Search NASA⌕ Search

Engineering topics

Weiss, Sharon M.

Publications and source records attributed to Weiss, Sharon M..

17 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Comparison of Single-Event Transients in an Epitaxial Silicon Diode Resulting from Heavy Ion-, Focused X-Ray-, and Pulsed Laser-Induced Charge Generation

Heavy ion, focused x-ray, and pulsed laser single event transient experiments are performed on a silicon epitaxial diode. Collected charge, transient rise times, and transient fall times are calculated and compared between the different sources. It is observed that these transient shape characteristics depend on the source (ion, x-ray, or laser), even when similar amounts of charge are generated. Finally, the observed differences are examined and explained in terms of basic charge collection mechanisms.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Single Event Transient Response of Vertical and Lateral Waveguide-Integrated Germanium Photodiodes

Pulsed-laser induced single event current measurements on two geometries of waveguide-integrated germanium photodiodes were conducted over a range of operating voltages to examine the impact of photodiode geometry on the transient response. Vertical PIN photodiodes exhibit transients with a duration that is relatively independent of the operating voltage while the transient duration in lateral PIN photodiodes depends on operating voltage. Furthermore, the experimental measurements facilitate identification of device dimensions that impact the transient response. In this work, these results can be used to identify potential radiation mitigation strategies for photodiodes operating in a radiation environment. Understanding the implications of design choices is critical for designing integrated photonic systems that balance system performance with tolerance for radiation degradation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Comparison of Sensitive Volumes Associated with Ion-and Laser-Induced Charge Collection in an Epitaxial Silicon Diode

A sensitive volume is developed using pulsed laser-induced collected charge for two bias conditions in an epitaxial silicon diode. These sensitive volumes show good agreement with experimental two photon absorption laser-induced collected charge at a variety of focal positions and pulse energies. When compared to ion-induced collected charge, the laser-based sensitive volume over predicts the experimental collected charge at low bias and agrees at high bias. Here, a sensitive volume based on ion-induced collected charge adequately describes the ion experimental results at both biases. Differences in the amount of potential modulation explain the differences between the ion-and laser-based sensitive volumes at the lower bias. Truncation of potential modulation by the highly doped substrate at the higher bias results in similar sensitive volumes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Photonic crystal nanobeam biosensors based on porous silicon

Photonic crystal (PhC) nanobeams (NB) patterned on porous silicon (PSi) waveguide substrates are demonstrated for the specific, label-free detection of oligonucleotides. These photonic structures combine the large active sensing area intrinsic to PSi sensors with the high-quality (Q) factor and low-mode volume characteristic of compact resonant silicon-on-insulator (SOI) PhC NB devices. The PSi PhC NB can achieve a Q-factor near 9,000 and has an approximately 40-fold increased active sensing area for molecular attachment, compared to traditional SOI PhC NB sensors. The PSi PhC NB exhibits a resonance shift that is more than one order of magnitude larger than that of a similarly designed SOI PhC NB for the detection of small chemical molecules and 16-base peptide nucleic acids. Furthermore the design and fabrication of PSi PhC NB sensors are compatible with CMOS processing, sensor arrays, and integration with lab-on-chip systems.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Label-free detection of Herceptin ® using suspended silicon microring resonators

In this paper, highly sensitive detection of heat denatured Herceptin ® (trastuzumab), an important monoclonal antibody used in breast cancer therapeutics, is demonstrated using transverse magnetic (TM) mode suspended microring resonators (MRRs). The suspended MRRs are surface functionalized with a single chain fragment variable (scFv) recombinant antibody molecule (designated 2B4) that enables selective capture of denatured Herceptin molecules. Interaction between guided modes in suspended MRRs and Herceptin molecules captured on the surfaces of the suspended MRRs enable straightforward optical detection and quantification of the bound Herceptin molecules. Clinically relevant Herceptin detection at a concentration of 100 nM is demonstrated and negligible signal was obtained from the sensor when exposed to Avastin ® (bevacizumab), a negative control human therapeutic monoclonal antibody. Importantly, at least a 2-fold enhanced detection sensitivity is obtained by suspending the microring (MRR) over the underlying substrate, effectively increasing the sensing surface area. Experimental results are supported by three-dimensional finite-difference time-domain simulations and optical mode analysis. Finally, the use of a label-free silicon photonic platform for high sensitivity molecular detection is compatible with high-throughput, low-cost diagnostics employing on-chip sensor arrays.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Porous nanomaterials having three-dimensional patterning

Provided are methods for imprinting a porous material, the methods including applying a first stamp to a porous material having an average pore size of less than about 100 μm, the first stamp having at least a first portion having a first height, a second portion having a second height and a third portion having a third height, wherein the first height, second height and third height are different.

