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1. REPORT DATE (DD-MM-YYYY) July 2015

2. REPORT TYPEBriefing Charts

3. DATES COVERED (From - To) July 2015-August 2015

4. TITLE AND SUBTITLE Effect of Surface Omniphobicity on Drying by Forced Convection (Briefing Charts)

5a. CONTRACT NUMBER In-House

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S) Madani Khan, Jeffrey Alston, Andrew Guenthner

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NO.

Air Force Research Laboratory (AFMC) AFRL/RQR 5 Pollux Drive Edwards AFB, CA 93524-7048

9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)Air Force Research Laboratory (AFMC) AFRL/RQR 5 Pollux Drive 11. SPONSOR/MONITOR’S REPORT

Edwards AFB CA 93524-7048 NUMBER(S)

AFRL-RQ-ED-VG-2015-313

12. DISTRIBUTION / AVAILABILITY STATEMENT Distribution A: Approved for Public Release; Distribution Unlimited.

13. SUPPLEMENTARY NOTES Briefing Charts presented at STAR Closing Conference; San Jose, CA; 7 August 2015. PA#15451.

14. ABSTRACT Briefing Charts

15. SUBJECT TERMS

16. SECURITY CLASSIFICATION OF:

17. LIMITATION OF ABSTRACT

18. NUMBER OF PAGES

19a. NAME OF RESPONSIBLE PERSON

Kriss Vanderhyde

a. REPORT Unclassified

b. ABSTRACT Unclassified

c. THIS PAGE Unclassified

SAR 26 19b. TELEPHONE NO

(include area code)

661-275-5429 Standard Form

298 (Rev. 8-98) Prescribed by ANSI Std. 239.18

1DISTRIBUTION A: Approved for public release; distribution unlimited. AFRL Public Affairs Clearance #

Integrity Service Excellence

Effect of Surface

Omniphobicity on

Drying by Forced

Convection

Madani Khan

The City College of New York

STAR Program

August, 2015

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Background

• I am from Bangladesh.

• Education: The City College of New York

• Major: Chemistry; Minor: Education.

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Abstract

• Low energy surfaces can strongly repel both oil and water. Recently these

surfaces have been fabricated on various substrates including fabric, aluminum,

stainless steel and many other materials. In this experiment we explore the use of

low energy surface deposition on aluminum alloy, stainless steel and silicon

substrates, to enhance the drying rate of liquids removed from the surface by

forced convection. We control surface roughness by substrate abrasion and by

the growth of Al2O3 nanograss to enhance liquid repellence by use of a

hierarchical texture. Liquid repellence of the substrates is measured by contact

angles of the probe liquids, water and hexadecane. Samples are mounted on a

rigid stage constructed with a flat surface and a regulated air nozzle fixed to

provide flow parallel to the substrate surface. The velocities of probe liquid

droplets placed on the substrates are recorded via high-speed camera as they are

moved by a constant air flow. It is shown that drops on omniphobic and

superomniphobic surfaces move at increased velocity compared to untreated

surfaces, and leave behind less residual liquid, resulting in a faster drying rate. 2-

factor design of experiments (DOE) was implemented to explore the optimum

conditions for a fast drying low energy surface. The use of DOE and the results of

this experiment are merged into a lesson plan developed for 9th-12th grade

students. These results will serve as examples low energy surfaces and their

potential applications.

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Introduction

• Explore the use of low energy surface deposition

on aluminum alloy, stainless steel and silicon

substrates, to enhance the drying rate of liquids

removed from the surface by forced convection

• The velocities of probe liquid droplets placed on

the substrates are recorded via high-speed

camera as they are moved by a constant air flow

• 2-factor design of experiments (DOE) is

implemented to explore the optimum conditions

for a fast drying low energy surface

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Application

• The application of this work can be used in rocket

engines, rooftops, cars, umbrellas, tiles, oven,

paint, or any kind of fabrics.

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Design of Experiment (DOE)

• Systematic method to determine the relationship

between factors affecting a process and the

output of that process.

• Why?

– Saves time

– Lower cost

– Reduce product material and labor complexity

– Better design engineering

• Accessibility

– Microsoft Excel or online software

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Substrates

Stainless Steel Aluminum Silicon Wafer

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Roughness Values

Roughened Surface Crossly Sanded with Grit Size 2000Ra-Roughness Average (499.97nm) Rq- Root Mean Square (624.58 nm)Sm- Surface Material Volume (26.36 nm3/nm2)Sv- Surface Void Volume (66.06 nm3/nm2)

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Contact Angle

AFR .!-;i

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Gas-Flow System

.... ~

• •

0"YI(~~ 'I " 'NI'I '=:131~ "" ~ .. a. " a• tf • t ..... •

lrrllllllllrrrl l LJJ-IIrrrrlrrr rlrw 11111 I ""''''' 'rrruJ 1 w IIU11~

AFR .!-;i

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High-speed Video

• ~~I o em 1

0N\1'1'9N3 Nl 3Q'ir4

AFR .!-;i

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Result

0.7

0.75

0.8

0.85

0.9

0.95

2 min 5 min

Tim

e (

sec)

Boiling Time

Boiling Time vs. Drying Time

sec/cm

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Grit 1200 Grit 320

Tim

e (

sec)

Roughness

Roughness vs. Drying Time

sec/cm

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Conclusion

• Lower roughness leads to faster drying time.

• An irregular surface can cause pinning regardless

of silanization and contact angle, which disturbs

the trend of hysteresis.

• Higher boiling time leads to faster drying time.

• Water has a faster drying rate than hexadecane.

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Lesson Plan

• This lesson plan is directed for 9th-12th grade

students.

• Reading about ice-cream.

• Learning to make ice-cream through a DOE

optimization.

• The three factors are different weight percent of

salt per ice, fat content in dairy and shaking time.

• Measured output will be rating and average of

different ice-creams.

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Future Work

• Different type of liquids

• Durability

• Using the optimization from DOE to further

explore factors.

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Acknowledgement

• Funding and support was received by the STAR program and thank you to

the AFRL for a great research experience. Thank you to Dr. Jeffrey Alston and

Dr. Andrew Guenther for all their guidance and encouragement throughout

this the project. And a special thanks to my fellow STAR student: Nicholas

Rubel.

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Questions?

Questions? AFR IY i ,

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Flow System

Al Substrate Flow CellAFR .!-;i

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Creating Reentrant Surface

Before Sanding

•

AFR .!-;i

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After Sanding

Micro-scale

E llm ,

AFR .!-;i

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Nano-grass Growth

Nano-scale

c llm )

Air

AFR .!-;i

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SEM Image

AFR .!-;i

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Low Surface Energy

Low Surface Energy

E J.lm )

'/ '

AFR .!-;i

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Flow System

Al Substrate Flow CellAFR .!-;i

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Trapping Plastron

1 Dry ..... I I Under WateiJ ......

AFR .!-;i