A dual-reference study design for understanding and improving AAV genome size analysis.

Recombinant adeno-associated virus (rAAV) is the leading platform of gene delivery for its long-lasting gene transformation and low immunogenicity. Characterization of the integrity and purity of the rAAV genome is critical to ensure clinical potency and safety. However, current rAAV genome characterization methods that can provide size assessment are either time-consuming or not easily accessible to general labs. Additionally, there is a lack of right reference standard for analyzing long single-stranded DNA (ssDNA) fragments. Here, we have developed an ssDNA assay on a microfluidic capillary electrophoresis platform using ssDNA reference standard. This assay provides size calling for ssDNA fragment, a detection sensitivity at ∼89 pg/µL (3 × 1010  GC/mL AAV) for 5.1 kb ssDNA fragment, and a turnaround time at ∼100 s per sample with a high throughput sample analyzing capability. Moreover, we have observed that the annealing of AAV ssDNA subsequent to its release from the capsid might introduce an additional double-stranded DNA (dsDNA) peak. This phenomenon is dependent on the sample processing workflow. To avoid the risk of mischaracterization, we recommend the use of dual-reference standards in combination with other orthogonal methods to have a comprehensive understanding of the rAAV genome size and integrity.

Submicron-Thickness Ultraflexible Organic Light-Emitting Diodes via a Photoregulated Stripping Strategy.

With the rapid advances in imperceptible and epidermal electronics, the research on ultraflexible organic light-emitting diodes (OLEDs) has become increasingly significant, owing to their excellent flexibility and conformability to the human body. It is highly desirable to develop submicrometer-thick ultraflexible OLEDs to enable the devices to seamlessly conform to the surface of arbitrary-shaped objects and still function properly. However, it remains a huge challenge for currently reported OLEDs due to the lack of an appropriate stripping strategy. Here, for the first time, we develop a facile photoregulated stripping strategy for the fabrication of high-performance ultraflexible OLEDs with submicron thickness. Under ultraviolet (UV) irradiation, the surface adhesion force of the ultrathin photopolymer membrane can be adjusted from 16.9 to 5.1 N/m, thereby effectively controlling the laminating and detaching process. Based on this strategy, the resultant device thickness is as low as 0.821 µm, which is the lowest record among flexible OLEDs reported to date. More remarkably, excellent electrical properties with a maximum current efficiency (CE) of 62.5 cd/A, an external quantum efficiency (EQE) of 17.8%, and a low turn-on voltage of 2.5 V are realized, which are superior to almost all of the reported ultraflexible OLEDs with thicknesses below 10 µm. Based on versatile ultraflexible OLEDs, all-organic and skin-mounted displays are successfully realized by employing a conformable organic thin-film transistor (OTFT) as the driver. This work offers a feasible strategy for advancing OLEDs from flexible to ultraflexible, showing significant application potential in future epidermal electronics and conformal displays.

Transfer-Printing of Insoluble Conducting Polymer for Soft 3D Conformal All-Organic Transistors.

The development of high-precision insoluble conducting polymer patterns for soft electronics is extremely challenging, mainly because of the incompatibility of the synthesis process with the underlying layers. In this study, a novel transfer-printing method is designed that enables the fabrication of photolithographic insoluble conducting polypyrrole (PPy) electrode patterns on soft substrates with high precision, demonstrating compatibility with various soft organic functional layers. Excellent mechanical stability, good biocompatibility, ultra-smooth surface, and outstanding conformability are observed. The photolithographic PPy electrode patterns, combined with an elastic organic semiconductor and dielectric, produce conformal all-organic transistors with mobility of 1.8 cm2 V-1 s-1 . This study paves the way to use insoluble conducting polymers to develop complex, high-density flexible patterns and offers a promising organic electrode for the new-generation soft all-organic electronics.

Dielectric Design of High Dielectric Constant Poly(Urea-Urethane) Elastomer for Low-Voltage High-Mobility Intrinsically Stretchable All-Solution-Processed Organic Transistors.

