Transcranial Acoustic Metamaterial Parameters Inverse Designed by Neural Networks

Objective:The objective of this work is to investigate the mapping relationship between transcranial ultrasound image quality and transcranial acoustic metamaterial parameters using inverse design methods.Impact Statement:Our study provides insights into inverse design methods and opens the route to guide the preparation of transcranial acoustic metamaterials.Introduction:The development of acoustic metamaterials has enabled the exploration of cranial ultrasound,and it has been found that the influence of the skull distortion layer on acoustic waves can be effectively eliminated by adjusting the parameters of the acoustic metamaterial.However,the interaction mechanism between transcranial ultrasound images and transcranial acoustic metamaterial parameters is unknown.Methods:In this study,1,456 transcranial ultrasound image datasets were used to explore the mapping relationship between the quality of transcranial ultrasound images and the parameters of transcranial acoustic metamaterials.Results:The multioutput parameter prediction model of transcranial metamaterials based on deep back-propagation neural network was built,and metamaterial parameters under transcranial image evaluation indices are predicted using the prediction model.Conclusion:This inverse big data design approach paves the way for guiding the preparation of transcranial metamaterials.

Excitation-wavelength-dependent fluorescent organohydrogel for dynamic information anti-counterfeiting

Anti-counterfeiting labels with various fluorescent colors are of great importance in information encryption-decryption,but are still limited to static information display.Therefore,it is urgent to develop new materials and encryption-decryption logic for improving the security level of secret information.In this study,an organohydrogel made up of poly(N,N-dimethylacrylamide)(pDMA)hydrogel network and polyoctadecyl methacrylate(pSMA)organogel network that copolymerized with two fluorophores,6-acrylamidopicolinic acid moieties(6APA,fluorescent ligand)and spiropyran units(SPMA,photochromic monomer),was prepared by a two-step interpenetrating method.As UV light of 365nm and 254nm can both cleave C_(spiro)-O bonds of SPMA,and the green fluorescence of 6APA-Tb^(3+) can only be excited by 254nm light,the organohydrogel displays yellow and red under the irradiation of 254nm and 365 nm,respectively.In addition to wavelength selectivity,these two fluorophores are thermal-responsive,leading to the fluorescence variation of the organohydrogel during heating process.As a result,secret information loaded on the organohydrogel can be decrypted by the irradiation of UV light,and the authenticity of the information can be further identified by thermal stimulation.Our fluorescent organohydrogel can act as an effective anti-counterfeiting label to improve the information security and protect the information from being cracked.

Interfacial Reinitiation of Free Radicals Enables the Regeneration of Broken Polymeric Hydrogel Actuators

Living organisms,from plants to animals,have inspired and guided the design and fabrication of polymeric hydrogels with biomimetic morphology,shape deformation,and actuation behavior.However,the existing polymeric hydrogels are fragile and vulnerable,which seriously hinders further application.Therefore,endowing hydrogels with a biomimetic self-growth property and regenerating the macroscopic shape of hydrogels after they suffer significant damage are highly desirable for the next generation of adaptive biomimetic hydrogels.Inspired by the tail regeneration of geckos,we herein report an efficient and universal strategy of interfacial diffusion polymerization(IDP),which can regenerate the polymeric layer at a solid–liquid interface,thereby growing new hydrogels on the existing hydrogel layers.Through changing the solvent viscosity and/or monomer type of the hydrogel precursor,diverse new hydrogels have been regenerated to endow the initial hydrogels with additional fluorescent functions and/or actuating properties.Due to the high efficiency and universality of IDP,an injured hydrogel actuator can be repaired,regenerated,and recovered to its initial condition,even after suffering severe damage such as cutting or piercing.We believe that the regeneration strategy of polymeric hydrogels will inspire the design of biomimetic materials and motivate the fabrication of the next generation of soft robots with adaptive and multifunctional properties.

Antifreezing and Stretchable Organohydrogels as Soft Actuators

Inspired by the freezing tolerance performances found in living creatures, an effect approach is presented to develop novelantifreezing polymeric organohydrogel actuators. Through construction of a bilayer hydrogel including a nonresponsivepolyacrylamide (PAAm) layer and a pH-responsive polyacrylic acid (PAA) layer in the presence of a mixed solvent of water andglycerol, organohydrogel actuators that could produce various shape deformations at subzero temperatures have been achieved,and the actuating speed could be tuned by adjusting the temperature and the ratio between glycerol and water. Moreover, aseries of application demonstrations including a weightlifting robot, artificial valve, and robotic arm have been displayed. Inaddition, by introducing the ionic compound KI into the glycerol-based organogel, flexible conductors that could perform stablesensing performance over a wide range of temperatures from -30℃ to 60℃ have been developed.

Mechanochemical transformation of fluorescent hydrogel based on dynamic lanthanide-terpyridine coordination

As a burgeoning research field, ultrasound-responsive materials have attracted intense interest in healthcare research. However, the basic mechanism of sonochemical effect in the quasi-solid state is far from being well understood than those in the solution. Herein, we showcase mechanochemical transformations of europium(Ⅲ) complexes in a supramolecular hydrogel matrix. With the combination of labile terpyridine-europium complexes(TPY-Eu^(3+)) as mechanochromic moieties and an ultrasound-responsive fluorogen(URF) as a molecular tweezer, the hydrogel produces a notable fluorescence change in response to ultrasound. The mechanochemical transformation was elucidated by molecular dynamics(MD) simulations, and fully probed and evidenced by electrochemical experiments, X-ray photoelectron spectroscopy(XPS), and attenuated total reflectance-Fourier transform infrared(ATR-FTIR) spectroscopy.

Fluorescent Organohydrogel with Thermal-Induced Color Change for Anti-counterfeiting

Smart fluorescent patterns enable dynamic color variation under external stimuli,showing a much higher security level in the field of anti-counterfeiting.However,there is still lacking of a simple and convenient way to achieve dynamic fluorescence changes.Herein,a fluorescent organohydrogel made up of a poly(N,/N-dimethylacrylamide-co-isopropylacrylamide)(p(DMA-NIPAM))hydrogel network and a polyflauryl methacrylate)(PLMA)organogel network was fabricated via a two-step interpenetrating technique.The former network bears naphthalimide moieties(DEAN,green fluorescent monomer)and the later contains 6-acrylamidopicolinic acid(6APA,fluorescent ligand),leading to emitting green fluorescence.When Eu^(3+) was introduced and coordinated with 6APA,the organohydrogel displays red fluorescence,which can further emit yellow after applying thermal stimulus.Furthermore,by adjusting the proportion of comonomers,various organohydrogels can be obtained,which can be programmed and act as an effective platform for the encryption and decryption of secret information.

Progress in aggregation-induced emission-active fluorescent polymeric hydrogels

Aggregation-induced emission(AIE)-active fluorescent polymeric hydrogels(FPHs)are the marriage of AIE-active materials and polymeric hydrogels.Different from the widely studied AIE-active materials that are primarily used in solution or dry solid state,they feature a three-dimensional crosslinked polymer network that can absorb water without dissolving.Consequently,they are known to bear many advantageous properties such as soft wet nature,tissue-like mechanical strength,biocompatibility,biomimetic self-healing feature,facilely tailored structure,as well as responsive fluorescence and volume/shape changes,thus representing a promising category of luminescent materials with many frontier uses.This Review is intended to give a systematic summary of the recent progress in this young but flourishing research area,with particular focus on their design and preparation.Current challenges and future outlooks in this field are also discussed in order to attract new interests and inspire more efforts.