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While the conventional electronics like computers and smartphones is built around silicon integrating billions of transistors and is manufactured using complex, costly and wasteful processes in multi-billion dollar foundries , The printed and flexible electronics aim to replace this by “organic” semiconductors which are long chains of thousands of repeating molecules (a plastic), made with materials based on carbon. Organic semiconductors can be made to be soluble, and can be turned into an ink.
This means it’s possible to print electronic circuits, with the potential to manufacture components as fast as printing newspapers. The conductive ink is typically used to make a conductive trace or a simple component (like an antenna) which is printed onto Thermoplastic Polyurethanes (TPUs), polyester or kapton. A printer would do this by applying different inks onto the film. As the inks dried, they would turn into wires, transistors, capacitors, LEDs and all the other things needed to make displays and circuits. This fast-growing technology makes it possible to print circuits, sensors, memory, batteries and displays, all onto thin, lightweight, flexible substrates.
Printed and Flexible electronics have already started to appear in our daily lives, for example in car manufacturing with printed aerials, smart textiles with pressure sensors to recognize seat occupancy and self-dimming rearview mirrors, or in the medical field with medical test strips with diagnostic electrodes. Engineers at the University of California San Diego have developed a flexible wearable sensor that can accurately measure a person’s blood alcohol level from sweat and transmit the data wirelessly to a laptop, smartphone or other mobile device.
Researchers at the University of Tokyo have developed “optoelectronic skin”, with an ultra-thin, flexible LED display that can be worn on the back of your hand. China has developed a new electronic paper, heralded as “the world’s first graphene electronic paper,” by Chen Yu, general manager of Guangzhou OED Technologies. The material can be used to create hard or flexible graphene displays, used in electronic products such as e-readers and wearable smart devices.
Printed and flexible electronics have thus far failed to achieve widespread adoption due to significant unresolved technical challenges. Major gaps exist between expectations and performance of printed electronics in the areas of logic, memory, analog circuitry, power, and light generation. Flexible Hybrid Systems is a Combination of flexible printed materials and flexible silicon-based ICs to create a new class of flexible electronics.
The convergence of the use of PFE, with its advantages in available envelope and format, with the performance of conventional electronics has become known as the hybrid approach. A PFE hybrid is created when nonprinted technologies, such as single crystalline silicon ICs, are integrated with PFE. Flexible hybrid integration of printed electronics and conventional silicon ICs has become an accepted near-term solution for flexible system commercialization.
FHE leads the next revolution in electronics; it is the technology that will enable much of the Internet of Things and a generation of electronics in novel forms and mediums. FHE enables the attachment of ultra-thin semiconductor/sensor devices to flexible, conformable, stretchable substrates, such as fabrics or aircraft wings, or to flexible systems such as soft robotic exoskeletons and prosthetics. These technologies can be leveraged to improve devices and components by reducing the footprint and volume, directly applying them to an item or substrate, and integrating devices into common current products, says NextFlex.
Military Applications
Printed electronics are largely being adopted in the aerospace & defense industry owing to their lightweight, less complexity, and high reliability, which ultimately results in their low maintenance requirements. Moreover, R2R printed electronics technology reduces wiring in different systems used in aircraft that include in-flight entertainment systems and aircraft structural health monitoring systems. Needed for displays, antenna, SHM, eGear, eTextiles, eHarvesting. Rollability for stowage and transportation.
Dr. Pellegrino, of the Sensors and Electron Devices Directorate, said he would describe the Army’s approach to flexible electronics, beginning with a discussion of the term itself. The word “flexible,” he said, is important in itself, but along with flexibility come other attributes: “it can be inherently rugged, is likely to save packaging weight and cost, and can be printed by a roll-to-roll or other large-scale and efficient process.” All these attributes have value for the Army; for example, a flexible or “conformable” material may have great medical value, such as the ability to incorporate various multifunctional sensors that detect situational awareness, stress, fatigue, or mental function, or to place sensors in conformable bandages.
Sensors in flexible materials may be used by the military not only for people, but also for vehicles, engines, or temporary structures. Many applications of flexible displays, he said, can find similar or even identical uses in both the military and the civilian commercial marketplace. The military versions may have to be packaged more ruggedly to endure operation in extreme environments, such as higher temperature or lower humidity, with no change in capability. The military also likes to be an early adopter, he said, so it can maintain a technology edge and give its soldiers an advantage.
