Development Of Stretchable Electronics Research Articles

신축성 전자소자를 위한 전도성 재료 인쇄의 최근 동향

Printed electronics received a great attention in both research and commercialization since it allows fabrication of low-cost, large area electronic devices on various substrates. Printed electronics plays a critical role in facilitating stretchable electronics since it allows patterning newly developed stretchable conductors which is difficult to be achieved with conventional silicon-based microfabrication technologies, such as photolithography and vacuum-based techniques. To realize printed electronics which is necessary for the development of stretchable electronics, printing technologies, formulation of conductive inks, and integration of functional devices have been widely investigated in the recent years. This review summarizes principles and recent development of printing techniques, materials for stretchable conductors and their applications in stretchable electronics using various printing techniques. The challenge is that only a few researches satisfying both excellent materials properties and good printability were reported. Future efforts will greatly expand the possibilities of using printed electronics for stretchable electronics.

Ultra‐robust stretchable electrode for e‐skin: In situ assembly using a nanofiber scaffold and liquid metal to mimic water‐to‐net interaction

AbstractThe development of stretchable electronics could enhance novel interface structures to solve the stretchability–conductivity dilemma, which remains a major challenge. Herein, we report a nano‐liquid metal (LM)‐based highly robust stretchable electrode (NHSE) with a self‐adaptable interface that mimics water‐to‐net interaction. Based on the in situ assembly of electrospun elastic nanofiber scaffolds and electrosprayed LM nanoparticles, the NHSE exhibits an extremely low sheet resistance of 52 mΩ sq−1. It is not only insensitive to a large degree of mechanical stretching (i.e., 350% electrical resistance change upon 570% elongation) but also immune to cyclic deformation (i.e., 5% electrical resistance increases after 330 000 stretching cycles with 100% elongation). These key properties are far superior to those of the state‐of‐the‐art reports. Its robustness and stability are verified under diverse circumstances, including long‐term exposure to air (420 days), cyclic submersion (30 000 times), and resilience against mechanical damages. The combination of conductivity, stretchability, and durability makes the NHSE a promising conductor/electrode solution for flexible/stretchable electronics for applications such as wearable on‐body physiological signal detection, human–machine interaction, and heating e‐skin. image

A Biologically Muscle‐Inspired Polyurethane with Super‐Tough, Thermal Reparable and Self‐Healing Capabilities for Stretchable Electronics

AbstractPolymeric elastomers play an increasingly important role in the development of stretchable electronics. A highly demanded elastic matrix is preferred to own not only excellent mechanical properties, but also additional features like high toughness and fast self‐healing. Here, a polyurethane (DA‐PU) is synthesized with donor and acceptor groups alternately distributed along the main chain to achieve both intra‐chain and inter‐chain donor‐acceptor self‐assembly, which endow the polyurethane with toughness, self‐healing, and, more interestingly, thermal repair, like human muscle. In detail, DA‐PU exhibits an amazing mechanical performance with elongation at break of 1900% and toughness of 175.9 MJ m−3. Moreover, it shows remarkable anti‐fatigue and anti‐stress relaxation properties as manifested by cyclic tensile and stress relaxation tests, respectively. Even in case of large strain deformation or long‐time stretch, it can almost completely restore to original length by thermal repair at 60 °C in 60 s. The self‐healing speed of DA‐PU is gradually enhanced with the increasing temperature, and can be 1.0–6.15 µm min−1 from 60 to 80 °C. At last, a stretchable and self‐healable capacitive sensor is constructed and evaluated to prove that DA‐PU matrix can ensure the stability of electronics even after critical deformation and cut off.

