Chemical and biological sensing technologies are critical in the current International Space Station (ISS) environment and for future manned planetary missions. However, the efficiency, reliability and overall utility of the sensing technologies have not been well established in the literature, nor in commercial platforms. Despite the transformative potential of nanomaterials, the performance of many of these nanosensors must be substantially improved and stabilized. The objective of the sensing thrust is:
- To fill the significant gap between fundamental studies of nanoscale functional materials and device engineering, and
- To significantly improve the reproducibility and performance of discrete biosensors, and create the next generation of nanosensing systems and devices.
To these ends, our team will use a unique combination of methods, including high-resolution techniques to characterize interfacial molecular recognition at the single molecule/structure level, synthesis of nanoparticles and assembly of higher-order structures with unprecedented precision, complexity and functional tunability, as well as the integration of nanomaterial-based devices and new sensing strategies.
1. Precision assembly of nanoparticles for bio-sensing
While precise higher-order-nanoparticle (NP) assemblies have a significant advantage over the traditional random NP aggregates that enhance signal-to-noise, the current ability to organize NPs into functional structures is underdeveloped, as neither lithography nor bottom-up self-assembly techniques have the requisite spatial resolution and precision.
In this project, we will employ a recently developed method that enables us to fold much longer single-stranded DNA directly on a surface, allowing us to form novel two-dimensional patterns of NPs. This method is versatile, which will let us utilize NPs of varying compositions and morphologies, establishing a platform that will be applicable in a wide range of situations.
2. Single molecular characterization
In this project, we will correlate knowledge gained from ultra-high-resolution microscopy techniques with the performance of biosensors. The recognition of biomarkers by biochemical ligands immobilized on surfaces is at the heart of biosensors and microarrays. While the ability to recognize biomarkers is intimately linked to the spatial arrangement and conformations of these probe molecules, we know very little about these molecular details. Having that knowledge is critical to improving the reliability and sensitivity of the devices.
3. Integrated sensing platforms
Development and implementation of automated and responsive "smart" sensors is an integral part of long-term missions. We will use directed assembly of NPs in soft matrices, such as liquid crystals and polymers, to form multifunctional sensors of high sensitivity coupled with remote and automatic operation.
Raman spectroscopy has the advantage of molecular specificity. The development of surface enhanced Raman scattering (SERS) has provided a solution to the sensitivity problem. A compact fiber optic platform for SERS-based systems that integrate NPs and NP assemblies will be developed for remote sensing, portable sensing and further sensitivity enhancement. We will:
- Fabricate the NPs and NP assemblies on the tip of multimode fibers for significantly higher sensitivity;
- Evaluate the planned SERS probe for the quantitative detection of various samples of current interest to ISS activities; and
- Integrate the SERS probe into a portable and alignment-free sensor prototype for use by non-spectroscopists.
A human-scale challenge of long-term missions to remote areas, either on Earth or off, is the need to carry out sophisticated medical diagnostics to monitor health. In medical emergencies, such diagnostics could be critical in deciding and recommending appropriate interventions. The lack of timely access to a sophisticated clinical laboratory should never be the limiting factor.
The goal of this project is to develop new modalities for performing quantitative and sensitive diagnostics in a manner that does not depend on power or specialized electronics, obviating the need for lab-based setups.