In some prognostic and diagnostic technologies, he said, the aircraft industry is in a position of leadership, having learned to place various sensors on airframes and air structures. Although these structures are not strictly regarded as flexible, they are carrying the kinds of cheap, printed electronics that can be situated in many ways. Such applications can be adapted directly into the military for use in both helicopter and general aviation.
A central need for the military is tracking the enormous flow of equipment and material that flows overseas and returns to the United States. A current goal, said Mr. Pellegrino, is to make better use of electronic circuits that can be placed easily on every kind of equipment and tracked accurately. He noted the leadership of Wal-Mart in this area, which has pioneered the use of printable electronic labels and other tracking devices for merchandise.
Beyond the level of sensors and circuits, he said, the Army would explore larger arrays and grids of devices that could be manufactured by a roll-to-roll or hybrid process. These arrays and grids, which could gather both geospatial and temporal information, might include flexible solar cells on tents, mess halls, or other structures in the field, generating their own power at efficiencies of at least 30 percent. This would reduce the logistical load of transported fuel. Already, he said, a number of balloons, airships, and other aerostats gather visible and some infrared data nearly around the clock, but their sensor pods are fairly expensive and require maintenance. These drawbacks could be reduced by turning the skin of the aerostat into a large-area sensor, coupled with a large-area charging device to provide some of its power. He said that the Army is also studying the use of sensors and reconfigurable antennas on the skin of aerostats, micro air vehicles, or small unmanned aerial vehicles.
Another area of rapid development, Dr. Pellegrino said, is microautonomous systems, such as microrobotics. In partnership with the Michigan Center for Microelectronics and Sensors, the Army is studying a number of handheld devices that can be released into urban buildings, for example, to gather information about hostages, weapons caches, and other conditions. Some concepts include various “backpackable” units that can release smaller robots capable of walking, flying, crawling, or hopping while carrying various sensors in their skins. These skins can also contain conformable photocells and antennas.
Dr. Pellegrino said that the current challenge is to integrate the many different building blocks that exist in bits and pieces—imaging sensors and arrays, energy harvesting and storage, manufacturing and packaging, multiscale modeling and simulation—into a coherent industry. He said that “first substantiations” of many of these applications had been achieved, including the order-of-magnitude improvement of mobility and stability over what is currently available in amorphous silicon technology. The primary “pacing issue,” he said, is the manufacturing and packaging technologies. “The people driving the applications would buy any of these things, this instant, if they existed,” he said. “They do exist, in configurations of ones and twos, but I can’t go place an order for 10,000 this afternoon.”
Developing the needed manufacturing science and capability, he said, depends on multiple complex challenges, such as reliability, resolution, placing the needed structures on the substrate, and encapsulation of large areas. “We believe there are lots of solutions potentially out there, but we need to integrate them for specific applications. We need to focus on applications, but also on the manufacturing to enable those applications. Then those orders will come.”
In the area of portable electronics, he said, a primary opportunity is to work at low cost. This is a result of moving past the current industrial approach of using foundries and masks into thinking in terms of custom design and rapid prototyping. “This is unique,” he said. In fact, he said, some tasks done by conventional processing take about six weeks, but with printing can be done in about six days. “There will be tremendous savings when we are able to print,” he said. “But you have to achieve the performance to make this more interesting.”
Dr. Shenoy, a program officer at the Microsystems Technology Office (MTO) at DARPA, reviewed some of the most promising and application-rich areas, including thermal applications, portable imaging technologies, and imaging sensors integrated with amplifying circuitry. In the last area, he said, neither the sensors not the amplifiers were yet good enough, and DARPA was working to address those challenges. Like Dr. Pellegrino, he emphasized the promise of physiological monitoring for warfighters, in which sensors could continuously monitor vital signs; he also mentioned structural prognostics, by which sensors could be placed on platforms to continuously monitor wear and tear on systems.
Other building blocks for printable electronics include operational amplifiers, which have been used for many years in conventional electronics. The current research question, he said, is whether this performance can be improved using printable electronics technologies, which would enable sensors that are flexible, can be distributed, and have other advances of flexible electronics. “The other building blocks are also very important,” he said, “including batteries that are printable. The challenge is really to improve the technology by developing the specific components, assigning performance metrics to them, and showing that we can actually achieve those metrics.”
