Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session T10: Focus Session: Physics of Biochips II |
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Sponsoring Units: DBP Chair: David Nolte, Purdue University Room: A106 |
Wednesday, March 17, 2010 2:30PM - 2:42PM |
T10.00001: Protein Detection on an Optical Balance Diffraction Grating Xuefeng Wang, David Nolte We have developed a sensitive biosensor for protein detection called the diffraction land-contrast BioCD (DLC BioCD) in which a substrate is patterned into a diffraction grating that has vanishing first-order diffraction based on a sensitive balance of surface reflction. The graging is patterned using photolithography, and protein that is immobilized on the grating drives it off balance to generate a considerable diffraction signal. We fabricated a DLC surface based on a thermal oxide silicon wafer. Gratings consisting of grooves 65 nm deep with an 8 $\mu $m periodicity are etched into 200 nm SiO$_{2}$ on a silicon wafer. The first-order diffraction is proportional to $\left| {r_1 -r_2 } \right|^2$ where $r_1 $ and $r_2 $ are the reflection coefficients on 200 nm SiO$_{2}$/Si and 135 nm SiO$_{2}$/Si. $r_1 \approx r_2 $ for 488 nm wavelength light at normal incidence, and the grating generates nearly zero first-order diffraction. After applying a protein layer on the SiO$_{2}$, the complex values of $r_1 $ and $r_2 $ change with different signs on the complex plane. Therefore the change of $\left| {r_1 -r_2 } \right|^2$ caused by protein is maximized while the near-zero background significantly improves the sensitivity for protein detection. Experiments show that the signal-to-noise ratio of the protein signals is improved by a factor of 4 compared to a conventional BioCD, with further improvements possible. [Preview Abstract] |
Wednesday, March 17, 2010 2:42PM - 2:54PM |
T10.00002: Plasmonic nanoantenna arrays for surface enhanced vibrational spectroscopy of proteins Ronen Adato, Ahmet Yanik, Jason Amsden, David Kaplan, Fiorenzo Omenetto, Mi Hong, Shyamsunder Erramilli, Hatice Altug Infrared absorption spectroscopy enables direct access to vibrational fingerprints of molecular bonds in the mid-infrared spectral region (3-20$\mu $m). Although intrinsic absorption cross-sections are nearly 10 orders of magnitude larger than corresponding Raman cross-sections, they are still small in comparison with those of fluorescent labels. Sensitivity improvements are required for the method to be applicable to single molecule / monolayer studies. Here we present work demonstrating the use of lithographically patterned arrays of nanoantennas to enhance the absorption signature of the protein Amide-I and II backbone vibrations. By examining both periodic and disordered antenna arrays, we observe the effect of diffractive coupling on the collective array resonances and the role in absorption enhancement. Specifically, we show that the higher quality factor resonances achievable with periodic arrangements can result in significant enhancements in absorption signals. By tuning array periodicity, we show that signals can be enhanced 10$^{4}$-10$^{5}$ fold, leading to the direct measurement of vibrational spectra of proteins at zepto-mole sensitivity levels. [Preview Abstract] |
Wednesday, March 17, 2010 2:54PM - 3:06PM |
T10.00003: Detection of specific proteins using SnO$_{2}$ nanobelt field-effect transistors Kan-Sheng Chen, Yi Cheng, N. Meyer, J. Yuan, L. Hirst, P.B. Chase, P. Xiong Label-free, electrical detection of proteins, including cardiac troponin I (cTnI) which is a clinically important indicator of myocardial injury, has been demonstrated using SnO$_{2}$ nanobelt field-effect transistors integrated within microfluidic channels. FETs with single biotinylated SnO$_{2}$ nanobelts show pronounced electrical conductance changes in response to streptavidin binding. The pH-dependence of the conductance changes is consistent with the predicted protonation of streptavidin and the specificity of the sensors' electrical responses are further confirmed via subsequent fluorescence imaging from streptavidin-coated quantum dots on the same devices. Finally, devices functionalized with biotinylated anti-cTnI antibodies exhibit high sensitivity to the specific antigen, while showing no measurable responses to control proteins such as BSA and cardiac tropomyosin. This study demonstrates the potential of the nanobelt FETs as portable sensors for rapid, on-site detection of biomedically significant markers. [Preview Abstract] |
Wednesday, March 17, 2010 3:06PM - 3:42PM |
