Chapter 12 Advanced Materials PDF

Advanced Materials  Biomaterials INTRODUCTION play an integral role in medicine today—restoring function and facilitating healing for people after injury or disease. Biomaterials may be natural or synthetic and are used in medical applications to support, enhance, or replace dama...

Advanced Materials  Biomaterials INTRODUCTION play an integral role in medicine today—restoring function and facilitating healing for people after injury or disease. Biomaterials may be natural or synthetic and are used in medical applications to support, enhance, or replace damaged tissue or a biological function. The first historical use of HYDROGEL- A biomaterial made up of a biomaterials dates to antiquity, when ancient network of polymer chains that are highly Egyptians used sutures made from animal sinew. absorbent and as flexible as natural tissue. Hydrogels have a number of uses including as The modern field of biomaterials scaffolds for tissue engineering, as sustained combines medicine, biology, physics, and release drug delivery systems, and as chemistry, and more recent influences biosensors that are sensitive to specific from tissue engineering and materials molecules such as glucose. science.  BIOMATER A biomaterial is “any substance or combination of substance synthetic or natural in origin, which can be used for any period of time, as a whole or as a part of a system which treats, augments, or replaces any tissue, organ, or function of the body” e.g. Suture, bone transplant and screws, cardiac pacemaker, Catheters, etc.  How are biomaterials used in current medical practice? Doctors, researchers, and bioengineers use biomaterials for the following broad range of applications: Medical implants, including heart valves, stents, and grafts; artificial joints, ligaments, and tendons; hearing loss implants; dental implants; and devices that stimulate nerves. Methods to promote healing of human tissues, including sutures, clips, and staples for wound closure, and dissolvable dressings. Regenerated human tissues, using a combination of biomaterial supports or scaffolds, cells, and bioactive molecules. Examples include a bone- regenerating hydrogel and a lab-grown human bladder. Molecular probes and nanoparticles that breakthrough biological barriers aid in cancer imaging and therapy at the molecular level. Biosensors to detect the presence and amount of specific substances and to transmit that data. Examples are blood glucose monitoring devices and brain activity sensors. Drug-delivery systems that carry and/or apply drugs to a disease target. Examples include drug-coated vascular stents and implantable chemotherapy wafers for cancer patients. ETHICS OF BIOMATERIALS NATURAL BIOMATERIALS  CLASSIFICATION OF NATURAL BIOMATERIALS These groups can be distinguished as those derived from proteins (for example, collagen, gelatin, silk, and fibrin); polysaccharides (cellulose, chitin/chitosan, alginate and agarose), or glycosaminoglycans (hyaluronic acid, chondroitin sulfate, dermatan sulfate, heparan sulfate and keratan sulfate).  NATURAL PROTEIN BIOMATERIAL Natural proteins are proteins that are extracted from natural sources such as animals, plants, or microorganisms. They are commonly used as biomaterials because they have good biocompatibility, biodegradability, and bioactivity.  Polysaccharides- Based Biomaterials Polysaccharides are natural, renewable materials that are biodegradable and biocompatible, making them ideal subjects for biomedical applications. There are several types of GAGs components including hyaluronic acid (HA), chondroitin sulfate (CS), dermatan sulfate, heparan sulfate, and keratan sulfate.  Glycosaminoglycans biomaterial Glycosaminoglycans (GAGs) represent a group of long unbranched polysaccharides consisting of repeating disaccharide units. Polysaccharides include cellulose, chitin, starch, hyaluronan, alginate, chitosan, dextran, etc.  CLASSIFICATION OF SYNTHETIC BIOMATERIALS In nature, a number of materials are available in industry along with its alloy but only few of them show biocompatibility, henceforth they exhibit excellent bio-functionality and have potential to employ as future implantation materials. Metals, polymers, ceramics and composites are some of the major classes of biomaterials that are extensively employed in biomedical applications. METAL CERAMIC POLYMERS  Materials Advantages Limitations Applications Enough vigor Enough stiffness, Enough elasticity Weight tolerating implants Outstanding tiredness Metals (Ti and its alloy, Ag, Au, May destroyed by rust, such as bone plates and pins, resistance Stainless steel etc.) Enough density, screws, dental root implants, Enough tensile strain and complex in preparation joint replacements, wires etc. compressive stress etc. Ecofriendly to living tissue Hard Covering for load bearing Enough vigor and firmness Ceramics (Alumina, Zirconia, Not flexible implants, medical sensors, Enough resistance to rust