Weiss, Sharon M.↗
DOE OSTI2016

Flow-Through Porous Silicon Membranes for Real-Time Label-Free Biosensing

A flow-through sensing platform based on open-ended porous silicon (PSi) microcavity membranes that are compatible with integration in on-chip sensor arrays is demonstrated. Because of the high aspect ratio of PSi nanopores, the performance of closed-ended PSi sensors is limited by infiltration challenges and slow sensor responses when detecting large molecules such as proteins and nucleic acids. In order to improve molecule transport efficiency and reduce sensor response time, open-ended PSi nanopore membranes were used in a flow-through sensing scheme, allowing analyte solutions to pass through the nanopores. The molecular binding kinetics in these PSi membranes were compared through experiments and simulation with those from closed-ended PSi films of comparable thickness in a conventional flow-over sensing scheme. The flow-through PSi membrane resulted in a 6-fold improvement in sensor response time when detecting a high molecular weight analyte (streptavidin) versus in the flow-over PSi approach. As a result, this work demonstrates the possibility of integrating multiple flow-through PSi sensor membranes within parallel microarrays for rapid and multiplexed label-free biosensing.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Comparative Kinetic Analysis of Closed-Ended and Open-Ended Porous Sensors

Efficient mass transport through porous networks is essential for achieving rapid response times in sensing applications utilizing porous materials. In this work, we show that open-ended porous membranes can overcome diffusion challenges experienced by closed-ended porous materials in a microfluidic environment. A theoretical model including both transport and reaction kinetics is employed to study the influence of flow velocity, bulk analyte concentration, analyte diffusivity, and adsorption rate on the performance of open-ended and closed-ended porous sensors integrated with flow cells. The analysis shows that open-ended pores enable analyte flow through the pores and greatly reduce the response time and analyte consumption for detecting large molecules with slow diffusivities compared with closed-ended pores for which analytes largely flow over the pores. Experimental confirmation of the results was carried out with open- and closed-ended porous silicon (PSi) microcavities fabricated in flow-through and flow-over sensor configurations, respectively. The adsorption behavior of small analytes onto the inner surfaces of closed-ended and open-ended PSi membrane microcavities was similar. However, for large analytes, PSi membranes in a flow-through scheme showed significant improvement in response times due to more efficient convective transport of analytes. The experimental results and theoretical analysis provide quantitative estimates of the benefits offered by open-ended porous membranes for different analyte systems.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Direct imprinting of porous substrates

Provided are methods of patterning porous materials on the micro- and nanometer scale using a direct imprinting technique. The present methods of direct imprinting of porous substrates (“DIPS”), can utilize reusable stamps that may be directly applied to an underlying porous material to selectively, mechanically deform and/or crush particular regions of the porous material, creating a desired structure. The process can be performed in a matter of seconds, at room temperature or higher temperatures, and eliminates the requirement for intermediate masking materials and etching chemistries.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Slow light Mach-Zehnder interferometer as label-free biosensor with scalable sensitivity

Our design, fabrication, and characterization of a label-free Mach–Zehnder interferometer (MZI) optical biosensor that incorporates a highly dispersive one-dimensional (1D) photonic crystal in one arm are presented. The sensitivity of this slow light MZI-based sensor scales with the length of the slow light photonic crystal region. The numerically simulated sensitivity of a MZI sensor with a 16 μm long slow light region is 115,000 rad/RIU-cm, which is sevenfold higher than traditional MZI biosensors with millimeter-length sensing regions. Moreover, the experimental bulk refractive index detection sensitivity of 84,000 rad/RIU-cm is realized and nucleic acid detection is also demonstrated.

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

Porous silicon ring resonator for compact, high sensitivity biosensing applications

A ring resonator is patterned on a porous silicon slab waveguide to produce a compact, high quality factor biosensor with a large internal surface area available for enhanced recognition of biological and chemical molecules. The porous nature of the ring resonator allows molecules to directly interact with the guided mode. Quality factors near 10,000 were measured for porous silicon ring resonators with a radius of 25 μm. A bulk detection sensitivity of 380 nm/RIU was measured upon exposure to salt water solutions. Specific detection of nucleic acid molecules was demonstrated with a surface detection sensitivity of 4 pm/nM.

47 OTHER INSTRUMENTATION↗
DOE OSTI2013

Surface engineered porous silicon for stable, high performance electrochemical supercapacitors

Silicon materials remain unused for supercapacitors due to extreme reactivity of silicon with electrolytes. However, doped silicon materials boast a low mass density, excellent conductivity, a controllably etched nanoporous structure, and combined earth abundance and technological presence appealing to diverse energy storage frameworks. Here, we demonstrate a universal route to transform porous silicon (P-Si) into stable electrodes for electrochemical devices through growth of an ultra-thin, conformal graphene coating on the P-Si surface. This graphene coating simultaneously passivates surface charge traps and provides an ideal electrode-electrolyte electrochemical interface. This leads to 10–40X improvement in energy density, and a 2X wider electrochemical window compared to identically-structured unpassivated P-Si. This work demonstrates a technique generalizable to mesoporous and nanoporous materials that decouples the engineering of electrode structure and electrochemical surface stability to engineer performance in electrochemical environments. Specifically, we demonstrate P-Si as a promising new platform for grid-scale and integrated electrochemical energy storage.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Three-dimensional patterning and morphological control of porous nanomaterials by gray-scale direct imprinting

We present a method for direct three-dimensional (3D) patterning of porous nanomaterials through the application of a premastered and reusable gray-scale stamp. Four classes of 3D nanostructures are demonstrated for the first time in porous media: gradient profiles, digital patterns, curves and lens shapes and sharp features including v-grooves, nano-pits and ‘cookie-cutter’ particles. Further, we demonstrate this technique enables morphological tuning and direct tailoring of nanomaterial properties, including porosity, average pore size, dielectric constant and plasmonic response. This work opens a rapid and low-cost route for fabricating novel nanostructures and devices utilizing porous nanomaterials, with promising applications spanning diffractive and plasmonic sensing, holography, micro- and transformation optics and drug delivery and imaging.

36 MATERIALS SCIENCE↗