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The trend toward precision medicine and point-of-care diagnostics necessitates advances in technologies to improve the time, cost, and technical expertise required for sensitive lab based assays. Current designs for portable diagnostic devices primarily utilize lateral flow immunoassays that have limited sensitivity and multiplexibility. To improve upon current lateral flow diagnostics, we have designed a sensor capable of providing rapid and portable identification of multiple genomic targets, specifically microRNAs. MicroRNA (miRNA) provide a promising set of biomarkers to replace proteins and antibodies for a range of disease conditions from cancer to HIV. For this work, we have advanced previous efforts with a single step displacement assay to allow direct integration with paper based Surface Enhanced Raman Spectroscopy (SERS) devices. Results show successful application of a single step displacement assay on printable nanoparticle substrates that will allow for simple fabrication of sensors for multiple miRNA sequences. Further, we show the potential for simultaneous detection of the multiplexed output from the displacement assay using inkjet-printed paper SERS devices.

A novel DNA sequence biosensor that utilizes enzyme-labeled probes and electrochemical detection via an interdigitated array (IDA) electrode on a microfluidic chip is presented. Sandwich structure DNA sequence recognition is performed by immobilizing a single stranded DNA (ssDNA) on the microchannel surface (primary probe) that is complementary to a portion of the target, followed by hybridization with target ssDNA and a second ssDNA (secondary DNA probe), which is complementary to another region of the target and is conjugated with β-Galactosidase (β-Gal). Surface confined β-Gal is detected by introducing its substrate, 4-aminophenyl-D-galactopyranoside (PAPG), into the system; β-Gal cleaves PAPG into the electrochemical active compound, p-amino phenol (PAP), which is detected by a Au IDA in a microfluidic channel. The signal is amplified by cycling its reduced and oxidized form between the interleaved anode and cathode. On the chips which are integrated in 60µm high channels, the oxidation currents show linear correlation to the immobilized target DNA concentration between 0 and 100nM. Currents collected on chips where 0 and 0.5nM target DNA is immobilized are significantly different. Similarly, on the chips integrated in the 35µm channels where target DNA is not introduced to form the sandwich (negative control), the oxidation current shows non-differentiable results whether PAPG is present or absent in buffer solution. On the contrary, on the chip where 0.1nM target DNA hybridized with probes, the oxidation current is significantly higher when the buffer contains PAPG. As the enzymatic reaction time increases from 15 to 30 seconds, the signal difference between PAPG and buffer solution almost doubled. By reducing the channel height from 60 to 35µm, the total assay time is reduced from 80 minutes to 35 minutes.

We have carried out the refractometric characterization on the whispering gallery mode (WGM) of a fused silica microsphere as the first step towards developing novel bio/chemical sensors with high sensitivity and high multiplexing capability. The WGM spectral position shifts when the refractive index of the surrounding medium is varied by adding ethanol to water. It is found that a sensitivity of 30 nm/RIU (refractive index units) and a refractive index detection limit on the order of 10-7 RIU can be achieved. Theoretical calculation is also performed and agrees well with the experimental data

The Stanford OCRL has designed HORNET-a novel optical packet-switched WDM MAN. The key advantages of HORNET are efficient bandwidth sharing among a large number of users and lower equipment cost than SONET. We are constructing an experimental testbed to investigate the capabilities of HORNET. The experimental results confirm the HORNET node's ability to transmit and receive optical packets with better than 10/sup -9/ BER, to correctly route packets according to their recovered destination node address carried by subcarrier signals, and to effectively handle data clock recovery on a packet-by-packet basis. The network simulation results on the queue depth and the packet latency prove the benefits of the VOQ over the single FIFO queue at heavy traffic load.

High capacity metropolitan area networks must be developed to enable future generations of high-speed multimedia Internet applications and services. This paper discusses emerging issues in the development of future optical metropolitan area networks and describes the pioneering research at Stanford University to address some of them. In particular, the HORNET project, which boasts a new architecture and novel subsystems for next generation high capacity metropolitan networks, is featured in this paper.