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The unique physicochemical properties of non-Ti-MXenes make them excellent class of materials for flexible and wearable electronics.
Abstract Substantial effort has been devoted to both scientific and technological developments of wearable, flexible, semitransparent, and sensing electronics (e.g., organic/perovskite photovoltaics, organic thin‐film transistors, and medical sensors) in the past decade. The key to realizing those functionalities is essentially the fabrication of conductive electrodes with desirable mechanical properties. Conductive polymers (CPs) of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) have emerged to be the most promising flexible electrode materials over rigid metallic oxides and play a critical role in these unprecedented devices as transparent electrodes, hole transport layers, interconnectors, electroactive layers, or motion‐sensing conductors. Here, the current status of research on PEDOT:PSS is summarized including various approaches to boosting the electrical conductivity and mechanical compliance and stability, directly linked to the underlying mechanism of the performance enhancements. Along with the basic principles, the most cutting edge‐progresses in devices with PEDOT:PSS are highlighted. Meanwhile, the advantages and plausible problems of the CPs and as‐fabricated devices are pointed out. Finally, new perspectives are given for CP modifications and device fabrications. This work stresses the importance of developing CP films and reveals their critical role in the evolution of these next‐generation devices featuring wearable, deformable, printable, ultrathin, and see‐through characteristics.
Provided herein are skin-mounted biomedical devices and methods of making and using biomedical devices for sensing and actuation applications. For example, flexible and/or stretchable biomedical devices are provided, including electronic devices useful for establishing conformal contact with the skin of a subject. Devices disclosed herein can comprise a plurality of sensing and/or actuating devices provided as part of a skin-mounted flexible or stretchable electronic circuit.
Abstract Automatic segmentation of key microstructural features in atomic-scale electron microscope images is critical to improved understanding of structure–property relationships in many important materials and chemical systems. However, the present paradigm involves time-intensive manual analysis that is inherently biased, error-prone, and unable to accommodate the large volumes of data produced by modern instrumentation. While more automated approaches have been proposed, many are not robust to a high variety of data, and do not generalize well to diverse microstructural features and material systems. Here, we present a flexible, semi-supervised few-shot machine learning approach for segmentation of scanning transmission electron microscopy images of three oxide material systems: (1) epitaxial heterostructures of SrTiO 3 /Ge, (2) La 0.8 Sr 0.2 FeO 3 thin films, and (3) MoO 3 nanoparticles. We demonstrate that the few-shot learning method is more robust against noise, more reconfigurable, and requires less data than conventional image analysis methods. This approach can enable rapid image classification and microstructural feature mapping needed for emerging high-throughput characterization and autonomous microscope platforms.
Smart contact lens has drawn extensive research interests due to the noninvasive real-time detection of the human body to provide biomedical information for health management. However, it has been difficult to accurately measure the physiological signals in tears, and the use of external power source has also hindered the future applications. Here, we demonstrated an organic electrochemical transistor based multiplexed sensors self-powered by the organic solar cells (OSCs). The integrated device was fabricated via simple process including solution blade-coating and thermal evaporation. OSCs were optimized to provide optimal operation voltage for the sensors that exhibit semilog-linear response to the glucose and calcium ions in tear fluids without any peripheral circuits. The sensing signals can be transmitted to the laptop wirelessly through a near filed communication unit. This integrated self-powered multiplexed sensing device will provide real-time monitoring of the biomarkers in tears, prospected to be installed on the smart contact lens for the early detection and diagnosis of diabetes.
Supercapacitors are widely recognized as a favorable option for energy storage due to their higher power density compared to batteries, despite their lower energy density.
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In recent years, important progress has been made in developing design strategies, materials, and associated assembly techniques that provide empowering approaches to electronics with unconventional formats, ones that allow useful but previously hard to realize attributes of function. Notable examples of the progress made include: light weight, large area, high performance electronics, optics, and photonics; electronic and optical systems with curvilinear shapes and capacities for accommodating demanding forms of mechanical flexure; new device form factors for use in sensing and imaging; the integration of high performance electronics in 3-D with demanding nanometer design rules; functional bioresponsive electronics; and advanced hybrid materials systems for lighting, energy storage, and photovoltaic energy conversion. In this report we highlight advances that are enabling such promising capabilities in technology-specifically, the fabrication of device elements using high performance inorganic electronic materials joined with printing and transfer methods to effect their integration within functional modules. Here, we emphasize in this review considerations of the design strategies and assembly techniques that, when taken together, circumvent limitations imposed by approaches that integrate circuit elements within compact, rigid, and essentially planar form factor devices, and provide a transformational set of capabilities for high performance flexible/stretchable electronics.
