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Direct optical polymer patterning As a platform for electronic devices, polymeric materials offer the advantages of intrinsic flexibility and stretchability relative to hard material devices. However, unlike materials such as silicon, there are few tools for large-scale patterning of monolithic devices. Zheng et al. developed an optical lithography technique for the high-throughput fabrication of transistor circuitry on stretchable substrates. In this method, ultraviolet light is used to control the local solubility of the polymer, which makes it possible to fabricate transistors on the micrometer scale. These devices can be made with high yield and excellent uniformity without compromising their electronic and mechanical characteristics. Science , abh3551, this issue p. 88

Intrinsically stretchable electronics can form intimate interfaces with the human body, creating devices that could be used to monitor physiological signals without constraining movement. However, mechanical strain invariably leads to the degradation of the electronic properties of the devices. Here we show that strain-insensitive intrinsically stretchable transistor arrays can be created using an all-elastomer strain engineering approach, in which the patterned elastomer layers with tunable stiffnesses are incorporated into the transistor structure. By varying the cross-linking density of the elastomers, areas of increased local stiffness are introduced, reducing strain on the active regions of the devices. This approach can be readily incorporated into existing fabrication processes, and we use it to create arrays with a device density of 340 transistors cm–2 and a strain insensitivity of less than 5% performance variation when stretched to 100% strain. We also show that it can be used to fabricate strain-insensitive circuit elements, including NOR gates, ring oscillators and high-gain amplifiers for the stable monitoring of electrophysiological signals. An all-elastomer strain engineering approach, which uses patterned elastomer layers with tunable stiffnesses, can be used to create intrinsically stretchable transistor arrays with a device density of 340 transistors cm–2 and strain insensitivity of less than 5% performance variation when stretched to 100% strain.

Feeling temperature and touch The range of receptors in our skin make it possible to sense when we are touching an object and also gives us a general sense of the temperature of that object. Achieving this in an artificial skin-like material has been a challenge because most of the approaches for sensing touch are themselves temperature sensitive. You et al. studied the ion relaxation dynamics in a conductive elastomeric film (see the Perspective by Liu). They show that the ion relaxation time can be used as a strain-insensitive intrinsic variable for detecting temperature and the capacitance can be used as a temperature-insensitive extrinsic variable for sensing the strain, thus decoupling the two so that their signals do not interfere with each other. Science , this issue p. 961 ; see also p. 910

We present a comprehensive investigation of mechanical properties of supramolecular polymer networks with rationally developed multistrength hydrogen-bonding interactions. Self-healing poly(dimethy...

Conjugation breakers (CBs) with different H-bonding chemistries and linker flexibilities are designed and incorporated into a diketopyrrolopyrrole (DPP)-based conjugated polymer backbone. The effects of H-bonding interactions on polymer semiconductor morphology, mechanical properties, and electrical performance are systematically investigated. We observe that CBs with an H-bonding self-association constant >0.7 or a denser packing tendency are able to induce higher polymer chain aggregation and crystallinity in as-casted thin films, resulting in a higher modulus and crack on-set strain. Additionally, the rDoC (relative degree of crystallinity) of the stretched thin film with the highest crack on-set strain only suffers a small decrease, suggesting the main energy dissipation mechanism is the breakage of H-bonding interactions. By contrast, other less stretchable polymer films dissipate strain energy through the breakage of crystalline domains, indicated by a drastic decrease in rDoC. Furthermore, we evaluate their electrical performances under mechanical strain in fully stretchable field-effect transistors. The polymer with the highest crack on-set strain has the least degradation in mobility as a function of strain. Overall, these observations suggest that we can aptly tune the mechanical properties of a polymer semiconductor by modulating intermolecular interactions, such as H-bonding chemistry and linker flexibility. Such understanding provides molecular design guidelines for future stretchable semiconductors.

