The role of biochar porosity and surface functionality in augmenting hydrologic properties of a sandy soil.

This paper reports studies to elucidate the potential relationships between porosity and surface functionality of biochar and soil water retention characteristics. The biochars studied were produced from pine wood (PW), hybrid poplar wood (HP), and pine bark (PB) at temperatures of 350°C and 600°C. The resulting materials were then oxidized under air at 250°C to generate oxygenated functional groups on the surface. All biochar were thoroughly characterized (surface and bulk properties) and their hydrological properties measured in blends with Quincy sand. We prepared 39 microcosms for this study to examine the effect of biochar functionalities and porosity on the hydro-physical properties of Quincy sand. Each biochar was thoroughly mixed with the soil at 20gkg-1. The field capacity, wilting point, and total available soil moisture of the bio-char/Quincy sand mixtures were measured for both dry and wet ranges. The soil water potentials and soil water contents were fitted using the model of van Genuchten. Our results indicated that the amount of oxygenated functional groups on the surface of biochars clearly differentiated the biochars in terms of hydrophilicity, with the oxidized biochars being superior, followed by the low-temperature biochars, while the high temperature biochars possessed lowest hydrophilicity. As a result, oxidized biochars exhibited better wettability compared to unoxidized biochars, regardless their feedstock source. Significant correlation occurred between the total acidic functional groups on biochar surface and water contents at different matric potentials. Over a wide range of soil water potentials, oxidized biochar-soil mixtures held more water than the unoxidized biochar-soil mixtures except in the region between -0.1 and -5kPa of ψ, which is near saturation. Soil water contents at different matric potentials were significantly inter-correlated (P<0.01) and correlated with bulk densities of biochar-amended soil samples.

Preparation and characterization of Kraft lignin-based moisture-responsive films with reversible shape-change capability.

Preparation of moisture-responsive Kraft lignin-based materials by electrospinning blends of Kraft lignin fractions with different physical properties is presented. The differences in thermal mobility between lignin fractions are shown to influence the degree of interfiber fusion occurring during oxidative thermostabilization of electrospun nonwoven fabrics, resulting in different material morphologies including submicrometer fibers, bonded nonwovens, porous films, and smooth films. The relative amount of different lignin fractions and degree of fiber flow and fiber fusion is shown to influence the tendency for the electrospun materials to be transformed into moisture-responsive materials capable of reversible changes in shape. Material characterization by scanning electron microscopy and atomic force microscopy as well characterization of the chemical and physical properties of Kraft lignin fractions by dynamic rheology, 1H and 13C NMR, and gel permeation chromatography combined with multiangle laser light scattering are presented. A proposed mechanism underlying moisture-responsiveness, shape change, and shape recovery is discussed based on the differences in chemical structure and physical properties of Kraft lignin fractions.

Design and validation of a compressive tissue stimulator with high-throughput capacity and real-time modulus measurement capability.

Mechanical stimulation has been shown to impact the properties of engineered hyaline cartilage constructs and is relevant for engineering of cartilage and osteochondral tissues. Most mechanical stimulators developed to date emphasize precision over adaptability to standard tissue culture equipment and protocols. The realization of mechanical characteristics in engineered constructs approaching native cartilage requires the optimization of complex variables (type of stimulus, regimen, and bimolecular signals). We have proposed and validated a stimulator design that focuses on high construct capacity, compatibility with tissue culture plastic ware, and regimen adaptability to maximize throughput. This design utilizes thin force sensors in lieu of a load cell and a linear encoder to verify position. The implementation of an individual force sensor for each sample enables the measurement of Young's modulus while stimulating the sample. Removable and interchangeable Teflon plungers mounted using neodymium magnets contact each sample. Variations in plunger height and design can vary the strain and force type on individual samples. This allows for the evaluation of a myriad of culture conditions and regimens simultaneously. The system was validated using contact accuracy, and Young's modulus measurements range as key parameters. Contact accuracy for the system was excellent within 1.16% error of the construct height in comparison to measurements made with a micrometer. Biomaterials ranging from bioceramics (cancellous bone, 123 MPa) to soft gels (1% agarose, 20 KPa) can be measured without any modification to the device. The accuracy of measurements in conjunction with the wide range of moduli tested demonstrate the unique characteristics of the device and the feasibility of using this device in mapping real-time changes to Young's modulus of tissue constructs (cartilage, bone) through the developmental phases in ex vivo culture conditions.