Carbon Fiber &Extracorporeal Devices

Adithy Kottangal

Carbon Fiber

MEEN 3344Oscar E. Corripio Luna

Carbon Fiber

• Also called graphite fiber.

• It is in the form of several long strands of a material mainly composed by carbon atoms.

• Each strand is 0.005 – 0.010 mm thick in diameter.

• First made by Dr. Roger Bacon.

Carbon Fiber.flv

Carbon Fiber

http://youtu.be/q0mQk1s4tKo

Advantages

• It has the greatest compressive strength of all reinforcing materials.

• High strength to weight ratio.• Low coefficient of thermal expansion.• Its density is much lower than the density of steel.

Applications

• Used to reinforce composite materials

• Used structurally in high-temperature applications.

• As an electrode with • high surface area and • impeccable corrosion • resistance.• Anti-static component.

Creation

• Spinning: A polyacrylonitrile plastic is spun into fibers which are then washed and stretched to the desired diameter.

• Stabilizing: fibers are heated with O2 to make their bonding more thermally stable.

• Carbonizing: fibers then are heated without oxygen, they lose non carbon atoms and bonded carbon crystals are made.

• Treating surface: the surface is slightly oxidized.• Sizing: fibers are coated and wounded into

bobbins.

Carbon Fiber’s Future

• Alternate Energy: wind turbines, compressed natural gas storage and transportation fuel cells.

• Fuel Efficient Automobiles: moving towards large production series cars.

• Construction Infrastructure: light weight pre-cast concrete, earthquake protection.

• Oil Exploration: Deep sea drilling platforms, buoyancy, umbilical, choke, kill lines and drill pipes.

Summary

• Carbon fiber composite manufacturing and application is fairly mature, however lifetime of composite structures is strictly defined to ~ 15 dpa, or a year in a fusion reactor. Tritium retention in CFC’s can be reduced, but never eliminated.

Extracorporeal Devices

Introduction• The applications of textile materials in

extracorporeal devices are receiving constant attention for more innovative developments to provide better care and cure, state S N Chaudhary and S P Borkar, who discuss both traditional and new developments in extracorporeal devices, such as artificial kidney, liver and lung. The textile scenario is rapidly changing from conventional textiles to apparel and household industry to hi-tech areas of industrial and medical applications. This change is due to constant research going on in different countries in the field of medical textiles. It is one of the most dynamically expanding sectors in the technical textile market. Hence with the advent of nonwoven micro-fiber meshes, nano-fibers spun by Electro spinning technique and hi-tech fibers, the applications of medical textiles is becoming an indispensable part in medicine and surgery. Medical textiles are broadly classified as non-implantable, implantable, extracorporeal devices, and healthcare and hygiene products.

What is Extra Corporeal Devices?

• Extracorporeal devices are mechanical organs that are used for blood purification

• include the artificial kidney (dialyser), the artificial liver, and the mechanical lung (blood oxygenator).

• These devices must possess certain requirements, including: » anti-allergic

» anti-carcinogenic properties

» good resistance to micro organisms

» antibacterial

» air permeability

» non-toxic and ability to be sterilized.

• The function and performance of these devices depend on the fibers used.

What is Extra Corporeal Devices?

• These devices lie outside (extra) the body (corporeal) andare usually connected to the patient by an arteriovenous shunt.In some respects they may be thought of as artificial organs.(A shunt is a means of diverting flow, in this case blood, from an arterythrough a device and then back into the body via a vein)

• Their function is based on the use of physical and chemicalprocesses to replace the function of a failed organ or to removean unwanted constituent from the blood. The patient’s bloodbefore entering these devices is infused with heparin to preventclotting.

• A variety of ancillary equipment may also be present tocomplete the system. This may include items such as pumps,flow monitors, bubble and blood detectors, as well as controlsystems for pressure, temperature, and concentration.

• It is important to note that these devices do not generallycontain any living cells. Devices containing living cells arecalled bioartificial organs.

• A variety of extracorporeal devices have been developed.Perhaps the best known are blood oxygenators that are used insuch procedures as open heart surgery and hemodialysis to replace the function of failed kidneys.

