The development of skinlike electronic devicesEskin eskin electronic

The development of skin-like electronic devices(E-skin) e-skin: electronic devices with flexible&stretchable networks and sensing functionalities that akin to human skin Yuhang Sun April/15/2016

Basic sense Touch (tactition) Sight Movement (vision) (balance) sense Hearing Taste (audition) (gustation) Smell (olfaction) Skin: largest sensory organ in human body , full of different types of sense receptors.

Outline • Originality • Materials mainly used • Four Transduction mechanisms • Novel Desirable Properties for E-Skin

originality applicable for autonomous artificial intelligence(robots) apply on/in human body to provide an unprecedented level of diagnostic and monitoring capabilities Luke skywalker was installed a hand with full sensory receptions

First e-skin in history • In 1985, General Electric(GE) built the first sensitive skin with 64 infrared sensor pairs on it, the resolution is 5 cm.

Materials & Considerations Goal: mechanical compliant(flex & stretch) Materials How to make it stretchable

1. Dielectrics(elastomers, polymers) • With addition of inorganic high k particles, especially suitable for flexible transistors. Elastomers(PDMS, PVDF)mixed with (Ti. O 2, Ba. Ti. O 3 or ionic liquid) PVDF+inoic liquid by Lee’s group [1]

2. CNT based or Graphene based active material • Carrier mobility: CNT: 10000 cm 2 V-1 s-1, graphene: 20000 cm 2 V-1 s-1 Graphene films deposit on Ni film(left)&Si. O 2(right)substrate by CVD[2]

3. Nanowire based-active materials Difficult to fabricate NWs into ordered array, LBL make it possible for NW to integrated on flexible substrate; expensive Layer by Layer(LBL) assembly for 3 D structure Nam’s group [3]

Transduction mechanism • 1. Piezoresistivity • transduce a change in the resistance of a device into a measurement of strain • Most extensively investigated • have been incorporated into highly flexible and stretchable devices using connections made from liquid metal, stretchable helical electrodes, stitched metallic electrodes

2. capacitance • C = ε 0 ε r A / d, • The change in d is commonly used to measure normal forces, • changes in A are typically used to measure shear forces • This method is not widely pursued: • I. reducing the pixel size of these devices for miniaturization reduces the capacitance and the signal-to-noise ratio • II. capacitive sensors are susceptible to interference from external sources

3. Piezoelectricity • Piezoelectricity refers to the ability of a material to generate a voltage in response to an applied force. • The force causes a change in the length and separation between dipoles in the material, leading to the build-up of compensating charges on the electrodes • Most popular piezoelectric materials: PZT(lead zirconate titanate)&Zn. O

4. Optics • convert a tactile input into an electrical output using light as an intermediate • Consist of light source, transmission medium, and detector Work reported by Bao’s group

Novel Desirable Properties for E-Skin • 1. biodegradable

2. Highly-integrated & 3. wireless detection • Which means e-skin can be transferred onto human body in a manner similar with human skin. it’s like a tattoo, made based on a water soluble based PVA, it can

Other ones • 4. self-powered • 5. self-healing • 6. temperature-detection • ……

citations • • • [1] K. H. Lee, M. S. Kang, S. P. Zhang, Y. Y. Gu, T. P. Lodge, and C. D. Frisbie, ""Cut and Stick" Rubbery Ion Gels as High Capacitance Gate Dielectrics, " Advanced Materials, vol. 24, pp. 4457 -4462, Aug 2012. [2] A. Reina, X. T. Jia, J. Ho, D. Nezich, H. B. Son, V. Bulovic, et al. , "Large Area, Few-Layer Graphene Films on Arbitrary Substrates by Chemical Vapor Deposition, " Nano Letters, vol. 9, pp. 30 -35, Jan 2009. [3] A. Javey, S. Nam, R. S. Friedman, H. Yan, and C. M. Lieber, "Layer-by-layer assembly of nanowires for three-dimensional, multifunctional electronics, " Nano Letters, vol. 7, pp. 773 -777, Mar 2007. [4] J. A. Rogers, "Epidermal electronics, " Abstracts of Papers of the American Chemical Society, vol. 243, p. 1, Mar 2012. [5] X. L. Wang, H. Hu, Y. D. Shen, X. C. Zhou, and Z. J. Zheng, "Stretchable Conductors with Ultrahigh Tensile Strain and Stable Metallic Conductance Enabled by Prestrained Polyelectrolyte Nanoplatforms, " Advanced Materials, vol. 23, pp. 3090 -+, Jul 2011. [6] K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, et al. , "Large-scale pattern growth of graphene films for stretchable transparent electrodes, " Nature, vol. 457, pp. 706 -710, Feb 2009.

Five key points • • • 1. what is e-skin(definition) 2. originality of developing e-skin(two aspects) 3. three main types of materials used 4. four transduction methods 5. novel properties