Assembly-Induced Dynamic Structural Color in a Host-Guest System for Time-Dependent Anticounterfeiting and Double-Lock Encryption.

Manipulation of periodic micro/nanostructures in polymer film is of great importance for academics and industrial applications in anticounterfeiting. However, with the increasing demand on information security, materials with time-dependent features are urgently required, especially the material where the same information can appear more than once on the time scale. Here, one concise strategy to realize time-dependent anticounterfeiting and "double-lock" information encryption based on a host-guest system is proposed, with one photoresponsive azopolymer as the host and one liquid-crystalline molecule as the guest. The system exhibits a tunable mass transport in pre-designed periodic micro/nanostructures by tailoring the process of cis-to-trans recovery of azo groups and assembly of mesogenic trans-isomers, resulting in a dynamic structural color in film. Taking advantage of this extraordinary feature, time-dependent dynamic anticounterfeiting has been achieved. More importantly, the time of each state's appearance in the whole process can be modulated by changing the host-guest ratio. Combining the manipulatable process of mass transport with the unique decoding method, the stored information in film can be decrypted correctly. This work provides an unprecedented dynamic approach for advanced anticounterfeiting technology with a higher level of security and high-end applications in information encryption.

Steerable mass transport in a photoresponsive system for advanced anticounterfeiting.

Numerous anticounterfeiting platforms using photoresponsive materials have been designed to improve information security, enabling applications in anticounterfeiting technology. However, fabricating sophisticated micro/nanostructures using bidirectional mass transport to achieve advanced anticounterfeiting remains challenging. Here, we propose one strategy to achieve steerable mass transport in a photoresponsive system with the assistance of solvent vapor at room temperature. Upon optimizing the host-guest ratio and the width of photoisomerized areas, wettability gradient is acquired just photo-patterning once, then bidirectional mass transport is realized due to the competition of mass transport induced by surface energy gradient of the material itself and flow of the solvent on the film surface with wettability gradient. Taking advantage of the interaction between solvent and film surface with wettability gradient, this bidirectional polymer flow has been successfully applied in multi-mode anticounterfeiting. This work paves a promising avenue toward high-level information storage in soft materials, demonstrating the potential applications in anticounterfeiting.

Capturing Doublet Intermediate Emitters by Chemically Crosslinking Confinement towards Spatiotemporal Encryption.

Photoluminescence is one of the most meticulous ways to manipulate light energy. Typical photoluminescent emitters are mostly stable substances with a pure photophysical process of spontaneous photon-emission from their excited states. Intermediate emitters are elusive attributing to their synchronous energy transfer process including photophysical and incomplete photochemical pathways. An intermediate emitter containing radicals is more difficult to be observed due to its inherent chemical reactivity. Here, these challenges are overcome by spontaneously formed space limitations in polymer crosslinking networks meanwhile chemically active intermediates are captured. These doublet intermediates exhibit unique long-wavelength emissions under chemically crosslinking confinement conditions, and their luminous mechanism provides a novel perspective for designing intermediate emitters with liquid-crystal character and photoresponsive features towards spatiotemporal encryption, promising for the detection of photochemical reactions and the development of fascinating luminescent systems.

Supramolecular Cation-π Interaction Enhances Molecular Solar Thermal Fuel.

Molecular solar thermal fuels (MOSTs), especially azobenzene-based MOSTs (Azo-MOSTs), have been considered as ideal energy-storage and conversion systems in outer or confined space because of their "closed loop" properties. However, there are two main obstacles existing in practical applications of Azo-MOSTs: the solvent-assistant charging process and the high molar extinction coefficient of chromophores, which are both closely related to the π-π stacking. Here, we report one efficient strategy to improve the energy density by introducing a supramolecular "cation-π" interaction into one phase-changeable Azo-MOST system. The energy density is increased by 24.7% (from 164.3 to 204.9 J/g) in Azo-MOST with a small loading amount of cation (2.0 mol %). Upon light triggering, the cation-π-enhanced Azo-MOST demonstrates one gravimetric energy density of about 56.9 W h/kg and a temperature increase of 8 °C in ambient conditions. Then the enhanced mechanism is revealed in both molecular and crystalline scales. This work demonstrates the huge potential of supramolecular interaction in the development of Azo-MOST systems, which could not only provide a universal method for enhancing the energy density of solar energy storage but also balance the conflicts between molecular design and the condensed state for phase-changeable materials.

On the understanding of dielectric elastomer and its application for all-soft artificial heart.

Although dielectric elastomer (DE) with substantial actuated strain (AS) has been reported 20 years ago, its scientific understanding remains unclear. The most accepted theory of DE, which is proposed in 2000, holds the view that AS of DE is induced by the Maxwell stress. According to this theory, materials have similar ratios of permittivity and Young's modulus should have similar AS, while the experimental results are on contrary to this theory, and the experimental AS has no relationship with ideal AS. Here, a new dipole-conformation-actuated strain cross-scale model is proposed, which can be generally applied to explain the AS of DE without pre-strain. According to this model, several characteristics of an ideal DE are listed in this work and a new DE based on polyphosphazene (PPZ) is synthesized. The AS of PPZ can reach 84% without any pre-strain. At last, a PPZ-based all soft artificial heart (ASAH) is built, which works in the similar way with natural myocardium, indicating that this material has great application potential and possibility in the construction of an ASAH for heart failure (HF) patients.

[Analysis of 163 rib fractures by imaging examination].

OBJECTIVE: To explore the applications of imaging examination on rib fracture sites in forensic identification. METHODS: Features including the sites, numbers of the processed imaging examination and the first radiological technology at diagnosis in 56 cases of rib fractures from 163 injuries were retrospectively analyzed. RESULTS: The detection rate of the rib fractures within 14 days was 65.6%. The initial detection rate of anterior rib fracture proceeded by X-ray was 76.2%, then 90.5% detected at a second time X-ray, while the detection rate of CT was 66.7% and 80.0%, respectively. The initial detec- tion rate of rib fracture in axillary section proceeded by X-ray was 27.6%, then 58.6% detected at a second time X-ray, while the detection rate of CT was 54.3% and 80.4%, respectively. The initial detection rate of posterior rib fracture proceeded by X-ray was 63.6%, then 81.8% detected at a second time X-ray, while the detection rate of CT was 50.0% and 70.0%, respectively. CONCLUSION: It is important to pay attention to the use of combined imaging examinations and the follow-up results. In the cases of suspicious for rib fracture in axillary section, CT examination is suggested in such false X-ray negative cases.