Q.1 Which biomaterial is most commonly used for the housing of implantable cardiac pacemakers due to its excellent biocompatibility and insulating properties?
Silicone rubber
Stainless steel
Titanium alloy
Polyethylene terephthalate (PET)
Explanation - Silicone rubber provides a flexible, inert, and electrically insulating enclosure, making it ideal for pacemaker housings.
Correct answer is: Silicone rubber
Q.2 What property of a biomaterial is most critical for ensuring reliable signal transmission in neural interface electrodes?
Young's modulus
Electrical conductivity
Thermal conductivity
Optical transparency
Explanation - Neural electrodes must conduct electrical signals efficiently to record or stimulate neural activity.
Correct answer is: Electrical conductivity
Q.3 Which of the following polymers is widely used for coating intracortical microelectrodes to reduce inflammatory response?
Polylactic acid (PLA)
Polyimide
Polyethylene glycol (PEG)
Polyvinyl chloride (PVC)
Explanation - PEG is hydrophilic and resists protein adsorption, minimizing foreign body reaction around electrodes.
Correct answer is: Polyethylene glycol (PEG)
Q.4 A bioresorbable stent must degrade at a controlled rate. Which material characteristic primarily controls this degradation?
Electrical resistivity
Crystalline grain size
Hydrolytic susceptibility
Magnetic permeability
Explanation - Bioresorbable polymers degrade mainly through hydrolysis; their susceptibility determines the rate.
Correct answer is: Hydrolytic susceptibility
Q.5 Which metal alloy is preferred for long‑term orthopedic implants because of its high strength and corrosion resistance in physiological environments?
Co‑Cr‑Mo alloy
Aluminum alloy
Copper‑zinc alloy
Nickel‑tin alloy
Explanation - Cobalt‑chromium‑molybdenum alloys combine high mechanical strength with excellent corrosion resistance in the body.
Correct answer is: Co‑Cr‑Mo alloy
Q.6 In a pulse oximeter, the light‑absorbing part of the sensor is made from which type of biomaterial?
Silicone elastomer
Hydrogel
Polystyrene
Gold foil
Explanation - Hydrogels can be molded to hold LEDs and photodiodes while maintaining comfort and good optical transmission.
Correct answer is: Hydrogel
Q.7 Which property of titanium makes it especially suitable for bone‑anchored hearing aid implants?
High electrical conductivity
Low density
Osseointegration capability
Magnetic susceptibility
Explanation - Titanium forms a stable oxide layer that promotes direct bone bonding, essential for hearing aid fixtures.
Correct answer is: Osseointegration capability
Q.8 A conductive polymer used in flexible biosensors is:
Polypyrrole
Polyethylene
Polypropylene
Polytetrafluoroethylene (PTFE)
Explanation - Polypyrrole exhibits intrinsic electrical conductivity and can be processed into thin, flexible films for biosensing.
Correct answer is: Polypyrrole
Q.9 Which of the following is a major advantage of using ceramic biomaterials in implantable pressure sensors?
High ductility
Low thermal expansion
High dielectric constant
Magnetic neutrality
Explanation - Ceramics such as alumina have high dielectric constants, improving capacitive sensor performance in pressure transducers.
Correct answer is: High dielectric constant
Q.10 What is the primary reason for coating metallic implants with hydroxyapatite (HA) layers?
To increase electrical conductivity
To improve corrosion resistance
To enhance osteointegration
To reduce magnetic interference
Explanation - HA mimics bone mineral, promoting bone cell attachment and growth onto the implant surface.
Correct answer is: To enhance osteointegration
Q.11 In a glucose biosensor, the enzyme glucose oxidase is immobilized on a platinum electrode. Which material property of platinum is most important here?
Biodegradability
Catalytic activity
Magnetic susceptibility
Optical clarity
Explanation - Platinum efficiently catalyzes the oxidation of hydrogen peroxide generated by the enzyme, enhancing sensor response.
Correct answer is: Catalytic activity
Q.12 Which material is typically used for the flexible leads of cochlear implants?
Polyimide
Stainless steel
Glass fiber
Silicon carbide
Explanation - Polyimide offers flexibility, thermal stability, and biocompatibility, making it ideal for implantable leads.
Correct answer is: Polyimide
Q.13 What is the main function of a dielectric coating on an implantable antenna?
To increase antenna gain
To prevent tissue heating
To protect against corrosion
To enhance signal bandwidth
Explanation - Dielectric coatings electrically insulate the antenna, shielding the metal from bodily fluids and preventing corrosion.
Correct answer is: To protect against corrosion
Q.14 Which of the following biomaterials exhibits piezoelectric properties useful for self‑powering implants?