The U.S. Department of Defense (DoD) has much interest in physical flexibility in electronic designs, to the extent that the DoD has made healthy investments in electronic innovator NextFlex. These investments include a recent $154 million award for an Army-led flexible electronics project. Department of Defense Secretary Ashton Carter visited Silicon Valley to awarded NextFlex $75 million in federal funding and announce a cooperative agreement to establish this Manufacturing Innovation Institute. The U.S. is to some extent playing catch up.
Formed in 2015, NextFlex is a consortium of companies, academic institutions, nonprofit organizations, and government organizations with a shared goal of advancing the U.S. position in flexible hybrid electronics (FHE) technology. The list is long and impressive, and includes Analog Devices, BAE Systems, Raytheon Technologies, WL Gore & Associates, Purdue University, and the University of Maryland.
NextFlex is working on numerous sensor projects, and Art Wall, director of fab operations at NextFlex, said that he is seeing opportunities for flexible and printed sensors in the military and consumer spaces. “Both military and civilian-focused companies have looked at what we have done in the flexible microcontroller space and realized that if we could attach or build flexible sensors compatible with the flexible microcontroller architecture, you’ve taken something that’s interesting and really made it applicable – something that people really can make use of,” Wall said. “We’re taking tech demonstrations and adding sensor capabilities that can make them a true product.”
The need for durability in the field versus mechanical shock and vibration is clear for many electronic devices, and flexibility built into components such as power supplies and display screens can make a difference in operating lifetimes for many devices. NextFlex is pursuing the development of flexible hybrid electronics (FHE) rather than conventional flexible circuits, with FHE combining printed circuits and components with discrete devices, such as silicon CMOS-based microprocessors and memory (see the figure). FHE technology is a viable candidate for many different types of wearable military electronic health monitors. It is also projected to have tremendous potential for a wide range of commercial electronic applications.
Phase is an important electrical parameter in many military electronic systems, and the phase behavior of FHE-based designs must be studied before the technology can be applied to critical electronic designs. The phase will vary with flexure but, by combining rigid integrated circuits (ICs) and printed circuits on flexible substrates, it is hoped that variations can be minimized and that FHE technology can be applied extensively to durable military electronic devices.
The NextFlex Manufacturing Innovation Institute works with the U.S. Army Combat Capabilities Development Command’s Army Research Laboratory (ARL) and entered into a second cooperative agreement with the U.S. Air Force Research Laboratory (AFRL). As part of the agreements, NextFlex attempts to commercialize FHE prototype circuits developed for the military as part of efforts to establish U.S. leadership in the technology.
“Flexible hybrid electronics is a new way to manufacture electronics that brings together digital additive manufacturing with traditional electronic components,” said Dr. Eric Forsythe, an Army physicist and government program manager for NextFlex. The FHE technology is projected to provide many advantages for future communications and sensor designs in command, control, communication, computers, cyber, intelligence, surveillance, and reconnaissance (C5ISR) systems.
Flexible Hybrid Systems (FHS)
FHS is a flexible electronics hybrid that is differentiated by the utilization of flexible silicon-on-polymer (SoP) ICs rather than conventional packaged ICs or bulk silicon bare die for the single crystalline silicon devices. SoP is a single crystalline IC technology that results from the conversion of conventional silicon wafers to SoP by replacing the majority of the silicon wafer with a polymer. SoP ICs retain the functionality of conventional devices, but are fully flexible and ultra thin.
FHS is a hybrid technology that utilizes SoP to provide the performance that PFE needs and the format that conventional packaged ICs or bare die cannot reliably provide. SoP has the capability to mitigate the reliability issue by having deformation characteristics much closer to PFE than bulk silicon
This approach addresses the full technology solution necessary for modern electronic products in the desired flexible format. FHS can include power sources and displays as part of the hybrid integration.
An FHS approach allows the ability to deliver a spatially distributed response to signals from spatially distributed sensing. With the ability to deploy sensors integrated with adequate processing and communication comes the opportunity for truly ubiquitous applications—smart surfaces, closed-loop diagnostics and therapeutics, and real-time monitoring of individuals or structures.