Stretchable organic transistors for skin-like biomedical applications require low-voltage operation to accommodate limited power supply and safe concerns. However, most of the currently reported stretchable organic transistors operate at relatively high voltages. Decreasing their operational voltage while keeping the high mobility still remains a key challenge. Here, the study presents a new dielectric design to achieve high-dielectric constant poly(urea-urethane) (PUU) elastomer, by incorporating a flexible small-molecular diamine crosslinking agent 4-aminophenyl disulfide (APDS) into the main chain of (poly (propylene glycol), tolylene 2,4-diiso-cyanate terminated) (PPG-TDI). Compared with commercial elastomers, the PUU elastomer as dielectric of the stretchable organic transistors shows the outstanding advantages including lower surface roughness (0.33 nm), higher adhesion (45.18 nN), higher dielectric constant (13.5), as well as higher stretchability (896%). The PUU dielectric enables the intrinsically stretchable, all-solution-processed organic transistor to operate at a low operational voltage down to -10 V, while preserving a substantial mobility of 1.39 cm2  V-1  s-1 . Impressively, the transistor also demonstrates excellent electrical stability under repeated switching of 10 000 cycles, and remarkable mechanical robustness when stretched up to 100%. The work opens up a new molecular engineering strategy to successfully realize low-voltage high-mobility stretchable all-solution-processed organic transistors.

Photolithographic Rugged Electrode for High-Density Low-Contact-Resistance Coplanar Organic Transistors.

The realization of high-performance photolithographic coplanar organic thin film transistors (OTFTs) is fundamental to boost cosmically commercial applications of organic electronics. However, photolithographic coplanar OTFTs generally suffer from poor charge injection and therefore poor filed-effect performance. Here, a simple and effective strategy is developed to fabricate photolithographic rugged electrodes, and successfully achieve high-density low-contact-resistance photolithographic coplanar OTFTs. Based on this versatile electrode, the wafer-scale photolithographic rugged electrode can be easily achieved, and the device density of the coplanar OTFTs is as high as 28000 cm-2 . The device shows excellent electrical properties with mobility up to 2.01 cm2  V-1  s-1 and Rc as low as 7.8 kΩ cm, which is superior to all the reported Ag-electrode coplanar OTFTs. This work shows a reliable strategy to reduce the contact resistance of photolithographic coplanar OTFTs and elucidates the effect of injection resistance (Rinj ) and access resistance (Racc ) on coplanar OTFTs.

Air/Liquid Interfacial Self-Assembled Intrinsically Stretchable IDT-BT Film Combining a Deliberate Transfer Adherence Strategy for Stretchable Electronics.

Indacenodithiophene-benzothiadiazole (IDT-BT) has emerged as one of the most promising candidates for stretchable electronics due to its good stretchability and high mobility. Here, we present an air/liquid interface self-assembly method for the stretchable IDT-BT films and design an air-side transfer adherence strategy for improving the carrier mobility of IDT-BT. By controlling the cosolvent ratio in solution and the solvent evaporation rate, the large-scale intrinsically stretchable IDT-BT film with the diameter as high as ∼3 cm was self-assembled at the air/liquid interface. The resulting stretchable film with lightweight and good uniformity could be easily transferred to curved objects such as flexible 3 M tape, glass ball, and seashell. It is found that the transfer adherence strategy of the semiconductor film significantly affects the carrier transport. The transfer adherence from air-side can effectively decrease the number of the adsorbed water molecules at semiconductor/dielectric interface, which presents the mobility as high as 2.98 cm2 V-1 s-1. Based on the air/liquid interface self-assembled IDT-BT film, the peeling process of the film for preparation of full stretchable transistors could be eliminated. The resulting intrinsically stretchable transistor exhibits mobility higher than that of the transistor with a conventional spin-coated film. Our research provides new pathways for preparing the stretchable films and intrinsically stretchable organic field-effect transistors and shows the promising potential of the air/liquid interface self-assembly strategy for stretchable electronics.

Highly Strain-Stable Intrinsically Stretchable Olfactory Sensors for Imperceptible Health Monitoring.

