Development of a Textile Based Protein Sensor for Monitoring the Healing Progress of a Wound

This article focuses on the design and fabrication of flexible textile-based protein sensors to be embedded in wound dressings. Chronic wounds require continuous monitoring to prevent further complications and to determine the best course of treatment in the case of infection. As proteins are essential for the progression of wound healing, they can be used as an indicator of wound status. Through measuring protein concentrations, the sensor can assess and monitor the wound condition continuously as a function of time. The protein sensor consists of electrodes that are directly screen printed using both silver and carbon composite inks on polyester nonwoven fabric which was deliberately selected as this is one of the common backing fabrics currently used in wound dressings. Three sensor designs were investigated to determine if any were suitable for protein detection. These sensors were experimentally evaluated and compared to each other by using albumin protein in phosphate buffered saline (PBS). A comprehensive set of cyclic voltammetry measurements were used to determine the optimal sensor design to provide the measurement of protein in solution. The best sensor was comprised of only silver conductive ink present to form the tracks outside the interface zone and a carbon only layer in the working and counter electrodes at the interface zone. This design prevents the formation of silver dioxide and protects the sensor from rapid decay, which allows for the recording of consecutive measurements using the same sensor. The chosen printed protein sensor was able to detect BSA at varying concentrations ranging from 30-0.3 mg/ml with a sensitivity of 0.0026µA/M.

A Detailed Interface Characterization of the Explosively Welded Three-Layered Ti Gr 1/Alloy 400/1.4462 Steel Clads Before and After Heat Treatment

The presented research focused on the microstructural characteristics of explosively welded three-layered Ti Grade (Gr) 1/Alloy 400/1.4462 steel clads before and after heat treatment being of large practical potential. Scanning electron microscopy (SEM) analyses have shown that both interfaces formed between the plates are continuous and without defects. The in-depth examination was dedicated to the upper Ti Gr 1/Alloy 400 interface, located closer to the explosive material, therefore, subjected to more extreme welding conditions. The presence of cubic phase Ti2Ni, hexagonal phase Ni3Ti, and tetragonal phase (Cu x Ni1−x)2Ti were confirmed within the melted zones, which slightly widened due to annealing, being an essential step in the manufacturing of these modern materials. Transmission electron microscopy observations in the nano scale confirmed the preliminary chemical composition analyses collected with energy-dispersive X-ray spectroscopy in SEM. They additionally revealed the interface zone microstructure transformation due to the annealing. It was evidenced that initially mixed phases in the form of grains, after heat treatment formed irregular bands arranged in the following sequence: Alloy 400/Ni3Ti/(Cu x Ni1−x)2Ti/Ti2Ni/Ti Gr 1. A clear segregation of Cu and Ni forming two separate layers was also noticed. These diffusion phenomena may influence the strength of the final product, therefore need further studies regarding the prolonged annealing state.

A Numerical Approach to Analyze Detail Mechanical Characteristic at the Crack Tip of SCC in Dissimilar Metal Welded Joints

The mechanical characteristic at the crack tip is one of the main factors affecting the stress corrosion cracking (SCC) in dissimilar metal welded joints (DMWJs). In this research, to evaluate the effect of heterogeneous material properties on the mechanical characteristic at the crack tip of DMWJs accurately, a heterogeneous material model of the SA508 Cl.3-Alloy 52M DMWJ was established based on USDFLD subroutine in ABAQUS. The comparison of the traditional “Sandwich” material model with the heterogeneous material properties, stress-strain conditions, and the plastic zone around the crack tip at the interference zone has been analyzed by the finite element method (FEM). The results indicated that the heterogeneous material model could characterize the mechanical properties of the SA508 Cl.3-Alloy 52M DMWJs accurately. In addition, the crack at the interface zone between materials will deflect along with the weld metal in two material models.

Spatial Temporal Condition of Recent Seismicity In The Northern Part of Sumatra

The condition of stress and recent seismicity in the seismic-prone area can be statistically analyzed with the Gutenberg-Richter relation. We apply this relation to the hypocenter distribution for the period 1970-2020 with M ≥ 4 and depth ≤ 200 km in the northern part of Sumatra. Spatially, The results obtained, a-values and b-values, figure a lateral heterogeneity and stress accumulation with dense structures at the interface zone in the subduction system and the northern segmentation of the Seulimeum fault. In time, both zones illustrate a slow time-to-failure cycle and seismic gap with high stress accumulation in the specific clusters with high seismic parameter values. The results of the spatial temporal analysis illustrate that each major earthquake event is usually preceded by a low statistical parameter value.

On the Disintegration of A1050/Ni201 Explosively Welded Clads Induced by Long-Term Annealing

The paper presents the microstructure and phase composition of the interface zone formed in the explosive welding process between technically pure aluminum and nickel. Low and high detonation velocities of 2000 and 2800 m/s were applied to expose the differences of the welded zone directly after the joining as well as subsequent long-term annealing. The large amount of the melted areas was observed composed of a variety of Al-Ni type intermetallics; however, the morphology varied from nearly flat to wavy with increasing detonation velocity. The applied heat treatment at 500 °C has resulted in the formation of Al3Ni and Al3Ni2 layers, which in the first stages of growth preserved the initial interface morphology. Due to the large differences in Al and Ni diffusivities, the porosity formation occurred for both types of clads. Faster consumption of Al3Ni phase at the expense of the growing Al3Ni2 phase, characterized by strong crystallographic texture, has been observed only for the weld obtained at low detonation velocity. As a result of the extended annealing time, the disintegration of the bond occurred due to crack propagation located at the A1050/Al3Ni2 interface.