Selenophene and Thiophene-Based Conjugated Polymer Gels

Conjugated polymer gels are promising materials that are intrinsically stretchable and conductive, which may play an important role in the development of stretchable electronics. In this work, a series of thiophene and selenophene-based conjugated polymers with similar molecular weight and low dispersity were synthesized and the gelation conditions of these polymers were studied. The electrical performance of both thin and bulk films of these conjugated polymer gels were investigated. Blade-coated gels that form the highest quality films can achieve a similar charge carrier mobility as a spin coated sample, showing that gels are indeed promising electronic materials. The most promising gels were studied as a stretchable device. The initial application of strain appears to lead to the lower mobility; however, the device stabilizes and retains the same mobility from 18% to 40% strain. Finally, a new cycle-doping method was developed to successfully dope the bulk gels to yield conductive films. This method allows one to monitor the changes in conductivity as a function of doping to ultimately achieve the highest conductivity. The cycle-doping method appears to be superior to the commonly used dip-doping method. Overall this work expands on the types of conjugated polymers gels that are useful for electronics, stretchable electronics, and conductive materials.

Localized modulus-controlled PDMS substrate for 2D and 3D stretchable electronics

Stretchable electronics have great importance for applications of wearable devices and electronic skin. Balancing and improving mechanical stretchability and electronic performance are the key challenges that restrict further development of stretchable electronics. In order to achieve stretchable electronics, it is crucial to choose appropriate substrates, among which PDMS is the most commonly used polymer due to its easy fabrication and low cost. In this paper, we propose a novel strategy and fabricate localized modulus-controlled PDMS for both 2D and 3D stretchable electronics. Based on a secondary cross-link effect, the modulus of cured PDMS can be enhanced and controlled by spin-coating different masses of curing agent. Using a laser-cut PI mask, the modulus-enhanced region can be defined by users. Through this simple method, the functional conductive thin-film materials (gold/Ag nanowires/reduced graphene oxide) can be well protected when the structural layer is stretched and the ‘barrel effect’ of a multi-material film (where different material films possess different stretchability) on one piece of substrate can also be solved. Besides this, compared with uniform PDMS, different 3D buckling structures can be formed on locally modified PDMS as a substrate by a pre-stretching and releasing process, illustrating a new way to control the 3D buckling structure.

PVDF-TrFE-Based Stretchable Contact and Non-Contact Temperature Sensor for E-Skin Application.

Development of stretchable electronics has been driven by key applications such as electronics skin for robotic or prosthetic. Mimicking skin functionalities imposes at a minimal level: stretchability, pressure, and temperature sensing capabilities. While the research on pressure sensors for artificial skin is extensive, stretchable temperature sensors remain less explored. In this work, a stretchable temperature and infrared sensor has been developed on a polydimethylsiloxane substrate. The sensor is based on poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) as a pyroelectric material. This material is sandwiched between two electrodes. The first one consists of aluminium serpentines, covered by gold in order to get electrical contact and maximum stretchability. The second one is based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) that has shown good electrical compatibility with PVDF-TrFE and provides the stretchability of the top electrode. Without poling the PVDF-TrFE, sensor has shown a sensitivity of around 7 pF.°C−1 up to 35% strain without any change in its behaviour. Then, taking advantage on infrared absorption of PEDOT:PSS, a poled device has shown a pyroelectric peak of 13 mV to an infrared illumination of 5 mW at 830 nm. This stretchable device valuably allows an electronic skin (e-skin) use for contact and more importantly non-contact thermal sensing.

Soft Elastomers with Programmable Stiffness as Strain-Isolating Substrates for Stretchable Electronics.

