Flexible Hybrid Electronics for Aerospace Applications

Transcription

1 Flexible Hybrid Electronics for Aerospace Applications B.J. Leever, M.F. Durstock, J.D. Berrigan, C.E. Tabor, A.T. Juhl Integrity Service Excellence AFRL/RXAS Materials & Manufacturing Directorate Air Force Research Laboratory Wright-Patterson AFB, OH

2 Outline AF Motivation for Flexible Hybrid Electronics Development Strategy Advanced Development Projects Gallium Liquid Metal Alloys Stretchable & reconfigurable electronics Printed Interconnects and Capacitors Stretchable & resilient electronics Soft Packaging Summary & Conclusions 2

3 AFRL: Turning Science Into Capability Driven by Service Core Functions *Updated after Print FY10 Funding Vectored by Air Force Strategy + S&T Vision/Horizons + Product Center Needs + MAJCOM Needs 6.1 Basic Research 6.2 Applied Research 6.3 Advanced Tech Demo Initial Operating Capability Timeline 3

4 Air Force Research Laboratory Technical Competencies AF Office of Scientific Research Aero-structure power and control Physics and electronic Mathematics, Information, and life sciences Aerospace Systems Turbine Engines High-Speed/Hypersonics Space and Missile Prop Aeronautical Sciences Structural and Control Sciences Directed Energy Lasers Beam Control High Power Microwaves Information Computing Architecture Information Exploitation Command & Control Human Performance Forecasting Training Decision Making Munitions Damage Mech Science Fuze Technology Munitions AGN&C Energetic Materials Terminal Seeker Sciences Munitions System Effects Science Sensors RF Sensing and Warfare EO Sensing and Warfare Trust in Complex Systems Space Vehicles Intelligence, Surveillance & Reconnaissance Responsive Space Space Situational Awareness Materials and Manufacturing Materials & Processes Materials Applications Manufacturing Technology 4

5 What are Flexible Hybrid Electronics? Electronics Manufacturing Services POWER Manufacturing Convergence for Application Spaces Human Monitoring Systems Asset Monitoring Systems Low-temperature Manufacturing Processes High-speed Automation Printed Components Thin Si CMOS Integrated Array Antenna Systems Soft Robotics 5

6 How could Flexible Hybrid Electronics Impact the Air Force? Man-Machine Interface Airman performance limits capability in MANY military missions.and new technologies are needed to sense, assess and augment the Airman-in-the-Loop Information Overload Missed Intelligence Threat/Danger Missed Today Future Embedded/Conformal Electronics for ISR/EW Information and tracking in contested environments is foundational to decision making and force projection Communication (conformal apertures) Distributed electronics for feedback and structural health monitoring Reconfigurable Electronics Lewis Integrated & Flexible Power (Mike Durstock) Energy limits operational capabilities and mission impact for unmanned vehicles and wearable electronics Issues: Cost & Weight Scale-up Durability Integrated Power harvesting, storage, and management Survivable Electronics Precision effects with smaller, low profile munitions pressing requirement for current and future platform effectiveness Robust electronics in extreme environments (shock, vibration, thermal) 6

7 Technology Development Strategy Accelerate development and transition of FHE technologies to Air Force functional materials community Phased plan for FHE technology insertions Conformal Antennas AM Design Rules Critical Pre-requisites: RPA Demo Human Performance Critical Pre-requisites: Composite Certification Hybrid-Materials Design Improved Conductive & Dielectric Inks Qual. Risk Reduction Rugged Flexible Electronics Embedded Sensors & Structural Antennas 7

8 Plasma Spray Direct Write MesoScribe Technologies Conformal & Integrated Antennas 8

9 Integrated Direct Write Electronics ManTech Program: Integrated Direct Write Electronics Simplify fabrication by locating electronics on vehicle exterior (vs. inside wing). Demonstrate printed heaters & thermistor for wing de-icing Demonstrate printed conformal antennas Demonstrate flexible IC as analog-todigital convertor Complete TRL/MRL assessment Fabricate and test PM: Ted Finnessy, AFRL/RXME 9

