Interstitial Channels Research Articles

Reduced graphene oxide-supported Na3V2(PO4)3/C cathode material synthesized by sol-gel method to improve electrochemical performances of sodium-ion batteries

Na-ion batteries are potential alternative to Li-ion batteries due to their low cost and abundance of sodium source. And Na3V2(PO4)3 is regarded as the most promising cathode material because of their high capacity and larger interstitial channels for fast Na ion migration. However, the disadvantage of low conductivity suppresses its practical applications. To increase electrochemical properties of the cathode, reduced graphene oxide-supported Na3V2(PO4)3/C (NVP/C-G) composite has been prepared, in which the graphene is used to accelerate movement of the electronics and Na ions. XRD characterizations show that the synthesized material is well corresponding to NASICON structure, and SEM image show that the graphene sheets are uniformly dispersed on surface of the composite. The initial capacity of the material is up to 103.5 mAh g−1 at 0.1 C, and 92.3 % and 92.1 % of capacities are maintained with discharge ratios of 0.5 C and 2 C over 500 cycles, proving a much better cycling stability compared with the Na3V2(PO4)3/C (NVP/C) particles. The enhanced discharge capacities and retention rate of the NVP/C-G could be ascribed to the tight contact between NVP/C and RGO sheets, which is beneficial to fast electron transport and better intercalation/deintercalation of Na+ through the nanoparticles. Therefore, the synthesized NVP/C-G displays highly potential for practical use in sodium-ion batteries.

KOH Activated Carbon Coated 3D Wood Solar Evaporator with Highest Water Transport Height and Evaporation Rate for Clean Water Production.

The water evaporation rate of 3D solar evaporator heavily relies on the water transport height of the evaporator. In this work, a 3D solar evaporator featuring a soil capillary-like structure is designed by surface coating native balsa wood using potassium hydroxide activated carbon (KAC). This KAC-coated wood evaporator can transport water up to 32cm, surpassing that of native wood by ≈8 times. Moreover, under 1kWm-2 solar radiation without wind, the KAC-coated wood evaporator exhibits a remarkable water evaporation rate of 25.3kgm-2h-1, ranking among the highest compared with other reported evaporators. The exceptional water transport capabilities of the KAC-coated wood should be attributed to the black and hydrophilic KAC film, which creates a porous network resembling a soil capillary structure to facilitate efficient water transport. In the porous network of coated KAC film, the small internal pores play a pivotal role in achieving rapid capillary condensation, while the larger interstitial channels store condensed water, further promoting water transport up more and micropore capillary condensation. Moreover, this innovative design demonstrates efficacy in retarding phenol from wastewater through absorption onto the coated KAC film, thus presenting a new avenue for high-efficiency clean water production.

Incorporation and substitution of ions and H2O in the structure of beryl

Abstract. Incorporation of ions into the crystal structure of beryl (Be3Al2[Si6O18]) can take place by direct ion-to-ion substitution of the framework components Al3+, Be2+ and Si4+ or by occupation of interstitial or structural channel sites. The most common impurities in beryl include transition metals, alkalis and H2O. It is accepted that the transition metals Mn, Cr and V directly substitute for Al at the octahedral site and induce colour. Similarly, the octahedral site can host Fe instead of Al. Nevertheless, it is shown that it remains disputed whether Fe can also be present at the tetrahedral, interstitial, or channel sites, and opposing hypotheses exist regarding these possibilities. However, in the case of Fe, not only the possible occupation of these sites remains under debate, but also their influence on the subsequent colour of beryl. Similarly, the residence of Li in the channels and at the Be tetrahedral or interstitial tetrahedral sites is still under debate. The presence of more than two types of H2O (type I and type II) in the structural channels of beryl is also unclear. This article aims to give an overview on the consensus and on the current debates found in the literature regarding these aspects. It mainly concentrates on the substitution by and the role of Fe ions and on channel occupancy by H2O.

Three-dimensional visualization of interstitial channels in the limbs of mini-pigs and a comparison with human meridians

Three-dimensional visualization of interstitial channels in the limbs of mini-pigs and a comparison with human meridians

Application of Biophysical Properties of Meridians in the Visualization of Pericardium Meridian.