ITRI, SEMI, CGU and NTSU Jointly Develop Flexible Hybrid Electronics Technology for Precision Sports
To promote precision sports, ITRI, SEMI, Chang Gung University, and National Taiwan Sport University signed an agreement in Sep 2018 to jointly develop flexible hybrid electronics and to formulate a developmental blueprint for related industrial technology. Focus will be on smart wearable products that will assist the athletic community in collecting and analyzing data.
Dr. Chih-I Wu, ITRI’s Vice President and General Director of Electronic and Optoelectronic System Research Laboratories, remarked that ITRI’s Flexible Hybrid Electronics Precision Motion Detection System utilizes wireless transmission technology to transfer myoelectric signals from the wearer of the device to a computer, and then uses algorithms to interpret muscle strength and fatigue. Integrated knowledge in various aspects of athletic training, the results can then be used in the course of training athletes or assisting in coaches’ tactical decisions.
Over the long run, the technological applications will be extended to the textile industry to assist in the development of smart clothing technology and help the industry move into high added-value markets.
AFRL, NextFlex collaboration on National Security
Lightweight, low-cost and flexible electronic systems are the key to next-generation smart technologies for military as well as consumer and commercial applications.
NextFlex describes FHE as the intersection of additive circuitry, passive devices, and sensor systems that may be manufactured using printing methods (sometimes referred to as printed electronics) and thin flexible silicon chips or multichip interposer structures. These devices take advantage of the power of silicon and the economies and unique capabilities of printed circuitry to form a new class of devices for IoT, medical, robotics, consumer and communication markets. FHE devices conform to any shape, but are also bendable, twistable, and stretchable.
An Air Force Research Laboratory-led project in conjunction with NextFlex, America’s Flexible Hybrid Electronics Institute, has resulted in the first ever, functional samples of flexible Arduino circuit board systems made by using a flexible hybrid electronics manufacturing process, setting the stage for smart technologies for the internet of things and sensor applications like wearable devices.
“The possibilities for FHE (flexible hybrid electronics) technology are virtually limitless,” said Dr. Benjamin Leever, AFRL Advanced Development Team leader and NextFlex government chief technology officer. “Proving the manufacturability of this technology through an open-source platform will expand FHE’s reach even further by providing everyone from industrial product developers, to high school students, the opportunity to innovate on new electronics concepts.”
An Air Force Research Laboratory-drove venture in conjunction with NextFlex, America’s Flexible Hybrid Electronics Institute, has brought about the main ever, practical examples of adaptable Arduino circuit board frameworks made by utilizing an adaptable crossover gadgets fabricating process, setting the phase for savvy advancements for the web of things (IoT) and sensor applications like wearable gadgets.
The form factor of electronic devices is often limited by traditional microcontrollers, which are fragile and rigid in design, complicating their integration with newer devices that may be flexible or curved in design, such as a smartwatch, or located in a difficult-to-access place, like a fuel tank sensor. The flexible Arduino can enable rapid innovation in flexible and wearable devices for applications including monitoring hydration status, glucose levels, heartrate and more.
Arduinos are microcontrollers, or incorporated circuits, that are programmable through open-source programming. While business gadgets commonly incorporate exclusive microcontrollers, Arduino can be utilized by anybody to rapidly model an electronic gadget. The adaptable Arduino can empower fast advancement in adaptable and wearable gadgets for applications including observing hydration status, glucose levels, heart rate and that’s only the tip of the iceberg.
In the process of developing the flexible hybrid device, the NextFlex team reduced the number of manufacturing process steps by more than 60 percent and the weight of the circuit by 98 percent, ultimately increasing the possibilities for design applications. This was achieved by replacing the traditional circuit board with a thin, flexible plastic sheet, eliminating the traditional microcontroller packaging, and implementing digital printing processes for circuit elements. The high performance of a traditional microcontroller circuit is maintained through this combination of surface-mounted and printed features.
“As we look to innovation from non-traditional sources, the flex Arduino can enable inventors inside and outside the Air Force to quickly demonstrate new flexible electronics concepts,” said Leever. “Moreover, the FHE manufacturing processes demonstrated by NextFlex in this project will be transformational for a number of Air Force applications. This technology may enable us to monitor the structural integrity of aircraft through sensors embedded in the wings or similarly monitor the real-time performance and health of an Airman through flexible sensor patches.”
