characteristics of infrared blocking, stealth and color

ⓒ 2019, The Korean Society of Clothing and Textiles. All rights reserved.

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I. Introduction

Because of the rising use of conductive materials in

the internet of things (IoT) within a personal computing

ecosystem, there has been a increasing interest in the

use of metal-processed fabrics as smart materials. In

addition, military forces have recognized the importance

of stealth apparel.

Stealth technology generally refers to a cover-up te-

chnology against all detection features, including the

opponent's radar, infrared detectors and visual detect-

ion. Therefore, the Stealth fabric can be described as a

fabric that covers and protects the body from exposure

to the opponent's detection. Previous studies have exa-

mined the stealth properties of fabrics coated with me-

tal nanoparticles like aluminum by using infrared ther-

mographic cameras. In some previous studies, the fab-

ric treated with metal nanoparticles showed a lower sur-

face temperature, better effects in terms of concealing

the body, and reduced infrared emission compared to

untreated samples (Han, 2016; Mao, Wang et al., 2014;

Mao, Yu et al., 2014; Wang et al., 2015).

In addition, Zhiping Mao reported that the low-inf-

rared (IR) emissivity of materials is important for mili-

tary purposes (Mao, Wang et al., 2014; Mao, Yu et al.,

2014).

Organic or inorganic compounds with low IR surf-

ace emission in the 8 to 14 μm wavelength range are also

important in military applications. Materials such as zinc

oxide (ZnO), indium tin oxide (ITO), and antimony-

Characteristics of Infrared Blocking, Stealthand Color Difference of Aluminum Sputtered Fabrics

Hye Ree Han†

Culture, Digital Seoul Culture Arts University

Received July 5, 2019; Revised August 10, 2019; Accepted August 15, 2019

Abstract

This study examines the stealth function of sputtered fabric with an infrared thermal imaging camera in terms of the thermal and infrared (IR) transmittance characteristics. Various base fabrics were selected, infrared imaging was performed, and infrared transmittance was measured. By infrared camera experiment it was found that the sample was concealed because it had a similar color to the surroundings when the aluminum layer was directed toward the outside. In addition, a comparison of the infrared thermographic image of the untreated sample and the sputtered sample in the laboratory showed that the difference in ΔE value ranged from 31 to 90.4 and demonstrated effective concealment. However, concealment was not observed in the case of the 3-layer (Nylon-Al-Nylon) model when a sputtered aluminum layer existed between two nylon layers. The direction of the sputtering layer did not affect the infrared transmittance in the infrared transmittance experiment. Therefore, it seems better to interpret the concealing effect in the infrared thermographic images by using thermal transfer theory rather than infrared transmittance theory. We believe that the results of this study will be applicable to developing high performance smart clothing and military uniforms.

Key words: Aluminum nanograin, Stealth, Heat transfer, Sputtering

†Corresponding author

E-mail: [email protected]

ISSN 2234-0793 (Print)ISSN 1225-1151 (Online)

Journal of the Korean Society of Clothing and TextilesVol. 43, No. 4 (2019) p.592~604

https://doi.org/10.5850/JKSCT.2019.43.4.592

[ Research Paper ]

Characteristics of Infrared Blocking, Stealth and Color Difference of Aluminum Sputtered Fabrics

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doped tin oxide (ATO) exhibit high reflectance and low

emissivity at infrared wavelengths, indicating that inf-

rared stealth functions have been demonstrated in pre-

vious studies (Mao, Yu et al., 2014).Burkinshaw et al. asserted that, in modern society,

IR surveillance technology has a significant impact on

military personnel and equipment (Burkinshaw et al.,

1996; Mao, Wang et al., 2014;). In addition, Bergeron

et al. reported that objects or humans can be easily det-

ected with an IR detector due to high emissivity and

thus, in many countries, low-emissivity materials have

focused on IR stealth technology (Bergeron et al., 2008;