In order to apply polymer semiconductors to stretchable electronics, they need to be easily deformed under strain without being damaged. A small number of conjugated polymers, typically with semicrystalline packing structures, have been reported to exhibit mechanical stretchability. Herein, a method is reported to modify polymer semiconductor packing-structure using a molecular additive, dioctyl phthalate (DOP), which is found to act as a molecular spacer, to be inserted between the amorphous chain networks and disrupt the crystalline packing. As a result, large-crystal growth is suppressed while short-range aggregations of conjugated polymers are promoted, which leads to an improved mechanical stretchability without affecting charge-carrier transport. Due to the reduced conjugated polymer intermolecular interactions, strain-induced chain alignment and crystallization are observed. By adding DOP to a well-known conjugated polymer, poly[2,5-bis(4-decyltetradecyl)pyrrolo[3,4-c]pyrrole-1,4-(2H,5H)-dione-(E)-1,2-di(2,2'-bithiophen-5-yl)ethene] (DPPTVT), stretchable transistors are obtained with anisotropic charge-carrier mobilities under strain, and stable current output under strain up to 100%.

Carbon materials with high specific surface areas are ideal support materials for many applications. However, high specific surface area and large pore volume usually render them with low bulk density, which is undesirable for applications aiming at high volumetric performance. Low bulk density stems from large interparticle‐free volume caused by inefficient random packing within the materials. Herein, a simple synthesis and assembly method is reported to afford dense carbon pellets with both high specific surface area and high bulk density, obtained from the ordered packing of low polydispersity carbon flower particles. The densely packed carbon flower particles exhibit similar specific surface area to their pressed powder analogs, while exhibiting a 66–84% increase in bulk density (0.815 g cm−3), and an ultrahigh volumetric surface area (1081 m2 cm−3). The advantages of our materials are demonstrated by supercapacitors, which achieve a high volumetric capacitance of up to 153 F cm−3. The results reinforce the importance of controlling particle size and shape for porous materials to reduce their bulk volume. The developed materials possessing high volumetric surface area will be useful for many applications, such as gas storage, supercapacitors, and batteries.

Narrowing the mechanical mismatch between tissue and implantable microelectronics is essential for reducing immune responses and for accommodating body movement. However, the design of implantable soft electronics (on the order of 10 kPa in modulus) remains a challenge because of the limited availability of suitable electronic materials. Here, we report electrically conductive hydrogel-based elastic microelectronics with Young’s modulus values in the kilopascal range. The system consists of a highly conductive soft hydrogel as a conductor and an elastic fluorinated photoresist as the passivation insulation layer. Owing to the high volumetric capacitance and the passivation layer of the hydrogel, electrode arrays of the thin-film hydrogel ‘elastronics’, 20 μm in feature size, show a significantly reduced interfacial impedance with tissue, a current-injection density that is ~30 times higher than that of platinum electrodes, and stable electrical performance under strain. We demonstrate the use of the soft elastronic arrays for localized low-voltage electrical stimulation of the sciatic nerve in live mice. Conductive and elastic hydrogel-based microelectronic arrays with high current-injection density and low interfacial impedance with tissue enable the localized low-voltage electrical stimulation of the sciatic nerve in live mice.

As a key component in stretchable electronics, semiconducting polymers have been widely studied. However, it remains challenging to achieve stretchable semiconducting polymers with high mobility and mechanical reversibility against repeated mechanical stress. Here, we report a simple and universal strategy to realize intrinsically stretchable semiconducting polymers with controlled multi-scale ordering to address this challenge. Specifically, incorporating two types of randomly distributed co-monomer units reduces overall crystallinity and longer-range orders while maintaining short-range ordered aggregates. The resulting polymers maintain high mobility while having much improved stretchability and mechanical reversibility compared with the regular polymer structure with only one type of co-monomer units. Interestingly, the crystalline microstructures are mostly retained even under strain, which may contribute to the improved robustness of our stretchable semiconductors. The proposed molecular design concept is observed to improve the mechanical properties of various p- and n-type conjugated polymers, thus showing the general applicability of our approach. Finally, fully stretchable transistors fabricated with our newly designed stretchable semiconductors exhibit the highest and most stable mobility retention capability under repeated strains of 1,000 cycles. Our general molecular engineering strategy offers a rapid way to develop high mobility stretchable semiconducting polymers., Designing intrinsically stretchable semiconducting polymers with suitable charge transport and mechanical properties required for stretchable electronic devices remains a challenge. Here, the authors report terpolymer-based semiconductors with intrinsically high stretchability and mobility.

