-term costs.

CONCEPT SUMMARY FOR CONCEPT 2: PRESSURE SENSITIVE

    FILM SYSTEM

DESCRIPTION OF CONCEPT

    Pressure sensitive film is inserted between the platen and the microplate. The film is removed and

    scanned to determine pressure distribution

    Reliability: Very reliable. Pressure sensitive film has been used in many industries and is a mature product. The simplicity of the system leads to high reliability. Film should not be used beyond its shelf

    life.

    Accuracy: Indeterminate. Manufacturer of film states 10% accuracy on readings. However, ultra-low pressure levels (less than 20 psi) have low accuracies and can only provide relative measurements.

    Ruggedness: Very rugged. System has few parts and film can be handled like normal paper.

    Ease of use: Easy to use. Proper alignment is not necessary. Although system is easy to use, proper interpretation of results is important for accuracy.

     7

    Area coverage: Maximum. A complete pressure profile across all mating surfaces is provided.

    Feedback time: Delayed. Information on pressure is obtained only after film is removed and scanned.

    Development cost: Low. Information is available with minimal development effort. Effort is required to determine proper grade of film.

Development time: Low.

    Advanced functions: None.

    Long-term costs: Medium. One sheet of pressure sensitive film for testing costs up to $5.

Versatility: Medium. System can be used with different microplates.

Overall, this concept provides a very fast path to obtaining pressure readings. However, the possibly low

    values may ultimately make this concept non-viable. Very little up-front investment is needed.

The main drawbacks to this concept are its long-term costs and difficulties in using the system for the

    desired low-pressure ranges.

The main advantages to this concept are its simplicity, low up-front costs, and complete coverage of the

    pressure surfaces.

RESOURCES FOR PRESSURE SENSITIVE FILM

http://www.fujiprescale.com/html.online_store.htn

CONCEPT SUMMARY FOR CONCEPT 3: TEKSCAN FORCE &

    PRESSURE SENSORS

DESCRIPTION OF CONCEPT

    Tekscan Pressure Sensors: Button shaped single sensors are placed strategically along the platen to

    measure the resistance. A small circuit measures the output voltage that is routed to a data acquisition box

    that plugs into the serial port of a computer. Readings are displayed in pounds.

Reliability: Medium to high reliability. This is a mature product.

Accuracy: Highly accurate. Accuracy range is +/- 2 to 10%

    Ruggedness: Medium. This system has several items which must be handled carefully in order to avoid misreads.

Ease of use: Intermediate. After the initial set up, the easy of use is relatively easy.

Area coverage: Medium. The entire platen cannot be covered at one time.

Feedback time: Instantaneous. Results can be read on a computer desktop.

    Development cost: Medium. The effort includes analysis of results, design of circuits and installation of software package.

     8

Development time: Medium. Circuits must be designed for each sensor that is used.

Advanced functions: None.

Long-term costs: Very low. The sensors can be used over again for different tests.

Versatility: Medium to High. This system can be used with different microplates.

This concept will provide different readings for each sensor. The values are in pounds and analysis will be

    interpolated to determine the force for the entire surface of the platen. The test set up requires that different

    circuits be designed for each sensor. Calibration is required to determine the accuracy of the test.

The main drawback is that it is limited to a number of pressure points and some development time is

    required.

The main advantage is that this test is accurate, versatile, and reliable.

CIRCUIT DIAGRAM FOR PRESSURE SENSORS

     9

RESOURCES FOR SENSOR VENDORS

http://www.tekscan.com/

    http://www.endevco.com/

    http://www.endevco.com/monitoring/monitoring_main.htm

CLIENT BRAINSTORMING FOLLOW-UP MEETING - SUMMARY

May 4, 2001

Attendance: Ken Chow, Marty Pollard, Lisa Gullo

I showed Marty our concept summaries for the strain gage concept and the pressure

    sensitive film concept. We talked about how the users actually set the pressure. Marty

    says they probably do both (turn the knob the extra 3/4 turn after opening the top as well

    as turning the knob an extra 3/4 turn while it's closed).

I reviewed our initial understanding of the 4-bar hinge linkage and how it pertains to

    setting the pressure. I indicated that the pressure is generated by the compliance between

    two points of the 4-bar linkage system. Marty feels the compliance is in the bonnet lid. I

    pointed out how the older 96 well unit has its "fixed" linkage bar poorly secured and how

    the new unit has the same bar rigidly attached. Wear and tear may result in loosening of

    this "fixed" linkage and therefore effect the pressure applied to the microplate. Marty

    says when he gets back to JGI he will examine the units to check for looseness of the

    "fixed" linkage.

We tried to imprint the "Low" pressure grade film with the 384 well thermal cycler unit,

    but it made no impressions.

I reviewed information gathered on the pressure sensitive film concept: cost of film, how

    it works. We briefly discussed the disadvantage of long-term costs associated with this

    concept. Marty says it is expensive but could be tolerable if it is the best solution.

Meeting action items and strategy:

    Since the pressure sensitive film requires no development effort, we will pursue the

    following plan:

    1. Purchase small quantities of the pressure sensitive paper (micro, ultra-low, and super-

    low grades)

    2. Concurrent to #1, plan and conduct an initial process for image analysis of imprinted

    film. The process includes creating known imprints, scanning an image of the

    imprinted film, and performing simple image analysis to correlate percent color

    saturation with pressure.

    3. Test out the pressure sensitive film concept on several thermal cycler units at JGI.

    This test will also be used to gather preliminary data.

     10

Report this document

For any questions or suggestions please email
cust-service@docsford.com