Mao, Wang et al., 2014). However, Valor et al. explai-

ned that the emissivity of the external environment is

not constant and can depend on variables such as temp-

erature, moisture, solar intensity, and cloudiness (En-

glish, 1999; Mao, Wang et al., 2014; Valor & Caselles,

1996).Under these conditions, an object would likely be

protected by low-emissivity materials and when viewed

with an IR-sensitive device, but detection may occur

if background conditions change. Therefore, it is nece-

ssary to select substances with favorable emissivity that

can naturally adapt to the external environment (Mao,

Wang et al., 2014). There are studies regarding infrared

camouflage fabrics used dyeing technology, as shown

below (Hui & Jianchun, 2007; Puzikova et al., 2008;

Rubežienė et al., 2008; Xu et al., 2009; Zhang & Zhang,

2008; Zhou et al., 2010).

Xu et al. studied the near-IR camouflaging effect of

dyed cotton fabrics and how background emissivity aff-

ects the camouflage mechanism. It was suggested that

near-IR camouflaging could be achieved by dyeing with

more than four colors rather than a single color (Xu et

al., 2009). Zhang and Zhang (2008) studied the dyeing

of cotton fabrics with vat dye to study camouflaging

properties suited to the reflectance of a greenish leaf in

the NIR (Near Infrared) region. A combination of dye-

ing, dyeing concentration (% o.w.f), and reflectance ac-

cording to weave of the fabric was also studied. When

the dyeing concentration of vat blue 13 was 1-2% o.w.f.,

the reflectance of the dyed fabric showed a similar over-

lap with greenish leaves in the red-shift region (Zhang

& Zhang, 2008). Hui and Jianchun (2007) studied dyed

samples using dispersed dye on polyester (PET) to mat-

ch the reflectance of visible green leaves in the NIR reg-

ions. For this purpose, CIE L*, a*, b* were measured

using a colorimeter, and the absorbance properties were

measured by a spectrometer. When the dye concentra-

tion of dispersed blue 56 was 1-2%, the absorbance spec-

trum overlapped with the reflectance spectrum of green-

ish leaves. In addition, it is described that the fabric

weave has a less significant effect on the reflection spec-

trum (Hui & Jianchun, 2007; Puzikova et al., 2008).

Many studies have examined the use of aluminum

sputtering on fabrics. Chu et al. (2002) fabricated trans-

parent porous anodic alumina nanostructure films by

sputtering aluminum on a glass substrate with an indium

tin oxide (ITO) film. These films are porous electrode

materials with good conductivities and large surface

areas (Chu et al., 2002). Agashe et al. (2004) studied

the electrical and optical properties of radio frequency

magnetron sputtered, aluminum-doped zinc oxide (ZnO:

Al) films. As a result, these films showed increased per-

meabilities in the near-IR wavelength range, suggest-

ing that they could be applied to optoelectronic devices

such as thin-film solar cells (Agashe et al., 2004; Agashe

et al., 2003; Aubert et al., 2011; Huffman et al., 1989;

Knotek et al., 1986; Li & Cuevas, 2009; Matsunami et

al., 2013; Shih & Zoh, 2014; Shuskus et al., 1974; Suter

et al., 1995).

The studies show examples of aluminum sputtering

on various substrates rather than fabric.

This study demonstrates the applicability of metal as

a smart material by sputtering it on fabric. Depla et al.

(2011) reported that many industrial and other surfaces

such as firefighters' suits and textile antennas could be

protected by coatings, thus providing hydrophobic, oleo-

phobic, and antibacterial properties to various materials.

He then applied metal and oxide coatings on woven and

nonwoven materials. He also suggested using an Al film

due to its high conductivity. In other prior reports, the

electromagnetic characteristics with metal coatings

were also studied (Alzaidi et al., 2012; Depla et al., 2011;

Jang et al., 2007). Several studies have examined sputt-

ered Al on fabrics (Deng et al., 2007; Han, 2019; Shahidi

Journal of the Korean Society of Clothing and Textiles Vol. 43 No. 4, 2019

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et al., 2007; Wei et al., 2006).

