In the rapidily changing and expanding landscape of nano-based applications and products, a nanomaterial must provide immediate tangible benefits to existing and evolving materials and products while also possessing the ability to expand and adapt to new, unseen nanomaterial market opportunities. MemPro’s advanced materials provide a number of benefits to existing and to not yet developed materials and products by providing the ability of ceramic nanofibers to be functionalized to meet specific application requirements, strengthen existing materials, or provide end-use product or material application protection through enhanced physical and chemical properties.
Surface area is a simple calculation: length x diameter x the mathematical constant Pi (π or about 3.14). To illustrate this, we can think of a fiber as a solid cylinder with a measurable length and diameter:
The surface area of this cylinder (ignoring the area of the top and bottom of the cylinder) is calculated by measuring the length (l) and the diameter (d) and then making the following calculation:
l x d x π = surface area
- For example, we can think of a piece of spaghetti as a cylinder, whose length is 10 3/8 (10.375) inches and whose diameter is 1/16 (0.0675) of an inch. Doing the calculation above tells us that the surface area (area of the outside of this piece of spaghetti) is about 2 square inches.
To illustrate the surface area advantage of nanofibers, we will use our spaghetti as an example.
- To create “nano-spaghettis” (each with a diameter of 100 nm), we would need to slice a single spaghetti lengthwise into 252,000,000 nano-spaghettis.
- If we measure length and diameter of a single nano-spaghetti and calculate the surface, we find that each nano-spaghetti has a surface area of 1/7,797 (0.000128) square inch.
- Multiplying this surface area times 252,000,000 nano-spaghettis gives us a total surface area (of all nano-spaghettis added together) of 32,323 square inches (about 225 square feet).
- This is 16,000 times more than the surface area of the single spaghetti that we sliced into nano-spaghettis!
Surface Area Leads to Functionality
By definition, a true nanofiber has a nominal diameter of 100 nanometers. A nanometer is one billionth of a meter or one millionth of a millimeter. The abbreviation for nanometer is “nm.”
More surface area means greater functionality in mechanical, chemical, electrical, catalytic and biomedical applications. Functionality has to do with physical contact, and more surface area creates more contact.
Functionality describes how a material adds a benefit to a product or process. In nanomaterials, functionality is directly related to size. For nanofibers the most convenient measurement of size is surface area.
Research has shown that fibers made by electrospinning have functionality in a wide variety of applications. For example:
- A recent study on dental composites suggests improvement in flexural strength, flexural modulus, and “energy-at-break” with nanofibers produced by electrospinning.
- A study describes electrospun nanofibers for enhancing structural performance of composite materials.
- A study describes the dielectric behavior of epoxy/nanofiber composites using nanostructured ceramic fibers obtained by electrospinning.
- The similarity between fibers made by electrospinning and fibers in the human body allows nanofibers to be considered for use in regenerative medicine and in tissue scaffolding.
Fiber Consistency is Quality
Traditional fiber manufacturing results in a mixture of fiber diameters. Electrospinning keeps diameters consistent. The PreciseFiber process is based on years of refining electrospinning and dealing with millions of production adjustments to make consistent fibers. The PreciseFiber process makes many fibers at a time, and it is scalable for high volume production.
Nanofibers in the diameter range of 80-120 nanometers have more surface area than fibers from traditional fiber-making methods. The following example shows how the PreciseFiber process makes surface area many times over other processes.
- We compare a traditional fiber-making process in which the mean fiber diameter (average of largest diameter and smallest diameter) is 500 nm to the PreciseFiber process with a mean fiber diameter of 100 nm.
- The 500 nm process has smaller and larger diameter fibers, ranging from 100 nm to 1,000 nm.
- The PreciseFiber process has smaller and larger diameter fibers, ranging from 80 nm to 120 nm.
- In both cases, we assume a normal distribution of fiber diameters with 40% at the mean diameter, 20% with diameters halfway between mean and maximum, 20% halfway between mean and minimum, 10% at maximum and 10% at minimum.
- In this example, the PreciseFiber process results in 32 times the surface area of fibers made by the traditional process, based on identical volume of fibers produced.
- Even a “flat” bell curve distribution (20% at each of the five diameters) results in a PreciseFiber advantage of 37 times the surface area of fibers made by the traditional process.
There is a trade-off between consistency of fiber diameter and the volume of fibers produced in a manufacturing run. The PreciseFiber process was developed to optimize output while maintaining fiber consistency and surface area predictability. The result is a higher cost for PreciseFiber-produced nanofibers than for fibers from other fiber-making processes. However, the PreciseFiber process creates more functional nanofibers than other fiber-making processes by controlling consistency of each fiber’s surface area.
MemPro’s nanofibers are often sufficient in small concentrations.
- Concentration is characterized as a “loading factor,” which is the percentage determined by dividing the volume (or mass) of the nanofibers by the volume (or mass) of the material into which the nanofibers are mixed.
Research reports on electrospun nanofibers suggest that low loading factors are sufficient for optimal functionality. The typically low loading factor (generally from less than 1%, up to 5%) keeps the cost of the nanofibers from having a significant effect on the cost of including nanofibers, while the functionality shines through as the benefit of nanofibers.
- For example, in catalytic filters, consisting largely of ceramic microfibers and ceramic nanofibers with catalyst metals embedded in the surface of the nanofibers, only 0.1% of the entire filter mass needs to be ceramic nanofibers for optimal catalytic performance.
With 30-40 times the surface area of fibers produced by other methods, PreciseFiber nanofibers are more functional than fibers produced by other methods.
MemPro works with customers to optimize the functionality of nanofibers and to keep the overall cost in line with customers’ profitability goals.
Over 17,000 research reports have the word “electrospinning” in published results, worldwide. This suggests a continuing interest in high-surface-area, consistent nanofibers made by a well-understood laboratory process—electrospinning.
As potential customers explore uses described in these reports, our customer-focused team and our PreciseFiber process are resources to develop and improve products and processes involving mechanical, chemical, electrical, catalytic and biomedical applications.
Investment in Quality
MemPro developed the PreciseFiber process after validating laboratory methods to make polymeric, ceramic and catalyzed nanofibers with significant financial encouragement from the National Science Foundation. Before the creation of the PreciseFiber process, MemPro was recognized with the 2007 NorTech Innovation Award for “combining polymeric and ceramic production techiques in an effort to dramatically reduce the costs of using catalysts in the production of pharmaceutical & biotech products, fine & bulk chemicals, as well as food & beverages.”
In 2008 and 2009 MemPro explored other fiber-making technologies known to produce high volumes of fibers. However, these other technologies fail to produce consistent, small-diameter fibers of the quality needed for global customers interested in functionality, as described in nanofiber research around the world.
The PreciseFiber process development began in 2010 with the first PreciseFiber system, which was constructed in Albuquerque, New Mexico, by a leading engineering company. We brought this first system to Northeast Ohio—the region known for electrospinning research and development at Case Western Reserve University and the University of Akron—for the initial shakedown and process modification. In 2011 we moved this first system to its current location in Broomfield, Colorado, where a second, higher volume system was under development.
The second PreciseFiber system became our scalable module for dedicated production of polymeric, ceramic and catalyzed nanofibers.
In developing these manufacturing systems, we learned that there are 12 inter-related variables in the PreciseFiber process, including chemistry, machinery and production environment. Changing one of these variables affects the 11 others, so “dialing in” the process involves a huge number of adjustments—470 million potential adjustments—to make consistent, high quality nanofibers.
Through a systematic approach we created manufacturing parameters so that we can now quickly take a new material and produce high quality nanofibers with a minimum number of adjustments.