Featured Application: Detailed chemical and structural changes to polylactid acid (PLA) from source material through 3D printing needs to be quantified in order to use PLA 3D printed structures for specific applications. This work was specifically motivated for specific applications for in situ synthesis of silver nanoparticles on printed PLA surfaces used in antimicrobial applications and the development and characterization of PLA constructs for tissue engineering.Abstract: Polylactic acid (PLA) is an organic polymer commonly used in fused deposition (FDM) printing and biomedical scaffolding that is biocompatible and immunologically inert. However, variations in source material quality and chemistry make it necessary to characterize the filament and determine potential changes in chemistry occurring as a result of the FDM process. We used several spectroscopic techniques, including laser confocal microscopy, Fourier transform infrared (FTIR) spectroscopy and photoacousitc FTIR spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) in order to characterize both the bulk and surface chemistry of the source material and printed samples. Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were used to characterize morphology, cold crystallinity, and the glass transition and melting temperatures following printing. Analysis revealed calcium carbonate-based additives which were reacted with organic ligands and potentially trace metal impurities, both before and following printing. These additives became concentrated in voids in the printed structure. This finding is important for biomedical applications as carbonate will impact subsequent cell growth on printed tissue scaffolds. Results of chemical analysis also provided evidence of the hygroscopic nature of the source material and oxidation of the printed surface, and SEM imaging revealed micro-and submicron-scale roughness that will also impact potential applications.

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Polylactic Acid (PLA) is an organic polymer commonly used in fused deposition (FDM) printing and biomedical scaffolding that is biocompatible and immunologically inert. However, variations in source material quality and chemistry make it necessary to characterize the filament and determine potential changes in chemistry occurring as a result of the FDM process. We used several spectroscopic techniques, including laser confocal microscopy, Fourier-Transform Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 3 April 2017 doi:10.20944/preprints201704.0010.v1Peer-reviewed version available at Appl. Sci. 2017, 7, , 579; doi:10.3390/app7060579 Infrared (FTIR) spectroscopy and photoacousitc FTIR spectroscopy, Raman spectroscopy, and X-ray photoelectron Spectroscopy (XPS) in order to characterize both the bulk and surface chemistry of the source material and printed samples. Scanning Electron Microscopy (SEM) and Differential Scanning Calorimetry (DSC) were used to characterize morphology, crystallinity, and the glass transition temperature following printing. Analysis revealed calcium carbonatebased additives which were reacted with organic ligands and potentially trace metal impurities, both before and following printing. These additives became concentrated in voids in the printed structure. This finding is important for biomedical applications as carbonate will impact subsequent cell growth on printed tissue scaffolds. Results of chemical analysis also provided evidence of the hygroscopic nature of the source material and oxidation of the printed surface, and SEM imaging revealed micro and sub-micron scale roughness that will also impact potential applications.

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Birnessite type layered manganese dioxides (δ-MnO2) have attracted considerable attention in recent years as 2D intercalation cathodes for rechargeable Li+, Na+, and Mg2+ batteries due to fast ion diffusion through their negatively charged δ-MnO2 sheets separated by interlayer cations and a stable Mn3+/4+ redox couple. Here we report the preparation and electrochemistry of zero and divalent copper co-intercalated birnessite type manganese dioxide (Cu00.03Cu2+0.21Na0.12MnO2·0.9H2O). The copper intercalated birnessite materials were fully characterized utilizing powder X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), transmission electron microscopy (TEM). The mixed valent nature of intercalated Cu0 and Cu2+ was confirmed by X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS). Electrochemical evaluation results show that zero valent copper intercalated birnessite exhibits higher discharge capability, improved cyclability, and lower impedance compared to the Cu2+ only intercalated (Cu0.26MnO2·1.0H2O) and Cu free Na birnessite (Na0.40MnO2·1.0H2O) materials. Remarkably, zero valent copper birnessite shows almost no fade after 10 cycles at 0.1 mV/s. Electrochemical impedance spectroscopy results suggest that charge transfer resistivity of Cu0 modified samples was much lower than that of Cu2+ and Cu free birnessite, indicating that the presence of a small amount of Cu0 improves the conductivity of birnessite and results in better electrochemical cyclability, rate capability, and lower impedance.