Applications


A1


Filtration
Filtration is necessary in many engineering fields. It was estimated that future filtration market would be up to US $700b by the year 2020. Fibrous materials used for filter media provide advantages of high filtration efficiency and low air resistance. Filtration efficiency, which is closely associated with the fiber fineness, is one of the most important concerns for the filter performance. In the industry, coalescing filter media are studied to produce clean compressed air. These media are required to capture oil droplets as small as 0.3 micron. It is realized that electrospinning is rising to the challenge of providing solutions for the removal of unfriendly particles in such submicron range. Since the channels and structural elements of a filter must be matched to the scale of the particles or droplets that are to be captured in the filter, one direct way of developing high efficient and effective filter media is by using nanometer sized fibers in the filter structure. In general, due to the very high surface area to volume ratio and resulting high surface cohesion, tiny particles of the order of <0.5 µm can be easily trapped in the electrospun nanofibrous structured filters and hence the filtration efficiency can be improved. There is one major manufacturer of electrospun products in the world, Freudenberg Nonwovens, which has been producing electrospun filter media from a continuous web feed for ultra high efficiency filtration markets for more than 20 years. This is perhaps one of the earliest commercial businesses relevant to electrospinning.



FNM’s nanofiber coated power plant air filter initial efficiency vs. conventional power plant air filter initial efficiency for 0.2 µm particles:

FNM’s nanofiber coated power plant air filter

80%

Benchmark power plant air filter 1

35%

Benchmark power plant air filter 2

25%


FNM’s nanofiber coated power plant air filter initial efficiency vs. conventional power plant air filter initial efficiency for 1 µm particles:

FNM’s nanofiber coated power plant air filter

98%

Benchmark power plant air filter 1

53%

Benchmark power plant air filter 2

55%


FNM’s nanofiber coated power plant air filter initial efficiency vs. conventional power plant air filter initial efficiency for 2 µm particles:

FNM’s nanofiber coated power plant air filter

99%

Benchmark power plant air filter 1

95%

Benchmark power plant air filter 2

95%


FNM’s nanofiber coated vacuum cleaner bags initial efficiency vs. conventional vacuum cleaner bags initial efficiency for 0.3 µm particles:

FNM’s nanofiber coated vacuum cleaner bag

65%

Benchmark vacuum cleaner bag 1

8%

Benchmark vacuum cleaner bag 2

34%

Benchmark vacuum cleaner bag 3

10%

Benchmark vacuum cleaner bag 4

10%

Benchmark vacuum cleaner bag 5

8%

Benchmark vacuum cleaner bag 6

9%

Benchmark vacuum cleaner bag 7

10%


FNM’s nanofiber coated vacuum cleaner bags initial efficiency vs. conventional vacuum cleaner bags initial efficiency for 1 µm particles:

FNM’s nanofiber coated vacuum cleaner bag

97%

Benchmark vacuum cleaner bag 1

70%

Benchmark vacuum cleaner bag 2

61%

Benchmark vacuum cleaner bag 3

69%

Benchmark vacuum cleaner bag 4

61%

Benchmark vacuum cleaner bag 5

68%

Benchmark vacuum cleaner bag 6

64%

Benchmark vacuum cleaner bag 7

74%


FNM’s nanofiber coated vacuum cleaner bags initial efficiency vs. conventional vacuum cleaner bags initial efficiency for 2 µm particles:

FNM’s nanofiber coated vacuum cleaner bag

99%

Benchmark vacuum cleaner bag 1

94%

Benchmark vacuum cleaner bag 2

88%

Benchmark vacuum cleaner bag 3

88%

Benchmark vacuum cleaner bag 4

85%

Benchmark vacuum cleaner bag 5

88%

Benchmark vacuum cleaner bag 6

86%

Benchmark vacuum cleaner bag 7

91%


FNM’s nanofiber coated window screen initial efficiency vs. conventional window screens and other nanofiber coated window screens initial efficiency for 0.4 µm particles:

FNM’s nanofiber coated window screen

27%

Benchmark nanofiber coated window screen

10%

Conventional window screen (non-coated)

