PRISM: ERC-LIFE, Feb 25, 2007 Overview of Flexible Electronics for LIFE James C. Sturm and Sigurd Wagner Department of Electrical Engineering Director, Princeton Institute for the Science and Technology of Materials (PRISM) Princeton University, Princeton, NJ USA sturm: , wagner: If you really need to reach me, my administrative ass’t. is Ms. Sheila Gunning,

PRISM: ERC-LIFE, Feb 25, 2007 Outline Conventional Microelectronics Large Area and Flexible Microelectronics Applications

PRISM: ERC-LIFE, Feb 25, 2007 Finished Silicon Wafer after fabrication Each square (cm x cm about) is its own circuit, with millions (billions) of connected transistors. 100’s of chips on wafer, typically. Also, miles and miles of wires (printed metal stripes) on them The process of making them is known as “Very Large Scale Integrated” technology (VLSI) Typical features sizes today = 0.1 micron = 100 nanometer = cm

PRISM: ERC-LIFE, Feb 25, 2007 One chip After it has been “diced” from the wafer. Also known as a “die” 0.5 – 2 cm on an edge, typically

PRISM: ERC-LIFE, Feb 25, 2007 Each metal leg of the package is connected to a mini-wire which is connected to the chip. Wire connection “pads”

PRISM: ERC-LIFE, Feb 25, 2007 The chip is put into a black plastic/ceramic package for use in applications Each metal leg of the package is connected to a mini-wire which is connected to the chip. These are ususally soldered into green “printed circuit boards” (e.g. 6” x 6”) that you see in electronic products Small, hard, and rigid,

PRISM: ERC-LIFE, Feb 25, 2007 Integrated Circuit Business Model 1.Make the transistors and wires on the chip smaller (nanotechnology) 2.chips are smaller and more chips fit on a wafer 3. The cost per chip is lower (or more on a chip for same cost): costs per function DROP over time (10 8 x in 35 years) 4.Increase sales through more applications enabled by low cost 5.The business problem: it is getting harder to make things smaller and still have the transistors work and be cheaper. So what do you do? (“End of Moore’s Law”)

PRISM: ERC-LIFE, Feb 25, 2007 Outline Conventional Microelectronics Large Area and Flexible Microelectronics Applications

PRISM: ERC-LIFE, Feb 25, 2007 Flat panel TV Princeton Macroelectronics Group Samsung Apple Computer

PRISM: ERC-LIFE, Feb 25, 2007 Real time image processing in PC Picture archiving and communications system (PACS) High performance display Flat panel detector High speed network Digital X-ray imager Princeton Macroelectronics Group Richard Weisfield, dpiX

PRISM: ERC-LIFE, Feb 25, 2007 Solar electric module Princeton Macroelectronics Group Akihiro Takano, Fuji Electric Advanced Technology

PRISM: ERC-LIFE, Feb 25, 2007 a pixellated surface switch, amplifier sensor actuator cell (pixel) interconnects Architecture of an electronic surface rigid, flexible, or deformable, or elastomeric substrate Steel foil, thin glass, rollable or stretchable plastic,... Princeton Macroelectronics Group “Backplane”: Electronics “Front plane”: End function

PRISM: ERC-LIFE, Feb 25, 2007 A liquid-crystal display Princeton Macroelectronics Group Frontplane

PRISM: ERC-LIFE, Feb 25, 2007 Was LCD readout (‘70s), laptop display (’80s), desktop monitor (90’s) Is flat screen TV, X-ray imager, thin-film solar cell (’00s) What will be next??? (’10s) Much of large-area electronics was invented at the RCA Labs in Princeton: - Paul Weimer … thin-film transistor in the ’60s - George Heilmeier *62 … liquid-crystal display in the ‘60s - David Carlson and Chris Wronski … amorphous-silicon thin-film solar cell in the ‘70s A brief history of large-area electronics