Intrinsically stretchable gas sensors possess outstanding advantages in seamless conformability and high-comfort wearability for real-time detection toward skin/respiration gases, making them promising candidates for health monitoring and non-invasive disease diagnosis and therapy. However, the strain-induced deformation of the sensitive semiconductor layers possibly causes the sensing signal drift, resulting in failure in achievement of the reliable gas detection. Herein, a surprising result that the stretchable organic polymers present a universal strain-insensitive gas sensing property is shown. All the stretchable polymers with different degrees of crystallinity, including indacenodithiophene-benzothiadiazole (PIDTBT), diketo-pyrrolo-pyrrole bithiophene thienothiophene (DPPT-TT) and poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-alt-[1,2,5]thiad-iazolo [3,4-c] pyridine] (PCDTPT), show almost unchanged gas response signals in the different stretching states. This outstanding advantage enables the intrinsically stretchable devices to imperceptibly adhere on human skin and well conform to the versatile deformations such as bending, twisting, and stretching, with the highly strain-stable gas sensing property. The intrinsically stretchable PIDTBT sensor also demonstrates the excellent selectivity toward the skin-emitted trimethylamine (TMA) gas, with a theoretical limit of detection as low as 0.3 ppb. The work provides new insights into the preparation of the reliable skin-like gas sensors and highlights the potential applications in the real-time detection of skin gas and respiration gas for non-invasive medical treatment and disease diagnosis.

Application of microfluidic chip electrophoresis for high-throughput nucleic acid fluorescence fragment analysis assays.

Nucleic acid fragment analysis via separation and detection are routine operations in molecular biology. However, analysis of small single-stranded nucleic acid fragments (<100nt) is challenging and mainly limited to labor-intensive polyacrylamide gel electrophoresis or high-cost capillary electrophoresis methods. Here we report an alternative method, a microfluidic chip electrophoresis system that provides a size resolution of 5nt and a detection time of one minute per sample of fluorescence-labeled DNA/RNA fragments. The feasibility of this system was evaluated by quantifying CRISPR-Cas9 cleavage efficiency and the detection resolution was evaluated by analyzing ssDNA/RNA adenylation and phosphorylation. We employed this system to study the RNA capping efficiency and double-stranded DNA unwinding efficiency in isothermal amplification as two examples for assay design and evaluation. The microfluidic chip electrophoresis system provides a rapid, sensitive, and high-throughput fluorescence fragment analysis (FFA), and can be applied for enzyme characterization, reaction optimization, and product quality control in various molecular biology processes.

Multimodal-Synergistic-Modulation Neuromorphic Imaging Systems for Simulating Dry Eye Imaging.

Inspired by human eyes, the neuromorphic visual system employs a highly efficient imaging and recognition process, which offers tremendous advantages in image acquisition, data pre-processing, and dynamic storage. However, it is still an enormous challenge to simultaneously simulate the structure, function, and environmental adaptive behavior of the human eye based on one device. Here, a multimodal-synergistic-modulation neuromorphic imaging system based on ultraflexible synaptic transistors is successfully presented and firstly simulates the dry eye imaging behavior at the device level. Moreover, important functions of the human visual system in relation to optoelectronic synaptic plasticity, image erasure and enhancement, real-time preprocessing, and dynamic storage are simulated by versatile devices. This work not only simplifies the complexity of traditional neuromorphic visual systems, but also plays a positive role in the publicity of biomedical eye care.

Calligraphy and Kirigami/Origami-Inspired All-Paper Touch-Temperature Sensor with Stimulus Discriminability.

The use of cost-effective renewable raw materials to develop electronic devices has been strongly demanded for sustainable and biodegradable green electronics. Here, by taking inspiration from the traditional calligraphy and kirigami/origami arts, we show a novel cuttable and foldable all-paper touch-temperature sensors fabricated by simply brushing the carbon black ink onto the cellulose paper followed by a layer-layer lamination strategy. The use of environmentally friendly common commodities in daily life including carbon black ink and cellulose paper as the main component materials of sensors effectively lowers the cost and has positive impacts on the environment and health. The sensors can be freely cut or folded into the targeted shapes and can even reversibly morph between 2D and 3D configurations without affecting device function. Additionally, the sensors show a discrimination capability toward pressure and temperature. Our fabrication strategy provides a promising approach for creating the low-cost eco-friendly sensors with a versatile pattern design and a morphing shape without sacrificing the global structural integrity and device functionality.

