Size Interconnectivity Research Articles

Fabrication and evaluation of gelatin cryogels for curcumin controlled release via transdermal iontophoresis

Transdermal drug delivery system delivers a drug through skin to the desired cells. Its use is limited due to the poor drug diffusion through the outer skin layer. The aim of this work was to fabricate and characterize the gelatin cryogel matrices for the targeted transdermal curcumin delivery via iontophoresis for the breast cancer treatment. The gelatin cryogels were fabricated at various concentrations under the freeze-drying method. FTIR, SEM, STA, and BET were utilized to characterize the gelatin cryogels and curcumin loaded gelatin cryogels. The curcumin release behavior was investigated under the effects of gelatin concentrations, electric fields, pig skin permeation, and pHs. The gelatin cryogel matrices possessed the interconnected pore sizes between 56.61 μm and 129.67 μm, in which the pore size increased with increasing gelatin concentration. The curcumin percentage released from the 1.5%v/v PSG cryogel was 89.7 %, relatively higher than the 0.8%v/v PSG cryogels. Under the effect of electric fields of 3V and 6V, the curcumin release percentages from the 1.5%v/v PSG cryogel were increased to reach 94.7 % and 96.0 %, respectively. For the release-permeation of curcumin through the pig skin, the curcumin release percentages from the 1.5%v/v PSG cryogel under the electric fields of 0V, 3V, and 6V became lower at 38.45 %, 46.33 %, and 72.33 %, respectively, as the pig skin was the obstacle in the curcumin diffusion. Slightly higher release rates and amounts of curcumin from the 1.5%v/v PSG cryogel were observed at the of pH 5.5 relative to the pH of 7.4, and at the electric field of 6V relative to 0V. The effect of applied electric field was shown to shorten the delivery time from the PSG cryogel. The 1.5%v/v PSG cryogel under applied electric field 6V was shown here as a potential biobased matrix to be used in the curcumin transdermal delivery via iontophoresis for cancer treatment.

Grain boundaries-dominated migration failure of copper interconnect under multiphysics field: Insight from theoretical modeling and finite element analysis

As the feature size of Cu interconnects in microelectronic devices are miniaturized into micro- and even nano-scale, the effects of grain boundaries (GBs) on the electromigration (EM) failure become more and more obvious. It is of fundamentally importance to investigate the grain boundaries dominated failure mechanism and lifetime of Cu interconnects. In this work, the interconnection models containing different grain boundaries were constructed by using finite element simulations. The simulation results indicate that the current density at Cu grain boundaries is lower, but the current will be increased locally, when it is almost perpendicular to grain boundaries. However, the temperature is higher locally at grain boundaries. In the early stage of atomic diffusion, thermal migration and stress migration also occur near grain boundaries, resulting in significant atomic segregation near grain boundaries, particularly at the intersection of grain boundaries and near the inclined grain boundaries with small angles to the current direction. The atomic diffusion is considerably accelerated as the density of grain boundaries is increased, but is slowed down by poorly connected columnar grain boundaries.

Enhancing understanding of pressure drop in carbon porous electrodes for vanadium redox flow batteries

The pressure drop in redox flow batteries contributes to internal energy loss in the battery system. The seamless carbon material is suitable for analyzing pressure drops due to its uniform structure of interconnected pores. The pressure drop of the full cell was measured with different interconnected pore sizes ranging from 4.7 μm to 47 μm. The pressure drop can be analyzed using a semi-theoretical equation based on the Kozeny-Carman equation. The presented semi-theoretical equation can assist in designing the interconnected pore structure of electrode materials for redox flow batteries. Additionally, the pressure drop in relatively thin (0.4 mm) electrodes can be analyzed using the Hagen–Poiseuille equation, indicating that the tortuous effect is negligible. The seamless carbon materials with various interconnected pore diameters exhibit a trade-off relationship between liquid permeability and current density.