Polyvinylidene fluoride (PVDF)
Polylactic acid (PLA)
Polyethylene glycol (PEG)
Polystyrene
Explanation - PVDF generates electric charge under mechanical stress, allowing conversion of body motion into electrical energy.
Correct answer is: Polyvinylidene fluoride (PVDF)
Q.15 A major limitation of using pure gold as a material for chronic neural electrodes is:
Low electrical conductivity
High Young's modulus causing tissue damage
Tendency to corrode in vivo
Poor biocompatibility
Explanation - Gold is stiff compared to brain tissue; its rigidity can cause micromotion‑induced inflammation over time.
Correct answer is: High Young's modulus causing tissue damage
Q.16 Which biomaterial property is most important for the insulating layer of a cuff electrode used on peripheral nerves?
Thermal conductivity
Dielectric strength
Magnetic permeability
Optical transparency
Explanation - High dielectric strength ensures the insulation prevents current leakage into surrounding tissue.
Correct answer is: Dielectric strength
Q.17 What is the chief reason for selecting silicone elastomers in the fabrication of artificial heart valves?
High tensile strength
Low friction surface
Electrical conductivity
Magnetic shielding
Explanation - Silicone's smooth, low‑friction surface reduces wear and blood clot formation in heart valve leaflets.
Correct answer is: Low friction surface
Q.18 In a wearable ECG patch, the conductive ink used for electrodes is typically composed of:
Silver nanoparticles
Copper wires
Aluminum foil
Iron filings
Explanation - Silver nanoparticles provide high conductivity while allowing printing onto flexible substrates.
Correct answer is: Silver nanoparticles
Q.19 Which material is most suitable for a biodegradable wireless telemetry capsule intended to dissolve after 6 months?
Poly(lactic‑co‑glycolic acid) (PLGA)
Polycarbonate
Silicone rubber
Stainless steel
Explanation - PLGA hydrolyzes into lactic and glycolic acid, safely resorbing in the body over a controlled period.
Correct answer is: Poly(lactic‑co‑glycolic acid) (PLGA)
Q.20 For an implantable pressure sensor using a capacitive transduction mechanism, which biomaterial is preferred for the dielectric layer?
Silicon nitride
Polydimethylsiloxane (PDMS)
Gold
Titanium
Explanation - PDMS is flexible, biocompatible, and has a suitable dielectric constant for capacitive sensing in soft tissues.
Correct answer is: Polydimethylsiloxane (PDMS)
Q.21 Which characteristic of a material determines its suitability for use in a magnetically actuated drug‑delivery implant?
Magnetic permeability
Thermal expansion coefficient
Electrical resistivity
Optical refractive index
Explanation - High magnetic permeability allows the implant to respond efficiently to external magnetic fields for actuation.
Correct answer is: Magnetic permeability
Q.22 The primary advantage of using a carbon‑based nanomaterial (e.g., graphene) in biosensor electrodes is:
High mechanical brittleness
Large surface area and conductivity
Magnetic properties
Low cost production
Explanation - Graphene offers a high surface‑to‑volume ratio and excellent electrical conductivity, enhancing sensitivity.
Correct answer is: Large surface area and conductivity
Q.23 Which of the following is a major cause of failure for implantable electronic devices that can be mitigated by using biocompatible encapsulation?
Mechanical fatigue
Electrostatic discharge
Corrosion from body fluids
Radiation damage
Explanation - Encapsulation isolates metal components from ionic body fluids, preventing corrosion and device failure.
Correct answer is: Corrosion from body fluids
Q.24 What is the main reason for using a thin layer of parylene‑C on implantable microelectronics?
To increase device flexibility
To provide a moisture‑impermeable barrier
To improve electrical conductivity
To make the device biodegradable
Explanation - Parylene‑C forms a pinhole‑free coating that protects electronics from moisture ingress.
Correct answer is: To provide a moisture‑impermeable barrier
Q.25 Which property of a biomaterial influences the rate at which a pacemaker lead becomes encapsulated by fibrous tissue?
Surface roughness
Bulk density
Thermal conductivity
Magnetic susceptibility
Explanation - Rougher surfaces promote protein adsorption and fibroblast attachment, accelerating fibrous encapsulation.
Correct answer is: Surface roughness
Q.26 A flexible neural probe requires a substrate that is both biocompatible and has a low modulus. Which material fits this requirement?
Silicon
Polyimide
Glass
Aluminum
Explanation - Polyimide offers flexibility, low modulus, and biocompatibility, making it suitable for soft neural interfaces.
Correct answer is: Polyimide
Q.27 Which of the following metals is avoided in long‑term implants due to its potential to cause allergic reactions?
Titanium
Cobalt
Nickel
Molybdenum
Explanation - Nickel is a known allergen and can provoke hypersensitivity reactions in some patients.
