Micro and Nanosystems - Volume 13, Issue 1, 2021

Background: The determination of the mechanical properties of biological samples using Atomic Force Microscopy (AFM) at the nanoscale is usually performed using basic models arising from the contact mechanics theory. In particular, the Hertz model is the most frequently used theoretical tool for data processing. However, the Hertz model requires several assumptions, such as homogeneous and isotropic samples and indenters with perfectly spherical or conical shapes. As it is widely known, none of these requirements are 100 % fulfilled for the case of indentation experiments at the nanoscale. As a result, significant errors arise in the Young’s modulus calculation. At the same time, an analytical model that could account complexities of soft biomaterials, such as nonlinear behavior, anisotropy, and heterogeneity, may be far-reaching. In addition, this hypothetical model would be ‘too difficult’ to be applied in real clinical activities since it would require a very heavy workload and highly specialized personnel. Objective: In this paper, a simple solution is provided to the aforementioned dead-end. A new approach is introduced in order to provide a simple and accurate method for mechanical characterization at the nanoscale. Methods: The ratio of the work done by the indenter on the sample of interest to the work done by the indenter on a reference sample is introduced as a new physical quantity that does not require homogeneous, isotropic samples or perfect indenters. Results: The proposed approach provides an accurate solution from not only a physical perspective but also a simpler solution which does not require activities such as the determination of the cantilever’s spring constant and the dimensions of the AFM tip. Conclusion: It has been observed from this opinion paper that the solution aims to provide a significant opportunity to overcome the existing limitations provided by Hertzian mechanics and apply AFM techniques in real clinical activities.

Background: Snail Mucus (SM) is secreted by the pedal gland of snails, and has a fibrous structure when it crawls upside down on the plane. It contains biologically active compounds that perform medical functions, such as glycol acid, natural antibiotics, and glycoprotein. Methods: For this paper, we prepared fibers using electrospinning to simulate this natural fiber for the first time, and we can produce the nanofiber with mucus from a snail. The effects of dissolution time and the spun solution were also investigated. Results: The results show that biomimetic nanofibers with different diameters can be obtained using electrospinning. When the concentration of the spun liquid was increased from 6 wt% to 8 wt%, a fiber with about a 200 nm diameter can be obtained. The adjustment of the concentration plays a crucial role in electrospinning. Conclusion: The investigation and utilization of biomimetic nanomaterials can promote the development of tissue engineering effectively.

With the rapid development of nanotechnology, stimulus-responsive nanofibers have in recent years, aroused the interest of many researchers. Due to their biocompatibility, favorable safety, and easy degradability, thermo-sensitive hydrogels, which are responsive to temperature change, have become increasingly attractive in the biomedicine field. Electrospinning is a unique fibrous manufacturing process in which a polymer solution is spun under a strong electric field to form into nanofibers. The porous structure and large surface area of electrospun nanofibers contribute significantly to the application of thermo-sensitive hydrogels in drug release systems, wound dressing materials, and biosensors. In the first part of this study, the mechanism of temperature sensitivity is detailed. Then the classification and preparation of electrospun thermo-sensitive hydrogels nanofibers are illustrated, followed by an introduction of their current applications in biomedical science. Finally, the current limitations and promise of electrospun thermo-sensitive hydrogels nanofibrous materials are presented.

Background: Flexure hinges have certain advantages, such as a simple structure, smooth movement, no need for lubrication, frictionless movement and high precision. The flexure hinge’s transfer of force and displacement relies on its deformation. Thus, stiffness is an important index for evaluating hinge flexibility. Objective: Stiffness analysis of the flexure hinges is necessary to be performed. This paper aims to present a unified stiffness model solving method of the flexible hinges with complex contour curves. Methods: The transfer matrix of a flexure hinge was derived based on balance equations and the virtual work principle with consideration of axial, shear, and bending deformations. The element stiffness matrix of a flexure hinge was obtained from the relationship between the transfer and stiffness matrices. In this manner, the unified formula of element stiffness of a general flexure hinge was established. By using this method, rigidity models of parabolic, corner-filled, and the right circular flexure hinge have been deduced. By taking the right circular flexure hinge as an example, the results obtained using this method were compared with those of methods provided in other studies and the finite element results. Results and Conclusion: The comparison results revealed that the proposed method increases the rigidity accuracy because the effect of the uneven distribution coefficient of shear stress was considered. The stiffness error was within 7%, which demonstrates the validity of this method. In contrast to the other methods, the proposed method can be applied by determining the first integral element stiffness of a common flexible hinge. Moreover, the proposed method provides better commonality, flexibility, and ease of programming. In particular, it is much easier for the flexure hinges with a complex contour curve. Transitivity can be used to calculate the rigidity after the flexure hinge has been divided into subunits, thus making it unnecessary to convert to the global coordinate system.

