21UPHE01 Materials Science

UNIT-IV: BIOMATERIALS
Biomaterials-Definition- the need for biomaterials- general properties- biocompatibility- biomaterial sources- advantages and
disadvantages- Metallic biomaterials-ceramic and glass biomaterials-polymeric biomaterials – examples - applications.
ONE MARK
1. In second harmonic generation, the frequency is ____________.
(a) Constant (b) Doubled
(c) Negative (d) All o f the above

2. In optical mixing, the sources of ___________ frequencies are mixed together

(a) Same (b) Different
(c) high (d) Low

3. Which of the following is not related to Kerr effects?

(a) Self-phase modulation (b) Cross-phase modulation
(c) Four-wave mixing (d) Stimulated Raman Scattering

4. The value of one nanometre is equal to______.

(a) 10-6m (b) 10-9m (c) 10-12m (d) 10-15m

5. ______ process is used to assemble atoms or molecules to form nanomaterials.

(a) Top down (b) Bottom up
(c) Ball mill (d) Condensation

6. Nanoparticles are obtained by breaking the bulk solids employing _______ method
(a) Top down (b) Bottom up
(c) Ball mill (d) Condensation

7. In mechanical grinding, hard materials are used to synthesis _______ materials

(a) Softer (b) harder
(c) magnetic (d) Glass

8. In which of the following atoms do not move from eachother?

(a) Sahpe memory alloys (b) Nano materials
(c) Dielectrics (d) Static materials

9. Which of the following is used to make both nano-particles and nano-powders?

(a) Chemical vapour deposition (b) Sol-gel technique
(c) Plasma arching (d) Electro deposition

10. Which method can be used to prepare iron nitriles nano-crystals using ammonia gas?
(a) Pulsed laser deposition (b) Sol-gel technique
(c) Electro deposition (d) Mechanical crushing

11. Which property of nanoparticles provides a driving force for diffusion?

(a) Optical Properties (b) High surface area to volume ratio
(c) Sintering (d) There is no such property

12. Nano crystalline materials synthesised by sol-gel technique results in a foam like structures
called ___________
(a) Gel (b) Aerosol (c) Foam (d) Aerogel
13. Which nanomaterial is used for cutting tools?
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(a) Fullerene (b) Aerogel
(c) Tungsten Carbide (d) Gold

14. What is the average particle size of ultra-fine grinders?

(a) 1 to 20 µm (b) 4 to 10 µm
(c) 5 to 200 µm (d) 50 to 100 µm

15. What does colloid mill produces?

(a) Wet and dry products (b) Emulsions and Solid dispersions
(c) Coarse and fine particles (d) Broad particles.

16. ____ is an open container usually cylindrical with uniform openings.

(a) Bowel (b) Screen
(c) Magnifier (d) Shredder

17. Ball mill is used for

(a) Crushing (b) Coarse grinding
(c) Fine grinding (d) Attrition

18. The Balls for ball mills are never made of

(a) Forged/cast steel (b) Lead
(c) Cast iron (d) Alloy steel

19. Carbon black is pulverised in a

(a) Hammer crusher (b) Ball mill
(c) Roll crusher (d) Gyratory crusher

20. Sol-gel method is ________ approach.

(a) Bottom up (b) Up bottom
(c) Top down (d) Down top

21. The sol-gel is a __________ of solid particle.

(a) Sublimation (b) Melting
(c) Colloidal suspension (d) Cool down

22. Sol-gel method is ________ chemical process.

(a) Dry (b) Wet
(c) Semi liquid (d) Semi solid

23. One of the advantages of sol-gel method is able to get uniform and _________ powder.
(a) Micro size (b) Large size
(c) Nano size (d) Small size

24. Sol-gel method can produce __________ systems.

(a) Uniform multi component (b) Non uniform multi component
(c) Multi component
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Biomaterials:
Definition:

