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?