Pressure Sensitive are nothing new. But they are expensive and can only measure pressure at inconspicuous places.
I want to highlight a few pressure-sensitive materials that we have explored for various engineering applications as alternatives to the traditional pressure transducer:
- Pressure sensitive paint
- pressure sensitive film
- Strain Reactive Polymers
In this article, I will give a brief overview of the three materials. Additional resources on where to purchase these materials and find more information are also in the same section. And as always, never be reluctant to contact Pressure Metrics if you have any questions!
Pressure sensitive paint
Pressure-sensitive paint (PSP) has been around for about 25 years. NASA created Pressure sensitive paint . They recognized the difficulty of measuring drag load on airfoils with traditional pressure sensors and researched alternatives. Now, other aerospace applications concerned with drag testing (such as automotive) use pressure-sensitive paint.
Pressure sensitive paint is based on the sensitivity of certain luminescent molecules to the presence of oxygen. Through a process called oxygen quenching, the fluorescence of molecules changes based on oxygen pressure.
The system consists of an illumination source to excite the molecules, a photodetector, then of course paint.
The advantage and applications
Pressure sensitive painting can save a lot of instrumentation time and money compared to methods using pressure indicating tape arrays. Therefore, wind tunnel testing uses, although the technology (oxygen sensitivity) was first explored for medicine.
There are a few downsides; the paint is quite a temperature sensitive, and the photodetector and light source can be expensive to install initially. NASA is working on a new version to increase its response time and reduce its temperature dependence. It provides an example model at an Air Force test facility with the paint applied.
We are by no means an expert on pressure indicating film, but we find them interesting! See some following resources that provide more information.
- Ohio state
- Innovative Science Solutions [PDF]
Pressure sensitive film
The pressure-sensitive film uses fairly intuitive technology. The film contains a color developing layer and a micro-encapsulated color layer. These microcapsules break and react with the adjacent color-forming layer when a definite pressure is out of the world. The results are monochromatic (one color) but the color shading will indicate the level of pressure.
Advantages of Pressure Sensitive
We have used fujifilm prescale products in the past to diagnose problems with our piezo production line. We manufacture these piezo packs under heavy load; and we do one “book” at a time, so the pressure is not uniform (by design). It is difficult to know exactly the distribution of pressure throughout the book due to the number of layers and the varying (and non-uniform) thickness and stiffness. Not to mention, high temperature – so it’s hard to model!
These films have become very useful in diagnosing problems with our rolling process. They uses in similar applications such as automotive (joint assembly and balancing), LCD display manufacturing, semiconductor lamination, and determining solder compression on printed circuit boards.
Strain Reactive Polymers
The last material on our list is the most obscure and it comes out of Duke University. They developed a polymer that releases a chemical signal (to change color) in response to stress. The most interesting thing about this elastomeric network configuration is that this process is completely reversible with full shape recovery. There isn’t much information on the technology other than this article they published in 2014. We have however been in contact with them, and they are very involving in exploring any business opportunities.
The most remarkable character of this material is its repeatability. The strain induced in the material leads to covalent activation of spirogyra.
One caveat though is how the material is quite temperature dependent. Although some folks here at Pressure Metrics points. How this behavior could be your advantage gives the right application and the right design.
Again, this material seems in its infancy. There isn’t much content and information about it. But the authors have expressed interest in exploring all business opportunities.
Staying in touch
If you want to learn more about the cool technology and materials we come across, subscribe to our engineering blog. We have planned a series of blogs on sharing best practices and additional resources to help other engineers. And if you would like to partner with us for a future development opportunity, do not hesitate to contact us! I hope we can work together on an exciting new technology soon, one with a great commercialization opportunity that we are both excited about!