The Air Force is interested in real-time, wearable, and minimally invasive monitoring of physiological and psychological traits to improve the readiness and performance of the warfighter. Reducing or removing false alarms from such wearables significantly enhance the chance for a successful mission accomplishment. Highly accurate human performance monitoring and health protection requires precise monitoring of chemical and biochemical biomarkers. However, the biomarker detection in physiologically relevant media, such as sweat, saliva, and exhaled breath faces significant challenges ranging from chemical interference to environmental extremity. In this presentation, we address the lessons learned from building minimally invasive sampling technologies that are needed for acquiring data about the concentrations of relevant biomarkers as the physiological and psychological indicators. We discuss the opportunities and limitations in the sampling mechanisms of the biomarkers that can occur in multiple phases, including the gas phase (breath) and/or liquid phase (sweat, blood, ISF). In addition, we provide insight on the limit of current state of the art technologies for deployable real-time biomarker monitoring, including but not limited to the number/property/concentration of the molecular biomarkers and their corresponding sensor selectivity/sensitivity. Finally, we show our ongoing in-house and collaboration research works on integrating these sensors to real-world platforms using unaltered samples to ultimately enable both real-time physiologic monitoring, as well as total exposure health protection.
The main goal of this research was to maintain the bulk charge carrier mobility of graphene, after deposition of the gate dielectric layer used for making transistor devices. The approach was introducing a thin film of deoxyribonucleic acid (DNA) nucleobase purine guanine, deposited by physical vapor deposition (PVD), onto layers of graphene that were transferred onto various flexible substrates. Several test platforms were fabricated with guanine as a standalone gate dielectric, as the control, and guanine as a passivation layer between the graphene and PMMA. It was found that the bulk charge carrier mobility of graphene was best maintained and most stable using guanine as a passivation layer between the graphene and PMMA. Other transport properties, such as charge carrier concentration, conductivity type and electrical resistivity were investigated as well. This is an important first step to realizing high performance graphene-based transistors that have potential use in bio and environmental sensors, computer-processing and electronics.
Due to their excellent electrical, optical, and mechanical properties, nanosized single wall carbon nanotubes (SWNTs)
have attracted significant attention as a transducing element in nano-bio sensor research. Controlled assembly, device
fabrication, and bio-functionalization of the SWNTs are crucial in creating the sensors. In this study, working biosensor
platforms were created using dielectrophoretic assembly of single wall carbon nanotubes (SWNTs) as a bridge between
two gold electrodes. SWNTs in a commercial SDS surfactant solution were dispensed in the gap between the two gold
electrodes, followed by applying an ac voltage across the two electrodes. The dielectrophoresis aligns the CNTs and
forms a bridge between the two electrodes. A copious washing and a subsequent annealing of the devices at 200 ᵒC
remove the surfactants and create an excellent semiconducting (p-type) bridge between the two electrodes. A liquid
gated field effect transistor (LGFET) was built using DI water as the gate dielectric and the SWNT bridge as the channel.
Negative gate voltages of the FET increased the drain current and applying a positive gate voltage of +0.5V depleted the
channel of charges and turned the device off. The biosensor was verified using both the two terminal and three terminal
devices. Genomic salmon DNA dissolved in DI water was applied on the SWNT bridge in both type of devices. In the
two terminal device, the conductance of the bridge dropped by 65x after the binding of the DNA. In the LGFET, the
transconductance of the device decreased 2X after the binding of the DNA. The binding of the DNA also suppressed
hysteresis in the Drain Current vs Gate Voltage characteristics of the LGFET.
In this study, we investigated the effect of substrates on the electrical properties of transferred graphene. A wide range of substrates such as silicon carbide (SiC), glass, kapton, photo-print paper, polydimethylsiloxane (PDMS) and Willow glass were selected based on their surface properties, flexibility and lattice match. Four monolayers of graphene were transferred onto each of these substrates. A comparative study of the electrical characteristics of the transferred graphene film only and graphene/guanine film on the different substrates was undertaken.
This paper is a review of the recent research in bio-based materials for photonics and electronics applications. Materials
that we have been working with include: deoxyribonucleic acid (DNA)-based biopolymers and nucleobases. We will
highlight work on increasing the ionic conductivity of DNA-based membranes, enhancing the direct (DC) current and
photoconductivity of DNA-based biopolymers, crosslinking of DNA-based biopolymers and promising applications for
DNA nucleobases.