Aims: The aim is to develop effective CO2 sorbent materials for fighting global climate change. Background: CO2 is one of the major combustion products which once released into the air can contribute to global climate change. There is a critical need for the development of new materials that can capture CO2 reversibly with acceptable energy and cost performance for these applications. Accordingly, solid sorbents have been reported to be promising candidates for CO2 sorbent applications through a reversible chemical transformation due to their high CO2 absorption capacities at moderate working temperatures. Objective: To evaluate the CO2 capture performance of γ-LiAlO2 and α-Li5AlO4 in comparison with other solid sorbents. Methods: By combining first-principles density functional theory with phonon lattice dynamics calculations, the thermodynamic properties of the CO2 capture reaction by sorbent as a function of temperature and pressure can be determined without any experimental input beyond crystallographic structural information of the solid phases involved. The calculated thermodynamic properties are used to evaluate the equilibrium properties for the CO2 adsorption/desorption cycles. Results: Both γ-LiAlO2 and α-Li5AlO4 are insulators with wide band gaps of 4.70 and 4.76 eV, respectively. Their 1st valence bands just below the Fermi level are mainly formed by p orbitals of Li, O and Al as well as s orbital of Li. By increasing the temperature from 0 K up to 1500 K, their phonon free energies are decreased while their entropies are increased. The thermodynamic properties of CO2 capture reactions by γ-LiAlO2 and α-Li5AlO4 are calculated and used for comparing with other wellknown sorbent materials. Conclusion: The calculated thermodynamic properties of γ-LiAlO2 and α-Li5AlO4 reacting with CO2 indicate that LiAlO2 could be used for capturing CO2 at warm temperature range (500-800 K) while α- Li5AlO4 could be used for capturing CO2 at high-temperature range (800-1000 K), which are in good agreement with available experimental data.

Background: Atomic Force Microscopy (AFM) Nanoindentation procedure regarding biological samples poses significant challenges with respect to the accuracy of the provided results. These challenges are related to the inhomogeneity of biological samples, various uncertainties in experimental methods and certain approximations regarding the theoretical analysis. The most commonly used theoretical model for data processing at the linear elastic regime regarding biological samples is the Hertz model. Objective: This paper focuses on the investigation of the resulting errors of the basic equation of the Hertz theory that depend on the ratio, indentation depth/indenter’s radius regarding the Young’s modulus calculation. Methods: An extended new equation is derived which takes into account the influence of the indentation depth/indenter’s radius ratio on the calculation of the Young’s modulus and can be easily used for calculations. The derived equation is further combined with equations which take into account the shape of the sample. Results: Several examples in the literature that do not take into account the value of the ratio indentation depth/indenter’s radius are reported and the related errors are calculated and discussed. Moreover, a rational explanation, regarding the extended differences of the Young’s modulus calculations using the same experimental results when these are processed using the Hertz model and the Oliver & Pharr analysis (which is the general model that applies for any axisymmetric indenter) is provided. Conclusion: A complete and reliable theoretical tool was developed (that takes into account the indentation depth/indenter’s radius ratio and the shape of the sample) which can be generally applied in order to reduce the errors produced by the current methodology (Hertz model).

Background: With the increase in the integration degree of the three-dimensional Integrated Circuit ( 3D I C) , the thermal power consumption per unit volume increases greatly, which makes the chip temperature rise. High temperature could affect the performance of the devices and even lead to thermal failure. So, the thermal management for 3D ICs is becoming a major concern. Objective: The aim of the research is to establish a micro-channel cooling model for a threedimensional Integrated Circuit (3D IC) considering the through-silicon vias (TSVs). Methods: By studying the structure of the TSVs, the equivalent t hermal resistance of each layer was formulated. Then the one-dimensional micro-channel cooling thermal analytical model considering the TSVs was proposed and solved by the existing sparse solvers such as KLU. Results: The results obtained in this paper reveal that the TSVs can effectively improve the heat dissipation, and its maximal temperature reduction is about 10.75%. The theoretical analysis is helpful to optimize the micro-channel cooling system for 3D ICs. Conclusion: The TSV has an important influence on the heat dissipation of 3D IC, which can improve its heat dissipation characteristic.

