Subsystem Level Design
ReviewP16104
Microfluidic Spectroscopy for Proteins within
CubeSats
Team Members
August Allen
Andrea Mazzocchi
Anna Jensen
Darin Berrigan
James Lewis
Mallory Rauch
Matthew Glazer
Agenda
• Subsystems
• Electrical
• Mechanical/Structural
• Spectroscopy
• Microfluidics
• Bill of Materials
• Updated Engineering Requirements
• Updated Risk Assessment
Electrical Subsystem
Electrical Prototyping
Required:
- Subsystem requires multiple different sensors to provide proper functionality.
- Final design must be in a small package and work without fault.
- Photodiode must detect luminescent proteins
Solution:
Breadboard testing using readily available breakout boards for microprocessor
and sensors. This will reduced overall development time and allow quicker
transition to custom designs and completed software. Test will determine the
minimum intensity of UV LED (acting as proteins) for proof of concept
Electrical Block Diagram
Electrical Block Diagram
Temperature sensors monitor
experiments and board status
Current sensors monitor power
consumption of major components
Position sensor registers proper
solenoid operation
Electrical Block Diagram
UV LED Illuminates Bioassay- Input and output filters are optical.
- Input Filter adds isolation from external sources i.e.
Sun.
- Output Filter eliminates UV LED output and provides
additional filtering against unwanted light.
- Photodiode output will be filtered for noise and
amplified to a readable voltage for the MCU.
Part Selection - Guidelines
- If possible select hardware with available or easily built development boards.
- Allows for confirming that all hardware will work with other subsystems and for the project over all
before moving to custom hardware.
- Attempt to source cheaper parts or similar analogs to final parts for testing. Save the budget for the final
product.
- Custom hardware is the end goal, having experience with the hardware before hand makes the final
testing easier.
Part Selection - Sensors
- Most sensors currently sourced from Adafruit due to
available dev boards.
- Research into available sensors will continue as to
allow for best possible selections
- UV light sensor will be able to measure output light at 350 nm
- Current sensor will log power consumption to report back to
cubesat and potentially allow for detecting issues if experiment fails
electrically.
- Some UV LEDs have been selected to test the light sensor for
operation in both the expected range and for what the proteins will
receive.
Part Selection - Microcontroller
Teensy 2.0 Development Board
- quick software development through arduino
- hardware resources fit our current requirements and also
allows for changes in requirements
-Onboard MCU (ATMEGA32U4) is a current option for the
MCU for final prototypes.
-Teensy can provide fallback if issues with custom designs
are encountered.
Testing
- Breadboard testing will confirm operations.
- Will allow for quick transition to custom hardware as we will know part selection
works.
Mechanical/Structural Subsystem
Chassis
http://www.clyde-
space.com/cubesat_shop/structures/1u
_structures/115_1u-chassis-walls
Walls
Lid
Bottom Base
Rails
1U Skeletized Chassis by Pumpkin Inc.
5052-H32 Aluminum
Walls - 1.27mm thick
Bases - 1.5mm thick
Rated for -40 to +85 °C
97.46mm X 97mm interior
Meets required NASA standards for
CubeSats as well as different
launchers
Chassis
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
Rapid prototyping to create a mockup
Structural Prototyping
Project Requirements:
The bioassay must fit into a 1U CubeSat.
The components and sensors of the bioassay are supported by a surrounding
structure.
As our bioassay develops and changes, so too will the design of the
surrounding structure.
Solution:
Rapid prototyping techniques such as CNC machining, laser cutting, and 3D
printing could potentially allow us to make quick and detailed changes to our
CubeSat structure. Currently there have been several uses of additive
manufacturing techniques in Cubesats.
Use of Rapid Prototyping in Cubesats
Pros:
Quick builds of structures for fit checks of non-functional parts
Part geometries that would otherwise be difficult to machine
Easy to update and edit CAD files for continuous revisions
Inexpensive material
Cons:
Inadequate material strength
Non-Solid construction/Porous Material
Considering our project’s scope does not require a launch capable structure, the
use of 3D printing and other rapid prototyping techniques will meet our needs.
Initial Testing: CAD Files
Chassis
Walls
Bases
Feasibility Prints and Model
Used Makerbot Replicator 2X
-Helps customers and ourselves visualize the
scale of a cubesat.
Vibrations - Model Analysis
Model Analysis
Using the overall mass and stiffness of a structure model analysis is used to find
the periods at which the structure will naturally resonate.