The biophysical properties of the meridian system, an important concept of traditional Chinese medicine, include low impedance, resounding voice, and high acoustic conductance, all of which are helpful for elucidating the essence of meridians. To visualize the human pericardium meridian (PC) based on the resounding voice property of meridians. Visualization of the PC was performed by injection of fluorescein sodium at the PC6 acupoint (Neiguan) on the PC. Before injection, percussion active points (PAPs) were identified by the virtue of their resounding voice properties. After injection, the trajectories of fluorescein migration throughout the body surface were recorded and analyzed. The distribution of fluorescein in the tissue was further studied using cross-sections of hind limbs of mini-pigs, in which fluorescein was injected into low impedance points. The identified PAP lines were colocalized with PC. Following intradermal fluorescein injection, 1-3 fluorescent lines, which were unrelated to the arm veins, were observed in 7 of 10 participants; 85.4% of fluorescent signals were coincident with PAPs and their intensity had a negative correlation with the body mass index (r = -0.56, p = 0.045). Cross-sections showed a Y-shaped fluorescence pattern where the two migration lines on the surface were the two vertices of the "Y." The trajectories of fluorescein in the body are suggestive of the anatomical structure of meridians. The PC is related to the deep horizontal interstitial channels that connect to the body surface through vertical interstitial spaces. These biophysical properties and techniques for meridian visualization are valuable for revealing the anatomical structure of meridians.

Temperature-affected nano-deformation behavior of nanometals in ultrahigh-strain-rate formation processes.

As metal forming processes move toward high speed, high throughput, high precision and small scale with temperature dependence, clarifying the fundamental nano-deformation behavior of metals is critical for the optimization of manufacturing processes, and the control of nano-optical, electrical, mechanical or surface properties. Unfortunately, limited by the time scale and sample size, the effect of temperature on the deformation behavior of nano-metals during the ultrahigh-strain-rate forming process remains largely unexplored. This study demonstrates the nonlinear effect of temperature on the formability of nano-metals for the first time. Temperatures below 673 K facilitated the formability of nano-metals benefiting from the temperature-promoted dislocation proliferation process, whereas temperatures above 673 K weakened the plasticity of the nano-metal due to the activation of phase transformation. Frequent phase transition activation and accelerated dislocation annihilation at high temperatures reduced interstitial transport channels and delayed atomic transfer. Based on the temperature response of nano-metals in deformation mechanisms, defect evolution behavior and formability, the constitutive model and nano-deformation mechanism map of nano-metals in ultrahigh-strain-rate forming processes are proposed. The objective of this work is to provide basic support for the reasonable matching of nano-forming technology and processing temperature, and the determination of the optimal process window through fundamental nano-deformation behavior exploration.

Micro and macroscopic structure evolution of few-walled carbon nanotube bundled network by high temperature anneal

High temperature anneal is of importance to create nanocarbon-based materials with excellent functions and performances. However, a comprehensive understanding on annealed nanocarbon assembly structures has been challenging. We successfully propose the micro and macroscopic structural analysis of 0.8–3.4 nm diameter few-walled carbon nanotube (CNT) bundled network by a multifaceted characterization, which were annealed over 1200–3000 °C in the form of a film as the case study. Up to 1800 °C carbonaceous impurities were removed to secure nanospace among nanotubes, i.e. interstitial channels important to design multiple functions. Beyond 1900 °C nanoscale graphitic particles were generated on the nanotube bundles, then grown to be micro-meter scale toward 3000 °C. Parallel to the particle growth, small diameter (<1.2 nm) nanotubes became undetected at 2200–2400 °C with a decrease in available interstitial channels, finally resulting in the nontubular, graphitized network structures at 2600–3000 °C. The anneal at 1200–1800 °C can afford the high purity CNT bundled network structures, and the higher temperature anneal led to the high crystallinity graphitized network structures. To understand the structural evolution, 14 different analytical methods were employed, and two-dimensional correlation analysis from the collected data revealed the synchronous and asynchronous structural parameters with the annealing temperature. Thus, we found that the structural changes occurred in 3 stages of 1200–1800 °C, 1900–2400 °C, and 2600–3000 °C. On the other hand, the electrical conductivity gradually decreased due to the removed carbonaceous impurities and the structure changes. Our findings can be an asset for carbon material science and pave a way toward nanocarbon applications with the films, fibers, and composites.

