Medical applications hollow fibers

The rationale for the development of such libers is demonstrated by their application in the medical field, notably hernoperfusion. where cartridges loaded with activated charcoal-filled hollow fiber contact blood. Low molecular weight body wastes dilTuse through the liber walls and arc absorbed in the fiber core. In such processes, the blood does not contact the active sorbent directly, but faces the nonloxic. blood compatible membrane. Other uses include waste industrial applications as general as chromates and phosphates and as specific as radioaclive/nudcar materials. 

Hollow membrane fibers are required for many medical application, e.g. for disposable dialysis. Such fibers are made by usmg an appropriate fiber spinning technique with a special inlet in the center of the spinneret through which the fiber core forming medium (liquid or gas) is injected. The membrane material may be made by melt-spinning, chemical activated spinning or phase separation. The thin wall (15-500 xm thickness) acts as a semi-permeable membrane. Commonly, such fibers are made of cellulose-based membrane materials such as cellulose nitrate, or polyacrylonitrile, polymethylmethacrylate, polyamide and polypropylene (van Stone, 1985). 

The overall membrane element shape comes in different types sheet, single tube, hollow fiber, and multi-channel monolith. Photographs of some commercial membrane elements are shown in Figure 5.1. The use of disks (or sheets) has been confined to medical, pharmaceutical and laboratory applications, while tubes and monoliths are employed in larger-scale applications ranging from removal of bacteria from wine and beer fermentation to oil-water separation to waste water ueatmenL... 

An early example of a patent on membrane contactor for gas transfer is in Ref. [12]. Harvesting of oxygen dissolved in water and discharging of CO2 to the water is presented in Ref. [13]. A membrane device to separate gas bubbles from infusion fluids such as human-body fluids is claimed in Ref. [14]. A hollow fiber membrane device for removal of gas bubbles that dissolve gasses from fluids delivered into a patient during medical procedures is disclosed in Ref. [15]. Membrane contactors have also found application in dissolved gas control in bioreactors discussed in Refs. [16-17]. 

Clarification of rough beer, vinegar and pasteurization of clarified beer by cross-flow ultrafiltration are also very common processes utilizing hollow fiber ultrafiltration. As seen in Table 1, an important number of membrane manufacturers specialize in medical and pharmaceutical applications. In pharmaceutical and biotechnology industries, hollow fiber membranes are used for the concentration, separation, and purification of physiological activators such as antibiotics, vaccines, enzymes, proteins and peptides, as well as blood purification (hemofiltration). As a physical barrier for bacteria and viruses, membranes are also a popular option for the production of purified water for hospitals and pharmacies. 

In dialysis, size exclusion is the main separation mechanism, while osmotic pressure and concentration difference drive the transport across two typically aqueous phases. While dialysis is used in some analytical separations, dialysis for the removal of toxins from blood (hemodialysis) is the most prominent application for hollow fiber technology in the biomedical field. The hemodialyzers are used to treat over one million people a year and have become a mass produced, disposable medical commodity. While the first hemodialyzers were developed from cellulosic material (Cuprophane, RC, etc.), synthetic polymers such as polyacrylonitrile, poly(ether) sulfone, and polyvinyl pyrrolidone are increasingly used to improve blood compatibility and flux. Hemodialyzer modules consist of thousands of extremely fine hollow fibers... 

Hollow fibers have been used since the 1960s in many applications such as reverse osmosis, ultrafiltration, membrane gas separation, artificial organs, and other medical purposes. There are several advantages to hollow fibers over the flat sheet membranes the most important is their high surface-to-volume ratio. The use of hollow fibers has become popular in many industrial sectors since Mahon first patented the hollow fiber membranes [56]. The morphology and performance of hollow fibers are complex functions of many parameters involved in their manufacturing. McKelvey summarized the effect of spinning parameters on the macroscopic dimensions of hollow fibers [57]. 

Dialysis Hollow fiber throwaway units for medical application. FOB cost = 100 for a surface area = 1 m. ... 

In terms of membrane area used and dollar value of the membrane produced, artificial kidneys are the single largest application of membranes. Similar hollow-fiber devices are being explored for other medical uses, including an artificial pancreas, in which islets of Langerhans supply insulin to diabetic patients, or an artificial liver, in which adsorbent materials remove bilirubin and other toxins. 

Applications aircraft interiors, automotive fuses, coatings, coil bobbins, dip switches, fiber optics connectors, hollow fiber, integrated circuits sockets, medical applications (due to the resistance to different methods of sterilization), membranes, microwave cookware, multipin connectors, printed circuit boards, transformer wire coatings, sight glasses ... 

Y. Matsuura, T Yamamoto, M Miyagi, Hollow fiber delivery of F2-exdmer laser light , Proc. SPIE Vol. 4253, p. 37-41, Optical Fibers and Sensors for Medical Applications, Israel Gannot Ed., 2001. 

U. Kubo, Y. Hashishin, Flexible Hollow Metal Light Guide For Medical CO2 laser , SPIE 494 Novel Optical Fiber Techniques For Medical Application 1984. 

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