4D imaging and quantification of the effect of a Phosphate-Based treatment on building materials by means of synchrotron X-ray Microtomography: New insights into the dynamic of the consolidation process

Diammonium hydrogen phosphate (DAP) solutions are used as consolidants for carbonate stone materials through the crystallization whithin the original matrix of newly formed crystalline phases. However, the formation mechanism of the new phases within the stone microstructure, and their effects on the porous system, strongly depend on the DAP molarity, the treatment method, and the stone microstructure. In this study, we obtained real-time quantitative information on the structural evolutions induced by the treatment process on the Noto limestone, a porous carbonate stone used as a building stone since antiquity, by synchrotron X-ray Microtomography. With the aid of 4D image analysis, microstructural modifications in terms of porosity, interconnection, and pore size distribution have been demonstrated in different stadia of the consolidation process, and the influence of molarity was asserted. This study paves the way for a deeper understanding of consolidation mechanisms and the effects induced overtime on the 3D microstructural features of porous materials by inorganic treatment.

Biomineralization of carboxymethyl cellulose-sodium alginate infused with cellulose nanocrystals for bone regeneration

The development of novel tissue constructs from both natural and synthetic biopolymers has attracted widespread attention among researchers, prior to its excellent outcomes in bone tissue regeneration. This research aims to investigate the biocompatibility of carboxymethyl cellulose (CMC)/sodium alginate (SA) embedded with cellulose nanocrystals (CNC) and its surface response due to the biomineralization process as potential implant material. The CMC/SA were prepared with and without CNC using water as the only solvent. It was then freeze-dried for up to 72 h before being further immersed in simulated body fluid (SBF) for comparative studies. Morphological observation by scanning electron microscope (SEM) showed that CMC/SA/CNC (SBF) displayed a spherical apatite structure amid interconnected porous materials with an average particle diameter between 95 and 148 nm. The apatite crystal indicated the existence of calcium (Ca) and phosphorus (P) elements, which was confirmed by energy dispersive X-ray analysis (EDX). All scaffolds showed a porosity of up to 90.13% with a moderate degradation rate and a water absorption value of up to 1100%. Overall, all scaffolds had open, interconnected pore sizes ranging from 40 to 400 µm. Attenuated total reflection – Fourier Transform Infrared (ATR-FTIR) spectroscopy and thermogravimetric analysis (TGA) curve showed a new existing peak and lower decomposition rate, respectively, for SBF-treated scaffolds. Stress-strain curve disclosed the highest tensile stress of CMC/SA/CNC (SBF) at 16.2 MPa and 15.75% strain effect. Preliminary in vitro cytotoxicity studies performed with human foetal osteoblast (hFOB) cells showed that cytocompatibility was more evident on CMC/SA/CNC (SBF) scaffolds. This study showed that scaffold-embedded CNC with SBF treatment could be hit upon as material selection for bone tissue engineering.

Low-latency wavelength-switched clock-synchronized intra-data center interconnects enabled by hollow core fiber.

Fast (nanoseconds) optical wavelength switching is emerging as a viable solution to scaling the size and capacity of intra-data center interconnection. A key enabling technology for such systems is low-jitter optical clock synchronization, which enables sub-nanosecond clock and data recovery for optically switched frames using low-cost methods such as clock phase caching. We propose and demonstrate real-time low-latency wavelength-switched clock-synchronized intra-data center interconnection at 51.2 GBd using a fast tunable laser (with ns scale switching time) and ultra-stable-latency hollow core fiber (HCF) for optically-switched data center networks. For wavelength-switched systems, we achieve a physical layer latency below 46 ns, consisting of 28 ns transceiver latency and a 18 ns inter-packet gap. Finally, we show that by exploiting the low chromatic dispersion and thermally-stable latency features of HCF, active clock phase tracking can be entirely eliminated.

Room-temperature, rapid, solid-state solder bonding technology for future ultra-high-density interconnects manufacturing

Developing ultra-high-density interconnects using current technologies presents certain limitations. It is because traditional solder joint technology employs a liquid-solid interfacial reaction process that makes it difficult to control the shape of the solder joint, thus limiting the size, pitch, and density of interconnects. Although the Cu–Cu direct bonding technique can help fabricate high-density interconnects, its high cost and limited application in consumer electronics present further challenges. In this study, we developed a simple, rapid, and cost-efficient method for fabricating high-density interconnects. We produced homogeneous submicron solder particles as small as 300 nm through ultrasonic treatment. The homogeneous size distribution was achieved by minimizing inter-particle ripening reactions, sluggish diffusion, and low Gibbs-Thomson chemical potential in the medium-entropy Sn–Bi–In-based solder particles. We dispensed the particle solution between two Cu substrates, and they bonded within 5 min at room temperature through a solid-state interfacial reaction. The shear strength of the bonding is around 14.8 ± 1.2 MPa. Our bonding technology shows potential for use in 3D integration to manufacture ultra-high-density interconnects.

