Robust photothermal anti-icing/deicing via flexible CMDSP carbon nanotube films.

Photothermal anti-icing/deicing technology is an environmentally friendly surface technology that can be applied to the surface of aircraft, vehicles or ships. However, it is still a huge challenge to develop a strong and stable flexible film that can efficiently convert light to heat. Here, based on a simple electrochemical method to construct a zinc oxide (ZnO) nanoneedles structure on the surface of the carbon nanotube film, a film with the function of condensed micro-droplet self-propelling (CMDSP) was successfully prepared. The prepared film has excellent light absorption capacity and high energy transfer efficiency (76.71%). The film has strong photothermal anti-icing/deicing performance. Under 4406 Lux light irradiation, even under low temperature conditions of -5 °C, the icing delay time exceeds 4 h. This novel characteristic is attributed to the CMDSP function on the surface and the ultra-fast evaporation mechanism, which can remove water droplets on the surface as quickly as possible. This function helps to design energy-saving equipment that requires high-power heating and deicing.

A first-principles study of the thermoelectric properties of rhombohedral GeSe.

Manipulation of crystal symmetry is an important strategy to tune the thermoelectric performance. High-symmetry thermoelectric materials benefit from high band degeneracy. With first-principles calculations and Boltzmann transport theory, we systematically investigate the electronic and phononic transport properties of rhombohedral GeSe with higher symmetry. At optimized carrier concentrations, the maximum power factors are found to be 5.86 mW m-1 K-2 for the p-type and 4.45 mW m-1 K-2 for the n-type, respectively. The high p-type power factor originates from the highly degenerated L and Σ bands and small energy offset between them, while the n-type one results from the weak electron-phonon coupling. More importantly, rhombohedral GeSe possesses anisotropic and low lattice thermal conductivities of 3.58 W m-1 K-1 and 1.96 W m-1 K-1 at room temperature in the intralayer and interlayer directions, respectively, which is associated with the giant phonon anharmonicity driven by the resonant bonding. Combining the high power factor and low thermal conductivity, the predicted ZT values for p-type and n-type doping can reach 2.02 and 2.37 at 800 K. This study offers insights into the thermal and charge transport properties in rhombohedral GeSe, and demonstrates that both p-type and n-type GeSe are potential high-performance thermoelectric materials.

Disparate strain response of the thermal transport properties of bilayer penta-graphene as compared to that of monolayer penta-graphene.

In this study, strain modulation of the lattice thermal conductivity of monolayer and bilayer penta-graphene (PG) at room temperature was investigated using first-principles calculations combined with the phonon Boltzmann transport equation. The thermal conductivities of both the monolayer and the bilayer PG exhibit a robust nonmonotonic up-and-down behavior under strain despite the effect of van der Waals (vdW) interactions, and the thermal conductivities of bilayer PG under strain are significantly reduced by up to 87%. Using phonon-level systematic analysis, the variation of thermal conductivity with the increasing strain was determined by increasing the phonon lifetime in specific phonon modes, and that with the reduction of strain was determined by the decrease of both phonon group velocity and phonon lifetime. Moreover, bilayer PG shows an unexpectedly different response to strain when compared with monolayer PG, and a significantly larger reduction (>60%) in the thermal conductivity of bilayer PG is achieved when the strain reaches 10% because the interlayer interactions enhance the phonon anharmonicity of the phonon modes of ultra-low frequency. Our study shows that bilayer PG will have tremendous opportunities for application in thermal management and two-dimensional nanoscale electronic devices owing to its largely tunable thermal conductivity.

1.7 µm wavelength tunable gain-switched fiber laser and its application to spectroscopic photoacoustic imaging.

Recently demonstrated bond-selective photoacoustic (PA) imaging has revealed the importance of 1.7 µm laser sources. In this Letter, we demonstrate a gain-switched thulium-doped fiber laser with continuous tuning from 1690 to 1765 nm by using an electrically driven acousto-optical tunable filter. Micro-joule laser pulses with a shot-to-shot intensity variation of 1.6% and a pulse duration of 150 ns are obtained. The laser source is then harnessed to implement a PA microscopy system, of which the lateral resolution is estimated to be 15.6 µm by scanning the edge of a black tape. The PA spectra of butter, rapeseed oil, and adipose tissue are measured, and they show a consistent absorption peak of around 1720 nm. Photoacoustic microscopy imaging of the adipose tissue demonstrates a high optical absorption contrast of lipids and the superiority of the laser for spectroscopic PA detection.

Moisture Effects on Acoustic Emission Characteristics and Damage Mechanisms of Balsa Wood Core Composite Sandwich under 4-Point Bending.

