Department of Industrial and Systems Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States.
Published: September 2021
AI Article Synopsis
Article Abstract
Here, we present a closed-loop controlled photopolymerization process for fabrication of hydrogels with controlled storage moduli. Hydrogel crosslinking was associated with a significant change in the phase angle of a piezoelectric cantilever sensor and established the timescale of the photopolymerization process. The composition, structure, and mechanical properties of the fabricated hydrogels were characterized using Raman spectroscopy, scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA). We found that the storage moduli of photocured poly(ethylene glycol) dimethacrylate (PEGDMA) and poly(-isopropylacrylamide) (PNIPAm) hydrogels could be controlled using bang-bang and fuzzy logic controllers. Bang-bang controlled photopolymerization resulted in constant overshoot of the storage modulus setpoint for PEGDMA hydrogels, which was mitigated by setpoint correction and fuzzy logic control. SEM and DMA studies showed that the network structure and storage modulus of PEGDMA hydrogels were dependent on the cure time and temporal profile of UV exposure during photopolymerization. This work provides an advance in pulsed and continuous photopolymerization processes for hydrogel engineering based on closed-loop control that enables reproducible fabrication of hydrogels with controlled mechanical properties.
This study evaluated the impact of silver particles, suspended in flower extract, on the physicochemical characteristics and release dynamics of antioxidant compounds in PVP (polyvinylpyrrolidone)-based hydrogel systems. The hydrogels were synthesized via photopolymerization with fixed amounts of crosslinker (PEGDA) and photoinitiator, while the concentration of the silver-infused extract was systematically varied. Key properties, including the density, porosity, surface roughness, swelling capacity, and water vapor transmission rate (WVTR), were quantitatively analyzed.
Xolography is a volumetric 3D printing technique utilizing intersecting light beams within a volume of photopolymer for a spatially controlled photopolymerization. Unlike layer-based methods, Xolography creates structures continuously within a closed photopolymer vat, eliminating the prevalent need for support structures and allowing full geometrical freedom at high printing speeds. The volumetric working principle does not rely on gravity, making Xolography an outstanding technology for additive manufacturing under microgravity conditions as illustrated in a set of experiments during a parabolic flight campaign.
This study investigated the effect of a theranostic-guided UV-A light corneal photo-reshaping technique on corneal elevation and wavefront aberration (WA) in human donor eyes. A specialized platform, combining UV-A light with corneal iontophoresis for controlled, patterned, riboflavin delivery, was used for both distribution assessment and concentration-driven photopolymerization of corneal proteins. In all cases, a consistent riboflavin concentration gradient, with lower levels in the central prepupillary zone, was recorded.
The synthesis of polymeric thermoset materials with spatially controlled physical properties using readily available resins is a grand challenge. To address this challenge, we developed a photoinitiated polymerization method that enables the spatial switching of radical and cationic polymerizations by controlling the dosage of monochromatic light. This method, which we call Switching Polymerizations by Light Titration (SPLiT), leverages the use of substoichiometric amounts of a photobuffer in combination with traditional photoacid generators.
Background: Gold nanoparticles can generate heat upon exposure to radiation due to their plasmonic properties, which depend on particle size and shape. This enables precise control over the release of active substances from polymeric pharmaceutical formulations, minimizing side effects and premature release. The technology of 3D printing, especially vat photopolymerization, is valuable for integrating nanoparticles into complex formulations.
