Due to ever-faster processor clock speeds, there is a rising need for increased bandwidth to transfer large amounts of data, noise-free, within computer and telecommunications systems. A related requirement is the demand for high bit-rate, short-haul links. Here, optical transmission paths are a viable alternative to high-frequency electrical interconnections, whereby layers with integrated waveguides are particularly suitable. The reasons for this include that a higher connection density can be achieved and the power dissipation, as well as interference from electromagnetic radiation, are significantly lower. The article presents general considerations and the results of research conducted by the German BMBF Project NeGIT, into the manufacture of circuit boards with embedded polymer optical waveguides. The electrical-optical boards were fabricated using precise photolithographic processes and standard lamination methods. They possess the thermal stability necessary for manufacturing processes and operational conditions, in terms of both bond strength and the stability of the optical properties. As part of this project, a design of an optical coupling in the daughter card and board backplane interfaces was developed and is presented as the centerpiece of this study.
Human embryonic stem cells (hESCs) play an important role in the fields of regenerative medicine, basic scientific research, tissue engineering and toxicology. Their unique morphology however makes them very sensitive to cryopreservation procedures. We recently introduced a surface dependent, enzyme- and serum-free method for the effective cryopreservation of bulk quantities of hESC colonies using direct immersion into liquid nitrogen (Beier et al., 2011 [5]). However, direct contact with liquid nitrogen risks contamination and cell infection and severely limits clinical application. This work introduces a modified method and a new combined cultivation and cryopreservation device to facilitate the surface dependent vitrification without contact with (possibly unsterile) liquid nitrogen. The technique allows the culture, cryopreservation, storage and post-thawing cultivation in the same device without detaching cell samples from the cultivation surface. Successful vitrification of bulk quantities of hESCs without direct liquid nitrogen contact is an important step towards automated cryopreservation processes for clinical applications of stem cells and other colony forming cell types.
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