10 Direct-Write Conformal Antenna on MQ-9 Need Additional communications capabilities are required on the MQ-9. Conventional approaches to add antennas often requires new tooling (high cost, long lead time) and drilling of holes in the carbon fiber structure. Fuselage is crowded with apertures for communications, leading to co-site interference. Technical Approach Retro-fit existing fleet with conformal antennas by simply replacing existing servo covers. Phase I Results Indoor range data showed VSWR and directivity comparable with COTS components. Design and direct-write Cu antenna onto servo cover using plasma spray technique. Minimize co-site interference by installing onto unique locations of aircraft. Cu removal from part required a grinder. Significant directivity benefit in crosspolarization performance due to location 10

11 Automotive: Printed Console Electronics Ford Demo: Ford Focus Console Thermoformed Silver Ink Electronics Air Force could achieve similar benefits such as elimination/reduction of wire harnesses in aircraft. 11

12 Moving Beyond Commercially Available Human Sensors AF Mission Areas COTS products focus on primarily on motion sensing, with limited cardiac sensing AF needs advanced biosignatures sensing for cognition, stress, fatigue, etc. Consumer products will not survive challenging AF environments AF needs unobtrusive devices with chemical and mechanical durability Traditional electronic components and packaging will not meet Air Force requirements. 12

13 Potential for Human Monitoring FHE Devices Flexible Hybrid Oral Biochemistry Sensing System Sensing lactate as indictor for fatigue. Numerous FHE materials & manufacturing challenges must be overcome to enable reliable & durable wearable sensing platforms. 13

14 Flexible Materials & Devices Research Leader: Dr. Benji Maruyama Developing critical Materials & Processes to enable flexible hybrid electronic systems for airman performance monitoring..lightweight, flex/stretch, conformal, multifunctional, robust, autonomous Novel materials Inherently strain-resilient Wafer thinning Liquid metals AMI Harvard Conformal & integrated printing approaches Rapid design cycle Enables retrofit Tailored materials and properties Innovative packaging schemes Flex and performance Ensure survivability Rogers 14

15 Integration & Packaging of Human Monitoring Components Flex Battery NFC Photovoltaics Printed antennas & interconnects Microcontroller ADC chip Comm Power Logic Sense A, B, Single Layer Graphene Biosensor (G-FET) Exposed 1-layer graphene 16X Mag Challenges: Reliable, low-resistance interconnects Energy dense & flexible batteries Biosensor platform development Integration into stretchable form-factor 15

16 In-House Additive Manufacturing Capabilities VERSATILE HIGH RESOLUTION LOW COST 3D PROTOTYPING LARGE AREA CUSTOMIZABLE MOTION CONTROL STAGE AEROSOL JET PRINTING INKJET PRINTING POLYJET PRINTING SLOT-DIE COATING Aerotech Motion Control Stage Optomec Aerosol Jet Deposition System Microfab JetLab 4xl-A Objet Connex 3 3D Printer ntact nrad Extrusion Coating System Multiple interchangeable dispensing configurations In-Line Multi-Material dispense point Fine features ( 10 µm) Thin layers ( 100 nm) Excellent accuracy & repeatability Inherently clog resistant Good balance between cost and performance Drop-on-Demand microdispensing ~10 µm minimum line width Solid 3D structures UV-curable polymers Rigid and flexible materials Up to 82 material characteristics in one print 20 nm to 100 µm Coating Thickness Scalable Selected area coating capable 16

17 Gallium Liquid Metal Alloys (GaLMAs) Led by Chris Tabor in collaboration with Michael Dickey (NCSU) Liquid Metal encapsulated in Elastomer 3D Electronics Flexible Stretchable Gallium Alloy Properties MP < 0C Viscosity Water Vapor pressure 0 Electrically conductive Non-Toxic Room Temperature Liquid Electronics Reconfigurable 17

18 On Going Progress Acid/Base Reactions with the Surface Oxide Concern: The spontaneous formation of the surface oxide causes residue of oxide and metal to remain in channels during fluid evacuation. Image Courtesy of NC State Univ.; Dickey Group React with the Oxide Ga 2 O 3 + 6HCl 2GaCl 3 + 3H 2 O Modify the Oxide Mechanically Rigid, Continuous Surface Individual Hydrated Metal Chlorides - H 2 O HCl Oxide Metal O H O H O H O H O H O H 18

19 GaLMA Printing and Processing Additive Manufacturing with Liquid Metals There are a variety of approaches being explored to accurately print and define GaLMA structures Filament Extrusion of GaLMAs Aerosol Jet Printing GaLMA Inks Freestanding 3-D Liquid Electronics Cook et al. in prep. 19

