Flexible Hybrid Electronics for Aerospace...
Transcript of Flexible Hybrid Electronics for Aerospace...
1Distribution Statement A: Approved for Public Release. Distribution is unlimited. Case # 88ABW-2016-1256.
Integrity Service Excellence
Flexible Hybrid Electronics
for Aerospace Applications
B.J. Leever, M.F. Durstock, J.D.
Berrigan, C.E. Tabor, A.T. Juhl
AFRL/RXAS
Materials & Manufacturing Directorate
Air Force Research Laboratory
Wright-Patterson AFB, OH 45433
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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
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AFRL: Turning Science Into Capability
*Updated after PrintFY10 Funding
Driven by Service Core FunctionsVectored by Air Force Strategy + S&T Vision/Horizons + Product Center Needs + MAJCOM Needs
Initial Operating Capability Timeline
6.1
Basic
Research
6.2
Applied
Research
6.3
Advanced
Tech Demo
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Space Vehicles
• Intelligence,
Surveillance &
Reconnaissance
•Responsive Space
•Space Situational
Awareness
Materials and
Manufacturing
•Materials & Processes
•Materials Applications
•Manufacturing
Technology
Sensors
•RF Sensing and
Warfare
•EO Sensing and
Warfare
•Trust in Complex
Systems
•Damage Mech Science
•Fuze Technology
•Munitions AGN&C
•Energetic Materials
•Terminal Seeker
Sciences
•Munitions System
Effects Science
Munitions
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
AF Office of
Scientific Research
•Aero-structure power
and control
•Physics and electronic
•Mathematics,
Information, and life
sciences
Air Force Research Laboratory
Technical Competencies
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What are Flexible Hybrid Electronics?
Thin Si CMOS
POWER
Low-temperature
Manufacturing Processes
High-speed Automation
Printed Components
Integrated Array
Antenna Systems
Asset Monitoring
Systems
Human Monitoring
Systems
Soft Robotics
Manufacturing Convergence
for Application SpacesElectronics Manufacturing
Services
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How could Flexible Hybrid Electronics Impact the Air Force?
Man-Machine InterfaceAirman 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
Embedded/Conformal Electronics for ISR/EW
Information and tracking in contested environments is foundational to decision making and force projection
Integrated & Flexible Power (Mike Durstock)Energy limits operational capabilities and mission impact for unmanned vehicles and wearable electronics
• Communication (conformal apertures)• Distributed electronics for feedback and structural health
monitoring• Reconfigurable Electronics
Survivable ElectronicsPrecision effects with smaller, low profile munitions pressing requirement for current and future platform effectiveness
• Robust electronics in extreme environments (shock, vibration, thermal)
Issues:•Cost & Weight•Scale-up•Durability
Integrated Power harvesting, storage, and management
Today
Future
Lewis
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Technology Development Strategy
• Accelerate development and transition of FHE
technologies to Air Force functional materials community
• Phased plan for FHE technology insertions
Embedded Sensors & Structural Antennas
Rugged Flexible Electronics
Human Performance
Conformal Antennas
15 16 17 18 19 20 21 22 23
Critical Pre-requisites:
• Composite Certification
• Hybrid-Materials Design
Critical Pre-requisites:
RPA Demo
AM Design Rules
• Improved Conductive
& Dielectric Inks
• Qual. Risk Reduction
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Plasma Spray Direct WriteMesoScribe Technologies
Conformal & Integrated Antennas
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Integrated Direct Write Electronics
PM: Ted Finnessy, AFRL/RXME
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-to-
digital convertor
• Complete TRL/MRL assessment
• Fabricate and test
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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.
• Design and direct-write Cu antenna onto
servo cover using plasma spray technique.
• Minimize co-site interference by installing
onto unique locations of aircraft.
Phase I Results
• Indoor range data showed VSWR and
directivity comparable with COTS
components.
• Cu removal from part required a grinder.
• Significant directivity benefit in cross-
polarization performance due to location
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Ford Demo: Ford Focus Console Thermoformed Silver Ink Electronics
Automotive: Printed Console Electronics
Air Force could achieve similar benefits such as elimination/reduction of wire harnesses in aircraft.
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Moving Beyond Commercially Available
Human SensorsAF 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.
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Potential for Human Monitoring
FHE Devices
Flexible Hybrid Oral Biochemistry Sensing SystemSensing lactate as indictor for fatigue.
Numerous FHE materials & manufacturing challenges must be
overcome to enable reliable & durable wearable sensing platforms.