Correct answer is: Nickel
Q.28 In a retinal prosthesis, which biomaterial is commonly used for the electrode array that contacts the retina?
Silicone rubber
Platinum‑iridium alloy
Aluminum oxide
Polystyrene
Explanation - Platinum‑iridium offers high conductivity and biocompatibility for delicate retinal stimulation.
Correct answer is: Platinum‑iridium alloy
Q.29 Which characteristic of a hydrogel makes it ideal for use as a drug‑release matrix in implantable devices?
High electrical conductivity
Swelling ability and water content
Magnetic properties
Rigidity
Explanation - Hydrogels absorb water, allowing diffusion‑controlled drug release over time.
Correct answer is: Swelling ability and water content
Q.30 The main advantage of using a ceramic (e.g., alumina) as a substrate for an implantable pressure sensor is:
High electrical conductivity
Excellent biocompatibility and chemical inertness
Flexibility
Magnetic responsiveness
Explanation - Ceramics resist corrosion and are biologically inert, providing a stable platform for sensors.
Correct answer is: Excellent biocompatibility and chemical inertness
Q.31 Which polymer is most frequently employed in the fabrication of stretchable electronic skin for medical monitoring?
Polyurethane (PU)
Polyethylene terephthalate (PET)
Polystyrene (PS)
Polycarbonate (PC)
Explanation - PU combines elasticity with good electrical properties, enabling stretchable sensor arrays.
Correct answer is: Polyurethane (PU)
Q.32 For an implantable antenna operating at 2.4 GHz, which dielectric constant range is optimal for the surrounding encapsulation material?
1–2
2–4
4–8
8–12
Explanation - A dielectric constant close to that of body tissue (≈4) minimizes impedance mismatch and maximizes efficiency.
Correct answer is: 2–4
Q.33 Why is Ti‑6Al‑4V alloy frequently selected for load‑bearing orthopedic implants?
Its high magnetic permeability
Low cost compared to stainless steel
High fatigue strength and corrosion resistance
Excellent electrical conductivity
Explanation - Ti‑6Al‑4V offers a superior strength‑to‑weight ratio and resists corrosion in the body, ideal for load‑bearing use.
Correct answer is: High fatigue strength and corrosion resistance
Q.34 Which of the following is a key advantage of using shape‑memory alloys (SMAs) in medical stents?
They are biodegradable
They can self‑expand at body temperature
They are electrically conductive
They are radiopaque
Explanation - SMAs like Nitinol recover a pre‑set shape when warmed to body temperature, allowing minimally invasive deployment.
Correct answer is: They can self‑expand at body temperature
Q.35 What is the main function of a Faraday cage made from biocompatible material around an implantable neurostimulator?
To increase battery life
To shield the device from external electromagnetic interference
To enhance signal strength
To facilitate tissue integration
Explanation - A biocompatible Faraday cage prevents unwanted EM fields from affecting the stimulator's operation.
Correct answer is: To shield the device from external electromagnetic interference
Q.36 Which material property is most important for the conductive pathways in a flexible cardiac rhythm monitor that adheres to skin?
High Young's modulus
Low thermal conductivity
High stretchability and conductivity
Magnetic permeability
Explanation - The pathways must remain conductive while conforming to skin motion without breaking.
Correct answer is: High stretchability and conductivity
Q.37 In a cochlear implant, the electrode array must be made from a material that is:
Highly magnetic
Electrically insulating
Electrically conductive and biocompatible
Transparent to visible light
Explanation - Conductivity is required for stimulation, while biocompatibility avoids tissue damage.
Correct answer is: Electrically conductive and biocompatible
Q.38 Which biomaterial is most commonly used for the encapsulation of implantable glucose sensors to allow glucose diffusion while preventing protein fouling?
Silicone gel
Polyethylene terephthalate (PET)
Poly(ethylene glycol) (PEG) hydrogel
Aluminum foil
Explanation - PEG hydrogel permits small molecules like glucose to diffuse while resisting protein adhesion.
Correct answer is: Poly(ethylene glycol) (PEG) hydrogel
Q.39 A bio‑electronic device that harvests energy from heartbeats uses which piezoelectric biomaterial?
PVDF (polyvinylidene fluoride)
Silicone rubber
Polyethylene
Polystyrene
Explanation - PVDF converts mechanical strain from heart motion into electrical energy.
Correct answer is: PVDF (polyvinylidene fluoride)
Q.40 Which property of a material is critical for maintaining signal integrity in an implantable telemetry coil?
High magnetic permeability
Low dielectric loss
High thermal conductivity
High optical reflectivity
Explanation - Low dielectric loss minimizes signal attenuation in the coil's electromagnetic field.
Correct answer is: Low dielectric loss
Q.41 Which polymer is often used for the substrate of flexible printed circuit boards (FPCBs) in wearable medical devices?