In fact, Al has high IR reflectivity and low emissivity.

Many theoretical and experimental studies have been

conducted to assess the effects of application of Al to

fabric by a sputtering process. However, these studies

did not elaborate on the relationship between IR shiel-

ding, thermal properties, and stealth functions. In addi-

tion, there are few studies where the stealth function of

Al-sputtered fabrics was assessed using IR cameras.

Hence, the applicability of Al-sputtered fabrics as stealth

clothing should be evaluated. It is critical to study stealth

clothing with IR cameras to increase the survival of fri-

endly military forces at night.

It is necessary to identify the stealth functions and

thermal characteristics of Al-sputtered fabrics. In addi-

tion, it is necessary to identify the stealth function of Al-

sputtered fabrics based on whether or not IR rays gene-

rated from the human body are blocked, and to analyze

the thermal characteristics of the Al-sputtered fabric.

The general applicability of Al-sputtered fabrics as clo-

thing should also be evaluated.

Therefore, the purpose of this study is to research the

changes in IR characteristics of Al-sputtered fabrics, to

analyze the thermal properties, and to clarify the prin-

ciple of stealth clothes. Various types of fabrics were

subjected to Al sputtering, and the IR transmittances of

the coated materials were measured. The stealth effects

were analyzed using an IR camera, and heat transfer

was predicted through calculation based on heat trans-

fer theory. Furthermore, the applicability of the coated

fabric as clothing was also evaluated.

II. Materials and Methods

1. Materials

The base fabrics used in this study are PET, nylon,

nylon-blended wool, cotton, and silk. Characteristics

of the samples are shown in <Table 1>.

The Al sputtering conditions on the base fabrics are

shown in <Table 2>. When sputtering was performed,

samples were circular with 19.5 cm diameter. An SRN

sputter coater (SRN120, SORONA, Korea) was used

to coat the base fabrics. A Schematic diagram of sputt-

ering system is shown in <Fig. 1>.

2. Characterization

1) Surface PropertiesThe surface conditions of the untreated and sputt-

ered samples were studied using a field-emission scan-

ning electron microscope (FE-SEM, S-4800, Hitachi,

Japan). To obtain clearer images, a Pt coating was dep-

osited for 30 seconds using a sputter coater (SCD 500,

BAL-TEC, Agent: Nano science, Korea) before ima-

ging with the FE-SEM.

Time(minute)

TemperatureBase pressure

(Torr)Process pressure

(Torr)Gas

(sccm)Power(W)

Distance(mm)

22.5 Room temperature 5×10-6 5×10-3 Ar, 60 DC 1000 Less than 140

Table 2. Sputtering conditions

PET fabric Nylon fabricLaminatedPET fabric

Silk fabric Cotton fabricNylon blended

wool fabric

Ingredient PET 100% Nylon 100%PET 100%, and PU laminated material

Silk 100% Cotton 100%Wool 79.1%, Nylon 20.9%

Fabric thickness (mm)

0.13 0.18 0.14 0.14 0.16 0.32

Weight(g/m2)

80.5 108.4 66.2 172.3 67.4 108.4

Table 1. Characterization of base fabrics


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2) CIE Lab of Infrared Thermal ImagingThe L*, a*, and b* values were measured using Im-

age J software to observe quantitative color changes,

and ΔL, Δa, Δb, and ΔE were calculated from the meas-

ured data. Color changes caused by the distance bet-

ween the sample and the human body was also tested.