Crosstalk Analysis of Delay-Insensitive Code in High-Speed Package Interconnects.

The development of integrated circuits has increased the size of chip interconnects, which has brought challenges to interconnect design in chip packages. The closer the spacing between interconnects, the higher the space utilization, which can cause severe crosstalk problems in high-speed circuits. In this paper, we applied delay-insensitive coding to the design of high-speed package interconnects. We also analyzed the effect of delay-insensitive coding on crosstalk improvement in package interconnects at 26 GHz for its high crosstalk immunity. Compared to the synchronous transmission circuit, the 1-of-2 and 1-of-4 encoded circuits designed in this paper can reduce crosstalk peaks by 22.9% and 17.5% on average at a wiring spacing of 1-7 μm, which can achieve closer wiring spacing.

Polyvinylpyrrolidone-bridged MXene skeleton constructed by photothermal assisted sacrificial template method for phase change materials with form stability and photothermal conversion

To realize the efficient storage and conversion of solar energy, it is still a great challenge to fabricate multifunctional phase change materials (PCMs) via green and environment-friendly technologies. In this work, robust MXene@polyvinylpyrrolidone (PVP) skeleton (MP) was constructed via photothermal assisted sacrificial template method. Then, vacuum impregnation of polyethylene glycol (PEG) was performed to obtain MXene@PVP/PEG composite PCMs (MPP). The results indicate that owing to the hydrogen bond bridging effect of PVP, the MP skeleton with high interconnection and uniform pore size overcomes the problem of fragile frameworks. The composite M1P1P with the same mass fraction of MXene and PVP possesses the optimum comprehensive properties, which has high latent heat of 140.5 J/g, favorable shape stability and photothermal conversion efficiency of 96.2%. Owing to the heterogeneous nucleation sites provided by the MXene nanosheets bridged by PVP through hydrogen bonds, the nucleation activation energy of PEG is reduced. In addition, the relative enthalpy efficiency of the composite M1P1P only slightly decreased by 0.9% and 1.6% even after 100 heating–cooling cycles and 20 photothermal cycles. This research provides a new strategy for preparing multifunctional PCMs with facile and energy-saving process, showing the promising prospects in solar energy conversion and storage and comprehensive utilization of waste heat.

<i>In Vivo</i> Evaluation of Calcium-Phosphate Ceramics with Highly-Interconnected Pores Using Porcine Tibia Defect Model

The aim of this study was to compare the difference in bone formation between hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) ceramics with similar porous structure. Porous HAp and β-TCP ceramics (total porosity: ~70%) with highly-interconnected structure were fabricated by firing calcium-phosphate fiber mixed with carbon beads (~150 μm). The size of highly-interconnected pores was measured by mercury intrusion technique. Each sample (ϕ4 mm × 8 mm) was implanted into the tibial bone defect (ϕ4.2 mm × 8 mm) of a pig (2 years old, male). After 6 weeks of implantation, undecalcified section was prepared and stained with hematoxylin and eosin (HE) stain. New bone area and remaining material area were evaluated.Interconnection sizes of HAp and β-TCP ceramics were 23.0 µm and 15.6 µm, respectively. New bone area of β-TCP ceramics was significantly higher compared to HAp ceramics. Remaining material ratio was 77.1 ± 3.3% for β-TCP ceramics whereas HAp ceramics remained stable. Bone formation in HAp ceramics was inhomogeneous compared to β-TCP ceramics in HE stained section. Although the β-TCP ceramics interconnection size was smaller, higher resorption may have played a positive role in homogeneous bone formation. According to the result of the study, it is suggested that highly-interconnected porous ceramics made by β-TCP could be a suitable material for bone regeneration.

