Development of a penetration friction apparatus (PFA) to measure the frictional performance of surgical suture

Nowadays there is a wide variety of surgical sutures available in the market. Surgical sutures have different sizes, structures, materials and coatings, whereas they are being used for various surgeries. The frictional performances of surgical sutures have been found to play a vital role in their functionality. The high friction force of surgical sutures in the suturing process may cause inflammation and pain to the person, leading to a longer recovery time, and the second trauma of soft or fragile tissue. Thus, the investigation into the frictional performance of surgical suture is essential. Despite the unquestionable fact, little is actually known on the friction performances of surgical suture-tissue due to the lack of appropriate test equipment. This study presents a new penetration friction apparatus (PFA) that allowed for the evaluation of the friction performances of various surgical needles and sutures during the suturing process, under different contact conditions. It considered the deformation of tissue and can realize the puncture force measurements of surgical needles as well as the friction force of surgical sutures. The developed PFA could accurately evaluate and understand the frictional behaviour of surgical suture-tissue in the simulating clinical conditions. The forces measured by the PFA showed the same trend as that reported in literatures

Passive Tracer Visualization to Simulate Aerodynamic Virus Transport in Noninvasive Respiratory Support Methods

BACKGROUND: Various forms of noninvasive respiratory support methods are used in the treatment of hypoxemic CO­VID-19 patients, but limited data are available about the corresponding respiratory droplet dispersion. OBJECTIVES: The aim of this study was to estimate the potential spread of infectious diseases for a broad selection of oxygen and respiratory support methods by revealing the therapy-induced aerodynamics and respiratory droplet dispersion. METHODS: The exhaled air-smoke plume from a 3D-printed upper airway geometry was visualized by recording light reflection during simulated spontaneous breathing, standard oxygen mask application, nasal high-flow therapy (NHFT), continuous positive airway pressure (CPAP), and bilevel positive airway pressure (BiPAP). The dispersion of 100 μm particles was estimated from the initial velocity of exhaled air and the theoretical terminal velocity. RESULTS: Estimated droplet dispersion was 16 cm for unassisted breathing, 10 cm for Venturi masks, 13 cm for the nebulizer, and 14 cm for the nonrebreathing mask. Estimated droplet spread increased up to 34 cm in NHFT, 57 cm in BiPAP, and 69 cm in CPAP. A nonsurgical face mask over the NHFT interface reduced estimated droplet dispersion. CONCLUSIONS: During NHFT and CPAP/BiPAP with vented masks, extensive jets with relatively high jet velocities were observed, indicating increased droplet spread and an increased risk of droplet-driven virus transmission. For the Venturi masks, a nonrebreathing mask, and a nebulizer, estimated jet velocities are comparable to unassisted breathing. Aerosols are transported unboundedly in all these unfiltered therapies. The adequate use of protective measures is of vital importance when using noninvasive unfiltered therapies in infectious respiratory diseases

Tuning the Structure and Ionic Interactions in a Thermochemically Stable Hybrid Layered Titanate-Based Nanocomposite for High Temperature Solid Lubrication

Solid inorganic lubricants are thermally stable but they are often limited by their lack of deformability, while organic lubricants have limitations in terms of thermal stability. In this study, a novel solid organic–inorganic nanocomposite lubricant that synergistically combines the thermochemically stable structure of a layered oxide with the relative softness of an organic polymer is presented. The nanocomposite is made by intercalating 11-aminoundecanoic acid in a lepidocrocite-type protonated titanate, H1.07Ti1.73O4. The amino acid molecules rapidly arrange to form a paraffinic bilayer in the gallery region of the layered host. This topotactic reaction yields a well-organized layered nanocomposite consisting of inorganic 2D titanate layers separated by amino acid molecules. Above elevated temperatures, 11-undecanoic acid polymerizes into nylon-11 confined between crystalline titanate monolayers. The lubricating properties of these nanocomposites up to 580 °C are determined using high-temperature pin-on-disc experiments using steel-steel contacts. The lubricative properties are based on the softening of the intercalated polymer above 200 °C. The encapsulation of the polymer chains by the inorganic titanate monolayers protects the organic component from thermal degradation and increases the thermal stability of the system

Thermochemical stability and friction properties of soft organosilica networks for solid lubrication

In view of their possible application as high temperature solid lubricants, the tribological and thermochemical properties of several organosilica networks were investigated over a range of temperatures between 25 and 580 °C. Organosilica networks, obtained from monomers with terminal and bridging organic groups, were synthesized by a sol-gel process. The influence of carbon content, crosslink density, rotational freedom of incorporated hydrocarbon groups, and network connectivity on the high temperature friction properties of the polymer was studied for condensed materials from silicon alkoxide precursors with terminating organic groups, i.e., methyltrimethoxysilane, propyltrimethoxysilane, diisopropyldimethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane and 4-biphenylyltriethoxysilane networks, as well as precursors with organic bridging groups between Si centers, i.e., 1,4-bis(triethoxysilyl)benzene and 4,4'-bis(triethoxysilyl)-1,1'-biphenyl. Pin-on-disc measurements were performed using all selected solid lubricants. It was found that materials obtained from phenyltrimethoxysilane and cyclohexyltrimethoxysilane precursors showed softening above 120 °C and performed best in terms of friction reduction, reaching friction coefficients as low as 0.01. This value is lower than that of graphite films (0.050 ± 0.005), a common bench mark for solid lubricants