ΔL, Δa, Δb, and ΔE were calculated using the follow-

ing equations (Habekost, 2013):

<Eq. 1> shows the change in ‘L’ value due to sput-

tering processing by subtracting the ‘L’ value of the

untreated fabric from the ‘L’ value of the sputtered

fabric. In CIELAB color space, ‘L (lightness)’ indic-

ates the degree of brightness. <Eq. 2> shows the change

in the ‘a’ value due to sputtering processing by sub-

tracting the untreated fabric ‘a’ from the ‘a’ value of

the sputtered fabric. In CIELAB color space, ‘a’ indic-

ates the degree of red-green. <Eq. 3> shows the change

in value of ‘b’ due to sputtering by subtracting the value

of untreated fabric ‘b’ from the value of ‘b’ of sput-

tered fabric. In CIELAB color space, ‘b’ indicates the

degree of yellow-blue. And ‘∆E’ in <Eq. 4> is the sum

of the color differences, the actual difference between

samples in CIELAB color space

...... Eq. 1.

...... Eq. 2.

...... Eq. 3.

...... Eq. 4.

Each parameter in <Eq. 1>–<Eq. 4> are defined

below.

Luntreated : value L of untreated sample

Ltreated : value L of sputtered sample

auntreated : value a of the untreated sample

atreated : value a of the sputtered sample

buntreated : value b of the untreated sample

buntreated : value b of the sputtered sample

3) IR Transmittance AnalysisAn IR intensity tester (infrared emitting diodes, 5 mm

Infrared LED, T-1 3/4 IR333-A, EVERLIGHT, Taiwan)

was used to measure the IR transmittance of the samples.

The incident IR intensity was 400 W/m2, and the major

IR wavelength was 940 nm.

Fig. 1. Schematic diagram of sputtering system.


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4) Air PermeabilityAir permeability was measured using an air permea-

bility tester (FX3300, Textest, Switzerland) in a 6.6 cm2

area according to the ASTM D737 (ASTM Internatio-

nal, 2018) method. The air permeability was obtained by

averaging three individual measurements at a pressure

of 250 Pa. The experimental value was converted into

an air permeation value using a calibration curve, where

the calibration data corresponds to air permeation meas-

urements in a 38.3 cm2. Measured air permeability val-

ues less than 1 (cm･s) were converted using <Eq. 5>,

while air permeability values greater than 1 (cm･s) were

converted using (Eq. 6).

y = 3.13x ...... Eq. 5.

y = 1.1x ...... Eq. 6.

x : Air permeability around 6.6 cm2 (cm3/cm2/s)

y : Air permeability around 38.3 cm2 (cm3/cm2/s)

III. Theory

The thermal properties of a multilayer fabric were

studied. Simulation results for the multi-layer fabric

based on heat transfer theory <Eq. 7> (Han, 2016) are

shown in <Fig. 2>. The thermal properties of a three-

layer fabric were calculated by further developing it

from a previous study (Han, 2016). The temperature

of the structure shown in <Fig. 2> below was calculated

using (Eq. 7). When heat transfer theory was introdu-

ced, the surface temperature was calculated by consid-

ering conduction in Materials 1 and 2, while conduct-

ion, convection, and radiation were considered at the

surface of Material 3. Here, Materials 1 and 3 are fabric

layers, and Material 2 is a sputtered aluminum layer.

...... Eq. 7.

In <Eq. 7>, <Fig. 2>, and <Fig. 5>, Q1, Q2, and Q3

are the heat transfer rates of Material 1, Material 2, and

Material 3, respectively. Q4 is the heat transfer rate from

Material 3 to the surroundings, and Q is the overall heat

transfer rate. A steady state is assumed, i.e., Q=Q1=Q2=

Q3=Q4. Herein, ε is the emissivity, σ is the Stefan-Boltz-

mann constant, and h is the heat transfer coefficient. k1,

k2, and k3 are the thermal conductivities of Material 1,

Material 2, and Material 3, respectively, and x1, x2, and

x3 are the thicknesses of Material 1, Material 2, and Ma-

terial 3, respectively. The surface temperature was cal-

Fig. 2. Heat transfer simulation for 3-layer materials (T1, T2, T3, T4: Temperature of boundary surface of Mat- erial 1, Material 2, Material 3, Material 4).