“As we look to innovation from non-traditional sources, the flex Arduino can enable inventors inside and outside the Air Force to quickly demonstrate new flexible electronics concepts. Moreover, the FHE manufacturing processes demonstrated by NextFlex in this project will be transformational for a number of Air Force applications. This technology may enable us to monitor the structural integrity of aircraft through sensors embedded in the wings or similarly monitor the real-time performance and health of an Airman through flexible sensor patches,” Benjamin Leever, the AFRL Advanced Development Team leader, and NextFlex Government Chief Technology Officer said.
NextFlex Launches $10 Million Funding Round for Flexible Hybrid Electronics Innovations in Aviation, Digital Health and National Security
NextFlex®, America’s Flexible Hybrid Electronics (FHE) Manufacturing Institute, released Project Call 4.0 (PC 4.0) in August 2018 — the latest call for proposals to fund projects that seek to further the development and adoption of FHE.
Project Call 4.0’s very diverse scope of needs represents technology and capability gaps that have been determined by the community over a wide range of application areas — from digital health to commercial aviation to national security needs. These areas cover the spectrum from encapsulation technologies for wearables, high performance and high layer count FHE, to 3-dimensional electronic design software, solutions for challenges in e-textiles, biochemical monitoring platforms and lightweight.
The project proposals should focus on the following manufacturing thrust areas (MTA): FHE device encapsulation, High layer count FHE processing with IC interface demonstration, Evaluation and development of connectors for FHE devices and e-textiles, Development of a carrier system appropriate for sheet-to-sheet FHE manufacturing, Advanced 3D electrical design software
Flexible battery integration and reference designs
To demonstrate these manufacturing capabilities, project proposals can focus on the following: Lightweight flexible electronics platform for UAVs and drones, Large-area sensor systems for structural health monitoring, and Minimally invasive wearable flexible devices for monitoring of fluid-based biomarkers.
The FlexTech Alliance
Formed in 2015 through a cooperative agreement between the US Department of Defense (DoD) and FlexTech Alliance, NextFlex is a consortium of companies, academic institutions, non-profits and state, local and federal governments with a shared goal of advancing U.S. Manufacturing of FHE. By adding electronics to new and unique materials that are part of our everyday lives in conjunction with the power of silicon ICs to create conformable and stretchable smart products, FHE is ushering in an era of “electronics on everything” and advancing the efficiency of our world.
The U.S. Department of Defense (DoD) has awarded FlexTech Alliance a Cooperative Agreement to establish and manage a Manufacturing Innovation Institute (MII) for Flexible Hybrid Electronics (FHE MII). FlexTech Alliance comprises 96 companies, 11 laboratories and non-profits, 42 universities, and 14 state and regional organizations.
“Flexible Hybrid Electronics (FHE) is an emerging technology that has the potential to reshape the electronics industry. Electronic devices can now be printed and attached to flexible, conformal materials like fabric or curved surfaces.” FHE has the potential to re-shape entire industries, from the electronic wearable devices market, to medical health monitoring systems, to the ubiquitous sensing of the world around us – also known as the Internet of Things.
FHE has wide range of applications from US military exploring FHEs for wearable electronics and beyond defense, including automotive, communications, consumer electronics, medical devices, health care, transportation and logistics, and agriculture. Flexible hybrid electronics, an emerging manufacturing capability, enables the integration of thin silicon electronic devices, sensing elements, communications, and power on non-traditional flexible substrates.
To be successful, the Institute will need to engage aspects of the integrated circuit (IC) industry, the graphics printing industry, and the electronic assembly/packaging industry. To complement the San Jose hub, key technology nodes will be linked and include IC thinning, system design and fabrication, integration and assembly, and FHE applications.
FHE Roadmap 3.0
The Institute will leverage the electronics industry and the high-performance printing industry, both well-established US industrial and academic areas of strength. A comprehensive roadmap was developed in collaboration with industrial partners, academics, and subject matter experts (SMEs) in a variety of fields.