Intrinsically and fully stretchable active-matrix-driven displays are an important element to skin electronics that can be applied to many emerging fields, such as wearable electronics, consumer electronics and biomedical devices. Here, we show for the first time a fully stretchable active-matrix-driven organic light-emitting electrochemical cell array. Briefly, it is comprised of a stretchable light-emitting electrochemical cell array driven by a solution-processed, vertically integrated stretchable organic thin-film transistor active-matrix, which is enabled by the development of chemically-orthogonal and intrinsically stretchable dielectric materials. Our resulting active-matrix-driven organic light-emitting electrochemical cell array can be readily bent, twisted and stretched without affecting its device performance. When mounted on skin, the array can tolerate to repeated cycles at 30% strain. This work demonstrates the feasibility of skin-applicable displays and lays the foundation for further materials development., To realize a skin-like display for human-electronics interfaces, intrinsically stretchable light-emitting, transistor and device interconnect components are needed. Here, the authors report a fully stretchable transistor driven active-matrix organic light-emitting electrochemical cell array.

Multielectrode arrays (MEAs) are essential tools in neural and cardiac research as they provide a means for noninvasive, multiplexed recording of extracellular field potentials with high temporal resolution. To date, the mechanical properties of the electrode material, e.g., its Young's modulus, have not been taken into consideration in most MEA designs leaving hard materials as the default choice due to their established fabrication processes. However, the cell-electrode interface is known to significantly affect some aspects of the cell's behavior. In this paper, we describe the fabrication of a soft 3D micropillar electrode array. Using this array, we proceed to successfully record action potentials from monolayer cell cultures. Specifically, our conductive hydrogel micropillar electrode showed improved signal amplitude and signal-to-noise ratio, compared with conventional hard iridium oxide micropillar electrodes of the same diameter. Taken together, our fabricated soft micropillar electrode array will provide a tissue-like Young's modulus and thus a relevant mechanical microenvironment to fundamental cardiac and neural studies.

For miniaturized capacitive energy storage, volumetric and areal capacitances are more important metrics than gravimetric ones because of the constraints imposed by device volume and chip area. Typically used in commercial supercapacitors, porous carbons, although they provide a stable and reliable performance, lack volumetric performance because of their inherently low density and moderate capacitances. Here we report a high-performing electrode based on conductive hexaaminobenzene (HAB)-derived two-dimensional metal−organic frameworks (MOFs). In addition to possessing a high packing density and hierarchical porous structure, these MOFs also exhibit excellent chemical stability in both acidic and basic aqueous solutions, which is in sharp contrast to conventional MOFs. Submillimetre-thick pellets of HAB MOFs showed high volumetric capacitances up to 760 F cm−3 and high areal capacitances over 20 F cm−2. Furthermore, the HAB MOF electrodes exhibited highly reversible redox behaviours and good cycling stability with a capacitance retention of 90% after 12,000 cycles. These promising results demonstrate the potential of using redox-active conductive MOFs in energy-storage applications. Metal–organic frameworks (MOFs) are attractive electrodes for supercapacitors but generally suffer from low electric conductivity and chemical stability. Here the authors report stable conductive MOFs based on hexaminobenzene linker with volumetric and areal capacitances in excess of 700 F per cm3 and 15 F per cm2, respectively.

Molecular additives are often used to enhance dynamic motion of polymeric chains, which subsequently alter the functional and physical properties of polymers. However, controlling the chain dynamics of semiconducting polymer thin films and understanding the fundamental mechanisms of such changes is a new area of research. Here, cycloparaphenylenes (CPPs) are used as conjugated molecular additives to tune the dynamic behaviors of diketopyrrolopyrrole-based (DPP-based) semiconducting polymers. It is observed that the addition of CPPs results in significant improvement in the stretchability of the DPP-based polymers without adversely affecting their mobility, which arises from the enhanced polymer dynamic motion and reduced long-range crystalline order. The polymer films retain their fiber-like morphology and short-range ordered aggregates, which leads to high mobility. Fully stretchable transistors are subsequently fabricated using CPP/semiconductor composites as active layers. These composites are observed to maintain high mobilities when strained and after repeated applied strains. Interestingly, CPPs are also observed to improve the contact resistance and charge transport of the fully stretchable transistors. ln summary, these results collectively indicate that controlling the dynamic motion of polymer semiconductors is proved to be an effective way to improve their stretchability.