To contribute to the development of sustainable composites, this work investigates the effects of moisture on the key AE characteristics related to the damage mechanisms of a bio-based balsa wood core sandwich in 4-point bending tests, including cumulative counts, amplitude, peak frequency, and duration. Novel triple dog-bone balsa wood core sandwich specimens with different MC (moisture content) were studied by comparing microscopic observations and a proposed two-step clustering approach in AE analysis. Three MC states, i.e., dry, 50% MC, and 120% MC, are discussed. GFRP (glass-fiber-reinforced polymer) laminate skin damages were found to be predominant in most GFRP-balsa sandwich specimens, but balsa wood core damages play a more important role as MC increases. The degradation of the bending stiffness of the sandwich was proven to be faster in the first linear stage of the moisture absorption curve, while the decrease in bending strength was more pronounced at the MC saturation level. Finally, for all of the dry and wet sandwich specimens, peak frequency and duration were proven to be more helpful in identifying damages associated with the lighter bio-based balsa wood core, such as balsa core damages and skin/core debonding.

Robust ultrahigh electromagnetic interference shielding effectiveness based on engineered structures of carbon nanotube films.

High-performance electromagnetic interference (EMI) shielding materials with ultrathin, flexible, and pliable mechanical properties are highly desired for high-end equipments, yet there remain large challenges in the manufacture of these materials. Here, carbon nanotube film (CNTF)/copper (Cu) nanoparticle (NP) composite films are fabricated via a facile electrodeposition method to achieve high electromagnetic shielding efficiency. Notably, a CNTF/Cu NP composite film with 15 µm thickness can achieve excellent EMI shielding efficiency of ∼248 dB and absolute EMI shielding effectiveness as high as 2.17 × 105 dB cm2 g-1, which are the best values for composite EMI shielding materials with similar or greater thicknesses. These engineered composite films exhibit excellent deformation tolerance, which ensures the robust reliability of EMI shielding efficiency after 20,000 cycles of repeated bending. Our results represent a critical breakthrough in the preparation of ultrathin, flexible, and pliable shielding films for applications in smart, portable and wearable electronic devices, and 5G communication.

Saliency enhancement method for photoacoustic molecular imaging based on Grüneisen relaxation nonlinear effect.

Photoacoustic molecular imaging technology has a wide range of applications in biomedical research. In practical scenarios, both the probes and blood generate signals, resulting in the saliency of the probes in the blood environment being diminished, impacting imaging quality. Although several methods have been proposed for saliency enhancement, they inevitably suffer from moderate generality and detection speed. The Grüneisen relaxation (GR) nonlinear effect offers an alternative for enhancing saliency and can improve generality and speed. In this article, the excitation and detection efficiencies are optimized to enhance the GR signal amplitude. Experimental studies show that the saliency of the probe is enhanced. Moreover, the issue of signal aliasing is studied to ensure the accuracy of enhancement results in the tissues. In a word, the feasibility of the GR-based imaging method in saliency enhancement is successfully demonstrated in the study, showing the superiorities of good generality and detection speed.

Non-invasive evaluation of endometrial microvessels via in vivo intrauterine photoacoustic endoscopy.

The endometrium microvessel system, responsible for supplying oxygen and nutrients to the embryo, holds significant importance in evaluating endometrial receptivity (ER). Visualizing this system directly can significantly enhance ER evaluation. Currently, clinical methods like Narrow-band hysteroscopy and Color Doppler ultrasound are commonly used for uterine blood vessel examination, but they have limitations in depth or resolution. Endoscopic Photoacoustic Imaging (PAE) has proven effective in visualizing microvessels in the digestive tract, while its adaptation to uterine imaging faces challenges due to the uterus's unique physiological characteristics. This paper for the first time that uses high-resolution PAE in vivo to capture a comprehensive network of endometrial microvessels non-invasively. Followed by continuous observation and quantitative analysis in the endometrial injury model, we further corroborated that PAE detection of endometrial microvessels stands as a valuable indicator for evaluating ER. The PAE system showcases its promising potential for integration into reproductive health assessments.

In vivo endoscopic optical coherence elastography based on a miniature probe.

