This project focused on creating a package for an optical system capable of detecting pathogens using Brewster Angle Straddle Interferometry. The final design included mounting illumination optics and a silicon wafer on an aluminum plate within ABS casing. Testing showed the silicon wafer could be repeatedly mounted within 0.25 degrees as required. Future work will focus on minimizing the package size and weight while maintaining modularity.

1. Analysis and Tes,ng
University of Rochester
Mechanical Engineering
Packaging of an Op,cal System for Pathogen Detec,on
Thomas BarreA, Connor Haddix, Nathan Hagstrom, Thomas Smith
Problem Defini,on
This project focuses on the crea,on of a package for a
device capable of detec,ng pathogens in a biological
sample using Brewster Angle Straddle Interferometry
(BASI), a method used to detect chemical bonding on a
surface. The device would have applica,ons in public
health and agricultural disease diagnosis, among other
fields. Outside of a laboratory environment, this
device could be used to quickly determine if specific
pathogens are present in a living organism.
Final Package Design
Requirements and Specifica,ons
LED source
Illumina,on Op,cs
Silicon Wafer
Sample
Imaging Camera
Fig 1. Layout of op,cal system
Fig 2. Model of final design
Requirement Specifica0on
Product must operate at normal temperature,
pressure, and humidity
1. Placement of silicon wafer must be repeatable within a
tolerance of +/- 0.25°
Product must be lightweight 2. Product must weigh under 15 lbs
Product footprint must be around the size of a
shoebox
3. Product must be no larger than 16” x 8” x 6”
Product must operate in weather-controlled
environment
4. The camera and silicon wafer must be separated by at least
100 mm
Product will be operated on flat, stable surface
5. The final illumina,on op,c and silicon wafer must be
separated by at least 100 mm
To maintain concentricity, the illumina,on op,cs were
mounted in a single lens tube, with cutouts in the side to
allow for posi,on adjustability for all components. A
kinema,c mount which allows for removal of the wafer was
designed to meet specifica,on 1. All components are
mounted on an aluminum jig plate using pin and slot
locators. A simple ABS case was made to prevent
interference from outside light.
Fig 3. Setup for evalua,on of Specifica,on 1, and results
To test the repeatability of the silicon wafer placement, a laser was
aimed at the wafer, and a target was placed at a distance of 2 m.
Using trigonometry, the change in angle was found from the
displacement of the laser spot on the target. The calculated mean
angle change was 0.0268° with a standard devia,on of 0.0231°,
which meets the specifica,on.
Conclusions and Future Work
The packaging philosophy of this op,cs system package is modular in
nature and therefore can be easily adapted for future design
itera,ons. The kinema,c mount and op,cs tube func,oned well
within the design constraints. Future addi,ons and changes to the
system will include minimizing package size and weight.
Acknowledgements
Reference
We thank Dr. Muir and Dr. Rothberg for useful design advice and
technical sugges,ons. We would also like to thank John Miller for
manufacturing advice and help.
Wang, Xiao, Tingjuan Gao and Lewis Rothberg. “Biomolecular Binding Using Brewster Angle Interferometry.” University
of Rochester. Rochester, NY. 20 July 2011. Web.
Brownlee, Lauren, Gary Ge, Sean Reid, and Pedro Vallejo-Ramirez. Pathogen Detec,on with Brewster’s Angle Straddle
Interferometer. Op,cal Design Descrip,on Document. Rev C. Feb. 24, 2016. Web.