Principles of blood purification

1. Principles of blood purification therapies are dialysis, filtration and adsorption.

2. Separation membranes and adsorbents are used in blood purification devices.

3. The membrane separation depends on membrane pore size.

4. Purification methods are hemodialysis (dialysis, membrane pore size 1 - 8 nm), hemofiltration (filtration, membrane pore size 3 - 60 nm), plasma exchange (filtration, porous membrane pore size 0.2 - 0.6 micrometer) and hemoadsorption.

5. Hemodialysis accounts for more than 90% of the blood purification treatment in the world which corresponds to 30 million treatments per year keeping 3,00,000 patients alive.

6. Hemodialysis includes removal of metabolic substances, adjustment of electrolytes and pH, removal of excess water by ultrafiltration and, dialysis which is usually a membrane separation process.

7. During the process, blood contacts with dialysate through a membrane (Figure 1).

8. Ultrafine membrane with blood on one side and dialysis fluid on the other, the urea molecules which are much more smaller than blood plasma get separated from blood by using ultrafiltration.

Textile materials for Extracorporeal devices

• Extracorporeal fibers are those used in mechanical organs such as hemodialyser (artificial kidney), artificial liver and mechanical lung. Textile materials used in extracorporeal devices for blood purification and the function of each device is shown in Table 1.

•  Table 1. Materials used in Extracorporeal Devices

Product application

Function System Fiber Type Key Points for medical use

Artificial Kidney To remove waste products from patient's blood

Hemodialysis (HD)Hemofiltration (HF)Hemodifiltration (HDF)

Hollow viscose,hollow polyster,fibre, cuprophan, Cuprammonium hollow fiber

Moderate mechanical strength and permeability, blood compatibility, suppression of complementary activation

Artificial Liver To separate and dispose of patient's plasma and supply fresh plasma

Plasmapheresis (PP)Hemoperfusion (HP)

Hollow Viscose Blood Compatibility, adsorptive activity

Mechanical Lung To remove carbon dioxide from patient's blood and supply fresh oxygen

Hemoperfusion (HP)

Hollow polypropylene fiber, hollow silicone, hollow silicone membrane

Gas exchange effect blood compatibility, suppression of blood plasma leak

Textile materials for Extracorporeal devices

• Fiber material design by copying fibers within the living body is very important in order to protect human health in an ever ageing society.

• The human body is a larger user of fiber material such as artificial kidney and artificial blood vessels. • Of course, the human body is itself a fiber manufacturer and produces various kinds• Of course, the human body is itself a fiber manufacturer and produces various kinds of fiber to protect our health. • The communication between nanofibers in a cell (DNA) and nanofibers in clothes will be possible by the middle of

the century.• A good example is the artificial kidney used for hemodialysis. • Historically regenerated cellulose fibers in the form of cellophane have been utilized to retain waste products from

blood. • Japan is the world leader in fiber technology to make 'Hollow fiber' for the artificial kidney. • Over the past 20 years, cellulosic membranes have improved considerably due to the ability form: (i) Thinner

membranes. (ii) Controlled pore size (iii) Improvement of surface properties. These are now the basis of the production of a range of artificial kidneys for treatment of chronic renal failure, and for this purpose the membranes are made from cuprammonium solution and saponified cellulose triacetate.

Now-a-days most cellulose membranes are of the hollow-

fibre type, which fall into two categories: • Conventional hollow fibres (AM-SD

Series)• In this latter series, the biocompatibility of

the cellulose membrane is improved by polyethylene glycol grafting technology.

• Specification for AK are as follows: Surface membrane, 0.8 - 2.0 m2; Inner diameter, 180 µm; Membrane thickness membrane, 15 µm. Ordinary hemodialysis membranes are believed to have a mean pore diameter of 2 - 3 nm. Biocompatible membranes have a larger pore size (4-10 nm).

• The sieving coefficient Sc, is defined as the ratio of substrate in the filtrate to that in supplying solution of ß2 microglobulin (molecular weight 11800, molecular size c 4.5 x 2.5 x 2.0 nm3) = 0.6 and Sc of albumin = 0.02.

• Biocompatible artificial kidney (AK) with standard and middle flux range (AD-Bio Series).