T10.00004: On the Geometry of Diffusion and the Limits of Biosensing Invited Speaker: As the future of Moore's law of transistor scaling appears uncertain, Electronics is trying to reinvent itself by broadening its focus to other areas including macroelectronics (electronics of large, possibly flexible and transparent displays), bioelectronics (e.g. nanobio sensors for geomomics, proteomics), and energy-harvesting (e.g. solar cells). In this talk, I focus on the recent progress in the field of bioelectronics, specifically on nanobiosensors for gene and protein identification. While capabilities of classical techniques based on optical detection of biomolecules is already impressive, the method is too expensive to preclude its routine use in clinical setting for personal medicine. As an cost-effective alternative, (optical) label-free electronic detection of biomolecules has long been a cherished dream for researchers involved in Genomics and Proteomics. Despite significant interest and almost monthly reports of groundbreaking experimental results in leading journals by researchers all over the world, the elements that dictate response of a biosensor has remained -- until recently -- poorly understood. In this talk, we discuss how the elementary use of fractal geometry of diffusion, percolative transport in random networks, electrolyte screening-limited response, etc. are finally allowing us to establish the performance potential of such sensors and how ``form' or geometry is fundamental in defining the sensitivity of biosensors. [Preview Abstract] |
Wednesday, March 17, 2010 3:42PM - 3:54PM |
T10.00005: Organic photodiodes with fast photoresponse integrated on printed circuit boards for biochip applications Sebastian Valouch, Siegfried Kettlitz, Celal \"Og\"un, Wiebke Sittel, Nico Christ, Simon Z\"ufle, Uli Lemmer Photodiodes based on organic semiconductors have the potential to provide cost effective optical detection and easy integration in biosensing applications. Polymer photodiodes with response times on the order of 10 ns have been used for optical interconnects showing the feasibility of high-speed applications for these devices [1]. To avoid the degradation of the devices by humidity and oxygen we have developed an encapsulation technique to integrate high-speed organic photodiodes onto standard printed circuit boards (PCBs). This technique uses stencil printing and capillary underfill, both methods widely used in the industry. As a result the devices are protected from ambient air by a 35 $\mu $m copper layer. Using this method we are able to build stable high-speed organic photodiodes with response times in the 10 ns range. This opens up a way for the integration of fast organic detectors for applications such as particle based lab-on-chip systems, optical flow cytometers and integrated x-ray detectors. [1] M. Punke, S. Valouch et al., IEEE Journal of Lightwave Technology 26, 816 (2008). [Preview Abstract] |
Wednesday, March 17, 2010 3:54PM - 4:06PM |
T10.00006: Diffusion, Surface Kinetics, and Detection in Solid-State Nanopores David Hoogerheide, Slaven Garaj, Jene Golovchenko Solid-state nanopores are promising sensors for single biomolecules. Most sensing applications rely on electronic detection of changes in the ionic transport through or across the nanopore in the 0.1--10 kHz frequency band. Our recent studies of the electronic noise properties of silicon nitride nanopores highlight both the suitability of nanopores for physical measurements and their limits of detection (PRL 102, 256804 (2009)). We explore the dependence of excess white noise, which is dominant at detection frequencies, on electrolyte concentration, temperature, and pH. We detect two distinct processes: number fluctuations and surface charge fluctuations. Number fluctuations arise from carrier diffusion through the nanopore and represent a fundamental limit of voltage-driven detection techniques. This sort of noise is minimized at high electrolyte concentrations in low viscosity solutions. In addition, the interaction of ions in the solution with the surface produces fluctuations in the surface charge, and hence the conductance. This noise varies strongly with pH. Both are masked by 1/f noise at low frequencies. The usefulness of these noise sources for measuring physical constants such as diffusivity and reaction kinetics will be discussed. [Preview Abstract] |
Wednesday, March 17, 2010 4:06PM - 4:18PM |
T10.00007: ABSTRACT WITHDRAWN |
Wednesday, March 17, 2010 4:18PM - 4:54PM |
T10.00008: Molecular diagnostics for low resource settings Invited Speaker: As traditional high quality diagnostic laboratories are not widely available or affordable in developing country health care settings, microfluidics-based point-of-care diagnostics may be able to address the need to perform complex assays in under-resourced areas. Many instrument-based as well as non-instrumented microfluidic prototype diagnostics are currently being developed. In addition to various engineering challenges, the greatest remaining issue is the search for truly low-cost disposable manufacturing methods. Diagnostics for global health, and specifically microfluidics and molecular-based low resource diagnostics, have become a very active research area over the last five years, thanks in part to new funding that became available from the Bill and Melinda Gates