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culated by deriving the Q value by trial and error. In add-

ition, the actual experimental material was assumed to

be a fabric, but it was assumed to be a solid material in

the calculation.

IV. Results and Discussion

1. Surface Properties

The surface of the sputtered samples was examined

using FE-SEM (Table 3). It was confirmed that Al grains

formed on the surface of the sputtered sample comp-

ared to the smooth surface of the untreated sample, reg-

ardless of the base fabric. In previous studies, it was

observed that grains did not form on the untreated phase

if SEM images were gathered after metal sputtering,

but rather formed on the sputtered surface (Han & Kim,

2018; Han et al., 2018; Shigesato & Paine, 1994).

The results obtained in this study are similar to those

in previous studies. The distribution of Al grains in the

SEM images is relatively uniform on PET, nylon, lam-

inated PET, and silk. In contrast, staple cotton has a rela-

tively uneven grain layer, and some of the grains seemed

to stick together. In the case of the nylon blended wool

fabric, the grain layer appears more uneven than other

filament yarns due to wool fibers that covered the surf-

ace. In general, synthetic fibers and silk are made of fila-

ments and have smooth surfaces, while natural fibers

have side twists, and the surface of wool is covered

with a scale that is hydrophobic. It is considered that

such inherent fiber structures also affect the aluminum

sputtering treatment.

2. Infrared Thermal Imaging Properties

1) Infrared Thermal Imaging according to Dis- tance between the Sample and the Body

Infrared imaging was performed at an atmospheric


Nylon blended wool fabric

Cotton fabric Silk fabric

Untreated(×100)

Untreated(×400)

Untreated(×20000)

Sputtered(×100)

Sputtered(×400)

Sputtered(×2000)

Table 3. FE-SEM images of specimens


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temperature of 20°C and 24% humidity. Images were

gathered at various distances between the sample and

the hand, for different base fabrics, and for aluminum

films deposited with different sputtering directions.

When the sample and the hand are in close contact, the

image of the IR camera is as shown in <Table 4>.

When the surface of the Al-sputtered layer faced

the back of the hand, the surface temperature was close

to the temperature of the hand. Therefore, when the Al

layer faces the back of the hand, the concealing effect

is observed. When the Al layer was directed to the out-

side air, the color of the sample was similar to the sur-

rounding environment, and the hand appeared camou-

flaged. This was observed with all six sputtered sam-

ples. A previous study presented IR images for a sam-

ple on a 35°C hot plate sputtered at 1000 W for 10 min-

utes in an external temperature of 15°C. When the metal

layer was directed to the outside air, the surface color

appeared different depending on the base fabric (nylon,

cotton/ PET, SMPU nanoweb, PET) (Han, 2016).

In this study, the surface temperature<Fig. 3> was

slightly different depending on the base fabric type.

Fabrics (PET, nylon, laminated PET, and silk) made of

filament fibers showed slightly lower surface tempera-

tures than fabrics made of staple fibers (nylon-blended

wool and cotton). This is because more uniform fibers

allow a more uniform aluminum layer to form during

sputtering, and heat transfer occurs faster. The surface

temperature of the 3-layer model showed a similar

temperature to that of the hand surface temperature,

and the concealing effect was low.

2) Lab MeasurementThe values of ΔL, Δa, Δb, and ΔE were calculated


Nylon blended wool fabric

Cotton fabric Silk fabric

Untreated

Al phaseup

Al phasedown

3-layermodel

Table 4. Infrared thermal imaging for different base fabrics


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<Table 6> by using a colorimeter to observe quantita-

tive color changes based on the infrared thermographic

images, as previously described (Table 4)–(Table 5).

The L, a, and b values of the outside air were L=79.0,

a=–10.3, and b=77.0, respectively.