Optical coherence elastography (OCE) is a functional extension of optical coherence tomography (OCT). It offers high-resolution elasticity assessment with nanoscale tissue displacement sensitivity and high quantification accuracy, promising to enhance diagnostic precision. However, in vivo endoscopic OCE imaging has not been demonstrated yet, which needs to overcome key challenges related to probe miniaturization, high excitation efficiency and speed. This study presents a novel endoscopic OCE system, achieving the first endoscopic OCE imaging in vivo. The system features the smallest integrated OCE probe with an outer diameter of only 0.9 mm (with a 1.2-mm protective tube during imaging). Utilizing a single 38-MHz high-frequency ultrasound transducer, the system induced rapid deformation in tissues with enhanced excitation efficiency. In phantom studies, the OCE quantification results match well with compression testing results, showing the system's high accuracy. The in vivo imaging of the rat vagina demonstrated the system's capability to detect changes in tissue elasticity continually and distinguish between normal tissue, hematomas, and tissue with increased collagen fibers precisely. This research narrows the gap for the clinical implementation of the endoscopic OCE system, offering the potential for the early diagnosis of intraluminal diseases.

In-vivo assessment of a rat rectal tumor using optical-resolution photoacoustic endoscopy.

Optical-resolution photoacoustic endoscopy (OR-PAE) has been proven to realize imaging on the vascular network in the gastrointestinal (GI) tract with high sensitivity and spatial resolution, providing morphological information. Various photoacoustic endoscopic catheters were developed to improve the resolution and adaptivity of in-vivo imaging. However, this technology has not yet been validated on in-vivo GI tumors, which generally feature angiogenesis. The tumor causes thickened mucosa and neoplasia, requiring large depth-of-field (DOF) in imaging, which contradicts to high-resolution imaging. In this work, a novel catheter was developed with a high resolution of ∼27 µm, providing a matched DOF of ∼400 µm to cover the vessels up to the submucosa layer. Optical-resolution photoacoustic endoscopic imaging was first performed on in-vivo rat rectal tumors. In addition, to further characterize the vessel morphology, tumor-suspected regions and normal regions were selected for quantification and analysis of vessel dimension distribution and tortuosity. All the results suggest that the OR-PAE has great application potential in tumor diagnosis, evaluation, and monitoring of therapeutic efficacy.

Hydrogel Microneedle Patches Loaded with Stem Cell Mitochondria-Enriched Microvesicles Boost the Chronic Wound Healing.

Rescuing or compensating mitochondrial function represents a promising therapeutic avenue for radiation-induced chronic wounds. Adult stem cell efficacies are primarily dependent on the paracrine secretion of mitochondria-containing extracellular vesicles (EVs). However, effective therapeutic strategies addressing the quantity of mitochondria and mitochondria-delivery system are lacking. Thus, in this study, we aimed to design an effective hydrogel microneedle patch (MNP) loaded with stem cell-derived mitochondria-rich EVs to gradually release and deliver mitochondria into the wound tissues and boost wound healing. We, first, used metformin to enhance mitochondrial biogenesis and thereby increasing the secretion of mitochondria-containing EVs (termed "Met-EVs") in adipose-derived stem cells. To verify the therapeutic effects of Met-EVs, we established an in vitro and an in vivo model of X-ray-induced mitochondrial dysfunction. The Met-EVs ameliorated the mitochondrial dysfunction by rescuing mitochondrial membrane potential, increasing adenosine 5'-triphosphate levels, and decreasing reactive oxygen species production by transferring active mitochondria. To sustain the release of EVs into damaged tissues, we constructed a Met-EVs@Decellularized Adipose Matrix (DAM)/Hyaluronic Acid Methacrylic Acid (HAMA)-MNP. Met-EVs@DAM/HAMA-MNP can load and gradually release Met-EVs and their contained mitochondria into wound tissues to alleviate mitochondrial dysfunction. Moreover, we found Met-EVs@DAM/HAMA-MNP can markedly promote macrophage polarization toward the M2 subtype with anti-inflammatory and regenerative functions, which can, in turn, enhance the healing process in mice with skin wounds combined radiation injuries. Collectively, we successfully fabricated a delivery system for EVs, Met-EVs@DAM/HAMA-MNP, to effectively deliver stem cell-derived mitochondria-rich EVs. The effectiveness of this system has been demonstrated, holding great potential for chronic wound treatments in clinic.

Molecular switch for tuning ions across nanopores by an external electric field.

Active control of ion transport in nanoscale channels is attracting increasing attention. Recently, experimental and theoretical results have verified that depending on the charged surface of nanopores, the solution inside nanopores can contain either negative or positive ions, which does not happen in macroscale channels. However, the control of the surface chemistry of synthetic nanopores is difficult and the design of nanotubes with novel recognition mechanisms that regulate the ionic selectivity of negative and positive charges remains a challenge. We present here a design for an ion-selective nanopore that is controllable by external charges. Our molecular dynamics simulations show that this remarkable selectivity can be switched from predominantly negative to positive ions and that the magnitude of the ionic flux can be varied by changing the distance of the external charges. The results suggest that the hydration structures around ions play a prominent role in the selectivity process, which is tuned by the external charge. These studies may be useful for developing ways to control the behavior, properties and chemical composition of liquids and provide possible technical applications for nanofluidic field effect transistors.