High-Mobility Fungus-Triggered Biodegradable Ultraflexible Organic Transistors.

Biodegradable organic field-effect transistors (OFETs) have drawn tremendous attention for potential applications such as green electronic skins, degradable flexible displays, and novel implantable devices. However, it remains a huge challenge to simultaneously achieve high mobility, stable operation and controllable biodegradation of OFETs, because most of the widely used biodegradable insulating materials contain large amounts of hydrophilic groups. Herein, it is firstly proposed fungal-degradation ultraflexible OFETs based on the crosslinked dextran (C-dextran) as dielectric layer. The crosslinking strategy effectively eliminates polar hydrophilic groups and improves water and solvent resistance of dextran dielectric layer. The device with spin-coated 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) semiconductor and C-dextran dielectric exhibits the highest mobility up to 7.72 cm2 V-1 s-1 , which is higher than all the reported degradable OFETs. Additionally, the device still maintains high performance regardless of in an environment humidity up to 80% or under the extreme bending radius of 0.0125 mm. After completion of their mission, the device can be controllably biodegraded by fungi without any adverse environmental effects, promoting the natural ecological cycles with the concepts of "From nature, for nature". This work opens up a new avenue for realizing high-performance biodegradable OFETs, and advances the process of the "green" electrical devices in practical applications.

Highly Stable Nonhydroxyl Antisolvent Polymer Dielectric: A New Strategy towards High-Performance Low-Temperature Solution-Processed Ultraflexible Organic Transistors for Skin-Inspired Electronics.

Scarcity of the antisolvent polymer dielectrics and their poor stability have significantly prevented solution-processed ultraflexible organic transistors from low-temperature, large-scale production for applications in low-cost skin-inspired electronics. Here, we present a novel low-temperature solution-processed PEI-EP polymer dielectric with dramatically enhanced thermal stability, humidity stability, and frequency stability compared with the conventional PVA/c-PVA and c-PVP dielectrics, by incorporating polyethyleneimine PEI as crosslinking sites in nonhydroxyl epoxy EP. The PEI-EP dielectric requires a very low process temperature as low as 70°C and simultaneously possesses the high initial decomposition temperature (340°C) and glass transition temperature (230°C), humidity-resistant dielectric properties, and frequency-independent capacitance. Integrated into the solution-processed C8-BTBT thin-film transistors, the PEI-EP dielectric enables the device stable operation in air within 2 months and in high-humidity environment from 20 to 100% without significant performance degradation. The PEI-EP dielectric transistor array also presents weak hysteresis transfer characteristics, excellent electrical performance with 100% operation rate, high mobility up to 7.98 cm2 V-1 s-1 (1 Hz) and average mobility as high as 5.3 cm2 V-1 s-1 (1 Hz), excellent flexibility with the normal operation at the bending radius down to 0.003 mm, and foldable and crumpling-resistant capability. These results reveal the great potential of PEI-EP polymer as dielectric of low-temperature solution-processed ultraflexible organic transistors and open a new strategy for the development and applications of next-generation low-cost skin electronics.

Shape-Designable and Reconfigurable All-Paper Sensor through the Sandwich Architecture for Pressure/Proximity Detection.

All-paper sensors that are capable of free cutting and folding maximize the merits of papers, which fully utilize the unique potential of papers in cost effectiveness, flexibility, disposability, biodegradability, and a flexible design. However, most of the paper sensors have applied metals as the electrodes and polyimide/polydimethylsiloxane as the encapsulation/sensitive layers, limiting the advantages of the paper sensor. In this work, an all-paper, shape-designable, and reconfigurable capacitive pressure/proximity sensor is fabricated with multilayered tissue paper as the dielectric and polypyrrole printer paper as the electrode/encapsulation. Without the restriction of heterogeneous materials, the all-paper components enable the sensors' flexible shape design for freely cuttable and foldable 2D and 3D sensors including a 2D braille keyboard and even allow reconfiguration from a 3D box sensor to a 3D candy sensor. The all-paper sensor presents superior pressure-sensing performance (0.96 kPa-1 at <1.76 kPa and 0.09 kPa-1 at 1.76-22 kPa) and proximity-sensing ability. The sensing mechanism of the sensor is directly revealed from tissue paper changes using in situ 3D microscopy and dielectric measurement experiments. These results provide inspiration for realizing shape-designable and reconfigurable 3D sensors and fully demonstrate the application potential in omnidirectional perception, stretchable sensors, and green electronics.