This paper presents strain-effect transistors (SETs) based on flexible III-nitride high-electron-mobility transistors (HEMTs) through theoretical calculations. We show that the electronic band structures of InAlGaN/GaN thin-film heterostructures on flexible substrates can be modified by external bending with a high degree of freedom using polarization properties of the polar semiconductor materials. Transfer characteristics of the HEMT devices, including threshold voltage and transconductance, are controlled by varied external strain. Equilibrium 2-dimensional electron gas (2DEG) is enhanced with applied tensile strain by bending the flexible structure with the concave-side down (bend-down condition). 2DEG density is reduced and eventually depleted with increasing compressive strain in bend-up conditions. The operation mode of different HEMT structures changes from depletion- to enchantment-mode or vice versa depending on the type and magnitude of external strain. The results suggest that the operation modes and transfer characteristics of HEMTs can be engineered with an optimum external bending strain applied in the device structure, which is expected to be beneficial for both radio frequency and switching applications. In addition, we show that drain currents of transistors based on flexible InAlGaN/GaN can be modulated only by external strain without applying electric field in the gate. The channel conductivity modulation that is obtained by only external strain proposes an extended functional device, gate-free SETs, which can be used in electro-mechanical applications.
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A continuing program addresses the development of flexible multilayer electronic circuits and associated flexible cables. This development is undertaken to help satisfy aerospace-system-engineering requirements for efficient, lightweight electrical and electronic subsystems that can fit within confined spaces, adhere to complexly shaped surfaces, and can be embedded within composite materials. Heretofore, substrate layers for commercial flexible circuitry have been made from sheets of Kapton (or equivalent) polyimide and have been bonded to copper conductors and to other substrate layers by means of adhesives. The substrates for the present developmental flexible circuitry are made from thin films of a polyimide known as LaRC(TM)-SI. This polyimide is thermoplastic and, therefore, offers the potential to eliminate delamination and the need for adhesives. The development work undertaken thus far includes experiments in the use of several techniques of design and fabrication (including computer-aided design and fabrication) of representative flexible circuits. Anticipated future efforts would focus on multilayer bonding, fabrication of prototypes, and overcoming limitations.
Printed electronics and sensors enable new applications ranging from low-cost disposable analytical devices to large-area sensor networks. Recent progress in printed carbon nanotube electronics in terms of materials, processing, devices, and applications is discussed on page 4397 by A. Javey and co-workers. Here, the research challenges and opportunities regarding the processing and system-level integration are also discussed for enabling of practical applications.
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n-Type organic/polymeric semiconductors with high electron mobilities are highly demanded for future flexible organic circuits. Except for developing a new conjugated backbone, recent studies show that side-chain engineering also plays an indispensable role in boosting the charge-transporting property. In this paper, we report a new polymer PNDI2T-DTD with a representative n-type naphthalene diimide (NDI)–bithiophene backbone for high-performance n-type flexible thin-film transistors through branching/linear side-chain engineering strategy. Serving as the flexible side chains, the linear/branching side-chain pattern is found to be effective in tuning the preaggregation behavior in solution and the packing ordering of polymeric chains, resulting in the improvement of thin-film crystallinity. We report the electron mobility of the thin film of PNDI2T-DTD on flexible substrates can reach 1.52 cm 2 V –1 s –1 , which is approximately five times higher than that of PNDI2T-DT with the same conjugated backbone and only branching alkyl chains.
Stretchable electronic sensing devices are defining the path toward wearable electronics. High-performance flexible strain sensors attached on clothing or human skin are required for potential applications in the entertainment, health monitoring, and medical care sectors. In this work, conducting copper electrodes were fabricated on polydimethylsiloxane as sensitive stretchable microsensors by integrating laser direct writing and transfer printing approaches. The copper electrode was reduced from copper salt using laser writing rather than the general approach of printing with pre-synthesized copper or copper oxide nanoparticles. An electrical resistivity of 96 μΩ cm was achieved on 40-μm-thick Cu electrodes on flexible substrates. The motion sensing functionality successfully demonstrated a high sensitivity and mechanical robustness. Furthermore, this in situ fabrication method leads to a path toward electronic devices on flexible substrates.