• The biomaterials Cuprophan (CU) and acrylonitrile AN 69 membranes are both currently used in bioreactors and hemodialysers.

• appears to be very hydrophilic (due to OH groups in the cellobiose units of the cellulose molecule) as attested by a 22?0 water contact angle.

• Cuprophan, a cellulose membrane, has been the material of choice due to the selective removal of urea and creatinine while retaining nutritive molecules such as vitamin B12 in the bloodstream.

• Other medical applications of modified cellulose include hemodialysis membranes (vitamin E modified cellulose) and cellulose diacetate membranes.

Artificial kidney• The kidneys serve as filtering devices of the blood. • The nephrons, the working units of the kidney, filter waste materials out of the blood and produce

urine to secrete toxins from body. • The kidneys also maintain normal concentrations of body fluids, which play a key role in

homeostasis. • . In the natural kidney, ultrafiltration of the blood occurs through the glomerular capillaries leading

to the removal of waste products and the purification of blood. • In an artificial unit a membrane-dependent-ultrafiltration achieves essentially the same result. • hemodialysis is indispensable for people suffering from kidney disease.

Functions of an Artificial Kidney

• The function of the artificial kidney is achieved by circulating the blood through a membrane, which may be either a flat sheet or a bundle of hollow regenerated cellulose fibres in the form of cellophane that retain the unwanted waste materials.

• Multilayer fibres composed of numerous layers of needle-punched fabrics with varying densities may also be used and are designed to remove the waste materials rapidly and efficiently.

• The synthetic polymer substitute being experimented with is a polyethylene glycol-polyethylene terephthalate block copolymer membrane which can selectively filter.

• The synthetic polymer substitute being experimented with is a polyethylene glycol-polyethylene terephthalate block copolymer membrane which can selectively filter. The material used in dialysis membranes are regenerated cellulose, cellulose triacetate, acrylonitrile copolymer, poly (methyl methacrylate), ethylene-vinyl alcohol copolymer, polusulfone and polyamide which can be grouped as cellulose and synthetic polymer systems.

• The development of artificial kidneys depends on the development of hollow fibre membrane. • The purpose of the development of artificial kidney dialysis membrane is to mimic the ability of kidney to completely remove wastes like

urea and albumin.

Mechanical lung• Mechanical lungs use microporous

membranes that provide high permeability for gases (both O2 and CO2) but low permeability for liquid flow and functions in the same manner as the natural lung allowing oxygen to come into contact with the patient's blood.

• The mechanical lung was first developed as a device to replace lung function during heart surgery, and is now extensively used for this purpose in the USA (about 250,000 per year) and Japan (20,000 per year).

• A newer form of artificial lung can also be used as a supplementary respiratory device over a longer term to assist the breathing of patients suffering from acute lung or heart failure, or older people with weak lung function.

Functions of a Mechanical lung

• During the flow, oxygen, which is maintained at a high partial pressure, displaces carbon dioxide, thus effecting purification.

• In this devices, oxygen flows around hollow fibres at extremely low pressure.

• . Blood flow inside of the fibre.

• The oxygen permeats the micropores of the fibre and comes in contact with the blood.

• The pressure gradient between the blood and oxygen is kept near zero to prevent mixing of oxygen and blood.

• Red blood cells capture oxygen by diffusion process.

Artificial liver

• The liver is a remarkable organ; Like the skin, it can regenerate after severe trauma. In fact, a patient can recover with only 20% of his or her liver still functional, as the liver grows back.

• However, there is a point of 'No return' after which the liver cannot regenerate, and there are underlying disease conditions that, in some cases, make a transplant the only alternative.

• Unlike the heart, lung or kidneys, which have one primary function, the liver has multiple functions essential to maintain life including carbohydrate metabolism, synthesis of proteins, amino acid metabolism, urea synthesis, lipid metabolism, drug biotransformation and waste removal.

• Therefore the preferred artificial liver support system would perform these various liver functions.• The artificial liver utilises the functions of separating, disposing & supply of fresh plasma in hollow viscose fibres or membranes

similar to those used for artificial kidney to perform their function. • In the case of extracorporeal devices, cells are grown to confluence in devices resembling dialysis cartridges, and then inserted

into a 'Circuit' outside the patient's body, where blood from the patient flows through the cartridge, contacting the cells, and then back into the patient.

