We have developed a laser-based printing technique, called biological laser printing (BioLP). BioLP is a non-contact, orifice-free technique that rapidly deposits fL to nL scale volumes of biological material with spatial accuracy better than 5 microm. The printer's orifice-free nature allows for transfer of a wide range of biological material onto a variety of substrates. Control of transfer is performed via a computer-aided design/computer-aided manufacturing (CAD/CAM) system which allows for deposition rates up to 100 pixels of biological material per second using the current laser systems. In this article, we present a description of the apparatus, a model of the transfer process, and a comparison to other biological printing techniques. Further, examples of current system capabilities, such as adjacent deposition of multiple cell types, large-scale cell arrays, and preliminary experiments on creating multi-layer cell constructs are presented. These cell printing experiments not only demonstrate near 100% viability, they also are the first steps toward using BioLP to create heterogeneous 3-dimensional constructs for use in tissue engineering applications.

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We investigate experimentally and theoretically the effects of two different types of conductivity, electrical and ionic, upon magic-angle spinning NMR spectra. The experimental demonstration of these effects involves (63)Cu, (65)Cu, and (127)I variable temperature MAS-NMR experiments on samples of γ-CuI, a Cu(+)-ion conductor at elevated temperatures as well as a wide bandgap semiconductor. We extend previous observations that the chemical shifts depend very strongly upon the square of the spinning-speed as well as the particular sample studied and the magnetic field strength. By using the (207)Pb resonance of lead nitrate mixed with the γ-CuI as an internal chemical shift thermometer we show that frictional heating effects of the rotor do not account for the observations. Instead, we find that spinning bulk CuI, a p-type semiconductor due to Cu(+) vacancies in nonstoichiometric samples, in a magnetic field generates induced AC electric currents from the Lorentz force that can resistively heat the sample by over 200 °C. These induced currents oscillate along the rotor spinning axis at the spinning speed. Their associated heating effects are disrupted in samples containing inert filler material, indicating the existence of macroscopic current pathways between micron-sized crystallites. Accurate measurements of the temperature-dependence of the (63)Cu and (127)I chemical shifts in such diluted samples reveal that they are of similar magnitude (ca. 0.27 ppm/K) but opposite sign (being negative for (63)Cu), and appear to depend slightly upon the particular sample. This relationship is identical to the corresponding slopes of the chemical shifts versus square of the spinning speed, again consistent with sample heating as the source of the observed large shift changes. Higher drive-gas pressures are required to spin samples that have higher effective electrical conductivities, indicating the presence of a braking effect arising from the induced currents produced by rotating a conductor in a homogeneous magnetic field. We present a theoretical analysis and finite-element simulations that account for the magnitude and rapid time-scale of the resistive heating effects and the quadratic spinning speed dependence of the chemical shift observed experimentally. Known thermophysical properties are used as inputs to the model, the sole adjustable parameter being a scaling of the bulk thermal conductivity of CuI in order to account for the effective thermal conductivity of the rotating powdered sample. In addition to the dramatic consequences of electrical conductivity in the sample, ionic conductivity also influences the spectra. All three nuclei exhibit quadrupolar satellite transitions extending over several hundred kilohertz that reflect defects perturbing the cubic symmetry of the zincblende lattice. Broadening of these satellite transitions with increasing temperature arises from the onset of Cu(+) ion jumps to sites with different electric field gradients, a process that interferes with the formation of rotational echoes...

The initial decomposition products of 3-nitro-1,2,4-triazol-5-one (NTO) are characterized using laser-induced decomposition of a solid sample. Heating of solid NTO samples is achieved by irradiation with 7 ns pulses of 266 nm laser light while the gas-phase products are detected using 118 nm single-photon ionization in a time-of-flight mass spectrometer. Product translational temperatures and relative product yields are obtained by analysis of time-of-arrival scans. The translational temperature depends linearly on decomposition laser fluence and agrees with the results of a calculation of the temperature rise in the irradiated volume using the heat conduction equation. The relative product yields are used to determine the percent decomposition of NTO as a function of temperature. The temperature dependence of the experimental fractional decomposition is consistent with that obtained from an RRKM calculation of the temperature dependence of NTO unimolecular decomposition. The temperature dependence of the relative product yields is used to identify the initial channels. The initial reaction appears to be bimolecular with a net loss of an O atom to yield nitroso-TO. Early unimolecular reactions include loss of NO2 and nitro−nitrite rearrangement followed by loss of NO.