Application of hydrogels in tissue engineering and innovative strategies such as organ printing, which is based on layered 3D deposition of cell-laden hydrogels, requires design of novel hydrogel matrices. Hydrogel demands for 3D printing include: 1) preservation of the printed shape after the deposition; 2) maintaining cell viability and cell function and 3) easy handling of the printed construct. In this study we analyze the applicability of a novel, photosensitive hydrogel (Lutrol) for printing of 3D structured bone grafts. We benefit from the fast temperature-responsive gelation ability of thermosensitive Lutrol-F127, ensuring organized 3D extrusion, and the additional stability provided by covalent photocrosslinking allows handling of the printed scaffolds. We studied the cytotoxicity of the hydrogel and osteogenic differentiation of embedded osteogenic progenitor cells. After photopolymerization of the modified Lutrol hydrogel, cells remain viable for up to three weeks and retain the ability to differentiate. Encapsulation of cells does not compromise the mechanical properties of the formed gels and multilayered porous Lutrol structures were successfully printed.
Epoxy polymers are frequently used for constructing buildup layers. Atop the dielectric polymer metal layers are plated by means of a wet-chemical electroless and/or electroplating process. The adhesion of the plated metal layers to this polymer surface is of prime importance for reliability of the interconnection. An increase in the roughness of the polymer surface plays an important part in the adhesion strength of plated metal layers by increasing the total area of interface between both layers. Hence, the evolution of polymer surface roughness with time due to the chemical treatment is of prime importance for determining the reliability of interconnections. A kinetic study of wet solution swellers and oxidizers is made, based on atomic force microscopy roughness measurements. Each chemical or combination of chemical treatments in a certain sequence has its influence on the evolution of roughness. The evolution of surface roughness also indicates the mechanisms that lead to the formation of roughness on the surface. Different models are proposed to explain the influence of sweller agents on polymer surface roughness. The kinetics of roughness formation under influence of swellers is modeled and the bases of the influence of swellers on oxidizing treatments are examined. Improvement of interconnection technology is essential for allowing increased signal frequencies and higher density of functions for future electronics. In order to meet the necessary improvements, sequential high-density buildup layers and microvia technology have been developed ͑Fig. 1͒. This research started in the late 1990s. 1 A wiring density of 100-150 m, defined as the sum of the width and the distance between copper interconnections ͑e.g., wires͒, is required in order to be able to mount unpackaged chips on the boards, through flip chip or wire bonding. 2 Most of the printed circuit boards ͑PCBs͒ used today are fabricated with a glass-epoxy resin on which metals ͑usually copper͒ are plated and patterned in order to realize interconnections between different components placed on top of the substrate. A good adhesion between the copper and the polymer is of prime importance for reliability of the interconnection. 3 By chemical treatment of the surface the characteristics ͑physical and chemical͒ of it can be changed in order to improve adhesion. It is obvious that the surface properties of the polymer are important for adhesion of the metal to the polymer. Hence, there is intense recent research into improving the adhesion of plated copper onto polymer surfaces. Many processes involve Ar plasma activation, followed by a surface graft polymerization. [4][5][6][7] Composites are also formed to improve adhesion. 8,9 However, because of the much lower prize of wet chemical treatments compared to composites or plasma ͑vacuum͒ processes, these treatments are preferred industrially. The adhesion strength of a solid-solid interface is largely determined by the bonding characteristics and structure of the interface. 10 The work required to pull an...
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