NASA CubeSat requirements prohibit 1st resonance frequency to be above 100
Hz
Modeling
Assumptions
Specifics regarding internal components unknown. Shapes and sizes were
estimated to serve as placeholders
CubeSat launched from PicoSatellite Orbital Deployer (P-POD)
P-POD is constrained along the rails (sides), but it allowed slight movement in
the vertical direction
Constrained in both x and y directions and allowed slight freedom in z
Results Mode 1: 56.271Hz
Mode 2: 152.1Hz
Mode 3: 156.3Hz
Mode 4: 157.75Hz
Mode 5: 171.79Hz
Mode 1 is significantly
lower than 100 Hz.
Changes to internal
components should
not result in drastic
changes.
Thermal
4 heat sources
Direct Solar radiation
Albedo (Radiation from sun bounces
off earth)
Earth Infrared
Internal heat generation
Experimenting with different
ways to incorporate all
sources into model
Direct
Solar
Albedo Infrared
http://cdn.phys.org/newman/gfx/news/hires/2013/3-johnshopkins.jpg
Spectroscopy Subsystem
Tryptophan Fluorescence
● Most proteins contain the amino acid tryptophan
● Tryptophan is an intrinsic fluorophore because it emits light when excited
○ Excitation Wavelength: 280 nm[1]
○ Emission Wavelength: 350 nm[1]
● Excitation of tryptophan occurs as it absorbs light from a UV LED
● Spectrograph of the emitted light will be recorded by a photodiode
[1]
http://dwb.unl.edu/Teacher/NSF/C08/C08Links/pps99.cryst.bbk.ac.uk/projects/gmocz/fluor.htm
Feasibility of UV LED
● UV LED is chosen over UV Laser due to cost and size requirements
● Cost of UV LED is approximately $150, therefore an in-depth feasibility study
before purchase should be performed
● Feasibility study
○ Beer Lambert Law - relates the attenuation of light to the properties of the material through
which the light is traveling
○ Fluorescence quantum yield - ratio of photons emitted to photons absorbed
○ Precedent for UV LED for intrinsic fluorescence
○ Next step: Determining viewing angle
Glossary of Terms
Maximum excitation and emission wavelength (nm): corresponds to the peak in the
excitation and emission spectra (usually one peak each)
Molar extinction coefficient (1/(M*cm)): measure of light attenuation by a chemical species.
Quantum yield: efficiency of the energy transferred from incident light to emitted fluorescence (#
of emitted photons/# absorbed)
Lifetime (in picoseconds): duration of the excited state of a fluorophore before returning to its
ground state. It refers to the time taken for a population of excited fluorophores to decay to 1/e
(≈0.368) of the original amount.
Stokes shift: difference between the max excitation and max emission wavelengths.
Fluorophore: chemical compound that absorbs light at a specific wavelength and emits light at a
longer wavelength.
Microfluidic Subsystem
Protein Concentration and Reagent Selection
Selected Reagent: Deionized Water
From two unrelated protocols
Protein Concentration: 20mg/mL
From two unrelated protocols
Volume of Protein/Reagent for Spectroscopy: 250uL
From benchmarking
Next Steps
Obtain hemoglobin
Further design wells to allow for filling of reagent and proteins
Microfluidic Channel/Well Design
Well design for proteins
Volume: 250uL
Diameter: 7mm
Height: 6.5mm
Well design for reagents
Volume: 1000uL
Diameter: 10mm
Height: 12.7mm
Integration of solenoid valve
Solenoid Valve Selection
Considered Characteristics
Dimensions
Orifice diameter
Power requirements
Cost
180 degree inlet/outlet separation
Originally designed for microfluidics
Normally Closed
Selected Solenoid- Gems Sensors & Controls M Series
Surface Coatings to Prevent Protein Adsorption
Polydimethylsiloxane (PDMS) is the material of choice for the channel and well
PDMS has a lot of positive characteristics
nontoxic
transparent
inexpensive
easy to use
CON: HYDROPHOBIC
Surface modification can be used to make it hydrophilic
Benchmarking (Surface Coatings)
Budgeting - Bill Of Materials (BOM)
Updated Engineering Requirements
Updated Risk Assessment
Team Vision
What did your team plan on doing this Phase?
Divide device into subsystems
Assign key members to each subsystem
Set goals within each subsystem
What did your team do this phase?
Electrical: Matt & James, created preliminary design, ordered parts
Mechanical/Structural: Anna & Darrin, began thermal/radiation analysis, prototyped structure
Spectroscopy: August & Mallory, determined best light source for assay
Microfluidics: Andrea & Mallory, found surface modification, selected solenoid valve, began design
Future Steps
Questions?