Polyimide
Polystyrene
Polyvinyl chloride (PVC)
Polytetrafluoroethylene (PTFE)
Explanation - Polyimide provides thermal stability, flexibility, and good dielectric properties for FPCBs.
Correct answer is: Polyimide
Q.42 In a bioresorbable cardiac patch, the material must degrade without causing:
Electrical interference
Inflammatory response
Magnetic attraction
Optical scattering
Explanation - Ideal degradable biomaterials break down into biocompatible by‑products that do not trigger inflammation.
Correct answer is: Inflammatory response
Q.43 Which of the following is an advantage of using titanium nitride (TiN) as a coating for neural electrodes?
Increased magnetic susceptibility
Higher electrical resistance
Improved charge injection capacity
Reduced mechanical strength
Explanation - TiN coatings allow higher charge densities without damaging tissue, enhancing stimulation safety.
Correct answer is: Improved charge injection capacity
Q.44 A key factor for the longevity of an implantable defibrillator's battery is:
High temperature operation
Low power consumption of the circuitry
Large physical size
High magnetic field exposure
Explanation - Reducing circuit power draw extends battery life, decreasing the need for replacement surgeries.
Correct answer is: Low power consumption of the circuitry
Q.45 Which biomaterial is used to fabricate the flexible, stretchable interconnects of a soft robotic prosthetic hand?
Carbon nanotube‑embedded silicone
Stainless steel wires
Aluminum foil
Glass fiber
Explanation - Embedding conductive CNTs into silicone creates stretchable, conductive pathways suitable for soft robotics.
Correct answer is: Carbon nanotube‑embedded silicone
Q.46 For an implantable temperature sensor, the thermistor material should have:
High magnetic permeability
A predictable resistance change with temperature
High optical reflectivity
Low dielectric constant
Explanation - Thermistors rely on a known resistance‑temperature relationship to measure temperature accurately.
Correct answer is: A predictable resistance change with temperature
Q.47 Which property of a material determines its suitability as a conductive trace in a flexible implantable EEG cap?
High Young's modulus
Low surface roughness
High electrical conductivity and flexibility
High thermal expansion
Explanation - The trace must conduct signals while bending with the scalp without cracking.
Correct answer is: High electrical conductivity and flexibility
Q.48 What is the primary purpose of using a biocompatible adhesive like medical‑grade cyanoacrylate in device assembly?
To increase electrical resistance
To provide a permanent mechanical bond without toxic leaching
To generate heat during curing
To enhance magnetic properties
Explanation - Medical cyanoacrylates bond components while meeting biocompatibility standards.
Correct answer is: To provide a permanent mechanical bond without toxic leaching
Q.49 Which material is preferred for the optical window of an implantable retinal prosthesis?
Silicon
Sapphire
Polystyrene
Aluminum
Explanation - Sapphire is transparent, biocompatible, and mechanically robust, making it suitable for optical interfaces.
Correct answer is: Sapphire
Q.50 In a wireless capsule endoscope, the antenna is often fabricated on a substrate made of:
Polyimide
Glass
Stainless steel
Copper
Explanation - Polyimide offers flexibility, heat resistance, and a low dielectric loss, ideal for tiny antennas.
Correct answer is: Polyimide
Q.51 A major factor limiting the use of pure silicon for long‑term implants is:
Low mechanical strength
High electrical resistance
Brittleness leading to fracture under cyclic loading
Magnetic properties
Explanation - Silicon's brittleness makes it unsuitable for dynamic mechanical environments inside the body.
Correct answer is: Brittleness leading to fracture under cyclic loading
Q.52 Which biomaterial is widely used for making the flexible substrate of a smart insulin‑delivery patch?
Polyethylene glycol (PEG)
Polyimide
Polyurethane (PU)
Polylactic acid (PLA)
Explanation - PU combines elasticity with chemical stability, enabling comfortable skin contact and device function.
Correct answer is: Polyurethane (PU)
Q.53 Why are ceramics like zirconia preferred for the bearing surfaces of joint replacements?
They are electrically conductive
They have high wear resistance and low friction
They are magnetic
They are biodegradable
Explanation - Zirconia ceramics provide a hard, smooth surface that reduces wear and particle generation.
Correct answer is: They have high wear resistance and low friction
Q.54 In an implantable bio‑sensor, the transducer element often uses which type of material to convert biochemical signals into electrical ones?
Conductive polymer
Insulating glass
Magnetic alloy
Optical fiber
Explanation - Conductive polymers can interact with biomolecules and change their electrical properties accordingly.
Correct answer is: Conductive polymer
Q.55 Which of the following is a key advantage of using biodegradable magnesium alloys for temporary orthopedic fixation devices?