Theoretical understanding of electrochemical phenomena in 2D electrode materials

Two-dimensional (2D) electrode materials present opportunities to enhance the efficiencies of electrochemical processes involved in electrocatalytic reactors, batteries, and supercapacitors. In this review, we discuss the theoretical basis of classical and quantum confinement effects, including how they modulate the performance of 2D electrode materials, in the light of recent experimental advances in the area. In particular, we discuss ion transport in the interstitial channels of 2D layers with and without spacers, the mechanisms and the underlying theories of mass and electron transport, and the effect of step edges, defects, and dopants on the mechanism and kinetics of electron transport in 2D electrode materials. We identify several opportunities for future work involving first-principles calculations, molecular dynamics simulations, as well as the development of analytical theories. Overall, this article not only provides a brief theoretical overview of electrochemical phenomena in 2D electrode materials, but also details several knowledge gaps in the field. ● Electrochemical phenomena in 2D electrode materials are discussed in the context of electrocatalytic reactors, batteries, and supercapacitors. ● Role of nanoconfinement in modulating the transport of molecules/ions and the structure/dynamics of electrical double layers is reviewed. ● Application and accuracy of various theories to model electron transfer in 2D electrode materials is discussed. ● Modulation of electrochemical activity of 2D materials due to edges, defects, and dopants is highlighted. ● Various knowledge gaps are outlined and the presented theoretical insights are contextualized with recent experimental results.

Liquid metal injected from interstitial channels for inhibiting subcutaneous hepatoma growth and improving MRI/MAT image contrast.

Liquid metal (LM) nowadays is considered a new biomedical material for medical treatment. The most common application of LM in medical therapy is taking LM as a carrier for oncology therapeutics. However, the feasibility and direct effect of LM in tumor treatment are still unknown, and how to delineate the negative resection margin (NRM) of the tumor is also a crucial problem in surgery. We aimed to inject LM into interstitial channels of extremities of mice to overlay the surface of the primary tumor to investigate the effect of LM on inhibiting tumor growth and highlight the NRM of the tumor. In this study, all 50 BALB/c-nude female mice were used to construct the transplanted HepG2-type hepatocellular carcinoma model. One week after the establishment of the model, the mice were divided into three groups, named LM group, PBS group and Control group by injecting different liquid materials into the forelimb interstitial channel of the mice. T2WI image on MRI and Magneto-acoustic tomography (MAT) were used to show the distribution of LM and PBS in vivo. The group comparisons of tumor growth and blood tests were evaluated by one-way ANOVA and post-hoc analysis. And the biocompatibility of LM to BALB/c nude mice was evaluated by histopathological analysis of LM group and control group. The volume change ratio of tumor was significantly lower in LM group than in PBS and Control group after 10 days of grouping. Compared with PBS and Control group, the main indexes of blood tests in LM group were significantly lower and close to normal level. In addition, the distribution of LM in vivo could be clearly observed under T2WI anatomic images and the crossprofile of the tumor in MAT. LM also has a obvious contrast in MRI T2WI and enhanced the amplitude of imaging signal in MAT. LM may inhibit the growth of transplanted hepatoma tumor through tumor encapsulation. In vivo, tumor imaging and LM distribution imaging were achieved by MRI T2WI, which verified that LM injected with interstitial injection made the NRM of tumor more prominent and had the potential of being MRI contrast agent. At the same time, LM could also be a new conductive medium to improve the imaging quality of MAT. Moreover, LM performed mild biocompatibility.

Thermally responsive ionic transport system reinforced by aligned functional carbon nanotubes backbone

Ion transport plays an important role in energy conversion, biosensors, and a variety of biological processes. Carbon nanotubes, especially for the carbon nanotubes arrays with controlled vertically aligned structures, have displayed great potential as a promising material for regulating ion transport behaviors in the applications of the nanofluidic devices and osmotic energy conversion. Herein, we demonstrate the thermo-controlled ion transport system through the vertically aligned multiwall carbon nanotubes arrays membrane modified by the thermo-responsive hydrogel in a simple and reliable way. The functional carbon nanotubes backbone with the inherent surface charge and interstitial channels structure renders the system improved ion transport behaviors and well controlled switching property by thermo. Based on the integrated properties, the energy output from osmotic power in this system could be regulated by the reversible temperature switches. Moreover, it can realize a higher osmotic energy conversion property regulated by the thermos, which may extend the practical application in the future. The system that combines intelligent response with controlled ion transport behaviors and potential osmotic energy utilizations presents a valuable paradigm for the use of carbon nanotubes and hydrogel composite materials and provides a promising way for applications of nanofluidic devices.