1. Session Proposal o Session Title NASA’s In Space Manufacturing and the On Demand Manufacturing of Electronics o Session Topic Primary -- Space Logistics, Autonomy, and Robotics; Secondary – Transformative Research and Technologies o Session Format: Panel Discussion. o Requested Session Duration: 60 minutes o Short Session Description: The goal of NASA’s On Demand Manufacturing of Electronics project is to develop and demonstrate the feasibility of a low-gravity, on-demand manufacturing system for flexible hybrid electronic devices on the International Space Station. This panel will feature several key collaborators and team members from the commercial sector, academia, and internal to NASA, each of which are contributing an unique and vital role to the design and implementation of this new technology system. o Extended Session Description (Please describe in detail the activity proposed, including how you intend to use the requested session duration. This session description will be provided to the reviewers for consideration and will not be displayed in the online agenda.): The session will be moderated by Curtis Hill, the Project Lead for the On Demand Manufacturing of Electronics (ODME), and he will start by giving a brief introduction to the ODME project which is working to produce a demo system for the manufacturing of electronic devices on the International Space Station. Panelists consisting of collaborators and team members to the ODME project will then give a brief (~5 min) introduction highlighting their contributions to the project, followed by time for Q&A from the audience. The panel will consist of: 1. Kenneth Church, nScrypt. nScrypt is a leader in multi-material printing with a modular system that incorporates a direct write thick film print head, a polymer fused filament fabrication print head, a laser sintering attachment, a drill head attachment for milling, and a pick and place. The system can print a layer and scan for accuracy of prints. The combination of multiple print heads and scanning allows for the on-demand production of intricate electronic components. 2. Andy Kurk, TechShot, Inc. Techshot, Inc. has collaborated extensively with NASA on the in space manufacturing of both printed electronics and fused metal materials. They are currently working to develop and integrate a test system for printed electronics, and a flight demonstration on the International Space Station is anticipated in 2024. 3. Ed Hendricks, NextFlex. NextFlex has the goal of advancing the manufacture of flexible hybrid electronics in the U.S. They are working with ODME on the development of AstroSense, an additively manufactured, wireless, flexible, and wearable health sensor. 4. Dr. Pradeep Lall, Auburn University. Professor Lall is the MacFarlane Endowed Distinguished Professor in the Department of Mechanical Engineering with a Courtesy Joint Appointment in the Department of Electrical and Computer Engineering and a Courtesy Joint Appointment in the Department of Finance. He is collaborating with NASA’s ODME project to develop multilayer printable devices and to develop techniques to test the quality of a printed electronic device. 5. Dr. Wei Gao, California Institute of Technology. Professor Gao is an Assistant Professor of Medical Engineering. His group is developing fully printed, flexible, and wearable biosensors for crew health monitoring in collaboration with NASA’s ODME project. In addition, they are working on using sweat to power biofuel cells for wearable, self-powered electronic devices. 6. Beth Paquette, NASA Goddard. The ODME branch at NASA Goddard is spearheading a sounding rocket flight demo to prove the capability of a printed electronic device with multiple sensors. In addition, they focus on thin film and flexible energy storage evaluations. o Session Goal(s)/Outcome(s): Please list the learning objectives and/or tangible outcomes (technical paper or other publication). The goal of this session is to highlight the internal and collaborative efforts of NASA’s On Demand Manufacturing of Electronics project to develop a system for printing electronics that will be tested on the International Space Station in 2024. In addition, the session with facilitate discussion with the community on the state of the art of printable electronics, current challenges, and new avenues for collaboration.
Electrides, with their excess electrons distributed in crystal cavities playing the role of anions, exhibit a variety of unique electronic and magnetic properties. In this work, we employ the first-principles crystal structure prediction to identify a new prototype of A 3 B electride in which both interlayer spacings and intralayer vacancies provide channels to accommodate the excess electrons in the crystal. This A 3 B type of structure is calculated to be thermodynamically stable for two alkaline metals oxides (Rb 3 O and K 3 O) . Remarkably, the unique feature of multiple types of cavities makes the spatial arrangement of anionic electrons highly flexible via elastic strain engineering and chemical substitution, in contrast to the previously reported electrides characterized by a single topology of interstitial electrons. More importantly, our first-principles calculations reveal that Rb 3 O is a topological Dirac nodal line semimetal, which is induced by the band inversion at the general electronic k momentums in the Brillouin zone associated with the intersitial electric charges. In conclusion, the discovery of flexible electride in combining with topological electronic properties opens an avenue for electride design and shows great promises in electronic device applications.
Rise in demand for wearable consumer electronics products has given an impetus to the development of flexible electronics technology encompassing flexible substrates and compatible circuitry. Also, additive manufacturing of flexible electronics is emerging rapidly via several techniques such as Inkjet and Aerosol Jet Printing (AJP). The basic component of all flexible circuits to be printed by these technologies is conductible ink, which is generally silver ink. Few studies exist on the printing of copper conductible ink and not many copper ink formulations are available in the market as that of silver inks. This study aims to develop a process development study for deposition of copper conductible lines on flexible substrates using the aerosol jet printing technology. The process development study includes investigation of photosintering parameters for obtaining desirable electrical resistance and shear load to failure values for the printed line. Different pre-drying techniques such as oven pre-drying and platen pre-drying have been used for improving the electrical and mechanical properties of the conductive traces. Techniques such as optical microscopy and white light interferometry have been used for the characterization of print quality of the conductible lines.