Stretchable electronics are of rapidly increasing interest due to their unique ability to function under complex deformations. Strain isolation of stiff functional components from the substrate represents a key challenge in the development of stretchable electronics since their mechanical mismatch may yield undesirable strains to degrade the device performance. The results presented here report an approach to develop a soft strain-isolating polymer substrate with programmable stiffness by spatioselective ultraviolet exposure for stretchable electronics. The approach being compatible with the well-established lithographic process reduces the fabrication complexity significantly and offers a simple yet robust strain-isolation mechanism to ensure the system stretchability of more than 100%. Combined experimental and numerical studies reveal the fundamental aspects of the design, fabrication, and operation of the strain-isolating substrate. Demonstration of this concept in a stretchable inorganic metal-based resistive temperature sensor and a stretchable organic photodiode array with unusually high performance shows the simplicity of the approach and the robustness in strain isolation in both component and device levels. This type of strain-isolation design not only creates promising routes for potential scalable manufacturing of stretchable electronics but also engineering opportunities for stretchable electronics involving the integration of various functional components, which require the quantitative control of the strain levels to achieve optimal performance.

Stretchable Aqueous Batteries: Progress and Prospects

The development of stretchable electronics is indispensable for realizing next-generation wearable devices, such as sensors, health care devices, and electronic skin. A key challenge for achieving complete and independent wearable devices is developing stretchable power sources. This issue should be addressed appropriately before the realization of wearable devices. Very recently, stretchable aqueous rechargeable batteries as power supplies have received much attention for wearable devices owing to their intrinsic safety and high power density. In this Perspective, we present the current status and the latest advances in research on stretchable aqueous batteries, especially aqueous Li-ion batteries and zinc-based batteries. Also, we briefly provide the design of stretchable materials and battery systems for stretchable aqueous batteries. Furthermore, an overview of general technical issues confronting their development is presented, and a brief discussion on the future outlook of this field is provided.

Mechanics designs for stretchable inorganic electronics

Conventional electronic devices based on inorganic semiconductor materials (e.g., silicon) are hard, rigid, and flat. Recent advances in mechanics have enabled development of stretchable inorganic electronics on compliant substrates, offering the performance of conventional electronic devices and the ability to deform such electronics into arbitrary shapes and making possible numerous applications ranging from wearable electronics to bio-integrated electronics. This article reviews the two main mechanics strategies used to produce stretchable inorganic electronics in recent years, namely, wavy design and island-bridge design. Specifically, this article reveals the deformation mechanisms used in each strategy and provides design guidelines for the development of stretchable electronics.

Characterization of Stretchable Interconnects Fabricated Using a Low Cost Metallization Transfer Process onto PDMS

The growing number of applications requiring conformal electronic devices incorporated into unconventional and dynamic surfaces has led to an increase in the development of stretchable electronics. Together with novel materials and fabrication processes, innovative conductive patterns are being developed in order to meet the needs of modern applications. Here, we present the design, fabrication, and characterization of first-order curved Peano structures fabricated using a newly developed thick film copper metallization transfer process onto PDMS. In order to maximize the stretchability of these structures, we present a characterization and analysis of the relationship between relative resistance and tensile strain in fabricated devices while systematically varying the geometric parameters of various curve designs. The response of the structures to cyclic failure and recovery is also characterized. These results demonstrate that the newly developed transfer process can be used to fabricate stretchable Peano curves and provide insight into the geometric optimization of these curves in stretchable electronics applications.

Rugged and breathable forms of stretchable electronics with adherent composite substrates for transcutaneous monitoring.

Research in stretchable electronics involves fundamental scientific topics relevant to applications with importance in human healthcare. Despite significant progress in active components, routes to mechanically robust construction are lacking. Here, we introduce materials and composite designs for thin, breathable, soft electronics that can adhere strongly to the skin, with the ability to be applied and removed hundreds of times without damaging the devices or the skin, even in regions with substantial topography and coverage of hair. The approach combines thin, ultralow modulus, cellular silicone materials with elastic, strain-limiting fabrics, to yield a compliant but rugged platform for stretchable electronics. Theoretical and experimental studies highlight the mechanics of adhesion and elastic deformation. Demonstrations include cutaneous optical, electrical and radio frequency sensors for measuring hydration state, electrophysiological activity, pulse and cerebral oximetry. Multipoint monitoring of a subject in an advanced driving simulator provides a practical example.