Background: Sand is one of the efficient sources of silicon. We get quite easily the plethora of sand from the river side, Bangladesh. Utilization of the superfluous sand can be assisted to enhance our economy. Methods: In this work, silicon is extracted from sand by metal–thermite reduction process and the sample of sand is collected from padma river Rajshahi, Bangladesh. The process is environmentally benign and low cost. The reduction of the sand was performed with Mg powder, and purification was done by leaching out with HCl and HF. We have studied the structural properties, chemical nature and physical morphology. Results and Conclusion: X-Ray Diffraction (XRD) confirmed that the presence of elemental Si in the samples produced by Mg-thermite reduction process and the particle size was found 25.72±1.3 nm in an average. Surface morphology has been studied using Scanning Electron Microscopy (SEM) and the particle size seemed around 30 to 40 nm which was comparable to the obtained particle size from XRD. Fourier Transform Infrared Spectroscopy (FTIR) showed the presence of Si-Si bonding in the investigating materials. The chemical nature of the sand has been studied by X-ray Fluorescence (XRF) analysis. Silicon content of sand was found about maximum 80%.

Background: Electrospun Cellulose Acetate (CA) nanofibrous membrane can be used in many areas such as biomedicine, water treatment. However, due to the strong hydrogen-bond interaction, the rare solvent can dissolve the CA and the resulting CA nanofibrous membranes always show bad morphology and poor performance. Aims: To research the effect of CaCl2-Formic acid (CaCl2-FA) solvent system on the morphology and structure of CA nanofibrous membrane. Methods: CA nanofibrous membrane was fabricated with a two-step dissolution method using the first step of CaCl2-FA solvent system followed by the second step of FA solvent solely. Subsequently, the CA nanofibrous membrane morphology and structure property were systematically investigated. Results and Conclusion: The results show that the CaCl2-FA can dissolve the CA efficiently. Additionally, the regenerated CA nanofibers are well-formed under all the CA concentrations with controlling fiber diameter ranging from 224.9 ± 38.6 nm to 367.8 ± 80.4 nm. The results suggest that this two-step dissolution method can be an effective and alternative approach to dissolve CA and regenerate CA nanofibrous membrane.

Background: Silk sericin has a significant influence on the regenerated silk solution and silk-based materials property, while few reports were found to investigate this topic. Aim: The aim is to discuss the effect of silk sericin content on the electrospun silk nanofibrous membrane. Methods: Four degumming conditions (none degumming, boiling water degumming, 0.05 % Na2CO3 degumming, 0.5 % Na2CO3 degumming) were carried out for a systematic investigation in terms of (1) the silk sericin content after degumming; (2) the morphology of regenerated silk nanofibrous membrane was characterized by a Scanning Electron Microscope (SEM); and (3) structural properties of regenerated silk nanofibrous membrane by Fourier transform infrared (FTIR) spectroscopy, X-Ray Diffraction (XRD). Result and Conclusion: The results show that 0.5 % Na2CO3 degumming results in poor spinnability. The solutions derived from none degumming and boiling water degumming present high viscosity, leading to a hard silk nanofiber fabrication process. The silk nanofiber from the 0.05 % Na2CO3 degumming shows an easier fabrication process and better nanofiber morphology. These results will benefit the silk-based materials preparation, biomedical and separation application.

Aim: To address the physical properties of the growing research topic based on inorganic and organic composite materials under the glassy regime. The incorporation of a small amount of organic content in inorganic chalcogenide alloy could be an interesting topic for the investigation. Such composite materials' optical and structural properties could define their prospective use. Objectives: Considering the prospective utility of the inorganic and organic composite materials, this report’s key goal was to demonstrate the structural and optical properties, like, absorption spectra, extinction coefficient (k), real dielectric constant (ε), imaginary dielectric constant (ε), refractive index (n), absorption coefficient (α) and optical energy band (Eg ) for the Se 55 Te 25 Ge 20 (GTS) alloy, Se 55 Te 25 Ge 20 +0.025% multiwalled carbon nano tubes (MWCNT) and Se 55 Te 25 Ge 20 +0.025 % bilayer graphene (GF) composites. Methods: To synthesize the materials, a direct melt-quenched technique was adopted. Materials microstructural and UV/Visible optical absorption were performed from the Field Emission Scanning Electron Microscope and UV/Visible optical spectrometer equipment’s. Results: The obtained experimental evidences revealed that materials’ optical properties and microstructures slightly altered owing to the incorporation of multi walled carbon nano tubes and bilayer graphene in Se 55 Te 25 Ge 20 regime. To correlate the inorganic-organic material interactions, a schematic has also interpreted based on the bond formation in the solids. Conclusion: The experimental evidences have revealed the existence of MWCNT and GF in the diffused form in GTS glassy configuration. The evidences have also revealed the diffused morphologies of the MWCNT and GF could not develop the specific structure within the complex configuration (although they have exhibited rather distinct morphologies), but they influenced the optical properties of the composite materials.