They are non‑conductive
They provide permanent load bearing
They gradually dissolve, eliminating the need for removal surgery
They are magnetic
Explanation - Magnesium alloys corrode safely in the body, allowing implants to disappear after healing.
Correct answer is: They gradually dissolve, eliminating the need for removal surgery
Q.56 The primary purpose of a hermetic seal in an implantable cardiac monitor is to:
Allow fluid exchange
Prevent ingress of bodily fluids that could damage electronics
Increase device flexibility
Facilitate wireless communication
Explanation - Hermetic sealing creates a watertight barrier, protecting sensitive components.
Correct answer is: Prevent ingress of bodily fluids that could damage electronics
Q.57 Which material characteristic is most important for a bio‑resorbable wireless power receiver that must operate for a limited period?
High magnetic susceptibility
Controlled degradation rate
High optical reflectivity
Low tensile strength
Explanation - The material must maintain function until the device's therapeutic purpose is fulfilled, then degrade safely.
Correct answer is: Controlled degradation rate
Q.58 A polymeric material used for a stretchable ECG electrode must possess:
High rigidity
Low electrical conductivity
High elasticity and conductive filler
Magnetic permeability
Explanation - Elasticity ensures conformity to skin; conductive fillers provide the necessary electrical pathways.
Correct answer is: High elasticity and conductive filler
Q.59 Which of the following biomaterials is most suitable for the conductive tracks of an implantable neuroprosthetic that must remain flexible for years?
Gold thin film
Copper wire
Carbon nanotube‑based ink
Aluminum foil
Explanation - CNT inks are flexible, retain conductivity under strain, and can be printed on soft substrates.
Correct answer is: Carbon nanotube‑based ink
Q.60 In an implantable pressure sensor, why is a low‑modulus encapsulation material advantageous?
It enhances electrical conductivity
It allows the sensor to deform with tissue, improving accuracy
It increases magnetic shielding
It reduces thermal expansion
Explanation - A compliant encapsulation follows tissue movement, ensuring the sensor measures true pressure changes.
Correct answer is: It allows the sensor to deform with tissue, improving accuracy
Q.61 Which property of a material is most critical for the safe operation of an implantable defibrillation coil?
High thermal conductivity
Low resistivity and high charge‑handling capacity
Magnetic permeability
Optical transparency
Explanation - Efficient delivery of high‑energy shocks requires minimal resistance and the ability to handle large charge densities.
Correct answer is: Low resistivity and high charge‑handling capacity
Q.62 Which biodegradable polymer is commonly used for temporary intravascular stents that dissolve after restoring blood flow?
Polyethylene terephthalate (PET)
Polylactic acid (PLA)
Polyvinyl chloride (PVC)
Silicone rubber
Explanation - PLA degrades via hydrolysis into lactic acid, which the body can metabolize, making it suitable for temporary stents.
Correct answer is: Polylactic acid (PLA)
Q.63 Which characteristic of a material influences the rate of fibrous capsule formation around an implanted electrode?
Surface hydrophobicity
Bulk density
Electrical conductivity
Magnetic susceptibility
Explanation - Hydrophobic surfaces tend to promote protein adsorption and subsequent fibrous encapsulation.
Correct answer is: Surface hydrophobicity
Q.64 The use of a thin gold layer on the surface of a neural probe primarily serves to:
Increase stiffness
Provide a biocompatible, conductive surface
Make the probe magnetic
Reduce optical clarity
Explanation - Gold is inert and conductive, reducing tissue reaction while enabling efficient electrical interfacing.
Correct answer is: Provide a biocompatible, conductive surface
Q.65 Which biomaterial is most widely used for the flexible substrate of an implantable retinal electrode array?
Polyimide
Stainless steel
Silicone oil
Aluminum
Explanation - Polyimide's flexibility, biocompatibility, and thermal stability suit delicate retinal devices.
Correct answer is: Polyimide
Q.66 A key reason for selecting a ceramic (e.g., alumina) feedthrough in an implantable pulse generator is:
High electrical conductivity
Low mechanical strength
Excellent electrical insulation and hermeticity
Magnetic properties
Explanation - Ceramic feedthroughs prevent fluid ingress while electrically isolating lead wires.
Correct answer is: Excellent electrical insulation and hermeticity
Q.67 In the design of an implantable drug‑eluting stent, the polymer coating must have:
High electrical conductivity
Controlled drug release kinetics and biostability
Magnetic responsiveness
Optical transparency
Explanation - The coating should release medication at a predictable rate while remaining stable in the arterial environment.
Correct answer is: Controlled drug release kinetics and biostability
Q.68 Which of the following is a primary benefit of using conductive hydrogels in brain‑machine interfaces?