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Biomaterials are special materials which provide an intimate contact with living tissues when
they are implanted into the body tissues or parts. Biomaterials are used for different biomedical
applications in the field of medicine. They are used to repair or replace damaged or diseased body
parts in the human or animal body. The different biomedical applications are surgical sutures and
needles, catheters, orthopaedic hip replacements, vascular grafts, implantable pumps, cardiac
pacemakers, etc. Even though newer materials like nuclear, magnetic, shape memory alloys,
composites, etc., are being developed for advanced applications, biomaterials require important
physicochemical properties to be used for implant applications.
In recent years, some of the newer biomaterials have come up due to requirements in the
medical field for different applications.
One of the earliest formal definitions of the word biomaterials was “a systemically and
pharmacologically inert substance designed for implantation within or incorporation with
living systems” and was coined by the Clemson University Advisory Board for Biomaterials in
1976. This definition, however, did not take into account the more recent bioactive agents or
biological entities (cells, cell fragments, proteins, nucleic acids, hormones, growth factors, or
drugs) carried by biomaterials or biodegradable systems. In time, several other definitions were
proposed.The European Society for Biomaterials (ESB) had two consensus conferences; in the ESB
Consensus Conference I (1999), biomaterial was defined as a “non-viable material used in a
medical device, intended to interact with biological systems.” It was later refined in 2005 at the
Consensus Conference II as “material intended to interface with biological systems to evaluate,
treat, augment or replace any tissue, organ or function of the body.”
“Biomaterials are substances implanted within or used in conjunction with the body,
designed to have properties closely matching that of the biological system, be stable enough for
the aimed use, have appropriate levels of bioactivity and are designed to partially or completely
fulfill the functions of the diseased, damaged or malfunctioning tissues and organs.”
THE NEED FOR BIOMATERIALS:
Human tissues and organs fail to perform ideally due to genetic makeup, age, sickness, or
accidents. Some of these disorders are treated by the use of bioactive agents called drugs. Others,
however, could not be rectified by provision of drugs and require the use of materials and devices.
For example, when a patient has diabetes type I, administration of insulin can be used to
control the blood glucose level, but in the case of a malfunctioning kidney, the abnormal blood
urea levels cannot be controlled by drugs. In this latter case, the problem is solved by
transplanting a kidney from a healthy donor of matching tissue type, or in the absence of a
transplantable organ, the kidney is supported through artificial means, for example, by routine
dialysis of the patient’s blood in a dialysis machine. If a dialysis machine is used, the removal of
the excess water, metabolic waste, and toxic compounds in the blood is achieved by filtration of
the blood against counter current flow of a basically salt solution called the dialysate (contains
Na+, K+, Ca+2, Mg+2 , acetate ion, colloidal iron, glucose). The goal here is to remove the waste
products while retaining all the essential constituents of the blood. Thus, the dialysis machine
used in this example is a biomedical device constructed of biomaterials.
Human kind has strived since the early ages to live a longer and healthier life and searched
for materials and tools to achieve these goals. He either found the tools or some models in nature,
or he developed or modified them further to be able to use them for his own benefit. This is how
the scientific and technological discoveries are made. In our age, detection of diseases became
easier with the development of diagnostic kits, faster and more effective treatment can be achieved
with the use of novel drugs, damaged or injured tissues can be repaired with the use of new
materials and technologies, and as a result longer and healthier living conditions are attained.

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Living things are constituted of billions of cells that come together to create a very complex
organism. The bodily functions are sustained as a result of the billions of simultaneous and/or
consecutive reactions which take place in harmony, trigger-ing one another, and in unison with all
the organs and systems. We do not pay special attention to what is happening in our body during
a normal day. We do not know when the digestive process in the stomach ends; we do not
voluntarily control the rhythm of our heart beat, our vision, or our hearing. The organs and tissues
which work so hard are also very sensitive, delicate, fragile, and susceptible to be damaged if they
are not properly cared for. When we are hurt, or when our system does not function properly due
to disease, a variety of treatment approaches are applied to remedy the situation. The
dysfunctional organ could be treated by introduction of some materials into the body such as
tooth fillings used in the treatment of tooth cavities, transplantation of healthy tissues as autografts
from the patient’s own body, or allografts from another human donor or xenografts from another
mammal such as in the case of kidney transplants. On the other hand, the damaged tissues could
be supported by high technology products and biocompatible materials such as the hip joints,
heart valves, and stents developed in the lab by researchers.
Table: Biomaterials Properties and their Applications

General Properties of Biomaterials:

Biomaterials due to their intended use in a very complex environment need to fulfillvarious
requirements. The most important and general ones are that they should:
1. Be biocompatible (nontoxic, non-carcinogenic, non-allergenic, etc.)
2. Have physical properties (e.g., density, form, porosity, surface roughness topography)
comparable to those of the tissue it replaces or is implanted in
3. Have appropriate mechanical properties (compressive, tensile, shear, impact)
4. Have appropriate service lives (stable for life or degrade within a matter of days or weeks
depending on the goal)
5. Have chemical properties similar to that of tissues (e.g., hydrophilic or hydro-phobic, have
similar functional groups)
6. Be processable and sterilizable without difficulty
7. Have appropriate bioactivity (mostly inert, but could have induction or conduction activities
or carry bioactive agents if needed)
8. Be economical and available.
BIOCOMPATIBILITY:
Materials which were developed during the period of 1950s to 1960s mainly as implants to

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the human body for multiple disciplinary applications like orthopaedics, cardiovascular surgery,
ophthalmology, and wound healing are known as first generation biomaterials. Generally,
materials like cellulose, acetates and polymers which are available in nature were used in the first
generation biomaterials. The important properties of the first generation biomaterials to be
considered are biocompatibility, biofunctionality and practicability. The foremost and the desired
characteristic of a biomaterial is its biocompatibility.
Biocompatibility is the ability of the surrounding tissues and the body as a whole to accept
an artificial material when it is implanted in the body.
Similarly, biofunctionality is the second important property of biomaterials. It is the ability of
the biomaterial to exhibit adequate physical and mechanical properties to augment or replace the
body tissues. The practicability is the amenability of the biomaterial to machine, or to form,
different shapes for ready usage at low cost. The first generation biomaterials and their
applications are given in Table.
Table: First Generation Biomaterials and their Applications

Biomaterial Sources:
The biomaterials used in solving human health problems are derived from a numberof
sources. These are (1) natural materials, (2) synthetic polymers, (3) metals, (4) ceramics, and (5)
composites. The following table summarizes some of the properties and uses of biomaterials

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(Table).The sources of the biomaterials are presented in Table.
These are natural materials, synthetic polymers, ceramics, metals, and composites. Natural
materials can be considered as biological polymers and also decellularized tissues. The major
difference is that decellularized tissues already have the geometry and texture of the original
tissue, whereas the biopolymers are solids which has to be processed into the form needed for the
application. The biopolymers presented as examples in thetable are of plant (cellulose), animal
(collagen, hyaluronic acid, chondroitin sulfate), insect (silk), microorganism (polyesters),
crustacean (chitosan is a derivative of chitin), and algae (alginate) origin. Since they all are made
by organisms, enzymes and most of the time templates are involved in their production. Thus,
their proper-ties are generally highly controlled.
They, however, have a major disadvantage: there are also enzymes that can hydrolyze and
degrade them. As a result, they all aredegradable in the biological system, or in other words, they
are biodegradable. Their sources are abundant and generally quite inexpensive. Since they are
polymeric materials, they are not highly crystalline, and as a result not strong enough for most
loadbearing applications. One major advantage is that their chemistry and mechanical properties
are very similar to those of the tissues and therefore quite compatible with the biological system.
Important applications of those are soft tissue replacements, including tissue engineering, wound
dressings, and cartilage substitutes. The synthetic polymers are, like the biological ones, not highly
crystalline, and therefore, they do not have high strength. Some, however, like ultrahigh molecular
weight polyethylene (UHMWPE) or poly (L-lactide), can crystallize significantly (35–55% for
UHMWPE [7] and 55% for PLLA [8]) and have significant strength. Although there are
hydrophilic ones, in general most of the synthetic polymers arehydrophobic (e.g., PMMA, PVC,
Teflon, Dacron, PE), and therefore their proper-ties are not similar to biological tissues and
biopolymers. As a result, their interaction with the tissues and tissue growth on or in these
biomaterials is limited. Also as a result of their hydrophobicity and chemistry, most are not
degradable. In the last decades, some degradable polymers were synthesized and used especially
in the production of scaffolds for tissue engineering applications. Polymeric materials whether
biological or synthetic can be processed into complex shapes under mild

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