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WEARABLES FOR PHYSIOLOGY-BASED

THERMAL MANAGEMENT

ARPA-E DELTA PI Meeting

Raleigh, NC

January 17-18, 2015

Overall design, integration and fabrication, Tech transfer

Human thermoregulation approachHuman subjects validation

PI: Roy Kornbluh; Co-PI: David HuberT2M: Philip von Guggenberg, Michael Corbett (Consultant, GM WEEL Technologies), Brian O’Boyle (BPO Designs)

PI: Craig HellerCo-PI: Dennis Grahn

PI: Qibing PeiCo-PI: Sungtaek Ju

3-year Effort builds upon innovations and experience of team members

Advanced materials and structures for heat transfer

Heat transfer analysis

ARPA-E DELTA PI MeetingJanuary 17-18, 2017

Raleigh, NC

© 2015 - 2017 SRI International – ARPA-E PI Meeting; Not for Public Distribution

002

Value Proposition and Uniqueness

Metric State of the Art Proposed Reason

COP (for 23 W cooling at 79⁰F)

≤1 (typical for Peltier cooling or Joule

heating)

>5 cooling, Max cooling with >8 hrs

before recharge

Noise 30 dB above perception threshold (conventional fans)

Below perception threshold

Noise not tolerated

Smart wearable that keeps you coolwith any clothing

Works in synergy with the body’s natural cooling system

Overcomes limitations of existing wearable cooling systems

Cooling is the harder challengeNotional work boot product

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Semi-active (low power) forced convection radiator built into footwear

Modeling indicates that active heat pumping is not necessary

Human subjects testing is validating and refining design

Description of the Technology

Glabrous tissue(soles, palms, face)

Non-glabrous (elsewhere)

Subcutaneous layer

Source: Sangiorgi, S., et al. (2004) J. Anat. 204:123; Manelli, A, et al. (2005) Eur. J. Morph. 42:173

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Key Interim Learning and Results Modeling backed by benchtop and human

subjects validation is key

Pivoted: Higher risk advanced material technologies not needed to meet program goals

Product development is a challenge requiring a diverse skill set

Perception of thermal comfort involves many complex factors

New concept• Product focused• Based on COTS

components

DT ~ ±5.5K

Electrocaloric polymer heat pumping with COP=13; 10x better than thermoelectric

Oscillating fan airflow; 5x less power than rotary fan

Tech insertion technologies• Enhance future performance• Reduce cost

Original concept required new technologies• Electroactive polymer fluid pump• Electrocaloric polymer heat pump

Flexible low-cost radiator technologies

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0.02

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0.08

0.1

0.12

0.14

0.16

8.0E-04 1.2E-03 1.6E-03 2.0E-03 2.4E-03 2.8E-03 3.2E-03 3.6E-03

Rad

iato

r A

rea

(m2)

Volumetric Air Flow (m3/s)

Radiator Area vs. Air Flow (1.1 cm thick)

+

+ Minimizing size, power, and noise is key to user adoption

Size

Power, Noise

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-1

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M F F M F F M M F F F F F F F F M F M

ΔA

SHR

AE

sco

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(co

ntr

ol -

trea

tmen

t) Treatment Effect (80°F circulating water)

Key Interim Learning and Results: Human Subjects Testing

1) Proof of concept - Temperature cycling (n=14).

Human subjects testing at Stanford is creating the knowledge base necessary for product design and system validation

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25

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Ta Ta &Twater

Ta (

°C)

Thermal comfort

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T Water (°C

)

Ta (

°C)

Time (min)

Temperature cycles

2) Design validation - Constant temperature (Ta= 80°F)Summer clothing

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control 80°F 65°F

ASH

RA

E sc

ore

(mea

n ±

SD)

Treatment

Thermal comfort (n=10)

Heat flux during resting high heat stress: 0.2-0.45 W/sq. cm.

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Control 80°F 65°F

he

at F

lux

(W/s

q. c

m)

Treatment

Heat flux

3) Design validation -Constant temperature (Ta= 80°F)Heavy Insulation (PPE gear) TH2O: 80°F and 65°F

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Summary

Proven:1. Thermal treatment at the foot can expand the

thermal comfort range.

2. At ambient temperatures ≤ 80°F the mandated heat flow (23W and COP>5) can be generated using circulating room temperature water.

Assumptions to be proven:1. A system incorporated into footwear will be a

desirable product.

2. A work boot based system is the best entry point.

Ongoing product/commercialization activities:1. Surveys and UX testing provide useful input but a

realistic end-user prototypes are critical for moving forward.

2. Continued dialogues with potential commercial partners.

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How You (DELTA Community) Can HelpWe want to share/exchange:

User acceptance: What will people really wear? What will they buy? • Market and user preference surveys (take our survey!)

Compare and utilize human subjects testing approaches and results• Stanford building effective model that includes thermal comfort

perception and heat flow Compare modeling approaches – particularly forced convection Materials and structures

• Low-cost flexible radiators• Better batteries or wireless charging?

Productization of soft goods with electronics and footwear design

Engage: Commercial partner to engage early

Beyond DELTA: expanded use cases Synergy with military, medical, first responder, athletic, outdoor and

humanitarian needs Use high COP electrocaloric heat pumping and enhanced airflow

techniques

Thanks to UC Berkeley, PARC and Otherlab for interactions

Your Photo Here

It takes a colony to achieve thermal comfort

Team resources for the community