|NRL / Materials / Chemistry / Code 6170 / Code 6177 / Research Areas||NRL Resources|
Current Areas of Research
Structure of Semiconductor Surfaces and Interfaces
We are studying the atomic-scale structure and chemistry of single crystal silicon, germanium, and III-V compound semiconductor surfaces, interfaces, and devices in UHV using STM and other surface analytical techniques. Because of the rapidly shrinking size of electronic devices, such studies are vital to the development of future Navy electronics.
Code 6177 continues to investigate new materials and phenomena that could have significant technological impact. Two recent systems include graphene/graphene oxide. Graphene, a single atomic sheet of graphite, is known to have superlative electronic and mechanical properties. By oxidizing graphene, we form graphene oxide which is an inexpensive yet highly functional material for chemical and biological sensing and nanoscale resonators. We are also investigating the electrical properties of bacteria active in bacterial batteries.
We are developing a nanomanufacturing platform based on scanning probe microscopy. The goal is to harness the uniquely high gradients in temperature and mechanical force to achieve high resolution, highly ordered nanostructures over wafer scale areas. Our specific approach uses heatable scanning probe tips as nanoscale soldering irons for the deposition of a wide range of materials. This particular technique is called thermal Dip Pen Nanolithography, or tDPN.
Biosensor Science and Technology
Building on our understanding of surface forces gained from fundamental AFM research, we have a broad, vertically integrated research effort on the development of biosensor systems. Our work ranges from the optimization of chemical methods to immobilize biomolecules on surfaces, to the development of biomolecular assays, to microfluidics engineering and sensor system integration. We are currently developing two novel biosensor systems using magnetic microbeads to probe for target biomolecules specifically bound to receptor-patterned surfaces, with an initial focus on detecting biological warfare agents. The microbeads serve both as reporter labels and as force transducers to allow “force discrimination”—a technique we developed that greatly reduces the background signal—enabling the identification of single biomolecular ligand—receptor interactions with high sensitivity and specificity. Assays using magnetic labeling and force discrimination have been developed for a variety of bacteria, viruses, and protein toxins (immunosandwich assays), and for oligonucleotide microarrays (hybridization assays). How the assays are incorporated into a practical sensor system depends on how the specifically bound beads are detected. We are currently perfecting two detection approaches, an optical system that images beads captured on a patterned nanoporous membrane, and a chip-based sensor system that directly detects beads using an array of giant magnetoresistive (GMR) magnetic field microsensors. We are also in the early stages of developing label-free biosensor systems based on bioFET devices (using InAs or carbon nanotubes), and exploring the use of magnetic bacteria as living sensing elements.
Analysis of Biomolecules in Human Matrices
We are developing procedures for the detection of various biomolecules in human matrices, with emphasis on the detection of drugs of abuse in human urine, saliva, sweat, and hair. The mechanisms of binding of drugs to hair and skin and the potential for passive incorporation of drugs to hair and skin and the potential for passive incorporation of drugs of abuse from the external environment are being investigated with emphasis on differences between cultural groups. Furthermore, hair has the potential for providing some drug use history, which will allow a more informed decision on inducting an individual into the service. Likewise, saliva and sweat are being explored as adjuncts to urine testing for drug screening/detection under certain field scenarios.
Wearable sensors and sensors packages are being developed for the continuous, non-invasive, remote monitoring of the drug use status of an individual. Such technology has applications mainly in the criminal justice environment. However, similar technology could be employed for fitness of duty monitoring and stress monitoring of individuals in the field and in combat operations. This technology will provide much more information on the health status of an individual than the current occasional testing. Recently, we have extended the application of our sensors to remote environmental monitoring of aqueous media.