A Superhydrophobic Smart Coating for Flexible and Wearable Sensing Electronics

Superhydrophobic surfaces have shown versatile applications in waterproofing, self-cleaning, drag reduction, selective absorption, etc. The most convenient and universally applicable approach to forming superhydrophobic surfaces is by coating; however, currently, superhydrophobic, smart coatings with flexibility and multiple functions for wearable sensing electronics are not yet reported. Here, a highly flexible multifunctional smart coating is fabricated by spray-coating multiwalled carbon nanotubes dispersed in a thermoplastic elastomer solution, followed by treatment with ethanol. The coatings not only endow various substrate materials with superhydrophobic surfaces, but can also respond to stretching, bending, and torsion-a property useful for flexible sensor applications. The coatings show superior sensitivity (gauge factor of 5.4-80), high resolution (1° of bending), a fast response time (<8 ms), a stable response over 5000 stretching-relaxing cycles, and wide sensing ranges (stretching: over 76%, bending: 0°-140°, torsion: 0-350 rad m-1 ). Moreover, multifunctional coatings with thicknesses of only 1 µm can be directly applied to clothing for full-range and real-time detection of human motions, which also show extreme repellency to water, acid, and alkali, which helps the sensors to work under wet and corrosive conditions.

[1]  W. D. de Heer,et al.  Carbon Nanotubes--the Route Toward Applications , 2002, Science.

[2]  Jing Kong,et al.  Superwetting nanowire membranes for selective absorption. , 2008, Nature nanotechnology.

[3]  G. Yin,et al.  Stable biomimetic superhydrophobicity and magnetization film with Cu-ferrite nanorods , 2007 .

[4]  J. González‐Benito,et al.  Effects of ozone in surface modification and thermal stability of SEBS block copolymers , 2010 .

[5]  J. Zou,et al.  Preparation of a Superhydrophobic and Conductive Nanocomposite Coating from a Carbon‐Nanotube‐Conjugated Block Copolymer Dispersion , 2008 .

[6]  P Tabeling,et al.  Slippage of water past superhydrophobic carbon nanotube forests in microchannels. , 2006, Physical review letters.

[7]  John A. Rogers,et al.  Highly Sensitive Skin‐Mountable Strain Gauges Based Entirely on Elastomers , 2012 .

[8]  Claire J. Carmalt,et al.  Robust self-cleaning surfaces that function when exposed to either air or oil , 2015, Science.

[9]  Thomas Schimmel,et al.  The Salvinia Paradox: Superhydrophobic Surfaces with Hydrophilic Pins for Air Retention Under Water , 2010, Advanced materials.

[10]  Lydéric Bocquet,et al.  Low-friction flows of liquid at nanopatterned interfaces , 2003, Nature materials.

[11]  Lei Jiang,et al.  Stable, Superhydrophobic, and Conductive Polyaniline/Polystyrene Films for Corrosive Environments , 2006 .

[12]  R. Blossey.  Self-cleaning surfaces — virtual realities , 2003, Nature materials.

[13]  Ching-Ping Wong,et al.  Growth and electrical characterization of high-aspect-ratio carbon nanotube arrays , 2006 .

[14]  Nicola Pugno,et al.  Multifunctionality and Control of the Crumpling and Unfolding of Large-Area Graphene , 2012, Nature materials.

[15]  Doris Vollmer,et al.  Candle Soot as a Template for a Transparent Robust Superamphiphobic Coating , 2012, Science.

[16]  Nae-Eung Lee,et al.  Transparent Stretchable Self-Powered Patchable Sensor Platform with Ultrasensitive Recognition of Human Activities. , 2015, ACS nano.

[17]  Haonan Si,et al.  Flexible and Highly Sensitive Strain Sensors Fabricated by Pencil Drawn for Wearable Monitor , 2015 .

[18]  R. N. Wenzel.  RESISTANCE OF SOLID SURFACES TO WETTING BY WATER , 1936 .

