3D printing is an additive manufacturing (AM) technique that has quickly disrupted traditional design and manufacturing strategies. New structures can be manufactured that could not be fabricated using other methods. These new capabilities are considered by many to hallmark a historic shift representative of a new industrial revolution. Exciting utilities of this evolving technology are the fields of biomedical engineering and translational medicine, particularly in applying three-dimensional (3D) printing toward enabling on-demand fabrication of customized tissue scaffolds and medical device geometries. AM techniques are promising a future where on-demand production of patient-specific living tissues is a reality. In this review, we cover the rapid evolution and widespread concepts of a bio-“ink” and bioprinted devices and tissues from the past two decades as well as review the various additive manufacturing methods that have been used toward 3D bioprinting of cells and scaffolds with a special look at the benefits and practical considerations for each method. Despite being a young technology, the evolution and impact of AM in the fields of tissue engineering and regenerative medicine has progressed rapidly. We finish the review by looking toward the future of bioprinting and identify some of the current bottlenecks facing the blossoming industry.

A detailed study of the electric deflection of molecular beams of (C6H6)2, (C6F6)2, and C6H6–C6F6 is reported. Although no resolved microwave or radio frequency transitions were observable, examination of unresolved beam transitions at radio frequencies were useful in establishing that the homomolecular dimers (C6H6)2 and (C6F6)2 are asymmetric rotors while the heteromolecular dimer C6H6–C6F6 is a symmetric top. From analysis of the quantitative electric deflection the dipole moment of C6H6–C6F6 is 0.44±0.04 D.

3D bioprinting has emerged as a technology that can produce biologically relevant structures in defined geometries with microscale resolution. Techniques for fabrication of free-standing structures by printing into granular gel media has been demonstrated previously, however, these methods require crosslinking agents and post-processing steps on printed structures. Our method utilizes one-step gelation of silk fibroin within a suspension of synthetic nanoclay (Laponite), with no need for additional crosslinking compounds or post processing of the material. This new method allows for in situ physical crosslinking of pure aqueous silk fibroin into defined geometries produced through freeform 3D printing.

A. B. Elkowitz and R. E. Wyatt, J. Chem. Phys. 62, 3683 (1975). 16 Accurate 3-D calculations for J >0 in the neighborhood of the resonance are very difficult to perform because of the large number of basis functions required in the close-coupling expansion. We do however have some preliminary 3-D J >0 results which are in agreement with the italicized statement about the 2-D system. 17 Since the distinguishable-atom nonreactive probability P^^X N (J) is very similar in both energy and J dependence to PQO-M 12^) * w e expect that the nonreactive integral cross section a 0 o->i^ should also have a peak at the resonance energy. This implies that the effect of atom indistinguishability should not appreciably alter the conclusions of this analysis. 18 The smallness of this cross section may lead to experimental detection difficulties, and other reactive systems may be more favorable candidates for experimental investigation. The point we are making is nevertheless of significant conceptual importance, namely that resonances can exist and play an important role in chemically reactive collisions for which the corresponding potential energy surface does not have an attractiveIn 1970 Buhl and Snyder 1 discovered a new molecular transition at 89190 MHz in several interstellar sources. Since they could not identify with certainty the species responsible for this emission they named it X-ogen. Later that year Klemperer 2 postulated that this mysterious line was actually due to the molecular ion HCO + , whose theoretically predicted rotational constant agreed very well with that corresponding to the X-ogen frequency and which was expected to be a fairly stable and abundant species under the conditions prevailing in the interstellar clouds.well. 19 The individual partial-wave contributions to the differential cross sections are highly oscillatory in nature, and fairly slight calculational inaccuracies in the elements of the scattering matrix element for one partial wave are usually enough to upset the delicate balance between partial waves which leads to nonoscillatory differential cross sections, thereby resulting in strong spurious oscillations. It is reasonable to expect that the presence of resonances in some of the partial waves which contribute significantly to the cross sections should have a similar effect, as is experimentally observed for inelastic electron scattering. for a counter-example, see J. R. Stine and R. A. Marcus, Chem. Phys. Lett. 2j), 575 (1974). 24 For example, the distorted-wave method [K. T. Tang and M. Karplus, Phys. Rev. A 4, 1844 (1971)] and the one-vibrational-basis-function method [G. Wolken and M. Karplus, J. Chem. Phys. 60 f 351 (1974)].Since that time this identification of X-ogen as HCG + has become fairly generally accepted, although it has not been definitely proven. Strong support for it has come recently from Snyder et al., 3 who have reported observation of an interstellar line at 86 754 MHz which they identify as H 13 CO + . More recent theories 4 ' 5 of the processes involved in f...

The results of microwave and radio frequency spectroscopy of the weakly bound complexes of hydrogen fluoride with carbon dioxide and carbonyl sulfide are presented. The following spectroscopic constants are determined:                           A nearly linear hydrogen bonded equilibrium structure with an O–H bond length of ∼1.9 Å is consistent with all the experimental data. The stretching force constant, estimated from the distortion constant to be ks = 0.021 mdyne/Å for CO2–HF, appears anomalously small for such a short bond.