Aims: This study aimed to eliminate metallic contaminants from drinking water by using electrospun bi-layered microfiber membranes. Background: Fast industrialization triggers environmental pollution. Heavy metals like silver, lead and aluminum are the major contaminants that are extremely toxic and accumulate in biological tissues through the food chain and cause a health hazard. Electrospinning is a promising technique among other conventional techniques of removing these metals from drinking water. Electrospun membranes possess suitable properties for microfiltration purposes. In this study, to fabricate electrospun membranes, polycaprolactone (PCL) and zeolites were used as materials. PCL polymer is biocompatible and biodegradable, and zeolite is microporous, which is good for filtration or molecular sieving application. Methods: Using the electrospinning technique, PCL, PCL/zeolite, PCL and PCL/zeolite bi-layered electrospun membranes were fabricated. The properties of the membranes were evaluated using different techniques. The performance of the membranes was tested by filtering Aluminum (Al) present in drinking water. Results: Scanning Electron Microscopy (SEM) and energy dispersive X-ray (EDX) analyses confirmed the removal of Al using the membranes. ICP-OES results showed more than 90% of Al removal using PCL and PCL/zeolite electrospun membranes. Conclusion: These membranes are non-toxic and biodegradable and have the potential to be used for microfiltration purposes.

Background: Valsartan is a poorly water-soluble drug having limited oral bioavailability. Its absorption and onset of action mostly depend on its solubility. Therefore, its solubility needs to be enhanced for maximum therapeutic action. Objective: The aim of this work is to formulate valsartan-mannitol Solid Dispersions (SDs) by bottom- up process based-freeze drying (lyophilization) techniques for solubility enhancement of valsartan. Methods: Valsartan is BCS class II drug having low aqueous solubility and low oral bioavailability. It needs to improve its solubility for the fastest onset of action. SDs were prepared using water as a solvent and tertiary butyl alcohol (TBA) as anti-solvent. A 3² (three level-two factors) response surface methodology was used to detect the effect of independent variables such as the amount of valsartan (X1) and the amount of mannitol (X2) on dependent variables such as solubility (Y1) and particle size (Y2). Results: Prepared SDs were characterized by employing solubility, particle size determination, Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), zeta potential, Fourier Transform Infrared Spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). The optimum values of solubility and particle size were 115.14μg/L and 242.5 nm, respectively. Conclusion: Solid dispersions of valsartan-mannitol were successfully prepared by simple lyophilization techniques and seem to be promising for enhancing dissolution rate (solubility) and oral bioavailability of valsartan.

Background: A THz Plasmonic Waveguide Based on Graphene Coated Bow-tie Nanowire (TPW-GCBN) has been proposed. The waveguide characteristics are investigated by the Finite Element Method (FEM). The influence of the geometric parameters on propagation constants, electric field distributions, effective mode areas, and propagation lengths is obtained numerically. The performance tunability of TPW-GCBN is also studied by adjusting the Fermi energy. The simulation results show that TPW-GCBN has better mode confinement ability. TPW-GCBN provides a promising alternative in high-density integration of photonic circuit for the future tunable micro-nano optoelectronic devices.: Surface plasmonpolaritons based waveguides have been widely used to enhance the local electric fields. It also has the capability of manipulating electromagnetic fields on the deepsubwavelength. Objective: The waveguide characteristics of TPW-GCBN should be investigated. The tunability of TPW-GCBN should be studied by adjusting Fermi energy (FE) which can be changed by the voltage. Methods: The mode analysis and parameter sweep in Finite Element Method (FEM) were used to simulate TPW-GCBN for analyzing effective refractive index (neff), electric field distributions, normalized mode areas (Am), propagation length (Lp) and Figure of Merit (FoM). Results: At 5 THz, Aeffof λ²/14812,Lp of ~2 μm and FoM of 25 can be achieved. The simulation results show that TPW-GBN has good mode confinement ability and flexible tunability. Conclusion: TPW-GBN provides new freedom to manipulate the graphene surface plasmons, and leads to new applications in high-density integration of photonic circuits for tunable integrated optical devices.

