No abstract

A flexible carbon fiber aerogel with a very high surface area for supercapacitor application is reported by carbonization and chemical activation of low-cost natural cotton with KOH. The carbon fibers in the aerogel present as a twisted and tubular structure. Depending on the amount of KOH used in the activation process, the specific surface area of aerogels ranges from 1536 to 2436 m2 g–1, while their electrical conductivity remains ∼860 S m–1. In spite of pore size in the range of 1.0–4.0 nm and pore volume mainly contributed by micropores, the carbon aerogel exhibits a high specific capacitance of 283 F g–1 (1 A g–1) in 6 M KOH aqueous electrolyte and retains a high capacitance retention of 224 F g–1 at current density up to 100 A g–1. Importantly, a symmetric capacitor built with the aerogel electrodes exhibits a rather small time constant (0.56 s). The superior capacitive performance of a CF electrode is closely related to its distinct structural advantage. The tubular carbon fibers that are several millimeters in length offer ultralong electronic and ionic pathways, while plenty of nanopores on the fiber walls created by KOH activation enable fast ion transport across the walls. Our results demonstrate that capacitive performance of the traditional microporous carbon, which is characterized by poor ion kinetics, can be significantly enhanced by properly engineering the electrode architecture.

A stretchable pressure sensor can provide highly sensitive and strain-unperturbed measurement to pressures on deformed skins.

Flexible and sensitive sensors that can detect external stimuli such as pressure, temperature, and strain are essential components for applications in health diagnosis and artificial intelligence. Multifunctional sensors with the capabilities of sensing pressure and temperature simultaneously are highly desirable for health monitoring. Here, we have successfully fabricated a flexible and simply structured bimodal sensor based on metal-organic frameworks (MOFs) derived porous carbon (PC) and polydimethylsiloxane (PDMS) composite. Attributed to the porous structure of PC/PDMS composite, the fabricated sensor exhibits high sensitivity (15.63 kPa), fast response time (<65 ms), and high durability (∼2000 cycles) for pressure sensing. Additionally, its application in detecting human motions such as subtle wrist pulses in real time has been demonstrated. Furthermore, the as-prepared device based on the PC/PDMS composite exhibits a good sensitivity (>0.11 °C) and fast response time (∼100 ms), indicating its potential application in sensing temperature. All of these capabilities indicate its great potential in the applications of health monitoring and artificial skin for artificial intelligence system.

No abstract

Organic electrochemical transistors (OECTs) represent an emerging device platform for next‐generation bioelectronics owing to the uniquely high amplification and sensitivity to biological signals. For achieving seamless tissue–electronics interfaces for accurate signal acquisition, skin‐like softness and stretchability are essential requirements, but they have not yet been imparted onto high‐performance OECTs, largely due to the lack of stretchable redox‐active semiconducting polymers. Here, a stretchable semiconductor is reported for OECT devices, namely poly(2‐(3,3′‐bis(2‐(2‐(2‐methoxyethoxy)ethoxy)ethoxy)‐[2,2′‐bithiophen]‐5)yl thiophene) (p(g2T‐T)), which gives exceptional stretchability over 200% strain and 5000 repeated stretching cycles, together with OECT performance on par with the state‐of‐the‐art. Validated by systematic characterizations and comparisons of different polymers, the key design features of this polymer that enable the combination of high stretchability and high OECT performance are a nonlinear backbone architecture, a moderate side‐chain density, and a sufficiently high molecular weight. Using this highly stretchable polymer semiconductor, an intrinsically stretchable OECT is fabricated with high normalized transconductance (≈223 S cm−1) and biaxial stretchability up to 100% strain. Furthermore, on‐skin electrocardiogram (ECG) recording is demonstrated, which combines built‐in amplification and unprecedented skin conformability.

No abstract

Methods and mechanisms for improvement of photocatalytic activity, are important and popular research topics for renewable energy production and waste water treatment. Here, we demonstrate a facile laser drilling method for engineering well-aligned pore arrays on magnetron-sputtered WS2 nanofilms with increased active edge sites; the proposed method promotes partial oxidation to fabricate WS2/WO3 heterojunctions that enhance the separation of photogenerated electron-hole pairs. The WS2 film after one, two, and three treatments exhibited photocurrent density of 3.9, 6.2, and 8 μA/cm2, respectively, reaching up to 31 times larger than that of pristine WS2 film along with greatly improved charge recombination kinetics. The unprecedented combinational roles of laser drilling revealed in this study in regards to geometric tailoring, chemical transformation, and heterojunction positioning for WS2-based composite nanomaterials create a foundation for further enhancing the performance of other 2D transition metal dichalcogenides in photocatalysis via laser treatment.