Foundation, the National Institutes of Health, and other sources. This has led to a number of interesting prototype devices that are now in advanced development or clinical validation. These devices include disposables and instruments that perform multiplexed PCR-based lab-on-a-chips for enteric, febrile, and vaginal diseases, as well as immunoassays for diseases such as malaria, HIV, and various sexually transmitted diseases. More recently, instrument-free diagnostic disposables based on isothermal nucleic acid amplification have been developed as well. Regardless of platform, however, the search for truly low-cost manufacturing methods that would result in cost of goods per disposable of around US{\$}1/unit at volume remains a big challenge. This talk will give an overview over existing platform development efforts as well as present some original research in this area at PATH. [Preview Abstract] |
Wednesday, March 17, 2010 4:54PM - 5:06PM |
T10.00009: Immunoassay on Free-standing Electrospun Membranes Andrew Steckl, Dapeng Wu, Daewoo Han For the purpose of immunoassay, electrospun membranes can be thought as the thread-like self-assembling of nano/microbeads. Non-woven membranes of electrospun poly(caprolactone) (PCL) fibers display excellent tenacity, flexibility and suitable surface energy. These PCL membranes exhibit easy handling in air, fast spreading and wetting in aqueous solution, and rapid adsorption of protein molecules by hydrophobic interaction. After a \textit{fold-and-press} process, the membrane porosity was reduced from $\sim $ 75{\%} to less than 10{\%}, while the thickness increased from $\sim $5 to 300 $\mu $m. The resulting fluorescence signal from adsorbed protein increased more than 120 times. With anti-HSA and HSA-FITC as an immunoassay model, a linear detection range from 500 ng/mL down to 1 ng/mL is obtained, with a detection of limit (LOD) of $\sim $ 0.08 ng/mL. By comparison, conventional nitrocellulose and thicker PCL fiber electrospun membrane displayed a much higher LOD of $\sim $100 ng/mL. Immunoassay on free-standing electrospun membrane successfully combines the low-cost and simplicity of conventional membrane immunoassay, with the fast reaction speed and high sensitivity characteristic of magnetic nano/microbeads bioassays. [Preview Abstract] |
Wednesday, March 17, 2010 5:06PM - 5:18PM |
T10.00010: Nanodevices based on Membrane-Carbon Nanotube Hybrid Structures Hye Jun Jin, Tae Hyun Kim, Seon Namgung, Seunghun Hong, Sang Hun Lee, Tai Hyun Park Proteins in cell membrane have been drawing attention due to their versatile functionalities such as ion transfer for neuronal activity and selective binding for sensory systems. However, it is still very difficult to manipulate and study those proteins because they easily lose their functionalities without lipid membranes. We developed a method to coat lipid membranes containing various functional membrane proteins on single-walled carbon nanotube (swCNT)-based field effect transistors (FETs). In this hybrid structure, the activity of membrane proteins can be monitored by underlying swCNT-FETs, allowing us to easily study the functionalities of membrane proteins. Furthermore, we built advanced devices based on these hybrid structures. For an example, we coated lipid membrane containing `olfactory receptors' on swCNT-FETs, resulting in `bioelectric nose' systems. The bioelectric nose system had high sensitivity and human nose-like selectivity to odorant molecules. This talk will also discuss about the future prospect of these membrane-CNT hybrid structures. [Preview Abstract] |
Wednesday, March 17, 2010 5:18PM - 5:30PM |
T10.00011: Scaling Behavior of Carbon Nanotube-based Biosensors Integrated on CMOS Signal-processing Circuits Byung Yang Lee, Moon Gyu Sung, Dong Joon Lee, Minbaek Lee, Joohyung Lee, Eunju Cho, Seunghun Hong, Sung Min Seo, Jun-Ho Cheon, Hyunjoong Lee, Suhwan Kim, Young June Park, In-Young Chung We built uniform arrays of carbon nanotube (CNT)-based biosensors via linker-free directed assembly strategy, where surface molecular patterns were utilized to direct the assembly of CNTs onto specific regions of the devices. The sensor arrays were utilized to detect ammonia and Hg$^{+}$ ions with high sensitivity and selectivity, and the scaling behavior of sensor sensitivity was studied by parallel detection of multiple sensors. We found that the scaling behavior of the sensor sensitivity can be explained by the combination of two effects: adsorption of analyte molecules onto CNT surface and the transconductance change of the CNT junctions. Furthermore, 64 CNT-based sensors were integrated with CMOS circuits into a single-die system-on-a-chip for the detection of glutamate, a neurotransmitter, by combining several technological breakthroughs such as efficient signal processing, uniform CNT networks, and biocompatible functionalization of CNT-based sensors. [Preview Abstract] |
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