Both self-healable conductors and stretchable conductors have been previously reported. However, it is still difficult to simultaneously achieve high stretchability, high conductivity, and self-healability. Here, we observed an intriguing phenomenon, termed “electrical self-boosting”, which enables reconstructing of electrically percolative pathways in an ultrastretchable and self-healable nanocomposite conductor (over 1700% strain). The autonomously reconstructed percolative pathways were directly verified by using microcomputed tomography and in situ scanning electron microscopy. The encapsulated nanocomposite conductor shows exceptional conductivity (average value: 2578 S cm–1; highest value: 3086 S cm–1) at 3500% tensile strain by virtue of efficient strain energy dissipation of the self-healing polymer and self-alignment and rearrangement of silver flakes surrounded by spontaneously formed silver nanoparticles and their self-assembly in the strained self-healing polymer matrix. In addition, the condu...

Introducing non-covalent crosslinking moieties to polymer semiconductors produces a stretchable and healable material suitable for wearable electronics. There is great interest and potential in the development of skin-inspired flexible and wearable electronic devices. Such devices require materials that twist, fold and bend with no loss in electronic—or material—properties. Zhenan Bao and colleagues report a conjugated polymer that also incorporates non-covalent interactions between adjacent chains, enabling the material to accommodate up to 100% strain whilst maintaining high charge-carrier mobility. In this proof-of-principle study the authors use the polymers to fabricate flexible and stretchable organic transistors that combine robustness with good electronic properties. Thin-film field-effect transistors are essential elements of stretchable electronic devices for wearable electronics1,2. All of the materials and components of such transistors need to be stretchable and mechanically robust3,4. Although there has been recent progress towards stretchable conductors5,6,7,8, the realization of stretchable semiconductors has focused mainly on strain-accommodating engineering of materials, or blending of nanofibres or nanowires into elastomers9,10,11. An alternative approach relies on using semiconductors that are intrinsically stretchable, so that they can be fabricated using standard processing methods12. Molecular stretchability can be enhanced when conjugated polymers, containing modified side-chains and segmented backbones, are infused with more flexible molecular building blocks13,14. Here we present a design concept for stretchable semiconducting polymers, which involves introducing chemical moieties to promote dynamic non-covalent crosslinking of the conjugated polymers. These non-covalent crosslinking moieties are able to undergo an energy dissipation mechanism through breakage of bonds when strain is applied, while retaining high charge transport abilities. As a result, our polymer is able to recover its high field-effect mobility performance (more than 1 square centimetre per volt per second) even after a hundred cycles at 100 per cent applied strain. Organic thin-film field-effect transistors fabricated from these materials exhibited mobility as high as 1.3 square centimetres per volt per second and a high on/off current ratio exceeding a million. The field-effect mobility remained as high as 1.12 square centimetres per volt per second at 100 per cent strain along the direction perpendicular to the strain. The field-effect mobility of damaged devices can be almost fully recovered after a solvent and thermal healing treatment. Finally, we successfully fabricated a skin-inspired stretchable organic transistor operating under deformations that might be expected in a wearable device.

Skin-inspired semiconductor that is intrinsically stretchable, self-healable, and strain-sensitive for advanced sensory devices., Skin-like sensory devices should be stretchable and self-healable to meet the demands for future electronic skin applications. Despite recent notable advances in skin-inspired electronic materials, it remains challenging to confer these desired functionalities to an active semiconductor. Here, we report a strain-sensitive, stretchable, and autonomously self-healable semiconducting film achieved through blending of a polymer semiconductor and a self-healable elastomer, both of which are dynamically cross-linked by metal coordination. We observed that by controlling the percolation threshold of the polymer semiconductor, the blend film became strain sensitive, with a gauge factor of 5.75 × 105 at 100% strain in a stretchable transistor. The blend film is also highly stretchable (fracture strain, >1300%) and autonomously self-healable at room temperature. We proceed to demonstrate a fully integrated 5 × 5 stretchable active-matrix transistor sensor array capable of detecting strain distribution through surface deformation.