[19]  Seiji Akita,et al.  Fully printed, highly sensitive multifunctional artificial electronic whisker arrays integrated with strain and temperature sensors. , 2014, ACS nano.

[20]  K Efimenko,et al.  Creating long-lived superhydrophobic polymer surfaces through mechanically assembled monolayers. , 2000, Science.

[21]  Ilker S. Bayer,et al.  Extremely stretchable and conductive water-repellent coatings for low-cost ultra-flexible electronics , 2015, Nature Communications.

[22]  Kara R. Lind,et al.  Thermal Processing of Silicones for Green, Scalable, and Healable Superhydrophobic Coatings , 2016, Advanced materials.

[23]  J. M. Bush,et al.  The hydrodynamics of water strider locomotion , 2003, Nature.

[24]  Yan Li,et al.  Poisson Ratio and Piezoresistive Sensing: A New Route to High‐Performance 3D Flexible and Stretchable Sensors of Multimodal Sensing Capability , 2016 .

[25]  Daniel M. Vogt,et al.  Embedded 3D Printing of Strain Sensors within Highly Stretchable Elastomers , 2014, Advanced materials.

[26]  Xuefeng Gao,et al.  Biophysics: Water-repellent legs of water striders , 2004, Nature.

[27]  Didem Öner,et al.  Ultrahydrophobic Surfaces. Effects of Topography Length Scales on Wettability , 2000 .

[28]  H. Erbil,et al.  Transformation of a Simple Plastic into a Superhydrophobic Surface , 2003, Science.

[29]  N. Lee,et al.  Stretchable, Transparent, Ultrasensitive, and Patchable Strain Sensor for Human-Machine Interfaces Comprising a Nanohybrid of Carbon Nanotubes and Conductive Elastomers. , 2015, ACS nano.

[30]  Xinjian Feng,et al.  Design and Creation of Superwetting/Antiwetting Surfaces , 2006 .

[31]  Jin Zhai,et al.  Super-hydrophobic surfaces: From natural to artificial , 2002 .

[32]  Benjamin C. K. Tee,et al.  Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes. , 2011, Nature nanotechnology.

[33]  W. Barthlott,et al.  Purity of the sacred lotus, or escape from contamination in biological surfaces , 1997, Planta.

[34]  Gareth H. McKinley,et al.  Superhydrophobic Carbon Nanotube Forests , 2003 .

[35]  K. Hata,et al.  A stretchable carbon nanotube strain sensor for human-motion detection. , 2011, Nature nanotechnology.

[36]  Zhiping Xu,et al.  Carbonized Silk Fabric for Ultrastretchable, Highly Sensitive, and Wearable Strain Sensors , 2016, Advanced materials.

[37]  L. J. Lee,et al.  Growth and alignment of polyaniline nanofibres with superhydrophobic, superhydrophilic and other properties. , 2007, Nature nanotechnology.

[38]  Stefan Seeger,et al.  Silicone Nanofilaments and Their Application as Superhydrophobic Coatings , 2006 .

[39]  T. Trung,et al.  Flexible and Stretchable Physical Sensor Integrated Platforms for Wearable Human‐Activity Monitoringand Personal Healthcare , 2016, Advanced materials.

[40]  Yei Hwan Jung,et al.  Stretchable silicon nanoribbon electronics for skin prosthesis , 2014, Nature Communications.

[41]  François Feuillebois,et al.  Effective slip over superhydrophobic surfaces in thin channels. , 2008, Physical review letters.

[42]  L. Gao,et al.  A Stretchable and Highly Sensitive Graphene‐Based Fiber for Sensing Tensile Strain, Bending, and Torsion , 2015, Advanced materials.

[43]  Pooi See Lee,et al.  Highly Stretchable Piezoresistive Graphene–Nanocellulose Nanopaper for Strain Sensors , 2014, Advanced materials.