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Supplementary Information
Polyurethane Foam Coated with Nanocomposite of Multi-Walled Carbon Nanotubes and Polyaniline for a Skin-Like Stretchable Array of Multi-Functional Sensors
Soo Yeong Hong, Ju Hyun Oh, Heun Park, Jun Yeong Yun, Sang Woo Jin, Lianfang Sun, Goangseup Zi, and Jeong Sook Ha*
S. Y. Hong, J. H. Oh, H. Park, J. Y. Yun, Prof. J. S. Ha
Department of Chemical and Biological Engineering, Korea University, Seoul 02453, Republic of Korea
E-mail: [email protected]
S. W. Jin, Prof. J. S. Ha
KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
L. Sun, Prof. G. Zi
Department of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02453, Republic of Korea
Keywords: Stretchable sensors, multi-functional sensors, liquid metal interconnections, carbon nanotube-polyaniline-polyurethane sponges, electronic skins
*Corresponding-Author: Prof. J. S. Ha, e-mail: [email protected]
Supplementary Note S1: Experimental procedure
Functionalization of negatively charged MWCNTs: MWCNTs (Aldrich, >90% carbon basis,
length 5–9 μm, outer diameter 110–170 nm) were refluxed in concentrated sulfuric acid and
nitric acid (3/1 v/v, Sigma-Aldrich) at 70 °C for 3 h. The functionalized MWCNTs were
rinsed with DI water several times using a cellulose ester membrane filter (ADVANTEC
MFS, Inc.; pore size 0.2 μm, diameter 47 mm). After osmosis filtration using a tube cellulose
membrane (Sigma; average flat width 33 mm, average diameter 21 mm), MWCNT-COOH
was obtained.
Synthesis of MWCNT-PANI nanocomposite: The MWCNT-PANI nanocomposite was
synthesized during the chemical polymerization of aniline monomer. 100 mg of MWCNT-
COOH in 60 mL of 3 M hydrochloric acid was sonicated for 5 min to obtain a uniform
suspension. A mixture of 25 mL of ethanol, 0.25 g of aniline monomer, and the suspension
were stirred for 40 min. Then, 0.38 g of aniline ammonium persulfate (APS, Sigma-Aldrich)
was dissolved in 20 mL of 1 M hydrochloric acid and slowly dropped into the suspension to
initiate the polymerization. The resulting reaction mixture was sonicated for 20 min and
allowed to react for 18 h at -14 °C with stirring so that aniline could be fully polymerized.
After polymerization, the products were rinsed with DI water and ethanol, and then dried in
ambient atmosphere. The colors of the bare MWCNT, PANI, and MWCNT-PANI
nanocomposite solutions are shown in Figure S2. The SEM images of bare MWCNT and
PANI are shown in Figure S3.
Preparation of multi-functional sensing foam (MFSF): The MWCNT-PANI nanocomposite
film was mixed with DI water to make up a concentration of 1 mg/mL. Polyurethane (PU)
foam (thickness: 700 μm, Elongation: >300%, young’s modulus: 0.3 MPa,) was pre-treated
with (3-aminopropyl) triethoxylane (APTES) self-assembled monolayer (SAM). Next, the
pre-treated PU foam was dipped into the solution and stored in a desiccator for 10 min. After
annealing of the PU foam in an oven at 65 °C for 20 min, the same process was repeated 20
times to obtain MFSF (resistance: 1.6 MΩ).
Liquid metal patterning: Lines of Galinstan (68.5% Ga, 21.5% In, and 10% Sn; Rotometals)
were directly printed using a stationary blunt syringe needle and a syringe pump (NE-300,
NEWERA) coupled with a motorized XYZ printer (TinyCNC-SE, TINYROBO) and an
optical imaging CCD camera. Galinstan was ejected from the syringe needle at a constant
flow rate by means of a syringe pump. The height of the syringe needle from the substrate
was controlled using a z-stage on the XYZ printer for height adjustment and a CCD camera
for visually detection of the needle in contact with the substrate (≈ ±5 μm). To initiate direct
printing, the stage was moved to the starting position, in order to make contact between the
liquid meniscus and the substrate. Galinstan from the syringe pump began to flow
immediately at the preset rate after the start of the stage movement. After final movement of
the syringe needle, the syringe pump was stopped. Detachment of Galinstan within the
syringe needle from the pattern was achieved by simultaneously increasing the height. A
mixture of Silbione (Silbione RT Gel 4717 A&B, Bluestar Silicones, USA) and PDMS (Dow
coming, Sylgard 184A) in 9:1 ratio was spin-coated on glass at 1000 rpm for 1 min. Then, it
was cured in a dry oven at 65 °C for 10 min, and the liquid metal was patterned by this
method to obtain “Layer 4” (thickness: 150 μm).
Characterization: Surface morphology and cross-section of the fabricated sensors were
investigated from the SEM (Hitachi S-4800) images. The electrical performance of the
sensors was measured using HP 4140B under ambient conditions. The MWCNT and
MWCNT-PANI nanocomposite were analyzed by micro-Raman spectroscopy using a diode
pumped solid-state laser (Omicron) at a wavelength of 532 nm under back-scattering
geometry, where a beam spot size was approximately 3 μm on the sample. Photographic
images were obtained using a Canon Eos-7D camera and a cellphone.