Aims: Adsorption conditions of propranolol hydrochloride onto MCF are optimized. Properties of this adsorption system are studied. The sustained release properties of propranolol hydrochloride in the loading system are also researched. Background: In today's society, demand for drugs is getting higher and higher. With the development of nanotechnology, it is easier to immobilize drugs on nanomaterials, which can easily transport drugs in the human body. It can control drug release, reduce side effects, improve drug efficacy, and develop drug orientation. Objective: The purpose of this study was to load propranolol hydrochloride, a drug for the treatment of heart disease and hypertension on the MCF nano-mesoporous material to prepare a sustainedrelease preparation and investigate the release law of propranolol hydrochloride in simulated human body fluid. Methods: Nanometer mesoporous MCF (mesocellular foams) silica material was prepared in acidic medium using triblock copolymer poly(ethylene glycol)-block-poly(propyl glycol)-block-poly(ethylene glycol) as template and tetraethoxysilane as silica source. Propranolol hydrochloride drug was incorporated into the MCF mesoporous material by the impregnation method to prepare MCF-propranol hydrochloride host-guest composite material. The loading amount of drug was calculated by spectrophotometry and difference subtraction method. Results: The loading amount of drug calculated by spectrophotometry and difference subtraction method was 385.5 mg·g^-1 (propranolol hydrochloride/MCF). The adsorption process of propranolol hydrochloride in MCF belongs to the quasi-second-order kinetic process. Adsorption process ΔH⁰ = -19.11 kJ·mol^-1, is an exothermic process, ΔG⁰ < 0, the adsorption process is a spontaneous process. The effective release time of drug lasted up to 32 h and the maximum cumulative released amount was 99.4 % through the experiment of drug sustained release in the simulated body fluid. In the simulated gastric juice, the release time of drug reached 6 h, and the maximum cumulative released amount was 56.6 %. When drug release time arrived at 10 h in the simulated intestinal fluid, the maximum cumulative released amount was 71.3 %. Conclusion: The influence of the release rate of propranolol hydrochloride molecules from MCF mesopores was demonstrated, since it results in a very slow drug delivery from the nanocomposite system. Thus, it is concluded that the prepared MCF is an efficient drug sustained-released carrier.

Background: In this article, we have proposed a new reversible quantum circuit block along with the Quantum Cost (QC), Constant Input (CI), Garbage Output (GO) and delay optimized code converter using quantum circuit block. Methods: Initially, new quantum circuit block has been designed and later reversible code converter circuits have been implemented using it. The proposed new quantum block used to design 2’s complement code converter (2SCCC), cost efficient BCD to Excess-3 Code Converter (BECC) and can also be used to implement different logic functions. The QC of proposed quantum circuit block is 8. The QC and delay of the proposed 2SCCC is 8 and 1 respectively. Similarly, the QC and delay of the proposed BECC is 11 and 2, respectively. The proposed cost efficient BECC is designed using two NOT gate, one Feynman gate and one new quantum circuit block with QC is 11. Results: The improvement of QC for 2SCCC and BECC is 27.27 % and 21.43%, respectively. The improvement of delay for 2SCCC and BECC are 66.67% and 50%, respectively, compared with respect to the latest reported results. Conclusion: So the improvement of QC and delay are very high using QCB.

Aim: This paper proposed the design and development of 4-Bit Gray Code Counter Circuit Using Reversible Logic Gate. Methods: The 4-Bit Gray Code Counter Circuit can be design using SAM gate, Feynman gate (FG), double Feynman gate (DFG) and NOT gate. The proposed circuit is the combined application of 4-bit binary asynchronous counter and 4-bit binary to gray code converter circuit. Results: The proposed gray code counter is designed using four no. of SAM gate, three no. of DFG, one FG and seven reversible NOT gate. The QC, GO and CI of proposed circuit are correspondingly 30, 4 and 7. Conclusion: The novel reversible gray code counter have been designed using existing reversible logic gate. The proposed gray code counter is designed using four no. of SAM gate, three no. of DFG, one FG and seven reversible NOT gate. The QC, GO and CI of proposed circuit are correspondingly 30, 4 and 7.

In the Research Article entitled “Transient Analysis of Poly (3,4-Ethylenedioxythiophene) Poly (Styrenesulphonate) (PEDOT: PSS)- Polyfluorene Organic Polymer Layer Light Emitting Diode” published in Micro and Nanosystems, 2020, Vol. 12, No. 3, figure 2 has been revised as figure 3 was incorrectly duplicated in place of figure 2. The correct figure is as follows: