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A novel, ultra low-cost surface enhanced Raman spectroscopy (SERS) substrate has been developed by modifying the surface chemistry of cellulose paper and patterning nanoparticle arrays, all with a consumer inkjet printer. Micro/nanofabrication of SERS substrates for on-chip chemical and biomolecular analysis has been under intense investigation. However, the high cost of producing these substrates and the limited shelf life severely limit their use, especially for routine laboratory analysis and for point-of-sample analysis in the field. Paper-based microfluidic biosensing systems have shown great potential as low-cost disposable analysis tools. In this work, this concept is extended to SERS-based detection. Using an inexpensive consumer inkjet printer, cellulose paper substrates are modified to be hydrophobic in the sensing regions. Synthesized silver nanoparticles are printed onto this hydrophobic paper substrate with microscale precision to form sensing arrays. The hydrophobic surface prevents the aqueous sample from spreading throughout the paper and thus concentrates the analyte within the sensing region. A SERS fingerprint signal for Rhodamine 6G dye was observed for samples with as low as 10 femtomoles of analyte in a total sample volume of 1 [micro]L. This extraordinarily simple technique can be used to construct SERS microarrays immediately before sample analysis, enabling ultra low-cost chemical and biomolecular detection in the lab as well as in the field at the point of sample collection. 10.1021/ac102475k

We developed a novel on-column micro gas chromatography ([micro]GC) detector using capillary based optical ring resonators (CBORRs). The CBORR is a thin-walled fused silica capillary with an inner diameter ranging from a few tens to a few hundreds of micrometers. The interior surface of the CBORR is coated with a layer of stationary phase for gas separation. The circular cross section of the CBORR forms a ring resonator and supports whispering gallery modes (WGMs) that circulate along the ring resonator circumference hundreds of times. The evanescent field extends into the core and is sensitive to the refractive index change induced by the interaction between the gas sample and the stationary phase. The WGM can be excited and monitored at any location along the CBORR by placing a tapered optical fiber against the CBORR, thus enabling on-column real-time detection. Rapid separation of both polar and nonpolar samples was demonstrated with subsecond detection speed. Theoretical work was also established to explain the CBORR detection mechanism. While low-nanogram detection limits are observed in these preliminary tests, many methods for improvements are under investigation. The CBORR is directly compatible with traditional capillary GC columns without any dead volumes. Therefore, the CBORR-based [micro]GC is a very promising technology platform for rapid, sensitive, and portable analytical devices.

We developed a novel miniaturized and multiplexed, on-capillary, refractive index (RI) detector using liquid core optical ring resonators (LCORRs) for future development of capillary electrophoresis (CE) devices. The LCORR employs a glass capillary with a diameter of ~100 [micro]m and a wall thickness of a few micrometers. The circular cross section of the capillary forms a ring resonator along which the light circulates in the form of the whispering gallery modes (WGMs). The WGM has an evanescent field extending into the capillary core and responds to the RI change due to the analyte conducted in the capillary, thus permitting label-free measurement. The resonating nature of the WGM enables repetitive light-analyte interaction, significantly enhancing the LCORR sensitivity. This LCORR architecture achieves dual use of the capillary as a sensor head and a CE fluidic channel, allowing for integrated, multiplexed, and noninvasive on-capillary detection at any location along the capillary. In this work, we used electroosmotic flow and glycerol as a model system to demonstrate the fluid transport capability of the LCORRs. In addition, we performed flow speed measurement on the LCORR to demonstrate its flow analysis capability. Finally, using the LCORR's label-free sensing mechanism, we accurately deduced the analyte concentration in real time at a given point on the capillary. A sensitivity of 20 nm/ RIU (refractive index units) was observed, leading to an RI detection limit of [10.sup.-6] RIU. The LCORR marries photonic technology with microfluidics and enables rapid on-capillary sample analysis and flow profile monitoring. The investigation in this regard will open a door to novel high-throughput CE devices and lab-on-a-chip sensors in the future.

The liquid core optical ring resonator (LCORR) has recently shown promise as a high-sensitivity label-free lab-on-a-chip biological--chemical sensor. We investigate experimentally and theoretically the temperature dependence of the LCORR to establish a noise baseline, which will enable us to implement a temperature stabilization mechanism to reduce the thermally induced noise and to improve the sensor detection limit. Our studies involve analysis of the thermo-optic and thermomechanical effects of fused silica and aluminosilicate glass as they impact LCORR performance. Both thick-walled and thin-walled LCORRs are investigated to elucidate the contribution of water in the core to the thermal response of the LCORRs. Theoretical calculations based on Mie theory are used to verify the experimental observations. OCIS codes: 230.5750, 140.4780, 170.4520, 290.4020.

The decision for psychiatric hospitalization after deliberate self-poisoning (DSP) is not well understood. This study, a longitudinal cohort study of 3,148 consecutive DSP patients found 920 (29.2 %) subjects were referred for psychiatric hospitalization, 576 (18.3%) on involuntary basis. A logistic regression analysis showed increased risk for: age 25 or older, homelessness, unemployment, previous self-harm, psychiatric inpatient treatment within 12 months, earlier psychiatric inpatient treatment, suicidal ideation or plan, mood or psychotic disorders, and lower clinician experience; and lower risk for being married/defacto, and after hours presentation. Recommendation for psychiatric hospitalization was based on complex decision making. These findings have implications for clinical practice guidelines, service costs, and service organization.

Surface-enhanced Raman spectroscopy (SERS) is a widely studied technique capable of adding single-molecule detection capability to the rich information provided by Raman spectroscopy. In this article, we show an additional […]