Figure S1. Optical images of MWCNT (left), PANI (center), and MWCNT-PANI (right)
suspensions.
Figure S2. SEM images of (a) Bare MWCNT, (b) PANI (inset shows a high-resolution
image), and (c) silver nanowire (Ag NW) (d) Cross-sectional SEM image of the Ag NW
sticker.
Figure S3. SEM images of the MWCNT-PANI nanocomposite.
Figure S4. Raman spectra of MWCNT-PANI nanocomposite (blue) and MWCNT (black).
Figure S5. (a) Schematic of the fabrication process for stretchable multi-functional sensor
array. (b) Assembly of prepared layers and liquid metal interconnection.
Figure S6. (a–c) The width and resistance of the printed liquid metal with different syringe
needles: (a) 21G, (b) 25G, and (c) 30G. (d) A syringe pump dispenses liquid metal while an
x-y-z motorized stage moves relative to the syringe. A computer synchronizes the movement
and a camera captures images of the resulting structures. (e) Normalized resistance (R/R0) of
the liquid metal patterning with varying strain (0–50%). (f) Normalized resistance (R/R0) as a
function of number of stretching cycles under a strain of 50%. R0 and R are the resistances
before and after stretching, respectively.
Figure S7. (a) Current response of the pressure sensor to various pressures for MWCNT
(black circles) and MWCNT-PANI composite (blue circles). (b) Output voltage responses of
the temperature sensors to temperature gradient for PANI (green circles) and MWCNT-PANI
composite (blue circles). (c) Schematic of applying both temperature and pressure, and the
corresponding changes in current and output voltage.
Figure S8. Optical images while measuring the temperature of (a) Fingertip and (b) Wrist
using an infrared radiation thermometer.
Figure S9 . Bare MWCNT based gas sensor: (a) Response time and recovery time as a
function of NH3 concentration. (b) Sensitivity vs. NH3 concentration.
Table S1. Comparison of gas sensor performance in this work with that in previous reports.
a)S = sensor sensitivity, b)Tres = response time (Tres), and c)Trec = recovery time (Trec)
Figure S10. Schematic representation of ammonia adsorption and the corresponding electron
transfer in the MWCNT-PANI nanocomposite (left), and the corresponding band diagram
(right).[6]
Figure S11. (a) Response of a sensor to 25 ppm NH3 during six cycles of adsorption and
desorption. (b) Response and recovery of a gas sensor exposed to 25 ppm NH3 at room
temperature.
Figure S12. Dimensions of the stretchable MF sensor array with embedded Galinstan
interconnections.
Figure S13. Photographs of Silbione/PDMS adhesion on hand skin with repeated
attachment/detachment: after the first time (left), after 10 times (center), and after washing
with soap and water (right)
Figure S14. (a) Photograph of wearable MF sensor array on the back of the hand, in contact
with a small ice cube (left). Temperature (center) and pressure (right) distribution. The
corresponding mapping of (b, c) the temperature and pressure distribution via measurement
of the normalized current and output voltage with wrist attachment. Here, I0 and I indicate the
current before and after the attachment of the sensor to the wrist.
Figure S15. Optical image and schematic illustration of the MF sensor array of
temperature/pressure, and an ammonia gas sensor, integrated using directly printed liquid
metal interconnections.
Reference
[1] He, L., Jia, Y., Meng, F., Li, M., Liu, J., Gas sensors for ammonia detection based on
polyaniline-coated multi-wall carbon nanotubes. Mater. Sci. Eng. B 163, 76–81 (2009).
[2] Wu, Z., Chen, X., Zhu, S., Zhou, Z., Yao, Y., Quan, W., Bin, L. Enhanced sensitivity
of ammonia sensor using graphene/polyaniline nanocomposite. Sens. Actuators B: Chem. 178
485–493 (2013).
[3] Patil, U. V., Ramgir, N. S., Karmakar, N., Bhogale, A. Debnath, A. K., Aswal, D.
K., Gupta, S. K., Kothari, D. C. Room temperature ammonia sensor based on copper
nanoparticle intercalated polyaniline nanocomposite thin films. Appl. Surf. Sci. 339, 69-74
(2015).
[4] Wang, J. Yang, P., Wei, X. High-Performance, Room-Temperature, and No-
Humidity-Impact Ammonia Sensor Based on Heterogeneous Nickel Oxide and Zinc Oxide
Nanocrystals. ACS Appl. Mater. Interfaces 7, 3816-3824 (2015).
[5] Duy, L. T., Trung, T. Q., Dang, V. Q., Hwang, B.-U., Siddiqui, S., Son, I.-Y., Yoon,
S. K., Chung, D. J., Lee, N-E., Flexible Transparent Reduced Graphene Oxide Sensor
Coupled with Organic Dye Molecules for Rapid Dual-Mode Ammonia Gas Detection.
Adv.Funct. Mater. 26, 4329-4338 (2016).
[6] Abdulla, S., Mathew, T. L., Pullithadathil, B. Highly sensitive, room temperature gas
sensor based on polyaniline-multiwalled carbon nanotubes (PANI/MWCNTs) nanocomposite
for trace-level ammonia detection. Sens. Actuators, B 221, 1523-1534 (2015).