Suppressing Interface Strain for Eliminating Double-Slope Behaviors: Towards Ideal Conformable Polymer Field-Effect Transistors.

High-mobility polymer field-effect transistors (PFETs) are being actively explored for applications in soft electronic skin and low-cost flexible displays because of their superior solution processability, mechanical flexibility, and stretchability. However, most of high-mobility PFETs often deviate from the idealized behavior with variable mobility, large threshold voltage, and high off-state current, which masks their intrinsic properties and significantly impedes their practical applications. Here, it is first revealed that interface strain between polymer thin film and rigid substrate plays a crucial role in determining the ideality of PFETs, and demonstrate that various ideal conformable PFETs can be successfully fabricated by releasing strain. It is found that strain in film can be released by one-step peeling strategy, which can reduce π-π stacking distance and suppress generation of oxygen doped carriers, thereby obtaining linearly injected charge carriers and decreased carrier concentration in channel, eventually realizing ideal PFETs. More impressively, the fabricated ideal conformable PFET array displays outstanding conformability to curved objects, and meanwhile showing excellent organic light-emitting display driving capability. The work clarifies the effect of the interface strain on the device ideality, and strain can be effectively released by a facile peeling strategy, thus offering useful guidance for the construction of ideal conformable PFETs.

High-Performance Full-Photolithographic Top-Contact Conformable Organic Transistors for Soft Electronics.

Organic thin-film transistors (OTFTs) are identified to be the most promising candidate for next-generation wearable and implantable electronics because of their unique advantages including their flexibility, low cost, long-term biocompatibility, and simple packaging. However, commercialization of organic transistors remains an enormous challenge due to their low mobility and lack of scalable strategy for high-precise soft devices. Here, a novel photolithography fabrication strategy is proposed, which is completely compatible with various commercial organic semiconductor materials, for the first demonstration of the fully photolithographic top-contact conformable OTFTs with the device density as high as 1523 transistors cm-2. Excellent electrical and mechanical properties with device yield as high as 100%, field-effect mobility up to 1-2 cm2 V-1 s-1, and outstanding conformability are shown. This work provides a new strategy that can fully maximize the advantages of organic materials and photolithography technology, showing a great prospect in the development of high-performance, high-precise organic devices toward the commercialized and industrialized soft electronic products.

Blurred Electrode for Low Contact Resistance in Coplanar Organic Transistors.

Inefficient charge injection and transport across the electrode/semiconductor contact edge severely limits the device performance of coplanar organic thin-film transistors (OTFTs). To date, various approaches have been implemented to address the adverse contact problems of coplanar OTFTs. However, these approaches mainly focused on reducing the injection resistance and failed to effectively lower the access resistance. Here, we demonstrate a facile strategy by utilizing the blurring effect during the deposition of metal electrodes, to significantly reduce the access resistance. We find that the transition region formed by the blurring behavior can continuously tune the molecular packing and thin-film growth of organic semiconductors across the contact edge, as well as provide continuously distributed gap states for carrier tunnelling. Based on this versatile strategy, the fabricated dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) coplanar OTFT shows a high field-effect mobility of 6.08 cm2 V-1 s-1 and a low contact resistance of 2.32 kΩ cm, comparable to the staggered OTFTs fabricated simultaneously. Our work addresses the crucial impediments for further reducing the contact resistance in coplanar OTFTs, which represents a significant step of contact injection engineering in organic devices.

Cobweb-like, Ultrathin Porous Polymer Films for Ultrasensitive NO2 Detection.