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Flexible Materials & DevicesResearch Leader: Dr. Benji Maruyama
Developing critical Materials & Processes to enable flexible hybridelectronic systems for airman performance monitoring
……..lightweight, flex/stretch, conformal, multifunctional, robust, autonomous
Novel materials• Inherently strain-resilient• Wafer thinning• Liquid metals
Innovative packaging schemes• Flex and performance• Ensure survivability
Conformal & integrated printing approaches• Rapid design cycle• Enables retrofit• Tailored materials and
properties
AMI
Harvard
Rogers
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Integration & Packaging of Human
Monitoring Components
Exposed 1-layer graphene
Single Layer Graphene Biosensor (G-FET)
16X Mag
CommPower
LogicSense A, B, …
► Flex Battery
► NFC
► Photovoltaics
► Microcontroller
► ADC chip
Challenges:
► Reliable, low-resistance interconnects
► Energy dense & flexible batteries
► Biosensor platform development
► Integration into stretchable form-factor
► Printed antennas & interconnects
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In-House Additive Manufacturing Capabilities
16
Aerotech Motion Control Stage
Multiple interchangeable dispensing configurations
In-Line Multi-Material dispense point
CUSTOMIZABLE MOTION
CONTROL STAGE
VERSATILE
AEROSOL JET PRINTING
Optomec Aerosol Jet Deposition System
Fine features (≥ 10 µm)
Thin layers (≥ 100 nm)
Excellent accuracy & repeatability
Inherently clog resistant
HIGH RESOLUTION
Microfab JetLab 4xl-A
Good balance between cost and performance
Drop-on-Demand microdispensing
~10 µm minimum line width
INKJET PRINTING
LOW COST
POLYJET PRINTING
Objet Connex 3 3D Printer
Solid 3D structures
UV-curable polymers
Rigid and flexible materials
Up to 82 material characteristics in one print
3D PROTOTYPING
nTact nRad Extrusion Coating System
20 nm to 100 µm Coating Thickness
Scalable
Selected area coating capable
SLOT-DIE COATING
LARGE AREA
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Gallium Liquid Metal Alloys (GaLMAs)
Gallium Alloy PropertiesMP < 0C
Viscosity ≈ WaterVapor pressure ≈ 0
Electrically conductiveNon-Toxic
Room Temperature Liquid Electronics
Reconfigurable
FlexibleStretchable
Liquid Metal encapsulated in Elastomer3D Electronics
Led by Chris Tabor in collaboration with Michael Dickey (NCSU)
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On Going ProgressAcid/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
Ga2O3 + 6HCl → 2GaCl3 + 3H2O
Mechanically Rigid, Continuous Surface
Individual Hydrated Metal Chlorides
HCl
React with the Oxide Modify the Oxide
OH
OH
OH
OH
OH
OH
Oxide
- H2O
Metal
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GaLMA Printing and ProcessingAdditive Manufacturing with Liquid Metals
Freestanding 3-D Liquid Electronics
Aerosol Jet Printing GaLMA Inks
Filament Extrusion of GaLMAs
There are a variety of approaches being explored
to accurately print and define GaLMA structures
Cook et al. in prep.
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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
Soft Electronics for Survivability
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Developing Printed Electronic Components
4. Printed
Electronic
Component
3. Ink Design
1. Printer Design
2. Printing Technique
Motion system
Motion controller
Interface software
Scripting language
Deposition system
Imaging
Alignment tools
Computer
…
Particulates
Reactive elements
Rheological modifiers
Solvents
Binders
Surface energy modifier
Stabilizers
…
Path planning
Loading protocol
Cleaning protocols
Alignment techniques
Stop-start compensation
…
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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
Close-up view of 3D printer setup (left) and optical image of
layered PVDF-HFP filaments (right). Scale: 100 μm
Material Conductivity
(S·cm-1)
Strain to
Failure
Bulk Cu 6.0·105 0.55
Bulk Ag 6.3·105 0.6
Silicone (SE1700) - 355
Ag in TPU 1.7·104 TBD
Ag in PMMA 8.0·102 TBD
Ag in SE1700 6.1·103 TBD
Ag in PVDF-HFP 2·104 TBD
Dupont (PE872) 4·103 TBD
Quantification of relationship between Ag loading, matrix and mechanical
properties currently underway.
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Flex Printer
• 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
PDMS
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Polymers for Flex Cap Printing
• Thin films (<20 µm)
• Poly(propylene)
• Poly(styrene)
• Poly(methyl
methacrylate)
• Poly(vinylidene
fluoride-co-
hexafluoropropylene)
𝜀𝑟𝐸𝐵𝐷 =𝑉𝐵𝐷𝐶
𝜀0𝐴
𝐶 = 𝜀0𝜀𝑟𝐴
𝑑
Ultraflex Flex 2801
PVDF-HFP
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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
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Control of Dielectric Film
• Printing offers good control of film thickness
• ~10 min/layer to print
• Little evidence of aging or relaxing of process-
related internal structure
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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 : 0.1 - 0.2 nF
Heig
ht (µ
m)
Position (mm)
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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
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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., 2015
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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
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Questions?
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Printing vs Conventional Casting
• Some minor morphological difference were
observed but mostly higher thicknesses
• Printed films matched dielectric behavior of
cast films