THE LYMPHATIC SYSTEM – A NEW LOOK AT OLD PROBLEMS

The lack of adequate methods for the simultaneous detection of lymphatic and blood microvessels in hollow organs does not make it possible to determine the morphological basis of lymph formation and lymph dynamics. In the relevant scientific literature, information about of the structural organization of the lymphatic system, obtained using transmission and scanning electron microscopy, does not provide exhaustive answers to the currently controversial and unresolved issues of the structural organization of the lymphatic microcirculatory bed. The purpose of the study is to presenting data on the organization of the initial lymphatic channel, obtained on the basis of the use of original impregnation methods. Studies were conducted on cats (n=17) and dogs (n=11). The microvascular bed of the intestine and epicardium was identified along with the surrounding tissues by impregnation. On histological preparations, endothelial trabeculae were identified in the lumen of non-muscular lymphatic microvessels of different diameters in the muscular layer and in the submucosa of the intestine. In the muscular layer of the intestinal wall, numerous interstitial channels were found that communicated with open lymphatic capillaries. In the submucosa of the intestinal wall of experimental animals, in addition to the classic capillaries that begin closedly, previously unknown structures were identified - open perivasal lymphatic microvessels and open lymphatic capillaries flowing into them. In the lumen of the perivasal lymphatics are arterioles or arteries. Lymphatic capillaries were in various functional states, which indicates their active peristalsis and suction capacity, which characterize them as utilizers of «biological debris». As a result of the conducted studies, new objective data on the structural organization of the initial lymphatic bed in hollow organs were obtained. The authors showed that the vasomotor activity of the initial lymphatics can serve as a morphological basis for the hypothesis of the initial lymphatic cycle, which consists of a resorption phase and an expulsion phase. The hydrostatic pressure drops in the lumen arising from such a two-phase vasomotor activity of the lymphatics indicate their important role in the process of lymph formation and lymph circulation.

Hierarchical porous single-wall carbon nanohorns with atomic-level designed single-atom Co sites toward oxygen reduction reaction

Hierarchical pore structure is crucial for effective mass transfer and utilization of a number of active sites in single-metal atom catalysts. Here, we present a strategy for developing a hierarchical porous structure in single-wall carbon nanohorns with Co-Nx sites (Co/CNH) and maximizing their oxygen reduction activity. Thermal annealing is effective for generating hierarchical pore by removing amorphous carbons and opening internal and interstitial pore channels. Ammonia annealing modifies coordination structure and relieves local strain around cobalt atoms to form more ideal Co-N4-C moieties. DFT calculations reveal that the enhanced intrinsic catalytic activity (ik = 60.16 mA cm−2 for Co/CNH Air NH3 vs. 8.24 mA cm−2 for Pt/C) is attributed to the ligand-push effect of water molecules on the other side of Co-N4 sites. In a single-cell experiment, a power density of 742 mW cm−2 was achieved, which is the remarkably high value among M-N-C catalysts using commercialized membrane electrode assemblies (MEAs).

Recovering double-metal hydroxides precipitate from desalination process of saline wastewater as conditioner for excess sludge dewatering

The massively generated double-metal hydroxides (DHs) precipitate has restricted the application of the lime-aluminum precipitation method in the zero liquid discharge (ZLD) process of saline wastewater. Recovering DHs precipitate as conditioners for the dewatering of municipal sludge is a promising solution for above issue. In this study, individual use of DHs from the ZLD process, including ettringite (Ett), Friedel’s salt (FS) and their mixtures (EF), and combined use of the DHs and FeCl3 in sludge conditioning were investigated. The EF precipitate was commonly generated from the chloride precipitation process by the lime-aluminum method, and composed of 16.7% of Ett and 83.3% of FS. The dewaterability of excess sludge conditioned with FeCl3 prior to DHs was much better than opposite dosing sequence and individual use of DHs. Sludge conditioned by FeCl3 prior to EF possessed the best dewatering performance ascribing to its high fluidity, strong structure strength and uniformly dispersed mesoporous structure. The variations of extracellular polymeric substances (EPS) further confirmed that EPS were largely released after FeCl3 addition and then efficiently adsorbed by the subsequently added DHs, with the highest adsorption efficiency of 60% by EF. The kinetics for EPS adsorption also suggested that EF had the highest adsorption capacity compared to FS and Ett. Overall, FeCl3 addition could form interstitial channels in flocs by penetration and release external and intracellular substances, while the latter added EF, Ett could function as uniformly skeleton material and dispersing agent to improve EPS adsorption by FS. Hence, the synergic coupling of FeCl3 and DHs as chemical conditioner is inspirable and economically beneficial to ZLD and advanced sludge dewatering process.

Enhancing carrier flux for efficient drug delivery in cancer tissues

Ultrasound focused toward tumors in the presence of circulating microbubbles improves the delivery of drug-loaded nanoparticles and therapeutic outcomes; however, the efficacy varies among the different properties and conditions of the tumors. Therefore, there is a need to optimize the ultrasound parameters and determine the properties of the tumor tissue important for the successful delivery of nanoparticles. Here, we propose a mesoscopic model considering the presence of entropic forces to explain the ultrasound-enhanced transport of nanoparticles across the capillary wall and through the interstitium of tumors. The nanoparticles move through channels of variable shape whose irregularities can be assimilated to barriers of entropic nature that the nanoparticles must overcome to reach their targets. The model assumes that focused ultrasound and circulating microbubbles cause the capillary wall to oscillate, thereby changing the width of transcapillary and interstitial channels. Our analysis provides values for the penetration distances of nanoparticles into the interstitium that are in agreement with experimental results. We found that the penetration increased significantly with increasing acoustic intensity as well as tissue elasticity, which means softer and more deformable tissue (Young modulus lower than 50 kPa), whereas porosity of the tissue and pulse repetition frequency of the ultrasound had less impact on the penetration length. We also considered that nanoparticles can be absorbed into cells and to extracellular matrix constituents, finding that the penetration length is increased when there is a low absorbance coefficient of the nanoparticles compared with their diffusion coefficient (close to 0.2). The model can be used to predict which tumor types, in terms of elasticity, will successfully deliver nanoparticles into the interstitium. It can also be used to predict the penetration distance into the interstitium of nanoparticles with various sizes and the ultrasound intensity needed for the efficient distribution of the nanoparticles.

NaFe2PO4(MoO4)2: A Promising NASICON-Type Electrode Material for Sodium-Ion Batteries.

Searching for polyanionic electrode materials with high Na+ and electronic conductivity is pivotal to realize high-performance sodium-ion batteries. Here, we report a novel polyanionic-based NASICON-type compound, NaFe2PO4(MoO4)2 (NFPM), that does not crystallize in the common space group R-3c or C2/c but in the rare P2/c. The studies on bond valence sum maps show that NFPM has high Na+ conductivity because the large volumes of MoO4 groups make the interstitial channels wider, thus making the energy barrier of Na+ diffusion decrease along these channels. Density functional theory calculations demonstrate that NFPM has high electronic conductivity because the contribution of Mo 4d orbitals on the formation of the bottom of the conduction band makes the connected MoO4 groups take part in electron transport. Electrochemical tests exhibit that NFPM can deliver a capacity of ∼80 mAh g-1 with good reversible cyclability utilizing the Fe3+/Fe2+ redox couple. In situ X-ray diffraction measurements indicate that NFPM undergoes one-phase reaction mechanism in the process of charge and discharge.

Structure elucidation of luminescent centers in green emitting Eu2+ doped Si6-zAlzOzN8-z phosphors

Eu2+ doped Si6-zAlzOzN8-z (β-sialon) is a common green emitting phosphor used in white light emitting diodes. Due to its narrowband emission, a wide color gamut is realized in the liquid crystal display. Despite its importance in commercialized phosphors, the position of the luminescent center Eu2+ in the β-sialon crystal structure is not fully clarified. Herein we elucidate the position of the luminescent center Eu2+ by the single crystal X-ray diffraction technique. Eu is positioned at the interstitial site of (0, 0, 1/4) of the β-sialon crystal structure and coordinated by nine anions. Structural and elemental analyses show that almost all of the incorporated Eu are situated at the interstitial channel position.

N2 Gas Adsorption Sites of Single-Walled Carbon Nanotube Bundles: Identifying Interstitial Channels at Very Low Relative Pressure.

Utilizing the nanoscale space created by carbon nanotubes (CNTs) is of importance for applications like energy storage devices, sensors, and functional materials. Gas adsorption is a versatile, quantitative characterization method to analyze nanoscale pore sizes and volumes. Here, we inspected N2 adsorption to the nanospace formed by the bundles of single-walled CNTs with an average nanotube diameter of ca. 2.0 nm and its distributions of 0.7-4.1 nm. Based on comparisons among the as-grown, purified (opened), and heat-treated (closed) CNTs with similar geometric bundle structures, we found that the interstitial channels emerged from a very low relative pressure of approximately 10-8 by removing the impurities from the CNT bundles, which is the first empirical demonstration. These findings can not only be utilized to understand the structures of CNT films, fibers, and bulks but also applied to porous materials science.

Nanomaterial-aided seed regeneration in the global warming scenario: multiwalled carbon nanotubes, gold nanoparticles and heat-aged maize seeds

Seeds in soil seed-banks count amongst organisms that are the most vulnerable to the extreme temperatures predicted in certain models of global warming. This work aims to examine the possibility of a nanomaterial-aided resuscitation of heat-damaged hybrid maize (Zea mays L. “Albatross”) seeds through a study of their germinability and growth after high heat exposures. Heat energy at constant ‘dose’ was delivered at the three temperatures of 40, 50 and 60 °C (40–60) and at a much higher dose at 60 °C (+). Seed germinability and seedling growth indices were studied in the presence/absence of multiwalled carbon nanotubes (MWCNT) and our laboratory synthesised and characterised (SEM, DLS, FTIR, UV–Vis) gold nanoparticles (AuNP). Overall, the MWCNT outperformed the AuNP. The seemingly erratic germination outcomes were rationalised from the standpoint of the biomechanics of water entry into seeds with heat-damaged seedcoats. Ficksian diffusion calculations applied to the interstitial channels of the seedcoat and cellwall showed that the former but not the latter, was an effective barrier to MWCNT entry and that both easily allowed water entry. The MWCNT treatments appear to catalyse the recovery of the (+) seeds and seedlings, promote biomass and the root-to-shoot water transport, whilst the parabolic biomass trend for 40–60 suggests opposing temperature-regulated factors possibly involving reactive oxygen species. Summarising, growth indices of heat-damaged seeds show a strong non-monotonic dose dependence where the MWCNT significantly altered the response, catalysing the recovery of the high heat ‘dose’ set. These results hold promise for the application of nano-biotechnology to agriculture in the global warming scenario.

Nanospace-Assisted Anti-Oxidative Li Storage on Carbon Nanotubes

Lithium (Li) metal has attracted significant interest as a next-generation battery anodes due to its high theoretical specific capacity and low redox potential. However, inhomogeneous plating/stripping behavior of Li metal accelerates Li-consuming parasitic reaction and sometimes provokes an internal short circuit problem. In particular, its environmental vulnerability (e.g., notorious reactivity upon exposure to air and water) due to the electrochemical instability poses a formidable challenge to commercial applications, thus it should be resolved as an indispensable prerequisite in addition to resolving the concerns on cell performance and safety.Here, we report a new class of anti-oxidative Li reservoir based on nanospaces of carbon nanotube (CNT) bundles. The CNT bundles are formed by assembling themselves via van der Waals interactions, producing one-dimensional nanospaces (i.e., external grooves and interstitial channels). The Li preferentially stored in the interstitial channels is chemically stable against to air and water. Notably, the Li electrochemically extracted from Li-confined CNTs onto a copper (Cu) foil prohibits reliable electrochemical performance (e.g., stable charge/discharge behavior) comparable to those of pristine Li foils. We envision that this nanospace reservoir strategy will open a new avenue for development of environmentally tolerant, high-capacity Li storage.

Preliminary observation of the migration of sodium fluorescein along meridians in the limbs of mini-pigs

<p indent=0mm>Meridians are a core concept in traditional Chinese medicine (TCM) theory. It has been shown in many previous studies that meridians exist in the interstitium, the space through which interstitial fluids flow. Sodium fluorescein (SF) is a small, fluorescent, hydrophilic molecule. SF was injected into the low impedance points (LIPs) or the high impedance points (HIPs) on the limbs of healthy mini-pigs, as determined by a low impedance meridian locator (WQ6F30). Migration tracks were scanned by a digital camera (Canon 5D2) with a narrow band filter and colored flash lamps prior to and after SF injection. The relationships between superficial veins and SF tracks were analyzed using a projection vein finder (V800P). Tissues were frozen on dry ice, and the distribution of SF in the transverse sections of SF tracks was observed. Results reliably showed that seven migrating tracks along the low impedance line along meridians (LILM) were found when SF was injected at LIPs, three of which were on the outside of forelimb, three of which were on the inside of forelimb, and one of which was on the inside of hind limb. The average length of these migration tracks was <sc>5.13 cm.</sc> The migration tracks were 81.4% consistent with LILM, while no overlap was observed with veins. The shape of injected SF in the transverse sections was similar to an inverted triangle, and distributed in the muscle gap. No linear migration was observed when SF was injected at HIP, and the shapes of injected SF were nearly round by local diffusion. The length, width and length-width ratio of SF shapes between injections at LIPs and HIPs were significantly different (<italic>P</italic><0.01). These results imply that the concept of the meridian in TCM may be an unknown interstitial channel.