Wax-oil lubricants to reduce the shear between skin and PPE

Prolonged use of tight-fitting PPE, e.g., by COVID-19 healthcare workers leads to skin injuries. An important contributor is the shear exerted on the skin due to static friction at the skin-PPE interface. This study aims to develop an optimised wax-oil lubricant that reduces the friction, or shear, in the skin-PPE contact for up to four hours. Lubricants with different wax-oil combinations were prepared using beeswax, paraffin wax, olive oil, and mineral oil. In-vivo friction measurements involving seven participants were conducted by sliding a polydimethylsiloxane ball against the volar forearms to simulate the skin-PPE interface. The maximum static coefficient of friction was measured immediately and four hours after lubricant application. It was found that the coefficient of friction of wax-oil lubricants is mainly governed by the ratio of wax to oil and the thermal stability and morphology of the wax. To maintain long-term lubricity, it is crucial to consider the absorption of oil into the PPE material. The best performing lubricant is a mixture of 20 wt% beeswax, 40 wt% olive oil, and 40 wt% mineral oil, which compared to unlubricated skin, provides 87% (P = 0.0006) and 59% (P = 0.0015) reduction in instantaneous and 4-h coefficient of friction, respectively.

Wax-Oil Lubricants to Reduce the Shear Between Skin and PPE

Prolonged use of tight-fitting PPE, e.g., by COVID-19 healthcare workers leads to skin injuries. An important contributor is the shear exerted on the skin due to static friction at the skin-PPE interface. This study aims to develop an optimised wax-oil lubricant that reduces the friction, or shear, in the skin-PPE contact for up to four hours. Lubricants with different wax-oil combinations were prepared using beeswax, paraffin wax, olive oil, and mineral oil. In-vivo friction measurements involving seven participants were conducted by sliding a polydimethylsiloxane ball against the volar forearms to simulate the skin-PPE interface. The maximum static coefficient of friction was measured immediately and four hours after lubricant application. It was found that the coefficient of friction of wax-oil lubricants is mainly governed by the ratio of wax to oil and the thermal stability and morphology of the wax. To maintain long-term lubricity, it is crucial to consider the absorption of oil into the PPE material. The best performing lubricant is a mixture of 20 wt% beeswax, 40 wt% olive oil, and 40 wt% mineral oil, which compared to unlubricated skin, provides 87% (P = 0.0006) and 59% (P = 0.0015) reduction in instantaneous and 4-hour coefficient of friction, respectively.

Contribution to process digitisation of cold forging processes using additive manufactured tools

Cold forging tools become increasingly complex and require enhanced functionality, especially in the context of digitisation. Conventional subtractive manufacturing processes often reach their limits when the geometric complexity of the workpiece increases, hence additive manufacturing processes have become increasingly important in the last decades. Additive manufacturing processes have already been used in many fields of manufacturing technology to produce tool components with promising results, but the potentials of additive manufacturing processes have not yet been applied to cold forging tools. Therefore, the Institute for Metal Forming Technology (IFU) of the University of Stuttgart has developed an additive manufactured cold extrusion tool with integrated functional features. As functional features in the additive manufactured extrusion tool, a close contour glass fiber sensor for temperature measurement, a cooling system and a lubrication system for the controlled injection of minimal lubricant amounts during the forming process were integrated. Due to the integrated functional features, structural degradation appears in the tool, therefore the structural-mechanical tool properties were analyzed numerically with the FE-Software DEFORM 3D™ in this report as well. Furthermore, the additive manufactured cold extrusion tool was experimentally evaluated in sequentially executed extrusion operations. Thereby the integrated functional features were used and gathered data were recorded. As a result of the experimental forming tests, near-contour temperature measurements in the extrusion tool with and without the use of the integrated cooling system as well as the modification of the maximum punch forces by an inline lubricant application were obtained. In addition, the experimentally determined temperature fields in the extrusion die are validated with numerically calculated results.

Optimal operation of a rail lubrication device with respect to noise reduction and wheel/rail friction coefficient

During research work, three series of studies were performed to support the importance of using rail lubrication at tramway tracks in Budapest. The first task was to determine the noise reduction efficiency of automated rail lubrication: noise measurements were performed in case of lubricated rails with corrugations, non-lubricated rails with corrugations, grinded rails as well as grinded and lubricated rails. Once the conformity was determined, an additional task was to find the right lubricant. After the noise and braking effect tests of various lubricants, it was a legitimate need to determine the optimum lubricant application because the setting of the devices is based only on the experience of the Operator. Finally, the noise mitigation effect and the friction coefficient affecting the wheel/rail contact with different lubricant application settings were investigated simultaneously. It is important that the lubricant be applied in appropriate amount such that even the safe movement of the trams is guaranteed, but at the same time the noise reduction is satisfactory too. Based on the results, the authors make recommendations for the application of the rail lubrication devices.

The impact of topical lidocaine and timing of LMA removal on the incidence of airway events during the recovery period in children: a randomized controlled trial

Background The timing of laryngeal mask airway (LMA) removal remains undefined. This study aimed to assess the optimal timing for LMA removal and whether topical anesthesia with lidocaine could reduce airway adverse events. Methods This randomized controlled trial assessed one-to-six-year-old children with ASA I-II scheduled for squint correction surgery under general anesthesia. The children were randomized into the LA (lidocaine cream smeared to the cuff of the LMA before insertion, with mask removal in the awake state), LD (lidocaine application and LMA removal under deep anesthesia), NLA (hydrosoluble lubricant application and LMA removal in the awake state) and NLD (hydrosoluble lubricant application and LMA removal in deep anesthesia) groups. The primary endpoint was a composite of irritating cough, laryngeal spasm, SpO2 < 96%, and glossocoma in the recovery period in the PACU. The secondary endpoints included the incidence of pharyngalgia and hoarseness within 24 h after the operation, duration of PACU stay, and incidence of agitation in the recovery period. The assessor was unblinded. Results Each group included 98 children. The overall incidence of adverse airway events was significantly lower in the LA group (9.4%) compared with the LD (23.7%), NLA (32.6%), and NLD (28.7%) groups (P=0.001). Cough and laryngeal spasm rates were significantly higher in the NLA group (20.0 and 9.5%, respectively) than the LA (5.2 and 0%, respectively), LD (4.1 and 1.0%, respectively), and NLD (9.6 and 2.1%, respectively) groups (P=0.001). Glossocoma incidence was significantly lower in the LA and NLA groups (0%) than in the LD (19.6%) and NLD (20.2%) groups (P< 0.001). At 24 h post-operation, pharyngalgia incidence was significantly higher in the NLA group (15.8%) than the LA (3.1%), LD (1.0%), and NLD (3.2%) groups (P< 0.001). Conclusions LMA removal in the awake state after topical lidocaine anesthesia reduces the incidence of postoperative airway events. Trial registration ChiCTR, ChiCTR-IPR-17012347. Registered August 12, 2017.