Sequential process optimization for a digital light processing system to minimize trial and error.

In additive manufacturing, logical and efficient workflow optimization enables successful production and reduces cost and time. These attempts are essential for preventing fabrication problems from various causes. However, quantitative analysis and integrated management studies of fabrication issues using a digital light processing (DLP) system are insufficient. Therefore, an efficient optimization method is required to apply several materials and extend the application of the DLP system. This study proposes a sequential process optimization (SPO) to manage the initial adhesion, recoating, and exposure energy. The photopolymerization characteristics and viscosity of the photocurable resin were quantitatively analyzed through process conditions such as build plate speed, layer thickness, and exposure time. The ability of the proposed SPO was confirmed by fabricating an evaluation model using a biocompatible resin. Furthermore, the biocompatibility of the developed resin was verified through experiments. The existing DLP process requires several trials and errors in process optimization. Therefore, the fabrication results are different depending on the operator's know-how. The use of the proposed SPO enables a systematic approach for optimizing the process conditions of a DLP system. As a result, the DLP system is expected to be more utilized.

Decreased door-to-balloon time in patients with ST-segment elevation myocardial infarction during the early COVID-19 pandemic in South Korea: An observational study.

The coronavirus disease 2019 (COVID-19) resulted in a marked decrease in the number of patient visits for acute myocardial infarction and delayed patient response and intervention in several countries. This study evaluated the effect of the COVID-19 pandemic on the number of patients, patient response time (pain-to-door), and intervention time (door-to-balloon) for patients with ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI). Patients with STEMI or NSTEMI visiting a hospital in South Korea who underwent primary coronary intervention during the COVID-19 pandemic (January 29, 2020, to December 31, 2020) were compared with those in the equivalent period from 2018 to 2019. Patient response and intervention times were compared for the COVID-19 pandemic window (2020) and the equivalent period from 2018 to 2019. We observed no decrease in the number of patients with STEMI (P = .88) and NSTEMI (P = 1.00) during the COVID-19 pandemic compared to that in the previous years. Patient response times (STEMI: P = .39; NSTEMI: P = .59) during the overall COVID-19 pandemic period did not differ significantly. However, we identified a significant decrease in door-to-balloon time among patients with STEMI (14%; P < .01) during the early COVID-19 pandemic. We found that the number of patients with STEMI and NSTEMI was consistent during the COVID-19 pandemic and that no time delays in patient response and intervention occurred. However, the door-to-balloon time among patients with STEMI significantly reduced during the early COVID-19 pandemic, which could be attributed to decreased emergency care utilization during the early pandemic.

Optimization of the Projection Microstereolithography Process for a Photocurable Biomass-Based Resin.

Biomass materials, an important source of chemical feedstocks, could replace fossil fuels as a resource in the future. The chemical feedstocks from biomass materials are used in many medical and pharmaceutical products and in fuels, chemicals, and functional materials. Biomass materials are expected to be used in biomedical engineering fields, especially due to their low biotoxicity. By the way, most of the demand for bio-application fields is an application targeted for customized production, so a high formability is required for production. Research on three-dimensional (3D) printing technology capable of satisfying these requirements has been ongoing. Manufacturing additives need to be investigated to use biomass materials as a resin or bioink safely for 3D printing, which is a technique widely used in biomedical engineering fields. In this study, a projection microstereolithography (PµSL) system, a 3D printing technique, was made that uses a biomass-based resin. Biomass materials are designed to be photocurable for use in the PµSL process. Various PµSL process parameters were investigated using the biomass-based resin to determine the optimum fabrication conditions for 3D structures. This study demonstrated that a biomass-based resin can be used in the PµSL process. We provide a method for its application in various biomedical engineering fields.

Effect of Nonpharmaceutical Interventions on Transmission of Severe Acute Respiratory Syndrome Coronavirus 2, South Korea, 2020.

We analyzed transmission of coronavirus disease outside of the Daegu-Gyeongsangbuk provincial region in South Korea. We estimated that nonpharmaceutical measures reduced transmissibility by a maximum of 34% without resorting to a strict lockdown strategy. To optimize epidemic control, continuous efforts to monitor the transmissibility are needed.

Preparation of Flexible Electrodes Based on Silver Nanoparticles-Carbon Nanotubes (AgNPs-CNTs) and Elastomer Composites for Soft Electronics.

For flexible electronics devices, a composite of silver nanoparticles-carbon nanotubes (AgNPs-CNTs) and polydimethylsiloxane elastomer were well mixed using a planetary mixer and a 3-roll mill. The ratio of Ag/polymer was varied by adding different size of AgNPs and modified with 12 kinds of flexible electrode compositions. The electrical and mechanical stability of the electrode was measured by combining universal test machine and cyclic voltammetry at once and it showed remarkable stability during 200% strain and 100 cycle duration test. The stable and repeatable electrical circuit was demonstrated while bending and stretching the electrode even higher than 120% strain. Furthermore, the soft gripper incorporating a flexible electrode was fabricated to lift a thin target paper based on electroadhesive force.

Synthesis of BaTiO3 nanoparticles as shape modified filler for high dielectric constant ceramic-polymer composite.

Coral-like structured barium titanate (BaTiO3) nanoparticles were synthesized as filler for a high dielectric elastomer. The nanoparticle size, and shape, and the reactivity of the synthesis were modified according to temperature, time, pH, and precursor materials. Dielectric properties of poly(dimethylsiloxane) (PDMS) composites were estimated by volume fractions of BaTiO3 of 5, 10, and 15 vol% for both sphere and coral-like shapes. As a result, coral-like BaTiO3-PDMS composites had the highest dielectric constant of 10.97, which was 64% higher than the spherical BaTiO3-PDMS composites for the 15 vol% fraction. Furthermore, the phase transition process and surface modification were applied to increase the dielectric properties through calcination and improved particle dispersion in the elastomer using polyvinylpyrrolidone (PVP). The dispersion of the PVP coated BaTiO3-PDMS composite was improved compared to pristine BaTiO3 as shown by SEM imaging. The coral-like BaTiO3 embedded composite could be used for electronic devices such as piezoelectric devices or electro-adhesive grippers, which require flexible and high dielectric materials.

From lignocellulosic biomass to furans via 5-acetoxymethylfurfural as an alternative to 5-hydroxymethylfurfural.

A facile pathway to furan derivatives from lignocellulosic biomass via 5-acetoxymethylfurfural (AMF) was developed. AMF possesses advantageous properties due to its less-hydrophilic acetoxymethyl group relative to the hydroxymethyl group of 5-hydroxymethylfurfural (HMF). The hydrophobicity and chemical stability of AMF allowed practical isolation and purification to afford a highly pure product of up to 99.9 %. AMF was produced in good to excellent yields under mild conditions from 5-chloromethylfurfural (CMF) and alkylammonium acetates, both of which could be obtained directly from lignocellulosic biomass. Heterogeneous reactions with polymer-supported alkylammonium acetates were also established; this showed the feasibility of a continuous process for this pathway. AMF could be transformed into various promising furanic compounds, such as 2,5-furandicarboxylic acid (FDCA), 2,5-furandimethanol (FDM), and 5-hydroxymethyl-2-furanoic acid (HFA), in high yields.