Hydroxyapatite etc.) Less tiredness resistance dental and orthopedic and wear Variable mechanical vigor implants etc. Less density  Materials Advantages Limitations Applications Ecofriendly to living tissue Enough resilience Less vigor Contact lenses socket, heart Polymers (Nylon, silicon, Less load Variation in shape valves, blood vessels, artificial polyester etc.) Simple to construct Chance of degradation hearts, hip joint etc. High resistance to rust Physically powerful Required Enough resistance to rust Joint replacements, bone Composites /Bio composite steadiness/homogeneity and wear cement, Dental implants. Not easy to construct Ecofriendly to living tissue  CHARACTERISTIC The requirement of designing and selection criteria of biomaterial depends upon the type of medical application. The biomaterial must have some unique characteristics that can have potent application in biomedical field for longer duration without immune rejection Outstanding biocompatibility Sufficient mechanical properties High quality physical and chemical properties Enough resistance to wear Enough resistance to rust Osseo-integration (For bone implants) Smart Materials Materials that have been modified to respond in a controllable and reversible manner, altering some of their properties in response to external stimuli such as stress or temperature, electric or magnetic fields, pH levels, and chemical compounds. Components of Smart Matrials Data acquisition Collecting raw data needed for an appropriate sensing and monitoring of the structure. Data transmission Forward the raw data to the local or central command and control units. Command and Control Unit Collecting raw data needed for an appropriate sensing and monitoring of the structure. Data instruction Transmit the decisions and the associated instructions back to the member of the structure. Action Devices Take action by triggering the controlling units or devices. Types of Smart materials Piezoelectric Materials can convert mechanical energy into electrical energy and vice versa Shape Memory Materials have the ability to change the shape, even returning to their original shape, when exposed to a heat source, among other stimuli. Chromoactive Materials change colour when subjected to a certain variation in temperature, light, pressure, etc. Types of Smart materials Magnetorheological Materials Magnetorheological materials change their properties when exposed to a magnetic field. Photoactive Materials Photoactive materials absorb light and convert it into an electrical signal. Magnetosctrictive Materials Application of magnetic field to a ferromagnetic material and causes it to change shape Types of Smart materials Electrostrictive Materials Dielectric material is subjected to an electric field, then experiences strain Thermoelectric Materials Materials are subjected to temperature difference and produces a proportional output voltage. Thermochromic Materials Materials that change color depending on the temperature.  Applications of Smart Materials Synthetic spider web This material is five times stronger than steel, and also has great elasticity. Its potential uses include: bulletproof clothing, artificial skin for burns or waterproof adhesives. Graphene This material is used for batteries with more autonomy, cheaper photovoltaic solar cells, faster computers, flexible electronic devices, more resistant buildings, bionic limbs, etc. Metamaterials manufactured in the laboratory with unusual physical properties not found in nature and are the subject of research in fields such as the military, optics or telephony.  Applications of Smart Materials Shrilk This material is considered the ideal substitute for plastic — since its decomposition time is only two weeks and it also works as a stimulant for plant growth XPL a silicone-based polymer that adheres to the dermis like a second skin. This replicates the appearance of young, healthy skin by rejuvenating the look of the wearer. Introduction to Nanotechnology Nanotechnology is the manipulation of matter on a near-atomic scale to produce new structures, materials and devices. Matter can exhibit unusual physical, chemical, and biological properties at the nano scale, differing in important ways from the properties of bulk materials, single atoms, and molecules. Some nano structured materials are stronger or have different magnetic properties compared to other forms or sizes of the same material.  What are nanoparticles? Nano particles are particles that are between 1 and 100 nano meters in size. Nano particles can be made of a variety of materials, including gold, silver, and carbon nano tubes.  How Small Is “Nano”? In the International System of Units, the prefix "nano" means one-billionth, or 10-9; therefore, one nano meter is one-billionth of a meter. Examples: A sheet of paper is about 100,000 nano meters thick. A strand of human DNA is 2.5 nano meters in diameter. There are 25,400,000 nano meters in one inch. A human hair is approximately 80,000–100,000 nano meters wide. A single gold atom is about a third of a nano meter in diameter.  