Single-wavelength sO2 measurement based on Grüneisen-relaxation photoacoustic effect.

The photoacoustic effect-based sO2 measurement is attracting more and more attention due to its non-invasiveness and accuracy. Compared with the linear dual-wavelength method, the sO2 measurement based on single-wavelength excitation can be potentially applied with simplified system construction. However, the single-wavelength methods proposed in previous studies decreases the safety or lacks the in-depth resolution. This paper proposes a novel single-wavelength method based on the Grüneisen-relaxation (GR) nonlinear effects. It avoids the high fluence excitation with maintaining in-depth resolution and obtains the signals in hundreds of nanoseconds, simultaneously improving the safety and detection speed. The construction of a single laser source for GR effect generation makes the system stable. The sO2 quantification results of blood samples have a good consistency with the reference values. Our work provides a safer and faster measurement method, and a stable system, to promote its application in the clinical area.

Water harvesting on biomimetic material inspired by bettles.

Many organisms in nature such as beetles and cacti can survive in arid places by their own surface structures that are still able to collect mist. These surfaces have micro-nano structures that maintain a very low adhesion, allowing them to continuously collect and transport water. Here, we used a light curing three dimensional molding process to create a template for a water harvesting system inspired by the back of a beetle, a hydrogel-like beetle back surface for water transport. By changing the curvature structure of the water evacuation channels and altering the hydrophilic and hydrophobic properties of the surface, the designed large-scale artificial water harvesting study was made possible. The results show that if the surface has a proper curvature structure and hydrophobic density, the water collection on the super-impregnated surface is much higher than that on an ordinary hydrophobic surface. Based on this, a new efficient and environmentally friendly water collection scheme is proposed. The data show that the triangular tip structure imitating beetle-backed hydrogel surface collects the highest amount of water with a water weight of 16 g in 2 h. This study offers interesting prospects for designing a new generation of structural materials with a bionic structure distribution for high-efficiency water harvesting. The results of the study are useful for pushing the improvement of environmental-friendly water collection, transport and separation devices. Abbreviations: The dorsal shape of the beetle's back is critical for water collection. In this work, while redesigning the shape of the back of the beetle, the method of 3D printing the beetle back template was used to prepare the beetle back made of hydrogel, which greatly improved the water collection performance and has certain engineering application prospects.

A Miniature Multi-Functional Photoacoustic Probe.

Photoacoustic technology is a promising tool to provide morphological and functional information in biomedical research. To enhance the imaging efficiency, the reported photoacoustic probes have been designed coaxially involving complicated optical/acoustic prisms to bypass the opaque piezoelectric layer of ultrasound transducers, but this has led to bulky probes and has hindered the applications in limited space. Though the emergence of transparent piezoelectric materials helps to save effort on the coaxial design, the reported transparent ultrasound transducers were still bulky. In this work, a miniature photoacoustic probe with an outer diameter of 4 mm was developed, in which an acoustic stack was made with a combination of transparent piezoelectric material and a gradient-index lens as a backing layer. The transparent ultrasound transducer exhibited a high center frequency of ~47 MHz and a -6 dB bandwidth of 29.4%, which could be easily assembled with a pigtailed ferrule of a single-mode fiber. The multi-functional capability of the probe was successfully validated through experiments of fluid flow sensing and photoacoustic imaging.

Imaging biomarker for quantitative analysis of endometrial injury based on optical coherence tomography/ultrasound integrated imaging mode.

Precise evaluation of endometrial injury is significant to clinical decision-making in gynecological disease and assisted reproductive technology. However, there is a lack of assessment methods for endometrium in vivo. In this research, we intend to develop quantitative imaging markers with optical coherence tomography (OCT)/ultrasound (US) integrated imaging system through intrauterine endoscopic imaging. OCT/US integrated imaging system was established as our previous research reported. The endometrial injury model was established and after treatment, OCT/US integrated imaging and uterus biopsy was performed to evaluate the endometrial thickness, number of superficial fold, and intrauterine area. According to the results, three quantitative indexes acquired from OCT/US image and HE staining have the same trend and have a strong relationship with the severity of the endometrial injury. Accordingly, we developed three imaging markers for quantitative analysis of endometrial injury in vivo, which provided a precise mode for endometrium evaluation in clinical practice.