Reconfigurable data encoding schemes for on-chip interconnect power reduction in deep submicron technology

With technology scaling, size of both transistor and interconnects are reduced. Power dissipation due to dynamic switching is high in the interconnects. Suitable encoding schemes that reduces transition between data bits are used to minimize interconnect power dissipation. In this paper transition between data bits is minimized based on three novel data encoding schemes identifying the novel methods estimates bit transitions in a pair of data bits and performs half inversion or full inversion on one byte of data thus reducing the switching activity by 50%. The encoder and decoder for the three encoding schemes are modelled in verilog hardware description language (HDL) and implemented using application specefic integrates circuit (ASIC) flow targeting 32 nm. Technology over all power dissipation of encoding scheme is 1.04 μW in addition over head area of 210 cells with encoding delay of 340 ps. Encoder decoder register transfer logic (RTL) code is implemented and the total area required is 34980 units. The data encoding and decoding schemes are suitable for low power applications.

Metformin delivery via iontophoresis based on κ-carrageenan cryogels

Transdermal drug delivery system (TDDS) is the system for transmitting a drug through the skin into the blood circulation. In this work, κ-Carrageenan (κC) was used as the drug matrix material. The porous κC matrices were fabricated by dissolving the κC in deionized water to obtain hydrogels and then using the freeze-dryer to obtain cryogels. The porous (κC) matrices showed interconnected pore sizes varying between 6.05 to 25.8 nm. In the drug release experiments, the drug diffusion coefficient increased and the drug release duration was reduced with decreasing κC concentration due to the larger κC pore sizes. The diffusion coefficient increased with a shorter release time under the applied electric strength of +1.0 V due to the electro-repulsive force between the Metformin and the anode. For the drug release-permeation of the κC 0.8 % v/v cryogel through the pig skin under applied positive electrical potentials, the amounts of drug release-permeation and diffusion coefficients were enhanced with shorter durations relative to without electrical potential. The κC 0.8 % v/v matrix at the applied electric strength of +6.0 V has been shown here to be potential to be used as the Metformin transdermal controlled delivery patch for abdominal obesity and diabetes.

(Invited) Reaction-Diffusion Modeling for Reliability Assessment of Heterogeneously Integrated Packages

Heterogeneous Integration provides a powerful and cost-effective means for building complex Systems-in-Package (SiPs). Recently, sophisticated examples of heterogeneously integrated packages containing nearly 50 dies, many fabricated by different vendors on different technological nodes, have been demonstrated. In general, interconnect pitch scaling and integration of large number of dies on a package leads to an exponential increase in material interfaces. Furthermore, the shrinking of the size of vertical interconnects in proportion to the pitch makes them heterogeneous in material phase composition or susceptible to oxide growth at the bond interfaces. Thus, reaction-diffusion problems play a critical role in the reliability of Heterogeneously Integrated packages. In general, numerical modeling can serve as a critical aid to understanding the formation of the phases and their evolution with current or temperature. Two significant challenges to modeling reaction-diffusion problems are the derivation of governing balance laws at the moving interface and developing an efficient computational technique for tracking the motion of the interface. Diffuse interface methods that use implicit geometric description of the interface such as the phase field method is widely used for solving problems with moving interfaces. The disadvantages of implicit interface methods are the complexity of the governing equations in diffuse form, the need for adaptive mesh refinement near the interface and the computational expense due to the implicitization of the geometry. In this study, we describe the derivation of general thermodynamic conditions governing the motion of the interface and develop diffuse as well as sharp interface computational methods to simulate reaction-diffusion problems in general. We then model the growth of Cu-Sn intermetallic compound in microbumps as well as voiding in the solder joint under elevated temperature and current. The models are compared against observations of phase evolution in fabricated test devices.

Sustainable Lithium‐Ion Battery Separator Membranes Based on Carrageenan Biopolymer