PRISM: ERC-LIFE, Feb 25, 2007 Bend: Small deformation, elastic, one-time or repeated Conformally shape: Large deformation, plastic, one-time Stretch: Large deformation, elastic, repeated 3 degrees of shaping a “flexible” electronic surface Princeton E Ink - Princeton Princeton this case: steel foil substrate this case: plastic foil substrate elastomeric substrate

Data courtesy of David Mentley, iSuppli; Ken Werner, Nutmeg Consultants; Barry Young, DisplaySearch The display industry is developing the tools and is reducing the cost for making large electronic surfaces Large area electronics is growing like microelectronics in the early ’90s

PRISM: ERC-LIFE, Feb 25, 2007 Section of 300-ft. long roll-to-roll solar cell manufacturing line Energy Conversion Devices (USA) Industrial a-Si:H PE-CVD systems are huge Inline system for making solar cells on steel foil substrates

PRISM: ERC-LIFE, Feb 25, 2007 Silicon Thin Film Transistors on Flex Substrates Motorola TFT on steel 6 cm Deformable plastic for 3-D shapes E-ink display on backplane of a-Si TFT’s on steel foil

PRISM: ERC-LIFE, Feb 25, 2007 Outline Conventional Microelectronics Large Area and Flexible Microelectronics Applications: Think  Potential Large Area  Flex, Bend, Stretch, Deform  Backplane (electronics) + frontplane (function)  Arrays  Function:  sense light, temperature, strain, chemical properties, sound  control light, local heating (drug release?)  actuate: move, bend, squeeze  I will give 2 examples directed at medicine

PRISM: ERC-LIFE, Feb 25, 2007 A surround display Zenview A digital dashboard Miltos Hatalis, Lehigh U. A Cyberhand Cyberhand Project An e-Suit Givenchy Fall ‘99

PRISM: ERC-LIFE, Feb 25, 2007 Rigid Microelectrode Arrays In Vivo (Thanks to B. Morrison, Columbia and S. Wagner, Princeton) Brain Computer Interface Campbell, IEEE.Trans.Biomed.Eng., 1991 Micromachined silicon Cyberkinetics Neurotechnology Systems Titanium Fofonoff, IEEE Trans.Biome.Eng., 2004 Kipke, IEEE Trans.Neural Sys.Rehab.Eng, 2003 Silicon Michigan Probe Utah Array

PRISM: ERC-LIFE, Feb 25, 2007 Flexible vs. Stretchable MEAs Electrodes on  Polyimide (5 GPa)  Flexible  Ultimate limit 4% stretch Bending  PDMS (1 MPa)  Stretchable  Ultimate limit Max ~ 50% –Uniaxial  Maintains conduction Keesara, Proc.MRS, 2006 Polyimide PDMS gold film Chambers, Proc.MRS, 2003

PRISM: ERC-LIFE, Feb 25, 2007 Traumatic Brain Injury Model Complex organotypic brain slice culture Apply deformations consistent with TBI  Study the tissue response Morrison, J.Neurosci. Meth., 2006 CA1 CA3 DG Nissl

PRISM: ERC-LIFE, Feb 25, 2007 Application 2: (E-problem: file corrupted) Front plane: “electret sensor” S. Bauer, U. Linz, Austria Converts pressure to electricity  Array of pressure detectors – covering large area  Array of microphones over some array Converts electricity into motion  Can make thin film “breathe” in and out, local control  Will send rest of file later

PRISM: ERC-LIFE, Feb 25, 2007 END

PRISM: ERC-LIFE, Feb 25, 2007 Moore’s Law Not fundamental, just an observation Has continued despite many predictions of demise Billions of T’s on a single chip!!!!! (in DRAM memory, one bit requires one transistor)

PRISM: ERC-LIFE, Feb 25, 2007 How do they get all that stuff on the chip: It’s a Small World!! Feature Sizes on Integrated Circuits (millionths of meters, thousandths of millimeters) (billionths of meters, millionths of millimeters) Gate length is key number: often the smallest size of the width of a layer on a chip Where Nanotechnology came from! 2006: gate length ~ 30 nm in advanced production