Miniature intravascular photoacoustic endoscopy with coaxial excitation and detection.

Recent research pointed out that the degree of inflammation in the adventitia could correlate with the severity of atherosclerotic plaques. Intravascular photoacoustic endoscopy can provide the information of arterial morphology and plaque composition, and even detecting the inflammation. However, most reported work used a noncoaxial configuration for the photoacoustic catheter design, which formed a limited light-sound overlap area for imaging so as to miss the adventitia information. Here we developed a novel 0.9 mm-diameter intravascular photoacoustic catheter with coaxial excitation and detection to resolve the aforementioned issue. A miniature hollow ultrasound transducer with a 0.18 mm-diameter orifice in the center was successfully fabricated. To show the significance and merits of our design, phantom and ex vivo imaging experiments were conducted on both coaxial and noncoaxial catheters for comparison. The results demonstrated that the coaxial catheter exhibited much better photoacoustic/ultrasound imaging performance from the intima to the adventitia.

Circular array transducer based-photoacoustic/ultrasonic endoscopic imaging with tunable ring-beam excitation.

Photoacoustic/ultrasound endoscopic imaging is regarded as an effective method to achieve accurate detection of intestinal disease by offering both the functional and structural information, simultaneously. Compared to the conventional endoscopy with single transducer and laser spot for signal detection and optical excitation, photoacoustic/ultrasound endoscopic probe using circular array transducer and ring-shaped laser beam avoids the instability brought by the mechanical scanning point-to-point, offering the dual-modality imaging with high accuracy and efficiency. Meanwhile, considering the complex morphological environments of intestinal tracts in clinics, developing the probe having sufficient wide imaging distance range is especially important. In this work, we develop a compact circular photoacoustic/ultrasonic endoscopic probe, using the group of fiber, lens and home-made axicon, to generate relatively concentrated ring-shaped laser beam for 360° excitation with high efficiency. Furthermore, the laser ring size can be tuned conveniently by changing the fiber-lens distance to ensure the potential applicability of the probe in various and complex morphological environments of intestines. Phantom experimental results demonstrate imaging distance range wide enough to cover from 12 mm to 30 mm. In addition, the accessibility of the photoacoustic signals of molecular probes in ex vivo experiments at the tissue depth of 7 mm using excitation energy of 5 mJ has also been demonstrated, showing a high optical excitation efficiency of the probe.

3D-printed spider-web structures for highly efficient water collection.

Fog and moisture in nature are important freshwater resources, and the collection of these fog water is of great significance to arid regions. Inspired by the unique geometric structure of the spindle knot on spider silk, artificial fibers with periodic structures have been fabricated for water collection, which can effectively alleviate the problem of water shortage in arid areas. Traditional manufacturing methods are difficult to replicate the true shape of the spindle knot, and related research has encountered a bottleneck in improving water collection efficiency. 3D printing technology, which is different from traditional subtractive manufacturing, can directly replicate spider silk with periodic knots, making it possible to study water collection by artificial spider webs of various designs. Here, 3D printing technology is used to fabricate artificial spider webs with different geometric structures for efficient transportation and collection of water. In addition, the artificial spider web is treated with hydrophilic surfaces. In the humid environment for 2 h, the spider web with convex-concave multi-size spindle knots and multi-curvature connections has a maximum water collection capacity of 6.2g, and the mass of water collection is 35% higher than the existing best water collection artificial fibers. This work provides a sustainable and environmentally friendly route for the effective collection of humid air, and has certain reference value for the development of environmentally friendly water collection equipment.

In vivo evaluation of endometrium through dual-modality intrauterine endoscopy.

Female infertilities are highly associated with poor endometrial receptivity. A receptive endometrium is generally characterized by the normal uterine cavity, intact endometrial surface, appropriate endometrial thickness, and echo pattern. Acquiring comprehensive structural information is the prerequisite of endometrium assessment, which is beyond the ability of any single-modality imaging method. In this paper, we introduce a custom-made intrauterine dual-modality (OCT/ultrasound) endoscopic imaging system and achieve in vivo imaging of rabbit uteri, for the first time to our knowledge. The endometrial features of the injured uteri in both ultrasonic and OCT images are consistent with their corresponding pathology. The quantified parameters, including uterine thickness and endometrial surface roughness, show the correlation with the endometrial injury degree but with poor performance for injury classification. The combination of these parameters was proved to assess the degrees of endometrial injury more accurately. Our work shows the potential of the dual-modality system to be translated into a clinical tool, providing multiple quantitative imaging information and helping evaluate the endometrial receptivity and diagnose infertility.