Aiming to improve the sustainability of materials for lithium‐ion batteries (LIBs), this work reports on the development of novel membranes based on iota‐carrageenan biopolymer and their suitability as separator in LIBs applications. The membranes are prepared by freeze‐drying and its morphology, thermal, mechanical, and electrochemical properties are evaluated as a function of polymer concentration in the solution. Porous membranes with a degree of porosity above 90% and different interconnected pore sizes between 50 and 70 µm for both polymer concentrations are obtained. The electrochemical parameters of the membranes are influenced by the carrageenan polymer concentration, being 1.34 mS cm‐1, 3, 7, and 0.48 for ionic conductivity, tortuosity, MacMullin number, and lithium transference number, respectively, for the membrane prepared from the 4 wt% carrageenan content solution. The half‐cells cathodic prepared with the developed membranes show good cyclability and rate capability. The discharge capacity values obtained with the membrane prepared from 4 wt% carrageenan content are 145 and 25 mAh g‐1 at C/10‐ and 1C‐rates, respectively, demonstrating excellent battery cycling performance and long‐term stability. Thus, this work demonstrates that iota‐carrageenan biopolymer membranes developed by freeze‐drying can be used as separators for a next generation of more sustainable batteries.

Appropriate pore size for bone formation potential of porous collagen type I-based recombinant peptide.

IntroductionIn this study, we developed porous medium cross-linked recombinant collagen peptide (mRCP) with two different ranges of interconnected pore sizes, Small-mRCP (S-mRCP) with a range of 100–300 μm and Large-mRCP (L-mRCP) with a range of 200–500 μm, to compare the effect of pore size on bone regeneration in a calvarial bone defect.MethodsCalvarial bone defects were created in Sprague–Dawley rats through a surgical procedure. The rats were divided into 2 groups: S-mRCP implanted group and L-mRCP implanted group. The newly formed bone volume and bone mineral density (BMD) was evaluated by micro-computed tomography (micro-CT) immediately after implantation and at 1, 2, 3, and 4 weeks after implantation. In addition, histological analyses were carried out with hematoxylin and eosin (H&E) staining at 4 weeks after implantation to measure the newly formed bone area between each group in the entire defect, as well as the central side, the two peripheral sides (right and left), the periosteal (top) side and the dura matter (bottom) side of the defect.ResultsMicro-CT analysis showed no significant differences in the amount of bone volume between the S-mRCP and L-mRCP implanted groups at 1, 2, 3 and 4 weeks after implantation. BMD was equivalent to that of the adjacent native calvaria bone at 4 weeks after implantation. H&E images showed that the newly formed bone area in the entire defect was significantly larger in the S-mRCP implanted group than in the L-mRCP implanted group. Furthermore, the amount of newly formed bone area in all sides of the defect was significantly more in the S-mRCP implanted group than in the L-mRCP implanted group.ConclusionThese results indicate that the smaller pore size range of 100–300 μm is appropriate for mRCP in bone regeneration.

Research on flashover characteristics of typical interconnect structures on printed circuit board and influential factors under DC voltage

With the development of high-density and highly integrated electronic devices, the insulation characteristics between the interconnects of printed circuit boards (PCBs) are the key issues to be considered in their design and production. Most of the existing studies on insulation characteristics are based on parallel interconnect structures; however, the possibility of flashover or breakdown on PCB at parallel interconnects is relatively low compared to other irregular structures. The flashover characteristics of PCB interconnects need to be more comprehensively presented. In this paper, the commonly used interconnects were divided into three typical structures. Under the same DC excitation, the “interconnect with pad” structure had the most severe electric field concentration, and the insulation characteristic of this structure was the worse of the three. Furthermore, the effects of the distance between the interconnect and pad size on the flashover voltages of the “interconnect with pad” structure were investigated and explained by the maximum electric field strength, which could be approximately calculated by the existing equation.

Printing of NiTinol parts with characteristics respecting the general microstructural, compositional and mechanical requirements of bone replacement implants

NiTinol is considered to be an attractive candidate alloy for biomedical applications. The aim of this research was to obtain porous NiTinol parts that respected the general microstructural (having 30–80 vol% interconnected pores and pore sizes in the range of 100–600 μm), compositional (an impurity content of less than 500 ppm) and mechanical (an elastic modulus close to that of cortical bone (10–20 GPa) or cancellous bone (<3 GPa), higher strength than 100 MPa at 2% strain and adequate fracture elongation of at least 8%) prerequisites of implants used in bone replacement applications. This was done by printing parts using a laser powder bed fusion technique and by employing a slightly Ni-rich pre-alloyed NiTinol powder having ∼55.9 wt% Ni in its composition. In the next setup, different post-printing heat treatments were employed to adjust the microstructural, compositional and mechanical characteristics of the printed parts step-by-step with the mentioned ones required for the bone replacement implants. The effects of different printing parameters and conducted heat treatment procedures on the microstructure, composition, phase transformation characteristics and mechanical properties of dense and porous printed parts were also systematically discussed and results were correlated together. The developed porous parts (with ∼33 vol% interconnected porosity and ∼600 μm pore width size) were printed using the processing parameters: laser power = 120 W, scanning velocity = 1100 mms−1, hatch spacing = 0.08 mm and layer thickness = 0.03 mm. Regardless of being heat treated or not, the parts generally respected the mentioned targeted properties.