• Extracorporeal liver assist device (ELAD) or bioartificial liver (BAL). The principal goal of the ELAD is to circulate a patient's plasma extracorporeally through a bioreactor that contains metabolically active hepatocytes.

Functions of an Artificial liver

• The artificial liver utilizes hollow fibers or membranes similar to those used for the artificial kidney to perform their function.

• Organ cells are placed around the fibers and blood flows inside the fiber.

• Blood nutrients pass through the fiber wall to the oxygen cells and enzymes pass from the cells to the blood.

• The metabolism of the liver is very complicated which poses problems for the artificial liver.

• This can be solved by using a double lumen structure with a hollow fiber within a hollow fiber.

• Blood runs outside and in contact with liver cells and blood, and after purification it runs inside the fiber.

Hemodialysis• The basic functional unit of the kidney is the

nephron. Eachkidney contains about 1 million nephrons. Only about one-thirdof these nephrons are needed to maintain normal levels of wasteproducts in the blood.

• An external artificial kidney, a haemodialyser, is used which can perform many of the functions of a kidney.

• It is made up from a bundle of hollow fibres through which the blood circulates.

• The objective is to improve the surface of hollow fibres so that the leucocyte decrease does not occur.

• Hemodialysis includes removal of metabolic substances, adjustment of electrolytes and pH and removal of excess water by ultrafiltration and dialysis, which is usually a membrane separation process. Ultrafine membrane with blood on one side and dialysis fluid on the other, the urea molecules which are much more smaller than blood plasma get separated from blood by using ultrafiltration.

Basic operation of Hemodialysis• Heparinized blood flowsthrough a

device containing a membrane. The dialysate or exchange fluid flows on the membrane side opposite the blood.Solutes are exchanged by diffusion between the blood and thedialysate fluid.

• The membranes are usually made from such materials ascellulose, cellulose acetate, polyacrylonitrile and polycarbonate.The membrane surface area is on the order of 1 m2. Blood flowrates are in the range of several hundred ml/min and thedialysate flow rate is about twice that of the blood.

Basic operation of Hemodialysis

http://youtu.be/IQKQ4eoKfTg

Summary

• Advances in textile technology and advanced composite materials containing combinations of fibres and fabrics have been developed for application where biocompatibility and strength are required and will clearly bring a new and improved group of biomedical devices.

• As it is an interdisciplinary field, collaboration between medical and textile technocrats is the need of hour. Possible developments include pancreas, myocardium, bone and other replacements.

CONCLUSION

• Thus the application of textile in high performance and specialized fields are increasing day by day.

• There will be an increasing role for medical textile in future. Thus the textile will be used in all extra corporal devices, external or implanted materials, healthcare and hygienic products.

• Textile materials continue to serve an important function in the development of a range of medical and surgical products.

• The introduction of new materials, the improvement in production techniques and fiber properties, and the use of more accurate and comprehensive testing have all had significant influence on advancing fibers and fabrics for medical applications.

• As more is understood about medical textiles, there is every reason to believe that a host of valuable and innovative products will emerge.

References

• Edwards Vincent J, Buschle-Diller G & Goheen S C: Modified Fibres with Medical and Speciality Applications, Springer, Netherlands, 2006, pp 6, 35-45.

• Hongu T, Phillips G O & Machiko Takigami: New Millenium Fibres, The Textile Institute, Woodhead Publishing Ltd, Cambridge, England, 2005, pp 52-54,175,179-180, 254.

• Tarafdar N & Bose P: A Review of Application of Hollow Fibres in Extracorporeal Devices in Medical Textiles, Man-made Textiles in India, April 2005, pp 141-144.

• Rajendran S & Anand S C: Developments in Medical Textiles, Textile Progress, 32 (4) (2002), pp 12.

• Wooding C: Regenerated Cellulose Fibres, The Textile Institute, Woodhead Publishing Ltd, Cambridge, England, 2001, pp 147-148.

Questions???

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