20 Soft Electronics for Survivability Traditional Rigid PCBs Embedded Devices in Soft Matrix Mass Force Duration AFRL, RW AFRL, RW/RX Opportunities for Additive Manufacturing Solutions: Passive Devices: Printed conductors & dielectrics with device architectures insensitive to strain Techniques: Inkjet, Aerosol, Filamentary Packaging: Islands of varying modulus and conductivity Technique: Filamentary AFRL/RXAS 20

21 Developing Printed Electronic Components 1. Printer Design Motion system Motion controller Interface software Scripting language Deposition system Imaging Alignment tools Computer 2. Printing Technique Path planning Loading protocol Cleaning protocols Alignment techniques Stop-start compensation 4. Printed Electronic Component 3. Ink Design Particulates Reactive elements Rheological modifiers Solvents Binders Surface energy modifier Stabilizers 21

22 Inks Under Investigation for Filamentary Deposition Metal Fillers Dielectric and Polymer Matrix Ag (Particles, Flakes, Wires) Ni Nanostrands ASI Carbon egain (Liquid Metal) PMMA Polystyrene PVDF-HFP (various blends) Silicone Polyurethane Material Conductivity (S cm -1 ) Strain to Failure Bulk Cu Bulk Ag Silicone (SE1700) Ag in TPU TBD Ag in PMMA TBD Ag in SE TBD Ag in PVDF-HFP TBD Dupont (PE872) TBD Close-up view of 3D printer setup (left) and optical image of layered PVDF-HFP filaments (right). Scale: 100 μm Quantification of relationship between Ag loading, matrix and mechanical properties currently underway. 22

23 Flex Printer PDMS Aerotech gantry and controller Air bearing XY with 4 independent Z-axis Rotation axis option Multiple zoom camera Various tools can be attached as needed 23

24 Polymers for Flex Cap Printing Thin films (<20 µm) Poly(propylene) Poly(styrene) A C = ε 0 ε r d ε r E BD = V BDC ε 0 A Poly(methyl methacrylate) Poly(vinylidene fluoride-cohexafluoropropylene) PVDF-HFP Ultraflex Flex

25 Printing Capacitors Inherently a two material system Dielectric Conductor Defects often propagate up through subsequent layers Print and material defects contribute to dielectric breakdown Cross-section of PMMA cap 25

26 Control of Dielectric Film Printing offers good control of film thickness ~10 min/layer to print Little evidence of aging or relaxing of processrelated internal structure 26

27 Height (µm) Printing Process Development Material: PVDF-HFP Print time: 8 hours Yield: ~10% Capacitance : ~0.3 nf Material: PMMA Print time: 8 hours Yield: ~60 % Capacitance : 0.1 nf Material: PMMA, Print time: 8 hours, Yield: ~100 %, Capacitance : nf Position (mm) 27

28 Soft Electronics for Survivability Traditional Rigid PCBs Soft Packaging Scheme Printed Silicone Packaging AFRL, RW AFRL, RW/RX Combining rigid PCBs with Soft Packaging provides interim solution Printed silicone (PDMS) clearly prevents capacitor separation from PCB Electrical conductivity verified before and after test Considering stretchable conductors/interconnects to ensure electrical connectivity during test 28

29 Next Steps Ink Optimization (stability, viscosity, etc.) Nozzle development for multiscale and multi-material printing Improve parallel printing of multi-layer capacitors Printed Sensors and Actuators Integrating active electrical structures into complex mechanical structures Schaeffer and Ruzzene, J. Appl. Phys.,

30 Summary AF pursuing additive manufacturing to enable numerous capabilities including Human/airman performance monitoring Rugged/durable electronics Embedded electronics & optics Flexible Hybrid Electronics (rather than fully printed solutions) are near-term focus Liquid gallium metal alloy for interconnects & reconfigurable electronics Printed metals and dielectrics for flexible and resilient circuit elements Soft packaging with stretchable interconnects Key Challenges Ink development both metals & dielectrics Process enhancements in-situ process monitoring, improved resolution, etc. Multi-material print heads or print systems Disparate materials interfaces 30

31 Questions? 31

32 Printing vs Conventional Casting Some minor morphological difference were observed but mostly higher thicknesses Printed films matched dielectric behavior of cast films 32

33 Height (µm) Printing Faster and Better Multilayer Capacitors Delamination after 2 weeks of storage Capacitors in parallel Position (mm) 33