Additive Manufacturing and Surface Modification of Biomaterials using Selfassembled Monolayers - Biointerfaces: Where Material Meets Biology - page 34

superior fit compared to traditional designs, can reduce post-implant com-
plications by preventing implant migration. In addition, by modifying the
surface chemistry of the implant with drug/protein molecules specific to the
target site, biochemical interactions at the implant-host interface can be
optimised and post-implant complications can be reduced. This chapter will
discuss a novel methodology to produce customised and functionalised
biomedical implants by integrating a metal-based additive manufacturing
(AM) process to fabricate customised biomedical implants with surface
functionalisation using self-assembled monolayers.

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2.2 Additive Manufacturing
Additive manufacturing (AM) has developed from the early days of rapid
prototyping to enable the production of end-use parts. According to the
American Society for Testing and Materials (ASTM), AM is defined as 30 :
'The process of joining materials to make objects from 3D model data,
usually layer upon layer, as opposed to subtractive manufacturing
technologies'.
Although there are many terms used to describe AM, the most commonly
used terms are free-form manufacturing, rapid manufacturing, additive
fabrication, additive layered manufacturing and 3D printing.
AM was first developed for polymeric materials and now all types of ma-
terials including metals, ceramics and composites can be processed using
these techniques to varying levels of success. 31 Currently there are many
different AM processes available, most working on a layer-by-layer basis.
However, they differ through the form of the starting material and the
mechanism used to consolidate it. Some of the consolidation methods used
include the use of a laser or electron beam to selectively fuse polymer or
metal powdered material; curing of liquid resin with ultraviolet (UV) light;
extrusion of molten polymers from traversing nozzles; jetting of droplets
from an array of nozzles, similar to inkjet printing; and consolidation of
sheets of materials using ultrasonic vibrations. Table 2.1 lists and defines
the categories of AM processes in accordance with the ASTM International
Committee F42 on Additive Manufacturing Technologies published in
2010. 30
AM has gained considerable interest in recent years due to its ability to
build parts of complex geometries from three-dimensional (3D) model
data. 32 AM is capable of building parts of almost any geometry in a single
step regardless of the complexity of the part whereas conventional methods
often need further steps and time or it is impossible to do so. 33 Furthermore,
the use of AM speeds up the whole development process since there is no
need for dies/moulds and toolings. Hence, the use of AM to fabricate cus-
tomised one-off parts is faster and cheaper than traditional methods.
Some of the active industries for AM include aerospace, automotive, med-
ical, architectural, games, military, art, sport, construction and education;

.