The roadmap topics included different facets of application-specific devices/components for technology demonstration as well as various aspects covering design, materials, process, equipment, and test development that would enable realizing advanced manufacturing capabilities to meet the overall vision of the Institute and the FHE eco-system. The following topics were the focus of the Technical Working Groups that developed the roadmap:
Manufacturing Thrust Area (MTA)
- Device Integration and Packaging
- Printed Flexible Components and Microfluidics
- Materials
- Modeling and Design
- Standards, Test and Reliability
Technology Platform Demonstrators (TPD)
- Human Health Monitoring Systems
- Asset Monitoring Systems
- Integrated Array Antennas
- Soft & Wearable Robotics
Project Call 3.0 Details
Project Call 3.0 (PC 3.0) focuses on areas identified in the Flexible Hybrid Electronics (FHE) Roadmap developed by NextFlex Technical Working Groups.
PC Topic MTA 3.1: Printed Circuit Elements for RF and High-Speed Applications ($750K maximum government funds): Prototype and demonstrate direct-write printing of RF and high-speed circuit features and characterize electrical performance over frequency range, 1 MHz – 50 GHz. Applications for rapid prototyping and custom designs of RF circuits, antennas, hybrids, amplifiers, meta-materials, etc. Demonstrate the following attributes in prototypes for electrical characterization:
- Low resistance conductors and low dielectric material printing
- Printed RF transmission lines, differential pairs, waveguides and power dividers
- Low-loss chip interconnections including all printed connections
- Printed power/ground planes for impedance control
- Antenna elements; broadband, narrowband, beamforming, phased array, meta-material, FSS
- Cooling and heat management for high power
- Characterize conductor electrical stability over temperature
- Characterize conductor surface roughness and skin effect (as appropriate)
PC Topic MTA 3.2: Printed Passives for FHE including Materials, Tools, and Process Documentation ($500K maximum government funds): Projects in this topic area will produce optimized printing process recipes (including materials, equipment, and process) for passive components such as resistors, capacitors, and inductors. The resultant effort should improve the consistency and accuracy in tolerance for these printed passive elements from current state of the art. The target tolerance for printed passive components is ±10%. Printed passive proposals should include preliminary cost models as a comparison between printed passives and pick-and-place fully yielded components. The proposed program should include consideration and a proposed design for in situ test and repair of passives, but not necessarily demonstrating the capability in this phase.
PC Topic MTA 3.3: Z-Axis Interconnect and Via Formation ($200K maximum government funds): Projects in this topic area will identify best practice methods and process for producing Z-axis interconnects in FHE devices on multi-layer organic and film substrates. Various via formation methods may be utilized using conductor deposition techniques compatible with FHE. If laser processing is used, then the wavelength, pulse profile, and other process parameters should be documented so that the process may be reliably reproduced. In addition to the via formation, conductive interconnection in the z-axis should be tested and characterized, and basic reliability tests on these should be carried out.
PC Topic MTA 3.4: Additive and Semi-Additive Manufacturing Methods for High Density Interconnects ($500K maximum government funds): The objective of this project topic is to identify the most suitable additive or semi-additive manufacturing technologies for producing high density flexible circuits, defined as line width and spacing less than or equal to 50 μm. Additive manufacturing methods have shown promise in reducing manufacturing cost compared to subtractive, lithography based, approaches. Therefore, technologies proposed should show some potential cost reduction compared to current printed circuit board manufacturing methods as one factor. Proposed technologies should be able to achieve sheet resistances of 10 milliohms per square per mil or less; which is comparable to a 2-micron thick copper foil. Preference will be given to technologies enabling layer counts of two or more; especially those with functioning through vias
Flexible Electronics market
Market size from 2016 to 2026 IDTechEx find that the total market for printed, flexible and organic electronics will grow from $26.54 billion in 2016 to $69.03 billion in 2026. The majority of that is OLEDs (organic but not printed) and conductive ink used for a wide range of applications. On the other hand, stretchable electronics, logic and memory, thin film sensors are much smaller segments but with huge growth potential as they emerge from R&D.
Thin, flexible and printed batteries have the potential to be widely used in wearable and medical devices and will reach a market of over $400 million in a decade, according to IDTechEx report Flexible, Printed and Thin Film Batteries 2015-2025: Technologies, Forecasts, Players.
References and resources also include:
https://www.techexplorist.com/afrl-nextflex-creating-flexible-circuit-system/11309/