Properties of nanoparticles Increased reactivity: Nanoparticles have a larger surface area to volume ratio than larger particles. This means that they can react more quickly with other materials. Optical properties: Nano particles can absorb and scatter light in different ways than larger particles. This can be used to create new materials with unique optical properties. Electrical properties: Nano particles can conduct electricity better than larger particles. This can be used to create new electronic devices.  Applications of nanotechnology Medicine Nanotechnology can be used to develop new drugs, therapies, and diagnostic tools. For example, nano particles can be used to deliver drugs directly to cancer cells, which can improve the effectiveness of treatment and reduce side effects.  Applications of nanotechnology Electronics Nanotechnology can be used to create new electronic devices, such as transistors and sensors. For example, carbon nano tubes can be used to create transistors that are smaller, faster, and more energy-efficient than traditional silicon transistors.  Applications of nanotechnology Energy Nanotechnology can be used to develop new energy sources, such as solar cells and batteries. For example, nano particles can be used to create solar cells that are more efficient and less expensive than traditional solar cells. Challenges of nanotechnology Safety: The long-term safety of nano particles is still unknown. Some studies have shown that nano particles can be toxic to cells. Cost: The cost of manufacturing nano particles can be high. Public acceptance: There is some public concern about the potential risks of nanotechnology. Semiconductors A semiconductor is a substance that has specific electrical properties that enable it to serve as a foundation for computers and other electronic devices. It is typically a solid chemical element or compound that conducts electricity under certain conditions but not others. This makes it an ideal medium to control electrical current and everyday electrical appliances. Semiconductors have properties that sit between the conductor and insulator.  Most Commonly Used Semiconductor Materials Silicon Silicon is abundant in nature, making it relatively inexpensive Can withstand the high temperatures Can be easily doped with impurities to create n-type and p-type semiconductors Silicon forms a stable oxide layer on its surface, which can be used to insulate different parts of a circuit from each other. Silicon  Most Commonly Used Semiconductor Materials Germanium Has a lower band gap energy than silicon Suitable for high-frequency applications, such as microwave transistors and infrared detectors Much more expensive than silicon A highly sensitive material for detecting infrared radiation Able to withstand higher voltages and currents Germanium  Reasons why Silicon and Germanium are widely used Can be manufactured to a very high purity level Has the ability to change electrical characteristics (conductivity) from poor conductor to a good conductor  Working Principles The working principle of semiconductors lies in the controlled movement of electrons and holes, which are essentially the absence of electrons. The movement of these charge carriers can be influenced by applying an electric field, creating a flow of current. However, their conductivity can be altered by introducing impurities, a process called doping.  Doping Doping involves adding impurities to a semiconductor material to increase the conductivity addition of electrons. Lightly doped semiconductor has high resistance and low conductivity Heavily doped semiconductor has low resistance and high conductivity  Types of Impurities Trivalent Impurities Atoms that have 3 valence electrons This type of impurities has 1 electron deficiency, resulting in excess of holes Also called as acceptor atoms  Types of Impurities Pentavalent Impurities Atoms that have 5 valence electrons This type of impurities has 1 excess electron Also called as donor atoms  Two Types of Semiconductor Intrinsic Semiconductor A pure semiconductor, flawless crystals free of other elements’ flaws and impurities. At room temperature, a silicon crystal acts approximately like an insulator because it has only few electrons and holes produced by thermal energy  Two Types of Semiconductor Extrinsic Semiconductor A doped semiconductor The result of adding impurity atom to an intrinsic crystal to alter / increase its electrical conductivity  Types of Extrinsic Semiconductor N-Type Semiconductor Net charge is negative Majority carriers are electrons Produced when pentavalent atoms are added to the molten silicon producing excess of electrons  Types of Extrinsic Semiconductor P-Type Semiconductor Net charge is positive Majority carriers are holes Produced when Trivalent atoms are added to the molten silicon producing excess of holes