Printing, three-dimensional

The technology in nonstandard inkjet printers, which can be also used for various methods of drug delivery, has been reviewed (64). 

For a number of years after its initial development, inkjet printing was used to visualize and to print documents from computer output. Only in the late 1990s was it realized that inkjet printers could also be employed for other purposes, so as to create microarrays, to manufacture three-dimensional structures, to print electrical devices, and for usage in drug delivery A critical analysis from the perspective of fluid mechanics of the recent developments in nonstandard printing techniques has been done. 

Three-dimensional printing can be used to create resorbable devices with complex concentration profiles within the device (65). This method belongs to solid freeform fabrication methods. Both macrostructure and microstructure can be controlled. The application of this technology for the fabrication of polymeric drug delivery systems has been elucidated. 

Initially, the drug concentration profile is specified by a computer model, which is then built in the deposition process. Complex drug delivery systems can be created in this way, such as the release of multiple drugs or multiphasic release of a single drug. 

In a study, dyes have been used as model drugs in a matrix of biocompatible polymers. The release rate and the release time of the dyes can be controlled by the position of the dye within the system, or by the local composition and the microstructure that is formed in the course of the printing process (65). 

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This process uses a moving laser beam, directed by a computer, to prepare the model. The model is made up of layers having thicknesses about 0.005-0.020 in. (0.012-0.50 mm) that are polymerized into a solid product. Advanced techniques also provides fast manufacturing of precision molds (152). An example is the MIT three-dimensional printing (3DP) in which a 3-D metal mold (die, etc.) is created layer by layer using powdered metal (300- or 400-series stainless steel, tool steel, bronze, nickel alloys, titanium, etc.). Each layer is inkjet-printed with a plastic binder. The print head generates and deposits micron-sized droplets of a proprietary water-based plastic that binds the powder together. 

A novel method for producing ER formulations is a technology called three-dimensional printing (TheriForm technology) [147], which is similar to the one used in ordinary printers. The ink is here replaced with an active substance and carrier material. The layer-by-layer printing provides controlled placement of the active drug and thus of the release from the device [148],... 

Kastra, W.E. Palazzolo, R.D. Rowe, C.W. Giritliglu, B. Teung, P. Cima, M.J. Oral dosage forms fabricated by three-dimensional printing. J. Controlled Release 2000, 66, 11-17. 

Figure 1 3DP the principles. A schematic illustration of (A) the involvement of the CAD system and the printing process (B) the principle of the 3DP process in which a three-dimensional structure is huilt up from polymer/ceramic materials from a bubble jet nozzle. Abbreviation. 3DP, three-dimensional printing. Source. From Ref. 33. 

Figure 2 (A) Release profiles of levofloxacin from three implants I, n, and HI, with the stmctures shown helow. Implant I prepared by three-dimensional printing gives the profile labeled a, while b represents the behavior of implant I made by a conventional process implant II gives plot c, while implant 111 gives plot d. (B) Experimental (two-dimensional) geometrical stmctures as shown. These allow entrance of solvent from one upper or lower) face and produces the release patterns as shown. Source Part A from Ref. 33, and part B fi-om A.T. Florence (unpublished).

Figure 3 Breakaway tablets prepared by three-dimensional printing technology, showing in upper figure the principle and in the lower actual tablets at an intermediate stage of separation and in finally separated form.

Huang W, Zheng Q, Sun W, et al. Levofloxacin implants with predetermined microstracture fabricated by three dimensional printing. Int J Pharm 2007 339 33-38. 

Embossing is most frequently used as a method of decorating nonslip packaging materials, vinyl wall coverings, furniture laminates, building-panel laminates, textured foil for hot stamping, and other applications where the innate quality of three-dimensional printing is of value. 

Printed foamable composition is transferred from release paper to the object being printed and then heat activated to obtain a decorative, three-dimensional print. 

Three-dimensional printing or additive manufacturing (AM) techniques generally focus on the production of stand-alone, individual objects often for niche markets such as prostheses for medical applications. Recently, Deleersnyder (2013) started to use this technique for textile coating and even the production of accessories for apparel (see Figure 2.1) and other textiles. 

Three-dimensional printing 3D printing or 3DP) is a rapid prototyping (RP) technique that was developed in 1992 at the Massachusetts Institute of Technology (MIT) [109]. In contrast to 3D plotting of hot polymer melts, 3DP uses CAD models that can be obtained with a personal computer [110]. 3DP is a layered fabrication process in which a layer of powder is spread onto the powder bed on which the model will be created. Then a print head ejects... 

A three-dimensional printing process that produces copies of solid or surface models in plastic. This process uses a moving laser beam, directed by computer, to print or draw across sections of the model onto the surface of photo-curable liquid plastic. 

Three-dimensional printing was used for the production of bilayer tablets. Hydroxypropyl methyl cellulose and poly(acrylic add) were used as a hydrophilic matrix for the formation of a sustained release layer. The drug release is comparable with commercial counterparts. 

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