Rigid support for electrodes
Reduced impedance and improved tissue conformity
Magnetic shielding
Increased thermal conductivity
Explanation - Conductive hydrogels lower electrode impedance and match the softness of brain tissue, enhancing signal quality.
Correct answer is: Reduced impedance and improved tissue conformity
Q.69 What property of a material makes it suitable for a thermally activated shape‑memory stent?
High electrical conductivity
Superelasticity with a defined transition temperature
Magnetic susceptibility
Optical clarity
Explanation - Shape‑memory alloys like Nitinol expand at a specific temperature, enabling controlled deployment.
Correct answer is: Superelasticity with a defined transition temperature
Q.70 For a long‑term implanted optical sensor, the window material must have:
High optical transmission in the relevant wavelength range
High electrical resistance
Magnetic properties
Low thermal expansion only
Explanation - Transparency ensures that light can reach the sensor without attenuation.
Correct answer is: High optical transmission in the relevant wavelength range
Q.71 Which material is commonly used as a barrier layer to prevent ion migration in implantable thin‑film batteries?
Aluminum oxide (Al2O3)
Copper
Silicon
Polyethylene
Explanation - Al2O3 forms a dense, ion‑impermeable layer that protects battery components.
Correct answer is: Aluminum oxide (Al2O3)
Q.72 The main advantage of using a bio‑inert material such as titanium for the structural frame of an artificial hip joint is:
Excellent electrical conductivity
Low cost
Superior biocompatibility and corrosion resistance
Magnetic properties
Explanation - Titanium's inert oxide layer prevents adverse reactions and corrosion in the body.
Correct answer is: Superior biocompatibility and corrosion resistance
Q.73 Which material characteristic is essential for a wireless implantable sensor that relies on inductive coupling?
High magnetic permeability of the coil core
Low dielectric constant of the substrate
High optical reflectivity
High thermal conductivity
Explanation - A high‑µ core enhances magnetic field coupling, improving power transfer efficiency.
Correct answer is: High magnetic permeability of the coil core
Q.74 What is the primary reason for coating implantable electrodes with a thin layer of iridium oxide?
To increase stiffness
To enhance charge injection capacity and reduce impedance
To make the electrode magnetic
To improve optical transparency
Explanation - Iridium oxide provides a high surface area and stable electrochemical interface for neural stimulation.
Correct answer is: To enhance charge injection capacity and reduce impedance
Q.75 A flexible, biodegradable sensor for monitoring intracranial pressure can be fabricated from:
Silicone rubber
Poly(lactic acid) (PLA) combined with graphene
Stainless steel
Aluminum foil
Explanation - PLA offers biodegradability, while graphene imparts the necessary conductivity for sensing.
Correct answer is: Poly(lactic acid) (PLA) combined with graphene
Q.76 In the context of implantable medical devices, the term "bio‑fouling" refers to:
Corrosion of metal parts
Accumulation of biological material on device surfaces
Magnetic interference
Electrical shorting
Explanation - Bio‑fouling can impair device function; surface treatments aim to minimize it.
Correct answer is: Accumulation of biological material on device surfaces
Q.77 Which material is most suitable for a transparent, flexible substrate in a retinal implant that must transmit visible light?
Polyimide
Polyethylene terephthalate (PET)
Silicone
Polycarbonate
Explanation - PET is clear, flexible, and biocompatible, allowing light to reach photodiodes.
Correct answer is: Polyethylene terephthalate (PET)
Q.78 What property of a polymeric encapsulant is critical for protecting a high‑frequency implantable antenna?
Low dielectric loss at the operating frequency
High magnetic permeability
High electrical conductivity
High optical opacity
Explanation - Low loss ensures minimal attenuation of the RF signal transmitted by the antenna.
Correct answer is: Low dielectric loss at the operating frequency
Q.79 A bio‑resorbable electronic patch for cardiac monitoring must degrade after a few months. Which material combination best achieves this?
Silicone + gold
PLGA + magnesium micro‑coils
Stainless steel + epoxy
Titanium + PTFE
Explanation - PLGA provides a degradable matrix, while magnesium coils can safely dissolve after serving their purpose.
Correct answer is: PLGA + magnesium micro‑coils
Q.80 Why is titanium nitride (TiN) often chosen for the electrodes of deep brain stimulation (DBS) devices?
It is highly magnetic
It offers low impedance and high charge injection capacity
It is biodegradable
It is highly reflective
Explanation - TiN reduces impedance and tolerates high stimulation currents without tissue damage.
Correct answer is: It offers low impedance and high charge injection capacity
Q.81 Which characteristic is most important for the polymer used to encapsulate an implantable glucose sensor that must stay stable for years?
High water absorption
Low permeability to glucose
High long‑term chemical stability and low protein adsorption
Magnetic susceptibility
Explanation - Stability prevents degradation, while low protein adsorption reduces fouling that can impair sensor function.
