Transcript Silicon Nanowire - EA Water Pvt. Ltd.

Low-Cost Portable Sensors on
Mobile Platforms
Simarjeet Singh Saini
Our Vision
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Low cost optical sensors
Build around smart phones/tablets
GPS and Time stamps allow spatial and temporal maps
Wi-Fi connectivity allows easy installation and cloud
computing
• Social media access allows dissemination of knowledge
Sensing by the people, for the people
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Low Cost Sensors
• Light Scattering
• Nanophotonics chips
– Change color in presence of detectants
– Spectral shifts of ~ 600 nm/RIU; 6 times higher than competition
– Enables Surface Enhanced Raman Spectroscopy (SERS) for
fingerprinting
– Multiple chip technologies allow measurements in reflection or
transmission
• Cell-Phone Spectrometers
– Better than 0.3 nm spectral resolution
– All critical components built in-house in high yield low cost
technologies
Integration of the technologies provide a
vertically integrated solution
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For What!
Detection of Pathogens: Ensure safety of
drinking water
Detection of nitrates, nitrites, phosphates,
chlorides….
Detection of Heavy metals: Arsenic, mercury
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Light Scattering
• Qualitative Analysis
• ~ 25 mm2 area coverage
– an order of magnitude higher than 10× microscope
• Very low cost
– standard laser pointer, a pin-hole and CMOS detector; no
optics, no alignment
• Effectively acts as 40× microscope
• High Contrast Images
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Results
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Nanophotonics: Why does color sensing work?
In the right wavelength region:
 an average human eye can detect 1 nm spectral changes.
 In RGB components only G changes linearly
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Nanophotonics Chips
• A unique two-dimensional
nanophotonics chip has been
developed at UW.
• Sensing can be achieved by detecting
changes in spectra due to “Surface
Plasmonic effect” or detecting the
unique signature of the introduced
material due to the “Surface Enhanced
Ramon Scattering”.
Nanophotonics Chips
• Refractive index sensing
1 (Air)
1.3
1.35
Water
Ethanol
Air
20 nm
• Surface Sensing
Single Molecule Detection
1.39
Methanol
Virus Detection in Water: Bean PoD
Mottle Virus
Wavelength Shift (pm)
anti-BPMV
anti-SMV
300
Specificity seen as the
sensors that respond to the
BPMV virus are those that
present anti-BPMV antibodies.
250
200
150
100
50
0
0
10
20
Time (min)
30
40
1400
1200
Detection in complex real life
samples currently underway
1000
Axis Title
10 ng/ml detected.
800
600
400
200
0
0
200
400
600
800
Concentration (ng/ml)
1000
1200
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Low Cost Spectrometers
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Features
 Transmission based geometry: Small form factor
 Volume phase gratings:
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Fabricated with own recipe’s with 95 % yield
1800 lines/mm achieved
Grating efficiency of 74 % achieved. Further improvements in progress
Low-cost process: Less than $10 per grating instead of ~ $400 from
manufacturers
 Commercial low-cost optics
 Low stray light design using appropriate light blocking techniques
 2-D array allows
 Averaging signal over space removing temporal averaging: faster, lower
noise measurements
 Multi-channel integration: Multiple channels can be measured at same
time
 Hyper-spectral Imaging: doctor’s do not have to judge colors of moles;
consumers can judge freshness of food.
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Measurement of Light Source
• CFL lamp: high resolution (around 1nm) spectrum of CFL lamp
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Measurement of Nitrites
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Conclusion
• Cell-phones can revolutionize water safety
• Nanophotonics chips can enable next
generation sensors on the most ubiquitous
platform
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