Increasing performance demands and shorter use lifetimes of consumer electronics have resulted in the rapid growth of electronic waste. Currently, consumer electronics are typically made with nondecomposable, nonbiocompatible, and sometimes even toxic materials, leading to serious ecological challenges worldwide. Here, we report an example of totally disintegrable and biocompatible semiconducting polymers for thin-film transistors. The polymer consists of reversible imine bonds and building blocks that can be easily decomposed under mild acidic conditions. In addition, an ultrathin (800-nm) biodegradable cellulose substrate with high chemical and thermal stability is developed. Coupled with iron electrodes, we have successfully fabricated fully disintegrable and biocompatible polymer transistors. Furthermore, disintegrable and biocompatible pseudo-complementary metal–oxide–semiconductor (CMOS) flexible circuits are demonstrated. These flexible circuits are ultrathin ( 2 ) with low operating voltage (4 V), yielding potential applications of these disintegrable semiconducting polymers in low-cost, biocompatible, and ultralightweight transient electronics.

Graphene is a highly promising material for high speed, broadband, and multicolor photodetection. Because of its lack of bandgap, individually gated P- and N-regions are needed to fabricate photodetectors. Here we report a technique for making a large-area photodetector on the basis of controllable fabrication of graphene P-N junctions. Our selectively doped chemical vapor deposition (CVD) graphene photodetector showed a ∼5% modulation of conductance under global IR irradiation. By comparing devices of various geometries, we identify that both the homogeneous and the P-N junction regions contribute competitively to the photoresponse. Furthermore, we demonstrate that our two-terminal graphene photodetector can be fabricated on both transparent and flexible substrates without the need for complex fabrication processes used in electrically gated three-terminal devices. This represents the first demonstration of a fully transparent and flexible graphene-based IR photodetector that exhibits both good photoresponsivity and high bending capability. This simple approach should facilitate the development of next generation high-performance IR photodetectors.

Using non-chlorinated solvents for polymer device fabrication is highly desirable to avoid the negative environmental and health effects of chlorinated solvents. Here, a non-chlorinated mixed solvent system, composed by a mixture of tetrahydronaphthalene and p­-xylene, is described for processing a high mobility donor-acceptor fused thiophene-diketopyrrolopyrrole copolymer (PTDPPTFT4) in thin film transistors. The effects of the use of a mixed solvent system on the device performance, e.g., charge transport, morphology, and molecular packing, are investigated. p-Xylene is chosen to promote polymer aggregation in solution, while a higher boiling point solvent, tetrahydronaphthalene, is used to allow a longer evaporation time and better solubility, which further facilitates morphological tuning. By optimizing the ratio of the two solvents, the charge transport characteristics of the polymer semiconductor device are observed to significantly improve for polymer devices deposited by spin coating and solution shearing. Average charge carrier mobilities of 3.13 cm2 V−1 s−1 and a maximum value as high as 3.94 cm2 V−1 s−1 are obtained by solution shearing. The combination of non-chlorinated mixed solvents and the solution shearing film deposition provide a practical and environmentally-friendly approach to achieve high performance polymer transistor devices.

This work was supported by Air Force Office of Scientific Research (Grant No. FA9550-18-1-0143) for financial support. M.N. acknowledges financial support from the European Commission through a Marie-Curie Individual Fellowship (EC Grant Agreement Number: 747461). H.T. was supported by an appointment to the Intelligence Community Postdoctoral Research Fellowship Program at Stanford University, administered by Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the Office of the Director of National Intelligence. S.Z. and X.G. thank the financial support from U.S. Department of Energy, Office of Science, Office of Basic Energy Science under award number DE-SC0019361 and National Science Foundation Office of Integrative Activities #1757220. J.M. acknowledges Samsung Scholarship for financial support. Part of this work was performed at the Stanford Nano Shared Facilities (SNSF), supported by the National Science Foundation under award ECCS-1542152. GIXD measurement was carried out at the Stanford Synchrotron Radiation Laboratory (SSRL), a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences.

This review covers some of the most recent advances in stretchable and self-healing polymers and devices for Electronic skin (E-skin) applications. Applications for both stretchable and self-healing materials include, but are not limited to, electronics, displays, energy, the environment, and medicine. While the majority of organic materials can generally be rendered flexible, such materials are not stretchable, which is a key mechanical property necessary to realize applications of E-skin for prosthetics, artificial intelligence, systems for robotics, personal health monitoring, biocompatibility, and communication devices. In our effort to survey materials utilized in various components of an electronic device, we report herein recent advances in stretchable and self-healing conductors, semiconductors, and substrates. We highlight some key technologies recently developed in stretchable organic-based sensors, solar cells, light-emitting diodes, and self-healing electronic devices.