Tribochemistry of Bismuth and Bismuth Salts for Solid Lubrication

One of the main trends in the past decades is the reduction of wastage and the replacement of toxic compounds in industrial processes. Some soft metallic particles can be used as nontoxic solid lubricants in high-temperature processes. The behavior of bismuth metal particles, bismuth sulfide (Bi₂S₃), bismuth sulfate (Bi₂(SO₄)₃), and bismuth oxide (Bi₂O₃) as powder lubricants was studied in a range of temperatures up to 580 °C. The mechanical behavior was examined using a high-temperature pin-on-disc setup, with which the friction force between two flat-contact surfaces was recorded. The bismuth-lubricated surfaces showed low coefficients of friction (μ ≈ 0.08) below 200 °C. Above the melting temperature of the metal powder at 271 °C, a layer of bismuth oxide developed and the friction coefficient increased. Bismuth oxide showed higher friction coefficients at all temperatures. Bismuth sulfide exhibited partial oxidation upon heating but the friction coefficient decreased to μ ≈ 0.15 above 500 °C, with the formation of bismuth oxide-sulfate, while some bismuth sulfate remained. All surfaces were studied by X-ray diffraction (XRD), confocal microscopy, high-resolution scanning electron microscopy (HR-SEM), and energy-dispersive X-ray spectroscopy (EDS). This study reveals how the partial oxidation of bismuth compounds at high temperatures affects their lubrication properties, depending on the nature of the bismuth compound

Hybrid <i>n</i>‑Alkylamine Intercalated Layered Titanates for Solid Lubrication

The intercalation of different primary <i>n</i>-alkylamines in the structure of a layered titanate of the lepidocrocite type (H_1.07Ti_1.73O₄) for application in high-temperature solid lubrication is reported. The intercalation process of the amines was explored by means of <i>in situ</i> small-angle X-ray scattering (SAXS), with variations in alkyl chain length (3–12 carbon atoms) and the amine/titanate ratio. The intercalation process was found to be completed within 5 min after mixing of the precursors in water at 80 °C. The topotactic transformation of the layered titanate is driven by an acid–base reaction. The thermal degradation of the modified titanates was investigated by thermogravimetric analysis (TGA), and the chemical changes were investigated by temperature-dependent infrared spectroscopy (DRIFTS). The coefficient of friction of the lubricants was assessed by means of high-temperature pin-on-disc experiments up to 580 °C. The intercalation of amine rendered a deformable layered ceramic upon heating. It was found that the hydrocarbon chain length exerts an influence on the mechanical properties of the titanates, resulting in lower friction forces for lubricants with longer intercalated amine molecules. Films of solid lubricants with longer amine chain lengths showed coefficients of friction as low as 0.01, lower than that of the state-of-the-art material graphite

Supplementary Material for: Passive Tracer Visualization to Simulate Aerodynamic Virus Transport in Noninvasive Respiratory Support Methods

Background: Various forms of noninvasive respiratory support methods are used in the treatment of hypoxemic COVID-19 patients, but limited data are available about the corresponding respiratory droplet dispersion. Objectives: The aim of this study was to estimate the potential spread of infectious diseases for a broad selection of oxygen and respiratory support methods by revealing the therapy-induced aerodynamics and respiratory droplet dispersion. Methods: The exhaled air-smoke plume from a 3D-printed upper airway geometry was visualized by recording light reflection during simulated spontaneous breathing, standard oxygen mask application, nasal high-flow therapy (NHFT), continuous positive airway pressure (CPAP), and bilevel positive airway pressure (BiPAP). The dispersion of 100 μm particles was estimated from the initial velocity of exhaled air and the theoretical terminal velocity. Results: Estimated droplet dispersion was 16 cm for unassisted breathing, 10 cm for Venturi masks, 13 cm for the nebulizer, and 14 cm for the nonrebreathing mask. Estimated droplet spread increased up to 34 cm in NHFT, 57 cm in BiPAP, and 69 cm in CPAP. A nonsurgical face mask over the NHFT interface reduced estimated droplet dispersion. Conclusions: During NHFT and CPAP/BiPAP with vented masks, extensive jets with relatively high jet velocities were observed, indicating increased droplet spread and an increased risk of droplet-driven virus transmission. For the Venturi masks, a nonrebreathing mask, and a nebulizer, estimated jet velocities are comparable to unassisted breathing. Aerosols are transported unboundedly in all these unfiltered therapies. The adequate use of protective measures is of vital importance when using noninvasive unfiltered therapies in infectious respiratory diseases