Correct answer is: High long‑term chemical stability and low protein adsorption
Q.82 Which material is commonly used for the conductive traces in a flexible, implantable neural cuff that must withstand repeated bending?
Copper foil
Gold thin film on polyimide
Aluminum wire
Stainless steel ribbon
Explanation - Gold adheres well to polyimide and maintains conductivity under flexural stress.
Correct answer is: Gold thin film on polyimide
Q.83 In an implantable pressure transducer that uses a piezoresistive element, the sensing material must exhibit:
High thermal expansion coefficient
Large change in resistance with applied stress
Magnetic susceptibility
Optical transparency
Explanation - Piezoresistive sensors rely on resistance variation under mechanical deformation to measure pressure.
Correct answer is: Large change in resistance with applied stress
Q.84 Which of the following is a major advantage of using a polymeric material such as PDMS for the substrate of a stretchable bio‑sensor?
High Young's modulus
Excellent biocompatibility and flexibility
High electrical conductivity
Magnetic properties
Explanation - PDMS is soft, inert, and can conform to moving tissues, making it ideal for stretchable sensors.
Correct answer is: Excellent biocompatibility and flexibility
Q.85 What is the main reason for selecting a ceramic (e.g., alumina) insulator in high‑voltage implantable defibrillators?
Low dielectric constant
High breakdown voltage and biostability
Magnetic shielding
Optical transparency
Explanation - Ceramics can withstand high voltages without electrical failure and remain inert in the body.
Correct answer is: High breakdown voltage and biostability
Q.86 A flexible, implantable device that records EMG signals from muscles often uses which conductive material for its electrodes?
Silver/silver chloride (Ag/AgCl)
Aluminum
Nickel
Copper
Explanation - Ag/AgCl provides stable, low‑impedance contact with biological tissue for electrophysiological recordings.
Correct answer is: Silver/silver chloride (Ag/AgCl)
Q.87 For an implantable drug‑delivery system activated by an external magnetic field, the core material must have:
Low magnetic permeability
High magnetic permeability
High electrical resistivity
High optical absorption
Explanation - High µ materials respond strongly to external magnetic fields, enabling actuation of the device.
Correct answer is: High magnetic permeability
Q.88 Which material property is most relevant when selecting a polymer for a long‑term implanted optical fiber used in optogenetics?
Low optical attenuation
High electrical conductivity
Magnetic susceptibility
Thermal expansion coefficient
Explanation - Low loss ensures efficient light transmission to targeted neurons.
Correct answer is: Low optical attenuation
Q.89 Why are biodegradable magnesium alloys considered for temporary cardiac pacing leads?
They are magnetic
They provide permanent electrical conductivity
They naturally dissolve, eliminating the need for removal
They are highly radiopaque
Explanation - Magnesium alloy leads corrode safely after the pacing period, avoiding surgical extraction.
Correct answer is: They naturally dissolve, eliminating the need for removal
Q.90 Which of the following materials is most suitable for a flexible, implantable temperature sensor that must be electrically insulated?
Polyimide
Copper
Aluminum
Stainless steel
Explanation - Polyimide is an excellent electrical insulator while being flexible enough for implantation.
Correct answer is: Polyimide
Q.91 The primary purpose of a bio‑compatible, low‑modulus coating on an intravascular flow sensor is to:
Increase electrical conductivity
Reduce turbulence caused by the sensor
Enhance magnetic shielding
Improve optical clarity
Explanation - A compliant coating smooths the sensor surface, minimizing disturbance to blood flow.
Correct answer is: Reduce turbulence caused by the sensor
Q.92 Which property of a material is most important for the cathode in an implantable lithium‑ion battery?
High electrical resistivity
Low chemical reactivity with electrolytes
Magnetic permeability
Optical transparency
Explanation - Stability against the electrolyte prolongs battery life and prevents harmful by‑products.
Correct answer is: Low chemical reactivity with electrolytes
Q.93 A key advantage of using a conductive polymer (e.g., PEDOT:PSS) for electrode sites in a neural probe is:
Rigid mechanical properties
Reduced impedance and better tissue integration
High magnetic susceptibility
Low optical transmission
Explanation - Conductive polymers lower impedance and can be engineered to be soft, matching neural tissue mechanics.
Correct answer is: Reduced impedance and better tissue integration
Q.94 Which material is most appropriate for the encapsulating shell of an ingestible wireless pH sensor?
Silicone rubber
Aluminum
Stainless steel
Polyethylene terephthalate (PET) film
Explanation - Silicone is biocompatible, flexible, and can be formed into a protective shell that survives the GI tract.