Gas sensors based on polymer field-effect transistors (FETs) have drawn much attention owing to the inherent merits of specific selectivity, low cost, and room temperature operation. Ultrathin (<10 nm) and porous polymer semiconductor films offer a golden opportunity for achieving high-performance gas sensors. However, wafer-scale fabrication of such high-quality polymer films is of great challenge and has rarely been realized before. Herein, the first demonstration of 4 in. wafer-scale, cobweb-like, and ultrathin porous polymer films is reported via a one-step phase-inversion process. This approach is extremely simple and universal for constructing various ultrathin porous polymer semiconductor films. Thanks to the abundant pores, ultrathin size, and high charge-transfer efficiency of the prepared polymer films, our gas sensors exhibit many superior advantages, including ultrahigh response (2.46 × 106%), low limit of detection (LOD) (<1 ppm), and excellent selectivity. Thus, the proposed fabrication strategy is exceptionally promising for mass manufacturing of low-cost high-performance polymer FET-based gas sensors.

Strain-Discriminable Pressure/Proximity Sensing of Transparent Stretchable Electronic Skin Based on PEDOT:PSS/SWCNT Electrodes.

Pressure/proximity sensing as the essential function of electronic skin (e-skin) has become an emerging technological goal for new-generation electronic devices in a wide variety of application fields, for example, smart electronics, human-machine interaction, and prosthetics. However, the current research lacks pressure/proximity detection of the stretched e-skin, which ignores the key elastic characteristic of skin and hinders the development of e-skin. Here, the pressure/proximity detection of the transparent e-skin in the stretching state is demonstrated based on poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)/single-walled carbon nanotube (SWCNT). The high transparency of the e-skin realizes the visual imperception for wearable electronic systems. The perfect combination of stretchable SWCNT and highly conductive PEDOT:PSS endows the sensors with high stretchability and high discrimination capability toward strain, providing an effective way to overcome the interference of strain to realize accurate pressure/proximity detection of stretched e-skin at different strains.

Skin-like Ultrasensitive Strain Sensor for Full-Range Detection of Human Health Monitoring.

The development of strain sensors with high sensitivity and stretchability, which can accurately detect different human activities such as subtle physiological signals and large-scale joint motions is essential for disease diagnosis and human health monitoring. However, achieving both high sensitivity and stretchability is still an enormous challenge at the moment, particularly for intrinsically stretchable strain sensors. Herein, utilizing large differences in the conductivity and stretchability of micropatterned Au and SWCNTs, we present an ultrasensitive intrinsically stretchable strain sensor by a one-step photolithography process. Its high sensitivity is inspired from spiders' slit organ and the high stretchability is enlightened from spiders' neural pathway. The skin-like sensor exhibits many superior merits, including ultrahigh sensitivity (gauge factors of 7.1 × 104 to 3.4 × 106), wide detection range (up to 100% strain), excellent durability (1000 cycles), ultralow limit of detection (0.1% strain), fast response (1.3 ms), and minimal feature size (≤100 µm). These fascinating merits allow the strain sensor to precisely detect diverse human activities. This work opens up a feasible path to fabricate highly sensitive and stretchable strain sensors, presenting their promising potential in future personalized healthcare, as electronic skins, and being a portable friendly human-machine interaction system.

Ultrathin Air-Stable n-Type Organic Phototransistor Array for Conformal Optoelectronics.

Development of conformal n-channel organic phototransistor (OPT) array is urgent for future applications of organic complementary circuits in portable and wearable electronics and optoelectronics. In this work, the ultrathin conformal OPT array based on air-stable n-type PTCDI-C13H27 was fabricated. The OPT array shows excellent electrical and photoelectrical performance, good device uniformity, and remains stable in electron mobility by 83% after 90 days compared to the initial values. Eventhough mobility, on-state current, off-state current, and photocurrent of PTCDI-C13H27 thin film phototransistor show slight decrease with the decreased bending radius, the device still remains the stable photosensitivity as high as 104 when the device is freely adhered on the 2D surfaces and 3D hemispherical sphere, which is in a class with the highest photosensitivity for perylene diimide derivatives. These results present the promising application potential of our conformable air-stable n-type PTCDI-C13H27 OPTs as the photodetection system of curved artificial compound eyes in wearable and portable electronics and optoelectronics.