As a result, the L, a, and b values of the untreated

fabric and the Al phase down fabric were similar. This

can be confirmed from the ΔL, Δa, Δb, and ΔE values

in <Table 6>. It was found that the absolute values of

ΔL, Δa, Δb, and ΔE of the Al phase down were much

Al phase up Al phase down

ΔL Δa Δb ΔE ΔL Δa Δb ΔE

PET fabric 22.0 –53.7 27.7 64.3 –1.0 –06.3 –4.3 07.7

Nylon fabric 27.0 –76.7 39.7 90.4 –2.7 –10.3 –5.7 12.1

Laminated PET fabric 23.0 –63.0 26.0 71.9 –3.3 –09.7 –9.0 13.6

Nylon blended wool fabric 12.3 –30.7 15.3 36.4 –2.3 –05.3 –4.3 07.3

Cotton fabric 10.7 –26.7 11.7 31.0 –6.0 –14.7 –6.3 17.1

Silk fabric 13.0 –35.0 15.0 40.2 –5.3 –15.3 –6.7 17.5

Table 6. ΔL, Δa, Δb, ΔE values from infrared thermal imaging

Fig. 3. Fabric surface temperature for different base fabrics (distance between hand and fabric: 0 mm).

Untreated Al phase up Al phase down

L a b L a b L a b

PET fabric 55.7 60.7 48.3 77.7 0–7.0 76.0 54.7 67.0 44.0

Nylon fabric 52.0 68.3 36.3 79.0 0–8.3 76.0 54.7 58.0 42.0

Laminated PET fabric 56.7 59.7 50.7 79.7 0–3.3 76.7 53.3 59.3 41.7

Nylon blended wool fabric 59.7 53.0 55.0 72.0 –22.3 70.3 57.3 58.3 50.7

Cotton fabric 63.3 44.0 61.3 74.0 –17.3 73.0 69.3 29.3 67.7

Silk fabric 64.3 39.7 61.3 77.3 0–4.7 76.3 59.0 55.0 54.7

Table 5. Infrared thermal imaging in the lab


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smaller than those of the Al phase up, indicating that

there was little difference compared to the untreated

samples. In the case of the Al phase up, the ΔE value

reached as high as 31-90.4, and the concealing effect

was larger than the Al phase down. In addition, the

value of ΔE in synthetic fiber was higher (64.3-90.4)

than that of the natural fiber (31-40.2), indicating a

better concealing effect.

In contrast, when the Al layer was oriented toward

the outside air, the L value, indicating the brightness,

is 10.7-27 higher than that of the untreated fabric. This

is because the surface temperature of the sample is

relatively low, and the brightness is relatively high. In

the case of a value indicating the degree of change

from red to green, the value is small (–76.7 to –26.7)

when the Al layer is directed toward the outside air,

while the value is high. The red color is deep when the

Al layer faced the hand, and no concealing effect could

be observed.

3) Infrared Transmittance CharacteristicsThe IR transmittance measurements of the untreated

sample and the sputtered sample are shown in <Fig. 4>.

The IR transmittance of the untreated samples was

38.3-58.1% in all six samples. However, the transmit-

tance reduced remarkably from 14% to 0.5% when Al

sputtering was performed. This is probably due to the

high optical reflection of Al.

In the IR transmittance experiment, the direction of

the sputtering layer did not significantly affect the IR

transmittance when only one side was sputtered. This

disproves the idea that an image photographed by the

infrared photographic camera and IR transmittance do

not necessarily have the same tendency.

3. Interpretation of the Infrared Thermograp- hic Camera Stealth Function based on Heat Transfer

As mentioned above, the IR transmittance rate was

15% or less from the sputtered fabrics, regardless of

their directions. However, the concealing effect was

different, depending on the direction of a fabric. In add-

ition, when the Al-sputtered fabric faced the camera,

concealing was observed, but the 3-layer model fabric

(body-nylon-Al-nylon) <Fig. 5> did not show a conc-

ealing function. Therefore, we propose that the conc-

ealing effect in the IR thermographic image should be

interpreted as a thermal characteristic rather than an

IR radiation characteristic. In addition to the previous

study (Han, 2016), the heat transfer model was calcul-

ated. The value used for calculation is as shown in

<Table 7>.

