P16104: Microfluidic Spectroscopy for Proteins within CubeSats
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Detailed Design

Table of Contents

Team Vision for Detailed Design Phase

Goals for this Phase

  1. Continue creating prototypes of Microfluidic wells using PDMS
    • Work towards mitigating air pressure issue
    • Will it withstand vacuum sealing
    • Test with solenoids
  2. Testing solenoids with Electrical Systems
    • Control the movements of the solenoids with the micro-controller
    • Create a solenoid support structure
  3. Design a new method of vortexing other than vibration
    • Use oscillating solenoids to mix reagent?
    • Will wells be sealed or open to solenoid plungers
  4. Update responsivity curves for new filters
  5. Mitigate any remaining risks from previous phase
  6. Build a prototype of solenoid stand compliant with a 1u cubesat
    • CAD model design, use solenoid dimensions from Adafruit
    • Print using PLA plastic and get mounting hardware

Accomplishments

  1. Created one PDMS device compliant with our solenoids
    • Identified additional risks with solenoids
      1. Solenoids do not provide enough force
      2. They reduce our power budget
      3. They are relatively heavy for a Cubesat
    • Solenoids are relatively weak at the beginning of their throw
  2. Printed a solenoid support structure
    • Mounted both solenoids to structure
    • Able to translate vertically, not horizontally
  3. Responsivity curves for new filters are complete
    • Determined that a more expensive filter will allow more light to pass through while also allowing only the wavelength required to pass through.
    • A dramatic improvement over the current planned filter
    • Have specific values of intensity and sensitivity for certain wavelengths and the sensor.

Prototyping, Engineering Analysis, Simulation

Electrical Systems

When modeling the responsivity curve of the sensor, the two sources modeled was the UV LED emitter, and the emission spectrum of Tryptophan. When modeling, the factors considered include the responsivity of the sensor, the efficiency of Tryptophan conversion, and the relative wavelength intensities emitted by both the UV LED emitter and the Tryptophan.

The data above shows the responsivity of the LED and Tryptophan given an excitation to emission efficiency of 20%. The excitation and emission data can be found here and here. The data was obtained and posted on http://omlc.org/spectra/PhotochemCAD/html/091.html. The numbers in the last plot show the relative magnitudes contributed by the LED and tryptophan.

The magnitudes in the last plot show that the LED emitter contributes to the majority of the signal seen by the UV photo-sensor. A solution to this problem is to use an optical filter to minimize or eliminate light from the emitter, and maximize the response of emitting Tryptophan. The two filters analyzed were from www.edmundoptics.com.

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The data shows that there is a large performance difference between the two filters. If possible, the second filter should be used. However, the cost difference between the filters is also large. The first filter cost $35 to acquire while the second filter costs $180. Final purchasing decisions will be based on a cost-benefit analysis between the two filters.

Microfluidic Channel

 Iteration 3

Iteration 3

Iteration 3

Iteration 3

Iteration 3

Iteration 3

Iteration 3

Iteration 3

Spectroscopy

  1. Tryptophan emits 350 nm light when it absorbs 280 nm UV light
  2. Spectrograph of emitted light will be recorded by a photodiode
  3. Test early next semester on a protein with tryptophan residues
    • Glass cuvette with protein
    • Device with protein

LED Selection

  1. MTE280F13-UV selected as UV-LED from benchmarking
    • Low cost of $147 from Digikey
    • Flat lens with a diameter of 5.9mm
    • Power output of 1.5mW (Ocean Optics Deep UV LED is only 0.5mW)
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Drawings, Schematics, Flow Charts, Simulations

Electrical Systems

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Structural Systems

Chassis

1U Cubesat must fit into 10cm X 10cm X 10cm space,000cm^3 Volume. Chassis walls result in a working volume of 953.15cm^3;Walls - 1.27mm thick, Bases - 1.5mm thick, 97.46mm X 97mm X 97.46mm interior.
Chassis

Chassis

1U Skeletized Chassis by Pumpkin Inc. Meets required NASA standards for CubeSats as well as different launchers 5052-H32 Aluminum, Walls - 1.27mm thick, Bases - 1.5mm thick, Rated for -40 to +85 °C, 97.46mm X 97mm interior

The chassis itself is alodyned while the walls are hard anodized. This allows for the chassis to remain conductive creating a Faraday cage. If the chassis were completely hard anodized, it would become an electrical insulator. Able to easily integrate solar panels Price - $925.00. Unable to manufacture in house due to specialized material treatments. A mock-up will be created by CNC milling out of aluminum Will not have the same electrical properties as the original, but will have similar structural properties.

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Thermal Analysis:

Four sources of heat:Direct Solar radiation,Albedo (Radiation from sun bounces off earth), Earth Infrared, and Internal heat generation. Experimenting with different ways to incorporate all sources into model.
Thermal

Thermal

Specialized coatings and materials. Allow for increased thermal regulation of vital components. Gold plating: high heat retention - alpha/epsilon = 10 White paint: low heat retention - alpha/epsilon = 0.31

Experimented with white paint to discover the effects on temperature.

Radiation Coatings

Radiation Coatings

Solenoid Test Struture

Solenoid Dimensions

Solenoid Dimensions

Using CAD and the dimensions of both the PDMS iteration and the small solenoids, a mount was printed in PLA. This mount was used to hold the solenoids at a constant position relative to the microfluidic wells.

Completed mount with hardware

Completed mount with hardware

Solenoid mount with Iteration #3 and solenoids compared to a 1u cubesat

Solenoid mount with Iteration #3 and solenoids compared to a 1u cubesat

Bill of Material (BOM)

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Test Plans

Updated Engineering Requirements

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Microfluidic Channel

Microfluidic Channel Test Plan.

Spectroscopy

Spectroscopy Test Plan

Updated Systems Diagram

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Risk Assessment

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Link to Live Risks Document: Risks - Detailed Design.

Design Review Materials

The following presentation was given on December 10, 2015: Detailed Design Review

Plans for next phase

  1. Get more feedback from our customer as we begin running more tests with proteins.
  2. Purchase LED and optical filter
  3. Design and test microfluidic devices until a final working model is reached
  4. Begin designing the internal layout and structure of our payload
    • Think about cable management and compare to other Cubesats.
    • Where will all of cables route?
    • How many cables will our current electrical system require?
  5. Discuss Project Budget
  6. Discuss risks and actions for the next phase with team members

Individual Plans

Anna Jensen's Three Week Plan: Anna's Goals.

Mallory Rauch's Three Week Plan: Mallory's Goals.

Darin Berrigan's Three Week Plan: Darin's Goals.

August Allen's Three Week Plan: August's Goals.

Andrea Mazzocchi's Three Week Plan: Andrea's Goals.

James Lewis's Three Week Plan: James's Goals.

Matthew Glazer's Three Week Plan: Matt's Goals.


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