This document discusses lessons learned from over 40 product development cycles for wearable biometrics. Key challenges in building accurate wearables include optical noise, skin tone variations, sensor location, and the "crossover problem". User experience is critical, as wearables need to help users accomplish goals through design, accuracy, comfort and more. Hardware considerations like sensor size, spacing, and geometry impact signal quality. Software using active signal characterization can provide motion-tolerant heart rate sensing. Extensive product testing is needed to validate multiple use cases and biometrics. Choosing the right manufacturer with relevant experience is also important for success.

1. Building a wearable with
accurate biometrics:
Lessons learned from 40+
product development cycles
© 2017 Valencell, Inc
Ryan Kraudel
VP, Marketing

2. © 2017 Valencell, Inc
Photoplethysmography (PPG) – How it works

3. © 2017 Valencell, Inc
Many different form factors driving biometric wearables growth
Smart Watch Fitness Watch Fitness Band
Wired Earbuds Wireless Earbuds True Wireless
WearablesHearables

4. © 2017 Valencell, Inc
Top 5 Challenges in OHRM
Source: “Optical heart-rate measurement’s top 5 challenges” Dr. Steven LeBoeuf; EDN Magazine; 8-25-15
Optical Noise Skin Tone Blood Perfusion
Sensor Location Crossover Problem

5. Lessons Learned

6. © 2017 Valencell, Inc
User Experience is Critical – Start With the End in Mind
• What are your users trying to accomplish and how does your
device help them do it?
• How does UX drive customer expectations for design, accuracy,
battery life, comfort, ease of use, social community, etc?

7. ©2016 Valencell. Inc
Cadence
(Step Rate)
Time
Beats(Steps)/Min
Accuracy Matters
Accurate HRM
Mood Ring HRM
HRV
HR
Response
Peak HR/
VO2
max
HR Recovery
Crossover
Problem

8. © 2017 Valencell, Inc
Accuracy Matters

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Peak Amplitude
(Pulse Pressure)
RRi
(HRV, Cardiac Functioning)
Breathing Rate
(Metabolic Status)
Perfusion Variation
Heart Rate
Highly accurate PPG can be used to accurately
assess numerous biometrics
•Breathing Rate
•Heart Rate
Variability (HRV)
•Cardiovascular
Fitness
•Blood Pressure
•Blood Oxygen
•Cardiac
Efficiency
•Blood Perfusion

10. © 2017 Valencell, Inc
Accuracy Matters

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Take the Systems Approach to Biometric Sensors
Biometric sensor hardware and software
need to be designed to work together.

12. Lessons Learned
Hardware

13. © 2017 Valencell, Inc
Hardware: Size Matters
Epidermis
Dermis
Subcutaneous
Emitter Detector
Close (2 mm) source-detector spacing Wide (4 mm) source-detector spacing
spacing
Emitter
Detector
S/N ≅ 0.05 S/N ≅ 0.25
Wider spacing captures less total light, but it captures a much
higher ratio of “good light” (blood-flow scatter) to “bad light”
(motion-related scatter).
Epidermis
Dermis
Subcutaneous

14. © 2017 Valencell, Inc
Hardware: The Shadow Effect
Dimensions ~46mm x 46mmDimensions ~38mm x 12mm
Shadow Sensor Shadow Sensor

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Hardware: Other Important Factors
• Coupling
• Gross displacement
• Geometry of emitters & detectors
• Light guiding
• Wavelengths
Product Design and Materials
Optical Considerations

16. Lessons Learned
Software

17. © 2017 Valencell, Inc
Active Signal Characterization
Optical signal from blood flow, skin
motion, body motion, & environmental
noise (such as sunlight) is actively
characterized in real-time.
Software: Motion tolerant optical heart rate sensing combines
advanced sensor design + active signal characterization
Highly Accurate
PPG Signal
PPG Sensor Systems
Years of R&D have resulted in advanced
optomechanical designs and integration
expertise that optimize sensor signal quality.
PerformTek vs. CSHRM
n = 40
R2
= 0.99

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Software: Making it Work in Any Activity

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Software: What’s Next?
Continuous Heart Rate
Sleep monitoring
Temperature
Blood Pressure

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Software: Roadmap You Can Believe In
•Demonstrated track record of innovation
• IP and patents in wearable biometrics
•Multi-disciplinary team
• Engineering: electrical, mechanical, optical
• Testing: exercise science, medical science
•Third-party validation
• Independent testing and results
• Customer product reviews

21. Lessons Learned
Product Testing and Manufacturing

22. © 2017 Valencell, Inc
•Testing protocols that match the use cases: resting,
lifestyle activities, mild exercise, aggressive exercise,
interval training, etc.
•Minimum 30 participants of multiple physical
habitus, gender, & skin tone per prototype variant –
hundreds of data sets per product launch
•Biometric analysis that includes regression analysis
(R2
) & Bland-Altman analysis
•Diagnostic analysis that includes true positives, false
positives, true negatives, false negatives, & total
positives & negatives
•Ideally, there must be independent validation of
each metric
Extensive testing is critical to success

23. © 2017 Valencell, Inc
Get Expert Advice in Picking Your Manufacturer
• Has your contract manufacturer built a biometric wearable before?
• Have they built a Bluetooth wearable before?
• How do they test devices coming off the line?
• What are labor policies and working conditions?

24. © 2017 Valencell, Inc
Resources
Wikipedia
• PPG - https://en.wikipedia.org/wiki/Photoplethysmogram
• Wearables - https://en.wikipedia.org/wiki/Wearable_computer
• Hearables - https://en.wikipedia.org/wiki/Hearables
Blog
• Everything you need to know about OHRM -
http://valencell.com/blog/2015/10/optical-heart-rate-monitoring-what-you-need-to
-know/
• If you’ve already started a biometric wearable project, read this -
http://valencell.com/blog/2016/10/whack-a-moles-disappearing-features-and-oth
er-signs-your-biometric-wearable-project-needs-help/
Scientific Validation
• PubMed search for photoplethysmography -
https://www.ncbi.nlm.nih.gov/pubmed/?term=photoplethysmography

25. Q&A

26. Thank You!
Ryan Kraudel
VP, Marketing
kraudel@valencell.com
Twitter: @kraudel