Diverse signals generated from the sensing elements embedded in flexible electronic skins (e-skins) are typically interfered by strain energy generated through processes such as touching, bending, stretching or twisting. Herein, we demonstrate a flexible bimodal sensor that can separate a target signal from the signal by mechanical strain through the integration of a multi-stimuli responsive gate dielectric and semiconductor channel into the single field-effect transistor (FET) platform.

Biodetection using organic field-effect transistors (OFETs) is gaining increasing interest for applications as diverse as food security, environmental monitoring, and medical diagnostics. However, there still lacks a comprehensive, empirical study on the fundamental limits of OFET sensors. In this paper, we present a thorough study of the various parameters affecting biosensing using an OFET decorated with gold nanoparticle (AuNP) binding sites. These parameters include the spacing between receptors, pH of the buffer, and ionic strength of the buffer. To this end, we employed the thrombin protein and its corresponding DNA binding aptamer to form our model detection system. We demonstrate a detection limit of 100 pM for this protein with high selectivity over other proteases in situ. We describe herein a feasible approach for protein detection with OFETs and a thorough investigation of parameters governing biodetection events using OFETs. Our obtained results should provide important guidelines to tailor the sensor's dynamic range to suit other desired OFET-based biodetection applications.

High-mobility organic field-effect transistors (OFETs) are the basic units for a variety of high-performance electronic applications. Here, we review recent progress in controlling molecular packing and crystal growth in high-mobility, small molecular organic FETs. Strategies to tune molecular packing of organic semiconductors and their impact on charge transport are described. Methods for the controlled growth of single-crystal organic semiconductors required for large-area device construction are reviewed. Furthermore, the advantages, limitations, and potential of these methods are also discussed.

Trapping polymers to improve flexibility Polymer molecules at a free surface or trapped in thin layers or tubes will show different properties from those of the bulk. Confinement can prevent crystallization and oddly can sometimes give the chains more scope for motion. Xu et al. found that a conducting polymer confined inside an elastomer—a highly stretchable, rubber-like polymer—retained its conductive properties even when subjected to large deformations (see the Perspective by Napolitano). Science , this issue p. 59 ; see also p. 24

Thin-film field-effect transistors (FETs) are widely used to evaluate charge transport properties of semiconducting polymers. Discovery of high performance materials require design and synthesis of new polymers. However, most polymers require multi-step synthesis and are difficult to be obtained in a large scale for comprehensive device evaluations. Here, we report a simple method to cast semiconducting polymer films from solutions with polymer concentration as low as 0.5 mg/mL, which is substantially less than typical values (∼10 mg/mL) used in conventional spin coating method. Here, we demonstrate that using this method, our cast films of a previously-reported polymer (PDPP-TT2T) exhibited field-effect mobility (μhole = 0.89 ± 0.13 cm2 V−1 s−1, μe = 0.025 ± 0.005 cm2 V−1 s−1), which is comparable to the reported values using the same device geometry. Furthermore, we extend this method to examine cast films of a pair of polymers (PDPP-3T-Ref, PDPP-3T-Si) to study the effect of siloxane substitution in the side chains on the molecular packing and their subsequent FET performance. We observed that shorter π-stacking distance (3.61 A) for the siloxane-terminated polymer, when compared to that for the reference polymer (3.73 A), resulted in improved FET performance (e.g., μhole = 0.63 ± 0.046 cm2 V−1 s−1 for PDPP-3T-Si vs μhole = 0.17 ± 0.062 cm2 V−1 s−1 for PDPP-3T-Ref). Taken together, this work presents an efficient alternative film-casting approach to produce polymer FETs that consumes much less material for their fabrication, lending viability for evaluation of various polymeric materials.

Optical pressure sensors are highly responsive and are unaffected by surrounding parameters such as electronic noise, humidity, temperature, etc. A new type of optical pressure sensor is described that demonstrates the stretchability and transparency of a polydimethylsiloxane waveguide, while also serving as a substrate. The pressure sensors are both robust and easy to fabricate over a large area.