1%


FNM’s nanofiber coated window screen initial efficiency vs. conventional window screens and other nanofiber coated window screens initial efficiency for 1 µm particles:

FNM’s nanofiber coated window screen

39%

Benchmark nanofiber coated window screen

10%

Conventional window screen (non-coated)

2%


FNM’s nanofiber coated window screen initial efficiency vs. conventional window screens and other nanofiber coated window screens initial efficiency for 2.5 µm particles:

FNM’s nanofiber coated window screen

68%

Benchmark nanofiber coated window screen

25%

Conventional window screen (non-coated)

3%


FNM’s nanofiber coated cabin air filters initial efficiency vs. conventional cabin air filters initial efficiency for 0.4 µm particles:

FNM’s nanofiber coated cabin air filter

54%

Conventional (non-coated) cabin air filter

18%


FNM’s nanofiber coated cabin air filters initial efficiency vs. conventional cabin air filters initial efficiency for 1 µm particles:

FNM’s nanofiber coated cabin air filter

73%

Conventional (non-coated) cabin air filter

32%


FNM’s nanofiber coated cabin air filters initial efficiency vs. conventional cabin air filters initial efficiency for 2.5 µm particles:

FNM’s nanofiber coated cabin air filter

99%

Conventional (non-coated) cabin air filter

91%


AA1
AA5 AA3
AA4 AA2



Face mask
Air pollution and climate change are two complex environmental problems caused by human activities, both related to large consumption of fossil fuels. One of the major airborne pollutants, particulate matter (PM), has raised serious concerns in recent years. PM is categorized by the particle size as PM2.5 andPM10, referring to PM with particle size below 2.5 and 10 μm, respectively. PM2.5 with small particle sizes can penetrate bronchi and lungs and poses a severe health threat to the public. To filter airborne pollutants, face masks have been widely used as safety equipment. Commercial face masks are usually made of many layers of fibers (μm-size in diameter) and capture PM particles by a combination of physical barriers and adhesion. To achieve a high PM removal efficiency, these face masks need to be thick and hence are often bulky and resistant to air flow (featured by a large pressure drop ΔP across the face mask). Consequently, breathing through these face masks can be uncomfortable or even dangerous for elderly people and people with lung diseases. Nanofibers with large surface area to volume ratio have shown great potential in filtration applications, including air filtration, dust capture as well as absorbing and detoxifying biological and chemical contaminants. We recently demonstrated that polymer nanofibers with polar functional groups such as polyacrylonitrile, polyimide, and nylon-6 have strong affinity to PM pollutants and therefore show high removal efficiency at low pressure drop and high optical transparency. These nanofibers are promising for use in face masks to achieve both high PM capture efficiency and sufficient air permeability.



FNM’s face masks initial efficiency vs. conventional face masks initial efficiency for 0.3 µm particles:

FNM’s nanofiber coated mask

95%

Benchmark mask 1 without nanofiber coating

63%

Benchmark mask 2 without nanofiber coating

35%

Benchmark mask 3 without nanofiber coating

23%


FNM’s face masks initial efficiency vs. conventional face masks initial efficiency for 1 µm particles:

FNM’s nanofiber coated mask

99.9%

Benchmark mask 1 without nanofiber coating

95%

Benchmark mask 2 without nanofiber coating

97%

Benchmark mask 3 without nanofiber coating

97%


FNM’s face masks initial efficiency vs. conventional face masks initial efficiency for 2 µm particles:

FNM’s nanofiber coated mask

100%

Benchmark mask 1 without nanofiber coating

98%

Benchmark mask 2 without nanofiber coating

98%

Benchmark mask 3 without nanofiber coating

98%


AB1 AB2
AB3



Biomedical application
From a biological viewpoint, almost all of the human tissues and organs are deposited in nanofibrous forms or structures. Examples include: bone, dentin, collagen, cartilage, and skin. All of them are characterized by well-organized hierarchical fibrous structures realigning in nanometer scale. As such, current research in electrospun polymer nanofibers has focused one of their major applications on bioengineering. We can easily find their promising potential in various biomedical areas. Some examples are listed later.