Key
In previous research we have demonstrated improvements in device performance with the incorporation of a deoxyribonucleic acid (DNA)-based biopolymer into organic light emitting diodes, organic thin film transistors and other organic photonic and electronic devices. Here, we investigate nucleobases, nitrogen-containing biological compounds found within DNA, ribonucleic acid (RNA), nucleotides and nucleosides, for use in a few of those previously investigated photonic and electronic devices. Used as an electron blocking layer in OLEDs, a gate insulator for grapheme transistors and as a dielectric in organic-based capacitors, we have produced comparable results to those using DNA-based biopolymers.
We report transmission spectroscopy results from the mid- to far-infrared on graphene, grown by chemical vapor
deposition (CVD) on Cu. Similar results have been reported by several groups and their substrates of choice were
thermal Si dioxide, quartz, or SiC, where strong phonon absorption results in transmission blocking bands in midinfrared.
Silicon wafers (thickness ~ 500 μm), on the other hand, have transmission extending out to about 100 cm-1
when the doping level is low. Therefore, we choose to use Si wafers as the carrier substrates for transferred CVD
graphene. The complex refractive index of the Si substrate is measured by infrared spectroscopic ellipsometry. As a
result, continuous spectra (without blocking bands) in the range of 400 to 4000 cm-1 are obtained and they are modeled
by free carrier absorption (the Drude model) and interband transitions (considering the Pauli blocking.) From these, the
carrier density, carrier mobility, sheet resistivity, intraband scattering rate, and graphene layer number can be inferred. In
the far-infrared range, the absorption is dominated by the intraband free carrier absorption and it mainly results from the
interband transition in the mid-infrared range. Having continuous spectra using the Si substrates gives us the advantage
to model the whole spectral region (from far-infrared to mid-infrared) accurately.
This work details a proof of concept study for vapor phase selective sensing using a strategy of biorecognition elements
(BRE) integrated into a zinc oxide field effect transistor (ZnO FET). ZnO FETs are highly sensitive to changes to the
environment with little to no selectivity. Addition of a biorecognition element retains the sensitivity of the device while
adding selectivity. The DNA aptamer designed to bind the small molecule riboflavin was covalently integrated into the
ZnO FET and detects the presence of 116 ppb of riboflavin in a nitrogen atmosphere by a change in current. The
unfunctionalized ZnO FET shows no response to this same concentrations of riboflavin, showing that the aptamerbinding
strategy may be a promising strategy for vapor phase sensing.
Biomaterials such as nucleic acids and proteins can be exploited to create higher order structures. The biomolecular
components such as DNA and peptides have been used to assemble nanoparticles with high fidelity. Here, we use DNA
and peptides, and their preferential interaction with inorganic and carbon nanomaterials to form homogeneous hybrids.
The enhanced binding of Pt ions to both DNA and peptide functionalized nanoparticles mediates the assembly of carbon
nanotubes functionalized with DNA with peptide coated gold nanoparticles.
In this work, we show the use of single stranded DNA aptamers as selective biorecognition elements in a sensor based
on a field effect transistor (FET) platform. Aptamers are chemically attached to the semiconducting material in the FET
through the use of linker molecules and confirmed through atomic force microscopy and positive target detection.
Highly selective sensing of a small molecule, riboflavin is shown down to the nano-molar level in zinc oxide FET and
micro-molar level in a carbon nanotube FET. High selectivity is determined through the use of negative control target
molecules with similar molecular structures as the positive control targets with little to no sensor response. The goal of
this work is to develop a sensor platform where biorecognition elements can be used to functionalize an array of
transistors for simultaneous sensing of multiple targets in biological fluids.
Although a number of hypotheses have been presented to explain the enhanced electromechanical performance observed
in electroactive polymer nanocomposite materials, many of the underlying mechanisms responsible for this behavior
remain unclear. In this report, electric force microscopy (EFM) is used to investigate the near surface morphology of an
electroactive polyimide-based nanocomposite film containing SWNTs in an effort to gain insight into the electrical
interactions occurring at the polymer-electrode interface. As a means of measuring the proximity of SWNTs to this
interface, the depths of SWNTs buried beneath a processing-induced polymer skin layer are determined using EFM
measurements derived from a sample standard. In this way, evaluation of the ability for embedded SWNT structures to
behave as extensions of surface electrodes is possible, a scenario that could potentially reduce the applied field required
to elicit electromechanical actuation.
This paper demonstrates the use of DNA based biopolymers as semiconducting thin films in organic field effect
transistors. The "doping" of the DNA molecules with conductive polymers leads to a significant decrease of the
overall resistivity in the blend with effective free charge carrier mobilities comparable to other conductive polymers
such as Pentacene and P3HT. Baytron P as well as single wall carbon nanotubes (SWCNT) have been explored as "doping" conductive polymers.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.