Integrated Printed Moisture Sensors in Composite Structures (pdf).
Integrated Printed Moisture Sensors in Composite Structures (pdf).
Integrated Printed Moisture Sensors in Composite Structures (pdf).
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INTEGRATED PRINTED MOISTURE<br />
SENSORS IN COMPOSITE<br />
STRUCTURES<br />
Karen Bermes<br />
September 5, 2012
Clarification<br />
• <strong>Integrated</strong> sensor<br />
• Inside composite structures<br />
• <strong>Pr<strong>in</strong>ted</strong> electronics<br />
• Pr<strong>in</strong>ts conductive <strong>in</strong>ks to form circuit
High Performance Materials Institute<br />
“Improve the performance and affordability of<br />
advanced composite materials and structures.” [1]<br />
Multifunctional composite structure<br />
•Prosthetics<br />
•Thermal management<br />
•EMI shield<strong>in</strong>g<br />
Images retrieved from [1]
Why do we need moisture sensors?<br />
Boe<strong>in</strong>g 787<br />
• Comprised 50% by weight<br />
• <strong>Moisture</strong> can permeate through structure<br />
• Integrate sensor <strong>in</strong>to structure for detection<br />
o Th<strong>in</strong><br />
Retrieved from [2]
Fiber Optic <strong>Moisture</strong> Sensor<br />
• Index of refraction<br />
• Acts as a defect along path<br />
• Convert<strong>in</strong>g light to electrical signal can be<br />
expensive<br />
US Patent No. 4,221,962
Technology<br />
• Nanotechnology<br />
• Buckypaper<br />
• <strong>Pr<strong>in</strong>ted</strong> Electronics<br />
• OPTOMEC M 3 D Pr<strong>in</strong>ter<br />
• Controlled Environment Chamber<br />
• Vary humidity
Buckypaper (BP)<br />
• 250x stronger and 10x lighter<br />
than steel [1]<br />
• Electrically conductive<br />
• 25 μm thick<br />
• Randomly aligned carbon<br />
nanotubes (CNTs)<br />
• SW and MW<br />
• Large surface area<br />
Retrieved from [1]<br />
Retrieved from [3]
OPTPMEC M 3 D Pr<strong>in</strong>ter
Controlled Environment Chamber
Procedure<br />
• <strong>Pr<strong>in</strong>ted</strong> open circuit on polyimide<br />
• S<strong>in</strong>ter<br />
• Attach BP or pr<strong>in</strong>t CNT <strong>in</strong>k<br />
• Attach measurement materials/<strong>in</strong>struments<br />
• Silver paste<br />
• Gold and copper wire<br />
• Measure resistance <strong>in</strong> CEC while vary<strong>in</strong>g humidity
Parameters<br />
• Spac<strong>in</strong>g between silver electrodes<br />
• Pr<strong>in</strong>t<strong>in</strong>g multiple passes<br />
• Dry samples before test<strong>in</strong>g
Prediction<br />
• CNTs are electrically conductive<br />
• Pure water<br />
• Resistance will <strong>in</strong>crease with <strong>in</strong>creas<strong>in</strong>g<br />
humidity
Buckypaper Sensor
Resistance Ω<br />
Resistance vs. Relative Humidity BP<br />
9.1<br />
200μm NC BP Sensor<br />
9.05<br />
9<br />
8.95<br />
Decreas<strong>in</strong>g<br />
Increas<strong>in</strong>g<br />
8.9<br />
8.85<br />
8.8<br />
10 20 30 40 50 60 70 80 90 100<br />
% Relative Humidity
Resistance Ω<br />
Resistance vs. Relative Humidity BP<br />
9.25<br />
100μm NC BP Sensor<br />
9.2<br />
9.15<br />
9.1<br />
9.05<br />
Decreas<strong>in</strong>g<br />
Increas<strong>in</strong>g<br />
9<br />
8.95<br />
8.9<br />
0 20 40 60 80 100<br />
% Relative Humidity
Resistance Ω<br />
Resistance vs. RH Dried BP<br />
2.26<br />
Dried BP 200μm<br />
2.25<br />
2.24<br />
2.23<br />
2.22<br />
2.21<br />
2.2<br />
2.19<br />
2.18<br />
0 20 40 60 80 100<br />
% Relative Humidity
CNT <strong>Pr<strong>in</strong>ted</strong> Sensor
Resistance Ω<br />
Resistance vs. Relative Humidity CNT<br />
21000<br />
<strong>Pr<strong>in</strong>ted</strong> CNT Sensor 1<br />
20500<br />
20000<br />
19500<br />
19000<br />
18500<br />
18000<br />
Decreas<strong>in</strong>g<br />
Increas<strong>in</strong>g<br />
17500<br />
17000<br />
16500<br />
16000<br />
0 20 40 60 80 100<br />
% Relative Humidity
Hysteresis<br />
• Nonl<strong>in</strong>ear, cyclic reaction<br />
• The current state of a system is dependent on<br />
its past state, but nondependent on rate [4]<br />
• The goal is to develop a sensor with no<br />
hysteretic response.
Future Research Plans<br />
• Embed sensor <strong>in</strong>to composite structure<br />
• Test effect on structural <strong>in</strong>tegrity<br />
• Identify physical properties that cause different<br />
responses to changes <strong>in</strong> humidity<br />
• Improve design to avoid hysteretic responses
References<br />
[1] http://www.hpmi.net<br />
[2] http://www.boe<strong>in</strong>g.com<br />
[3] http://www-ibmc.u-strasbg.fr<br />
[4] Cruz-Hernandez JM and Hayward V 2001<br />
“Phase control approach to hysteresis<br />
reduction” Control Systems Technology, IEEE<br />
Transactions on 9(1) 17-26
Thank you<br />
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