Adopting self-healing, robust, and stretchable materials is a promising method to enable next-generation wearable electronic devices, touch screens, and soft robotics. Both elasticity and self-healing are important qualities for substrate materials as they comprise the majority of device components. However, most autonomous self-healing materials reported to date have poor elastic properties, i.e., they possess only modest mechanical strength and recoverability. Here, a substrate material designed is reported based on a combination of dynamic metal-coordinated bonds (β-diketone-europium interaction) and hydrogen bonds together in a multiphase separated network. Importantly, this material is able to undergo self-healing and exhibits excellent elasticity. The polymer network forms a microphase-separated structure and exhibits a high stress at break (≈1.8 MPa) and high fracture strain (≈900%). Additionally, it is observed that the substrate can achieve up to 98% self-healing efficiency after 48 h at 25 °C, without the need of any external stimuli. A stretchable and self-healable dielectric layer is fabricated with a dual-dynamic bonding polymer system and self-healable conductive layers are created using polymer as a matrix for a silver composite. These materials are employed to prepare capacitive sensors to demonstrate a stretchable and self-healable touch pad.

An electronic (e-) skin is expected to experience significant wear and tear over time. Therefore, self-healing stretchable materials that are simultaneously soft and with high fracture energy, that is high tolerance of damage or small cracks without propagating, are essential requirements for the realization of robust e-skin. However, previously reported elastomers and especially self-healing polymers are mostly viscoelastic and lack high mechanical toughness. Here, a new class of polymeric material crosslinked through rationally designed multistrength hydrogen bonding interactions is reported. The resultant supramolecular network in polymer film realizes exceptional mechanical properties such as notch-insensitive high stretchability (1200%), high toughness of 12 000 J m-2 , and autonomous self-healing even in artificial sweat. The tough self-healing materials enable the wafer-scale fabrication of robust and stretchable self-healing e-skin devices, which will provide new directions for future soft robotics and skin prosthetics.

We report here "aptatags," which consist of aptamer-modified silver nanoparticles (NPs) held together by an optical reporter. It is possible to use these materials to design a heterogeneous method for protein identification that takes advantage of the Raman signal enhancement by metallic nanostructures and the recognition capabilities of aptamers. Aptatags are formed by linking silver NPs with an organic dithiol molecule, followed by surface modification with thiolated single-stranded DNA (ssDNA) corresponding to the sequence of the aptamer probe. The sensing surface involves a silver layer containing the thiolated capturing aptamer and mercaptohexadecanoic acid to minimize nonspecific binding. The overall process provides excellent selectivity and sensitivity. Detailed characterization of the sensing surface by SERS maps and atomic force microscopy was carried out to understand how structural features lead to signal generation.

Metallic nanoparticles suspended in aqueous solutions and functionalized with chemical and biological surface coatings are important elements in basic and applied nanoscience research. Many applications require an understanding of the electrokinetic or colloidal properties of such particles. We describe the results of experiments to measure the zeta potential of metallic nanorod particles in aqueous saline solutions, including the effects of pH, ionic strength, metallic composition, and surface functionalization state. Particle substrates tested include gold, silver, and palladium monometallic particles as well as gold/silver bimetallic particles. Surface functionalization conditions included 11-mercaptoundecanoic acid (MUA), mercaptoethanol (ME), and mercaptoethanesulfonic acid (MESA) self-assembled monolayers (SAMs), as well as MUA layers subsequently derivatized with proteins. For comparison, we present zeta potential data for typical charge-stabilized polystyrene particles. We compare experimental zeta potential data with theoretically predicted values for SAM-coated and bimetallic particles. The results of these studies are useful in predicting and controlling the aggregation, adhesion, and transport of functionalized metallic nanoparticles within microfluidic devices and other systems.

Flexible electronics and optoelectronics have potential applications in energy generation, biomedicine, robotics and displays. Two recent demonstrations of highly stretchable polymer LEDs suggest that commercial devices may soon become viable.

A bioinspired microhairy sensor is developed to enable ultraconformability on nonflat surfaces and significant enhancement in the signal-to-noise ratio of the retrieved signals. The device shows ≈12 times increase in the signal-to-noise ratio in the generated capacitive signals, allowing the ultraconformal microhair pressure sensors to be capable of measuring weak pulsations of internal jugular venous pulses stemming from a human neck.

