That’s the direction we’re trying to head in. What we'd like to do overall with a vehicle system, or whatever it is we're dealing with, is make it smart, and drive that intelligence from the lower component level, from individual smart systems, leading up to a smart vehicle overall.
NTB: What are microfabricated sensors and, their size notwithstanding, what advantages do they have over conventional sensors?
Dr. Hunter: Microfabrication, as we use the term, is associated with the idea of using the silicon processing techniques used in the electronics industry and applying those to sensor technology. The idea behind a microfabricated sensor system, then, is to apply the silicon processing technology where one can batch fabricate things, that is, make many of the same thing at the same time, make them repeatable again and again, and be able to put multiple components into a very small space. This type of work was pioneered by one of our collaborators, C. C. Liu, at Case Western Reserve University. So, for example, say for our hydrogen sensor, one may have two sensors on that unit – one for low concentrations and one for higher concentrations – and a temperature detector and a heater. All of that is microfabricated, that is, using silicon processing techniques put onto a very small surface.
The advantages, then, are that first, they're smaller. They may be able to have more features associated with them. In silicon processing, you would hope for reproducibility each time. And issues such as power and weight are minimized because, for example, if you’re heating a microsensor, heating something small takes less power than a comparable element that’s larger.
In summary then, silicon processing applied to miniaturized sensor technology, which we refer to as microfabricated sensors, have advantages related to the capabilities you can build into the sensor structure, as well as the minimal impact that it has — at least as an ideal — associated with the application that you’re trying to meet. If you are going to start putting more sensors into a vehicle, they are going to have be small with minimal impact to the system.
NTB: Do sensors used in space have to be radiation hardened like semiconductors?
Dr. Hunter: This question I'm going to partly punt on. I am not the best person to talk about that, but I will give you an answer that is not quite the question you asked about, and do with it as you wish.
Typically with sensors in space, there are many parameters that might be measured and there may be a number of different types of sensors. There are sensors, for example, that measure temperature, strain, and the like. In some cases, and this is a little bit beyond my scope, in terms of radiation hardening, some materials are not necessarily easily damaged by radiation. Something like a platinum resistor that is used as a temperature detector is not something one usually worries about in terms of radiation hardening and radiation damage. However, a more complicated system with electronics can be affected because there are materials, for example, the silicon electronics, which can be affected by the radiation.
One thing that we've been working on is that we want sensors that are smart. We want, for example, the Lick and Stick approach with a microprocessor associated with it. And so as we have done our work towards making smart sensor systems ready for space, what we have encountered is that we have to take into account the fact that we have silicon electronics associated with our work. We then have to make sure that our smart sensor systems – if we want to try to move towards space implementation – are radiation hardened and able to handle a radiation environment. So, some of the work has involved radiation testing to make sure this basic Lick and Stick platform doesn't have anything that would be necessarily problematic associated with radiation. Now, the radiation environments vary and over time one will have to qualify each individual system.
NTB: Make it mission specific, I would imagine?
Dr. Hunter: Yes. Match it to the specific radiation environment.
NTB: In 1995 you were the co-recipient of an R&D 100 award for developing an automated hydrogen leak detection system that Ford installed on its automotive assembly lines, so you know some of the stuff you’re working on has potential commercial applications. What other types of sensor systems being developed by NASA do you envision finding their way into commercial applications?
Dr. Hunter: I'll note , for example, that we're working on the fire detection systems for which we received a 2005 R&D 100 award. It was meant to have applications associated with commercial aircraft cargo bay fire detection.
The high-temperature emissions work– we're working with the Navy to make what we call a high-temperature electronic nose to measure emissions coming from the back-end of a jet engine, and we’re interacting with, on that project, the Propulsion Instrumentation Working Group, which is a consortium of engine companies. So one would hope for a commercial product you might be able to use on jet engine test stands.
The work that we're doing in human health breath monitoring is part of a State of Ohio project that is meant to have a home monitoring system for asthma. We will move toward commercialization during the time of that project.