PLGA Coatings and PLGA Drug-Loading Coatings for Cardiac Stent Samples: Degradation Characteristics and Blood Compatibility

PLGA (Poly lactic-co-glycolic acid) and PLGA drug-loading coatings were prepared on 316 L stainless steel by electrostatic spray deposition (ESD). The surface morphology, three-dimensional morphology, and crystal structures of the coatings were observed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). Thermal properties, molecular weight, and coating composition were studied by differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and NMR. The degradation behaviors of the coatings were studied by mass changes, relative molecular mass and distributions, polymer compositions, thermal properties, and surface morphologies. The blood compatibilities of the coatings were investigated by platelet adhesion testing and dynamic coagulation times. SEM results indicated the drug-loading coating with 33% RAPA had the smoothest and most compact morphology. Addition of RAPA decreased the Tg of the PLGA coating, accompanied by partial crystallization that slowed the degradation rate of the drug-loaded coating. Microscopically, the morphology of the PLGA drug-loaded coating was coarser than the PLGA coating. The average surface roughness values of line and surface scannings were 16.232 nm and 39.538 nm, respectively. The surface of the drug-loading coating was micro uneven, and the macro smooth and micro multiphase separation structure helped improve its blood compatibility.

Effect of thermal modification on the surface quality of a coating applied to wood via the electrostatic spray deposition technique

The surface properties of thermally modified ash wood with a powder coating were investigated, and the results were compared to the unmodified wood. The wood specimens were sanded with 80 grit sandpaper and then pre-heated at 80 °C for 5 min in an infrared oven. The surface of the unmodified and the modified wood specimens were coated with an epoxy/polyester (1 to 1 ratio) hybrid coating using an electrostatic corona spray gun at the pilot plant established in the laboratory. The coatings on the wood specimens were cured at different curing conditions in an infrared oven, i.e., 120 °C/15 min, 140 °C/10 min, and 160 °C/10 min. The results showed that the thermal modification (TM) of the wood caused a slight decrease in the mechanical performance of the surface system (wood substrate and coating film). For example, the scratch and abrasion resistance of the unmodified specimens at the curing temperature of 120 °C were 3.33 N and 135 revolutions but were 3.12 N and 120 revolutions after the TM. However, the average surface roughness (1.26 mu) and contact angle (60.8°) of the distilled water on the cured coatings on the modified wood were lower than those on the unmodified wood (1.86 mu and 80.8°, respectively).

Stretchable MXene/Thermoplastic Polyurethanes based Strain Sensor Fabricated Using a Combined Electrospinning and Electrostatic Spray Deposition Technique

In this work, a novel flexible electrically resistive-type MXene/Thermoplastic polyurethanes(TPU) based strain sensors was developed by a composite process of electrospinning (ES) and electrostatic spray deposition (ESD). Compared with other deposition processes, the sensing layer prepared by ESD has better adhesion to the ES TPU nanofiber membrane and is not easy to crack during the stretching process, thereby greatly improving the working range of the strain sensor. Furthermore, we obtained the sandwich structure easily by ES on the surface of the sensing layer again. This will help make the stress distribution more uniform during the stretching process and further increase the strain sensing range. The ESD-ES strain sensors were attached on skin to monitor various human motions. The results demonstrate that our ESD-ES strain sensors have wide application prospects in smart wearable device.