Biomedical Engineering Reference
In-Depth Information
8.1 OVERVIEW
In recent years, improved understanding of structure function relationship in
tissues, tissue organization as well as biomaterial-host tissue interactions have
had a large infl uence on the selection, design and processing of biomaterials. Most
biomaterials need to undergo treatments that can enable them to possess proper-
ties and form/shape that is appropriate for the desired biomedical application.
Therefore, transformation of biomaterials to the fi nal device often requires a
series of processing steps such as purifi cation, fabrication, fi nishing, and steril-
ization. These processing methods normally vary with the type of biomaterial
used. Biomaterials are generally classifi ed into four types—metals, ceramics,
polymers, and composites—with each type being conventionally processed by
discrete methods. However, the choice of a processing technique for a specifi c
biomaterial-based device depends on the physicochemical properties of the mate-
rial as well as on the end application. This chapter provides an introduction to the
section on processing of biomaterials and briefl y discusses the conventional
methods for processing metals, ceramics, polymers and composites. In addition,
the chapter discusses processing/fabrication techniques that are used to manufac-
ture devices at the micro/nanometer scale that are gaining increasing importance
in the biomaterial-based device industry.
8.2 INTRODUCTION
The fi eld of biomaterials has seen three generations of biomaterials ranging from
glass eye and wooden teeth in the nineteenth century to advanced biomaterials
like cell-seeded scaffolds in the twenty-fi rst century [1]. Until the dawn of the
twenty - fi rst century, the materials used as biomaterials were non-viable metals,
ceramics, polymers or their combinations in different physical forms. The
evolution of biomaterials with time has resulted in the development of im-
proved fabrication techniques. Conventional fabrication techniques of common
biomaterials — metal - forging, casting, molding; ceramics - casting [2] ; polymers -
spinning, phase separation and composites-molding—have been modifi ed or
replaced by newer techniques which can process a wide variety of materials and
fabricate biomaterials that are more amicable for biomedical applications—rapid
prototyping, electrophoretic deposition [3] and laser assisted techniques [4]. The
function of biomaterials has also gradually evolved from conventional replace-
ment to more challenging repair and regeneration with the scale of biomaterial
application moving down from whole organ to tissue level. The challenging appli-
cations often demand post-fabrication processing of biomaterials to improve
surface fi nish, inertness, biocompatibility, and strength [5, 6], thereby leading to
the development of surface processing techniques [1].
The cellular scale response that implanted biomaterials receive is mainly
governed by their surface properties (chemistry and physical characteristics)
[7-9]. Improved understanding of the effect of biomaterial surface on cellular fate
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