Organic field-effect transistor (OFET) sensors can meet the need for portable and real-time diagnostics. An electronicreadout enzyme-linked immunosorbent assay using OFETs for the detection of a panel of three biomarkers in complex media to create a pre-eclampsia prognostic is demonstrated, along with biodetection utilizing a fully inkjet-printed and flexible OFET to underscore our ability to produce disposable devices.

Human skin is a remarkable organ. It consists of an integrated, stretchable network of sensors that relay information about tactile and thermal stimuli to the brain, allowing us to maneuver within our environment safely and effectively. Interest in large-area networks of electronic devices inspired by human skin is motivated by the promise of creating autonomous intelligent robots and biomimetic prosthetics, among other applications. The development of electronic networks comprised of flexible, stretchable, and robust devices that are compatible with large-area implementation and integrated with multiple functionalities is a testament to the progress in developing an electronic skin (e-skin) akin to human skin. E-skins are already capable of providing augmented performance over their organic counterpart, both in superior spatial resolution and thermal sensitivity. They could be further improved through the incorporation of additional functionalities (e.g., chemical and biological sensing) and desired properties (e.g., biodegradability and self-powering). Continued rapid progress in this area is promising for the development of a fully integrated e-skin in the near future.

Conjugated polymers, such as polyfluorene and poly(phenylene vinylene), have been used to selectively disperse semiconducting single-walled carbon nanotubes (sc-SWNTs), but these polymers have limited applications in transistors and solar cells. Regioregular poly(3-alkylthiophene)s (rr-P3ATs) are the most widely used materials for organic electronics and have been observed to wrap around SWNTs. However, no sorting of sc-SWNTs has been achieved before. Here we report the application of rr-P3ATs to sort sc-SWNTs. Through rational selection of polymers, solvent and temperature, we achieved highly selective dispersion of sc-SWNTs. Our approach enables direct film preparation after a simple centrifugation step. Using the sorted sc-SWNTs, we fabricate high-performance SWNT network transistors with observed charge-carrier mobility as high as 12 cm(2) V(-1) s(-1) and on/off ratio of10(6). Our method offers a facile and a scalable route for separating sc-SWNTs and fabrication of electronic devices.

We report a versatile biofunctional subwavelength photonic device platform for real-time detection of biological molecules. Our devices contain lipid bilayer membranes fused onto metal oxide nanowire waveguides stretched across polymeric flow channels. The lipid bilayers incorporating target receptors are submersed in the propagating evanescent field of the optical cavity. We show that the lipid bilayers in our devices are continuous, have very high mobile fraction, and are resistant to fouling. We also demonstrate that our platform allows rapid membrane exchange. Finally, we use this device to detect the hybridization of specific DNA target sequences in solution to complementary probe DNA strands anchored to the lipid bilayer. This evanescent wave sensing architecture holds great potential for portable, all-optical detection systems.

The objective of this project is to demonstrate new enabling technology for multiplex biodetection systems that are flexible, miniaturizable, highly automated, low cost, and high performance. It builds on prior successes at LLNL with particle-based solution arrays, such as those used in the Autonomous Pathogen Detection System (APDS) successfully field deployed to multiple locations nationwide. We report the development of a multiplex solution array immunoassay based upon engineered metallic nanorod particles. Nanobarcodes{reg_sign} particles are fabricated by sequential electrodeposition of dissimilar metals within porous alumina templates, yielding optically encoded striping patterns that can be read using standard laboratory microscope optics and PC-based image processing software. The addition of self-assembled monolayer (SAM) coatings and target-specific antibodies allows each encoded class of nanorod particles to be directed against a different antigen target. A prototype assay panel directed against bacterial, viral, and soluble protein targets demonstrates simultaneous detection at sensitivities comparable to state of the art immunoassays, with minimal cross-reactivity. Studies have been performed to characterize the colloidal properties (zeta potential) of the suspended nanorod particles as a function of pH, the ionic strength of the suspending solution, and surface functionalization state. Additional studies have produced means for the non-contact manipulation of the particles,more » including the insertion of magnetic nickel stripes within the encoding pattern, and control via externally applied electromagnetic fields. Using the results of these studies, the novel Nanobarcodes{reg_sign} based assay was implemented in a prototype automated system with the sample processing functions and optical readout performed on a microfluidic card. The unique physical properties of the nanorod particles enable the development of integrated microfluidic systems for biodefense, protein expression studies, and other applications.« less