A4



Medical prostheses
Polymer nanofibers fabricated via electrospinning have been proposed for a number of soft tissue prostheses applications such as blood vessel, vascular, breast, etc. In addition, electrospun biocompatible polymer nanofibers can also be deposited as a thin porous film onto a hard tissue prosthetic device designed to be implanted into the human body. This coating film with gradient fibrous structure works as an interphase between the prosthetic device and the host tissues, and is expected to efficiently reduce the stiffness mismatch at the tissue/device interphase and hence prevent the device failure after the implantation.



Tissue engineering
For the treatment of tissues or organs in malfunction in a human body, one of the challenges to the field of tissue engineering/biomaterials is the design of ideal scaffolds/synthetic matrices that can mimic the structure and biological functions of the natural extracellular matrix (ECM). Human cells can attach and organize well around fibers with diameters smaller than those of the cells. In this regard, nanoscale fibrous scaffolds can provide an optimal template for cells to seed, migrate, and grow. A successful regeneration of biological tissues and organs calls for the development of fibrous structures with fiber architectures beneficial for cell deposition and cell proliferation. Of particular interest in tissue engineering is the creation of reproducible and biocompatible three-dimensional scaffolds for cell ingrowth resulting in bio-matrix composites for various tissue repair and replacement procedures. Recently, people have started to pay attention to making such scaffolds with synthetic biopolymers and/or biodegradable polymer nanofibers. It is believed that converting biopolymers into fibers and networks that mimic native structures will ultimately enhance the utility of these materials as large diameter fibers do not mimic the morphological characteristics of the native fibrils.



A5



Wound dressing
Polymer nanofibers can also be used for the treatment of wounds or burns of a human skin, as well as designed for hemostatic devices with some unique characteristics. With the aid of electric field, fine fibers of biodegradable polymers can be directly sprayed/spun onto the injured location of skin to form a fibrous mat dressing, which can let wounds heal by encouraging the formation of normal skin growth and eliminate the formation of scar tissue which would occur in a traditional treatment. Non-woven nanofibrous membrane mats for wound dressing usually have pore sizes ranging from 500 nm to 1 µm, small enough to protect the wound from bacterial penetration via aerosol particle capturing mechanisms. High surface area of 5–100 m2/g is extremely efficient for fluid absorption and dermal delivery.



A6



Cosmetics
The current skin care masks applied as topical creams, lotions or ointments may include dusts or liquid sprays which may be more likely than fibrous materials to migrate into sensitive areas of the body such as the nose and eyes where the skin mask is being applied to the face. Electrospun polymer nanofibers have been attempted as a cosmetic skin care mask for the treatment of skin healing, skin cleansing, or other therapeutical or medical properties with or without various additives. This nanofibrous skin mask with very small interstices and high surface area can facilitate far greater utilization and speed up the rate of transfer of the additives to the skin for the fullest potential of the additive. The cosmetic skin mask from the electrospun nanofibers can be applied gently and painlessly as well as directly to the three-dimensional topography of the skin to provide healing or care treatment to the skin.



Drug delivery
Nanofiber systems for the release of drugs (or functional compounds in general) are of great interest for tumor therapy, as well as for inhalation and pain therapy. The nanostructured carriers must fulfill diverse functions. For example, they should protect the drugs from decomposition in the bloodstream, and they should allow the controlled release of the drug over a chosen time period at a release rate that is as constant as possible. They should also be able to permeate certain membranes (for example, the blood–brain barrier), and they should ensure that the drug is only released in the targeted tissue. It may also be necessary for the drug release to be triggered by a stimulus (either external or internal) and to continue only as long as necessary for the treatment. For some time, nanoparticles (of lipids or biodegradable polymers, for example) have been extensively investigated with respect to the transport and release of drugs. A variety of methods have been used for the fabrication of such nanoparticles, including spraying and sonification, as well as self-organization and phase-separation processes. Such nanoparticles are primarily used for systemic treatment. However, experiments are currently being carried on the targeting and enrichment of particular tissues (vector targeting) by giving the nanoparticles specific surface structures (for example, sugar molecules on the surface).



A7