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Although photochromic molecules have attracted widespread interest in various fields, solid‐state photochromism remains a formidable challenge, owing to the substantial conformational constraints that hinder traditional molecular photoisomerization processes. Benefiting from the significant color change upon radical generation, chemical systems enabling a photoinduced radical (PIR) behavior through photoinduced electron transfer (PET) could be ideal candidates for solid‐state photochromism within minimized need of conformational freedom. However, the transient nature of radicals causes a dilemma in this Scheme. Herein, we present a general crystal engineering strategy for rapidly generated (7‐s irradiation to saturation) and ultra‐stable (lasting 12 weeks) PIRs in the solid state, based on the anti‐parallel alignment of para‐hydroxyphenyl groups of persulfurated arenes to form a strong non‐covalent network for efficient PET and radical stabilization. Using this strategy, a PIR platform was constructed, with a superior photochromic behavior remaining in different solid forms (even in the fully‐ground sample) due to their transcendent crystallization ability. On this basis, our compounds can be further processed into reusable papers for light‐writing, accompanied by water fumigation for modulating the reversible process. This work provides new insights into addressing solid‐state photochromism and can inspire a wide range of optical material design from the switchable radical perspective. [ABSTRACT FROM AUTHOR]

Ultrathin devices are rapidly developing for skin‐compatible medical applications and wearable electronics. Powering skin‐interfaced electronics requires thin and lightweight energy storage devices, where solution‐processing enables scalable fabrication. To attain such devices, a sequential deposition is employed to achieve all spray‐coated symmetric microsupercapacitors (μSCs) on ultrathin parylene C substrates, where both electrode and gel electrolyte are based on the cheap and abundant biopolymer, cellulose. The optimized spraying procedure allows an overall device thickness of ≈11 µm to be obtained with a 40% active material volume fraction and a resulting volumetric capacitance of 7 F cm−3. Long‐term operation capability (90% of capacitance retention after 104 cycles) and mechanical robustness are achieved (1000 cycles, capacitance retention of 98%) under extreme bending (rolling) conditions. Finite element analysis is utilized to simulate stresses and strains in real‐sized μSCs under different bending conditions. Moreover, an organic electrochromic display is printed and powered with two serially connected μ‐SCs as an example of a wearable, skin‐integrated, fully organic electronic application. [ABSTRACT FROM AUTHOR]

H2O2 plays a significant role in a range of physiological processes where it performs vital tasks in redox signaling. The sensitivity of many biological pathways to H2O2 opens up a unique direction in the development of bioelectronics devices to control levels of reactive‐oxygen species (ROS). Here a microfabricated ROS modulation device that relies on controlled faradaic reactions is presented. A concentric pixel arrangement of a peroxide‐evolving cathode surrounded by an anode ring which decomposes the peroxide, resulting in localized peroxide delivery is reported. The conducting polymer (poly(3,4‐ethylenedioxythiophene) (PEDOT), is exploited as the cathode. PEDOT selectively catalyzes the oxygen reduction reaction resulting in the production of hydrogen peroxide (H2O2). Using electrochemical and optical assays, combined with modeling, the performance of the devices is benchmarked. The concentric pixels generate tunable gradients of peroxide and oxygen concentrations. The faradaic devices are prototyped by modulating human H2O2‐sensitive Kv7.2/7.3 (M‐type) channels expressed in a single‐cell model (Xenopus laevis oocytes). The Kv7 ion channel family is responsible for regulating neuronal excitability in the heart, brain, and smooth muscles, making it an ideal platform for faradaic ROS stimulation. The results demonstrate the potential of PEDOT to act as an H2O2 delivery system, paving the way to ROS‐based organic bioelectronics. [ABSTRACT FROM AUTHOR]

The paper combines two theoretical approaches – the method of grazing dynamical diffraction (which allows performing the nondestructive structural diagnostics of defects in the near‐surface layers) with efficient numerical simulation method (which enables computation of electron structure in realistically large systems with millions of atoms) – for studying electronic properties in uniaxially strained graphene layers with point defects: impurity atoms. Electron density of states (DOS) is proved sensitive to the direction of uniaxial tensile deformation and configuration of defects. If defects are distributed orderly, the band gap value (estimated from the DOS curves) varies nonmonotonically versus the stretching deformation along zigzag‐edge direction. In this case, the minimal tensile strain required for the band gap opening is found to be smaller than that for defect‐free graphene, and the maximum band gap value is close to that predicted for failure limit of the defect‐free graphene. The obtained results play a significant part for band gap engineering in graphene: via spatial configuring of defects and external tensile stresses. [ABSTRACT FROM AUTHOR]