The Interface Zone of Explosively Welded Titanium/Steel after Short-Term Heat Treatment

This work presents a detailed description of a bonding zone of explosively welded Ti/steel clads subjected to stress relief annealing, applied in order to improve the plasticity of the final product. The typical joint formed by the welding process possesses a characteristic wavy interface with melted regions observed mainly at the crest regions of waves. The interface of Ti/steel clads before and after annealing was previously investigated mostly in respect to the melted regions. Here, a sharp interface between the waves was analyzed in detail. The obtained results indicate that the microstructure of a transition zone of that area is different along the width. After the heat treatment at 600 °C for 1.5 hours, titanium carbide (TiC) together with α-Fe phase forms at the interface in local areas of relatively wide interlayer (~ 1 µm), while for most of the sharp interface, a much thinner zone up to about 400 nm, formed by four sublayers containing intermetallic phase and carbides, is present. This confirms that carbon diffusion induced by applied heat treatment significantly influences the final microstructure of the Ti/steel interface zone. Side bending tests confirmed high plasticity of welds after applied heat treatment; however, the microhardness measurements indicated that the strengthening of the steel in the vicinity of the interface had not been removed completely.

Interface characteristics and formation mechanism of plasma arc welding-brazing aluminum alloy/ultrahigh-strength steel joint

A butt welding-brazing joint of 5A06 aluminum alloy and DP1180 ultrahigh-strength steel was carried out by using plasma arc welding (PAW) with Al-Si welding wire. Interface characteristics, formation mechanism and mechanical properties of the joint were investigated. The results showed that the dissimilar joint contained bond zone, weld zone and Al/steel interface zone. During PAW, the inter-diffusion of Fe and Al and the interfacial reaction occurred, and the double-layer structure intemtallics (IMCs) composed of Fe4Al13 layer and Fe2Al5 layer were produced in the interface zone. The thickness and morphology of both IMC layers depended on different positions in the interface zone. The Fe2Al5 layer thickness decreased obviously and its morphology changed from continuous layer to discontinuous layer with the decrease of welding heat input. The average tensile strength of the joint was 88 MPa and the joint fractured at the Al/steel interface zone with the highest hardness (524 HV). The interface zone IMCs were the main factor of affecting the mechanical properties of aluminum alloy and ultrahigh-strength steel PAW joint.

Results of posterior lamellar femto-keratoplasty using two different lasers

Purpose. To evaluate the results of treatment of patients with pseudophakic bullous keratopathy (PBK) by the method of posterior lamellar femto-keratoplasty with ultrathin graft (FS-DSEK) harvested using two different lasers. Material and methods. The results of surgical treatment of 82 patients (82 eyes) underwent posterior lamellar femto-keratoplasty for PBK were analyzed. In the 1st group included 43 patients (43 eyes) with PBK underwent FS-DSEK using FS laser Femto-Visum (Optosystems, Russia). In the 2nd group included 39 patients (39 eyes) with PBK underwent FS-DSEK using LDV Z8 (Ziemer, Switzerland). Observation period was 1 year. Before and after surgery following indicators were evaluated: uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), postoperative astigmatism, central corneal thickness (CCT), graft thickness, center-periphery (C:P) ratio, endothelial cell density (ECD), endothelial cell (EC) loss, optical density. Results. Transparent engraftment at 1-year observation period was observed in 88% of cases. In the 1st group UCVA=0.22±0.11, BSCVA=0.32±0.12, in the 2nd group UCVA=0.18±0.08, BSCVA=0.29±0.1 (p>0.05). The maximum BSCVA in both groups was 0.6. Postoperative astigmatism was comparative in 2nd groups – 1.43±1.1 and 1.38±1.0 D, respectively (p>0.05). In the 1st group, CCT=549±31, graft thickness in the central zone – 83±12, C:P ratio – 0.92±0.05; in the 2nd group CCT=546±28, graft thickness – 80±10, C:P ratio – 0.94±0.06 (p>0.05). In the 1st group ECD – 1326±282, EC loss – 55±6%; ECD in the 2nd – 850±230, EC loss – 70±7% (p<0.05). According to the results of densitometry, optical density of the posterior layers of the cornea and «donor–recipient» interface zone was higher in the 2nd group, both in the central and in the paracentral zones: in the 1st group in the posterior layers of the stroma – 16.4±1.2 (0–2 mm) and 15.8±1.0 (2–6 mm), in the interface zone – 14.5±0.9 (0–2) and 13.9±0.8 (2–6), in the 2nd group in the posterior layers – 18.3±1.3 (0–2 mm) and 17.9±1.1 (2–6 mm), and in the interface zone – 17.3±1.2 (0–2 mm) and 17.0±1.0 (2–6 mm, p<0.05). Conclusions. FS-DSEK showed high efficiency for treating patients with PBK. Functional results were comparative in 2nd groups. Statistical analysis showed highest safety of transplanted endothelium in the 1st group at 1-year observation period. Key words: pseudophakic bullous keratopathy, femtosecond laser, posterior lamellar keratoplasty, corneal endotheliumultrathin graft.