Mechanical and Biological Properties of Magnesium- and Silicon-Substituted Hydroxyapatite Scaffolds.

Magnesium (Mg)- and silicon (Si)-substituted hydroxyapatite (HA) scaffolds were synthesized using the sponge replica method. The influence of Mg2+ and SiO44− ion substitution on the microstructural, mechanical and biological properties of HA scaffolds was evaluated. All synthesized scaffolds exhibited porosity >92%, with interconnected pores and pore sizes ranging between 200 and 800 μm. X-ray diffraction analysis showed that β-TCP was formed in the case of Mg substitution. X-ray fluorescence mapping showed a homogeneous distribution of Mg and Si ions in the respective scaffolds. Compared to the pure HA scaffold, a reduced grain size was observed in the Mg- and Si-substituted scaffolds, which greatly influenced the mechanical properties of the scaffolds. Mechanical tests revealed better performance in HA-Mg (0.44 ± 0.05 MPa), HA-Si (0.64 ± 0.02 MPa) and HA-MgSi (0.53 ± 0.01 MPa) samples compared to pure HA (0.2 ± 0.01 MPa). During biodegradability tests in Tris-HCl, slight weight loss and a substantial reduction in mechanical performances of the scaffolds were observed. Cell proliferation determined by the MTT assay using hBMSC showed that all scaffolds were biocompatible, and the HA-MgSi scaffold seemed the most effective for cell adhesion and proliferation. Furthermore, ALP activity and osteogenic marker expression analysis revealed the ability of HA-Si and HA-MgSi scaffolds to promote osteoblast differentiation.

3D printed‐polylactic acid scaffolds coated with natural rubber latex for biomedical application

AbstractThree‐dimensional (3D) printing is a rapidly growing technology and plays an emerging role in several biomedical applications. Polylactic acid (PLA) is one of the most common materials in 3D printing, however, it is chemically inert due to the absence of reactive side chain groups. In this context, in this work, the PLA scaffolds with two different geometries were produced and coated with natural rubber latex (NRL) extracted from the rubber tree Hevea brasiliensis. NRL presents bioactive substances that are related to its biological properties. The results revealed scaffolds with interconnected pores and pores sizes from 600 to 1300 μm. The NRL coatings caused a decrease in pore size. Infrared spectra showed that 2 NRL layers were more efficient in coverage. Compressive strength values obtained are in agreement with the spongy bones value (22–24 MPa for crossbar and 20–22 MPa for roundbar cube). Finally, the hemolytic activity of the PLA scaffold was 3%, while the scaffolds coated with 1 and 2 NRL layers presented values of 0%, indicating a potential use in biomedical applications due to the absence of hemolytic effects.

Double-layer TiO2 inverse opal-based quantum dot-sensitized solar cells

The operation of dye-sensitized solar cells and quantum dot-sensitized solar cells (QDSSCs) depends strongly on the photoanode material employed. This is addressed in the present work by developing photoanodes based on a double-layer TiO2 inverse opal material with different interconnected pore sizes in the bottom and upper layers for use in QDSSCs. The proposed photoanode material leads to better infiltration of the sensitizers and the hole transporting material through the entire depth of the TiO2 layer. Double-layer TiO2 inverse opal-based QDSSCs are demonstrated to facilitate the greater absorbance of quantum dots and obtain higher photocurrent and power conversion efficiency than QDSSCs adopting single-layer TiO2 inverse opal photoanodes. Various QDSSCs employing double-layer TiO2 inverse opal photoanodes with different pore sizes in the layers are tested. The CdS/CdSe co-sensitized solar cell adopting the optimum photoanode configuration and thickness provided the highest QDSSC conversion efficiency of 5.79%.