Biomaterials for MEMS

226 H. Zeng

propagation. 3D (volume) information on the sample structure can be obtained by

using computer reconstruction algorithms. 3D renderings of obtained data after

reconstruction are then made by electronically stacking up the slices. Quantitative

architectural parameters from the tomographic images can then be extracted.

MicroCT has become a powerful tool for biomaterials research. It is a non-

destructive and noninvasive procedure and suitable for in vivo applications. For

example, a few recent studies have looked into the imaging and quantification of

scaffold-bone interactions in vivo.

5,8,9

Direct μCT-based image analysis allows to

accurately quantify scaffold porosity, surface area, and 3D measures such as pore

size, pore distribution, and strut thickness.

10

Furthermore, it allows for a precise

measurement of bone growth into the scaffold and onto its surface (Fig. 10.1).

4

This methodology is useful for quality control of scaffold fabrication processes, to

assess scaffold degradation kinetics, and to assess bone tissue response.

10.2.2 X-ray Microdiffraction Technique

X-ray diffraction is the most commonly used technique for studying the 3-D

structures of solid materials. Its spatial resolution is limited by the X-ray beam

cross-section. In X-ray microdiffraction technique, x-rays are focused to a spot

size of one micron or less to perform x-ray diffraction experiments with very

high spatial resolution. X-ray microdiffraction is providing new insights in the

fields of materials science.

4

Materials properties such as strength and fatigue

resistance are highly dependent on microstructure. X-ray microdiffraction can

measure local variations in stress, orientation, and plastic deformation between

grains and within individual grains, helping us understand mechanical properties

Figure 10.1. 3D microCT image of hydroxyapatite scaffold (Engipore) loaded with sheep

BMSC and implanted in an immunodeficient mouse, showing newly formed bone (green)

onto the inner surface of the scaffold (yellow and red); the organic phase is blue. With

permission from.

4

For color reference, see page 275.

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