The proposition of increased innovation in network applications and reduced cost for network operators has won over the networking world to the vision of Software-Defined Networking (SDN). With the excitement of holistic visibility across the network and the ability to program network devices, developers have rushed to present a range of new SDN-compliant hardware, software and services. However, amidst this frenzy of activity, one key element has only recently entered the debate: Network Security. In this article, security in SDN is surveyed presenting both the research community and industry advances in this area. The challenges to securing the network from the persistent attacker are discussed and the holistic approach to the security architecture that is required for SDN is described. Future research directions that will be key to providing network security in SDN are identified.
A relatively low-cost fabrication method using soft lithography and molding for large-area, high-aspect-ratio microfluidic devices, which have traditionally been difficult to fabricate, has been developed and is presented in this work. The fabrication process includes novel but simple modifications of conventional microfabrication steps and can be performed in any standard microfabrication facility. Specifically, the fabrication and testing of a microfluidic device for continuous flow deposition of bio-molecules in an array format are presented. The array layout requires high-aspect-ratio elastomeric channels that are 350 µm tall, extend more than 10 cm across the substrate and are separated by as little as 20 µm. The mold from which these channels were fabricated consisted of high-quality, 335 µm tall SU-8 structures with a high-negative aspect ratio of 17 on a 150 mm silicon wafer and was produced using spin coating and UV-lithography. Several unique processing steps are introduced into the lithographic patterning to eliminate many of the problems experienced when fabricating tall, high-aspect-ratio SU-8 structures. In particular, techniques are used to ensure uniform molds, both in height and quality, that are fully developed even in the deep negative-aspect-ratio areas, have no leftover films at the top of the structures caused by overexposure and no bowing or angled sidewalls from diffraction of the applied UV light. Successful microfluidic device creation was demonstrated using these molds by casting, curing and bonding a polydimethylsiloxane (PDMS) elastomer. A unique microfluidic device, requiring these stringent geometries, for continuous flow printing of a linear array of 16 protein and antibody spots has been demonstrated and validated by using surface plasmon resonance imaging of printed arrays.
Protein arrays continue to increase in importance as tools for analysis of biological samples. This paper describes a new method for preparing bioarrays that is compatible with high throughput manufacturing. First, a native oxide terminated silicon substrate is coated with a monolayer of a polyethylene-glycol-containing silane. The coated substrate is then placed beneath a microlens array (MA) and the array is irradiated with a brief (4 ns) pulse of 532 nm laser light. The MA focuses the laser light onto the substrate, causing monolayer removal. The microlenses in the array employed in this work are square packed and have a spacing of 100 μm, that is, there are 10000 microlenses/cm2 in the optic and therefore 10000 spots/cm2 on surfaces patterned with this array. The patterned substrate is then immersed in a dilute (10-5 M) solution of a protein. Time-of-flight secondary ion mass spectrometry shows that all of the proteins studied, including avidin, BSA, ferritin, lysozyme, myoglobin, protein A, and streptavidin, adsorb selectively into the spots in the array. The stability of these adsorbed proteins is shown. The retention of activity of avidin after adsorption is demonstrated. Protein localization on the arrays is demonstrated using a microfluidic spotter. Additionally, it is shown that this method can be used to confirm the location of the metal (iron) in ferritin. It should be possible to generalize this analytical method to other metals that are loaded into ferritin
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