The thickness, thermal conductivity, and emissivity

of Al were taken from Han (2016). In addition, the heat

transfer coefficient of nylon, thermal conductivity, and

Fig. 4. Transmittance of IR according to the sample types.


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emissivity were taken from Han (2016). The heat trans-

fer coefficient of Al was determined from the calcul-

ated thermal conductivity found in Han (2016).Q was calculated to be 111.8W, and the surface tem-

perature (T4) was 32.9°C. In fact, the thermographic

camera results mentioned above agree with these val-

ues, and it appears that the 3-layer model with the Al

layer in the middle does not have the ability to conceal

objects from IR cameras.

4. Air Permeability

In this study, air permeability was measured to exa-

mine the comfort levels of the sputtered fabrics. The

experimental results are shown in <Fig. 6>, which show

that air permeability changes due to the sputtering pro-

cess are insignificant. This is probably because the sizes

of particles formed by Al sputtering are at the nanoscale

(Han, 2016; Han & Kim, 2018). It was found that the

direction of the Al-sputtered surface during measure-

ment of air permeability did not have any significant

effect on the measured data. That is, it can be confirmed

that the sputtering process does not affect air perme-

ability.

V. Conclusions

In this study, the stealth function of Al-sputtered

fabrics was studied using images gathered with IR

thermographic cameras. The base fabrics chosen were

PET, nylon, laminated PET, nylon-blended wool, cot-

ton, and silk. An aluminum sputtering process was used

to modify the IR transmittance, color difference, and

temperature changes, as well as determine the effective-

ness of concealment.

As a result, if a single-sided sputtered fabric was

placed on the human body, when the sputtering layer

was directed toward the outside air, it was observed to

show a hue similar to that of the surroundings. Thus a

concealing effect was observed with an IR thermogra-

phic camera. Experimental results show that the sputter-

ing layer showed a high L value when the sputtering

Thickness (m) Heat transfer coefficient Thermal conductivity (W/m⋅K) Emissivity (%)

Aluminum 0.000000605 475 205.0 0.11

Nylon 0.000180000 4 3.08×10-2 0.85

From Han (2016). p. 86-89.

Table 7. Materials properties used for calculations

Fig. 5. Heat transfer simulation of 3-layer model.


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layer was oriented toward the outer atmosphere. The

Δa value –76.7-–26.7 helps explain the concealing

effect. The value of ΔE reached up to 31-90.4, indica-

ting that the treated sample was significantly different

from the untreated sample. However, the sputtered alu-

minum layer on the base fabric was pointed toward the

hand and no concealing effect was observed, and the

3-layer model showed a similar surface temperature as

the hands. And synthetic fibers showed a lower surface

temperature than natural fibers, as shown by FE-SEM

images, which indicates that synthetic fibers are fila-

ment yarn and aluminium sputtering layers are uniform

as the fiber surface is smoother, making heat transfer

efficient and appearing at a lower surface temperature.

Because of the IR transmittance characteristic test,

the IR transmittance of the sputtered sample was rem-

arkably lower than that of the untreated sample, but dif-

ferences in IR transmittance measurements were insig-

nificant for various sputtering treatment directions.

Therefore, the sputtering direction did not significantly

affect the infrared transmittance rate. This suggests

that infrared transmittance does not affect the image

captured by the infrared thermographic camera. Based

on the heat transfer theory, the surface temperature of

the sputtered fabric surface of the 3-layer model was

found to be high. It was found through air permeability

tests that air permeability was not significantly influ-

enced by the sputtering process. It is expected that such

a fabric can be used for military uniforms, high-perfor-

mance apparel, smart clothing, among other materials.

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Hye Ree Han

Adjunct Professor, Culture, Digital Seoul Culture ArtsUniversity

characteristics of infrared blocking, stealth and color

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