Correct answer is: Silicone rubber
Q.95 What is the main function of a hydroxyapatite (HA) coating on a titanium hip implant?
To increase electrical conductivity
To improve bone bonding (osteointegration)
To make the implant magnetic
To provide optical transparency
Explanation - HA mimics bone mineral, encouraging direct bone growth onto the implant surface.
Correct answer is: To improve bone bonding (osteointegration)
Q.96 Which property of a polymeric material is essential for an implantable pressure sensor that must operate in a high‑humidity environment?
Low water absorption
High magnetic permeability
High thermal conductivity
Low dielectric constant
Explanation - Low moisture uptake prevents swelling and maintains sensor calibration.
Correct answer is: Low water absorption
Q.97 A bio‑resorbable stent made from poly(L‑lactide) (PLLA) degrades primarily through:
Oxidation
Hydrolysis
Photolysis
Thermal decomposition
Explanation - PLLA hydrolyzes in the aqueous body environment, breaking down into lactic acid.
Correct answer is: Hydrolysis
Q.98 Which material property is most important for a thin‑film electrode that will be exposed to chronic electrical stimulation?
High corrosion resistance
Low optical reflectivity
High magnetic susceptibility
Low thermal conductivity
Explanation - Long‑term exposure to body fluids and stimulation currents requires a material that resists corrosion.
Correct answer is: High corrosion resistance
Q.99 The use of a silicone‑based elastomer in a wearable cardiac monitor is mainly to:
Provide electrical conductivity
Offer a comfortable, skin‑friendly interface
Increase magnetic shielding
Improve optical clarity
Explanation - Silicone elastomers are soft, biocompatible, and adhere well to skin without irritation.
Correct answer is: Offer a comfortable, skin‑friendly interface
Q.100 Which material is most suitable for the optical fiber core of an implantable optogenetic stimulator?
Silica glass
Polyethylene
Aluminum
Stainless steel
Explanation - Silica offers low optical loss and can be fabricated into thin, flexible fibers for light delivery.
Correct answer is: Silica glass
Q.101 For a flexible neural probe that must survive repeated bending, the substrate material should have:
High Young's modulus
Low fracture toughness
Low modulus and high flexibility
High magnetic permeability
Explanation - A compliant substrate prevents mechanical strain on the delicate electrodes during motion.
Correct answer is: Low modulus and high flexibility
Q.102 Which characteristic makes poly(3,4‑ethylenedioxythiophene) (PEDOT) attractive for use in neural electrodes?
High stiffness
Excellent electrical conductivity and biocompatibility
Magnetic behavior
Optical opacity
Explanation - PEDOT provides low impedance and can be engineered to match tissue softness.
Correct answer is: Excellent electrical conductivity and biocompatibility
Q.103 A bio‑compatible, electrically insulating layer for an implantable antenna is often made of:
Parylene‑C
Gold
Copper
Aluminum
Explanation - Parylene‑C creates a thin, pinhole‑free moisture barrier while maintaining low dielectric loss.
Correct answer is: Parylene‑C
Q.104 Which material property is most important for a polymer used to encapsulate a flexible, implantable ECG sensor that will be exposed to body fluids for years?
High water permeability
Biostability and low water uptake
Magnetic susceptibility
Optical transparency
Explanation - Long‑term stability prevents degradation and maintains sensor performance.
Correct answer is: Biostability and low water uptake
Q.105 For a neural interface that must minimize immune response, the surface should be coated with:
Hydrophobic polymers
Hydrophilic PEG‑based hydrogels
Magnetic particles
Conductive metals
Explanation - PEG reduces protein adsorption and subsequent immune activation.
Correct answer is: Hydrophilic PEG‑based hydrogels
Q.106 Which material is commonly used as a substrate for stretchable, skin‑mounted bio‑sensors due to its combination of flexibility and thermal stability?
Polyimide
Silicone oil
Aluminum foil
Stainless steel
Explanation - Polyimide tolerates high processing temperatures while remaining thin and flexible.
Correct answer is: Polyimide
Q.107 A primary concern when using metal leads in an implantable device is:
Optical reflectivity
Corrosion and ion release
Magnetic attraction to external objects
Thermal conductivity
Explanation - Corrosion can degrade electrical performance and release potentially toxic metal ions.
Correct answer is: Corrosion and ion release
Q.108 Which property of a biomaterial determines its ability to be visualized under X‑ray imaging for postoperative monitoring?
Radiopacity
Electrical conductivity
Magnetic susceptibility
Optical clarity
Explanation - Radiopaque materials absorb X‑rays, appearing clearly on radiographs.
Correct answer is: Radiopacity
Q.109 In an implantable neurostimulator, the dielectric material separating the stimulation electrodes from the power circuitry must have:
High dielectric strength
Low magnetic permeability
High optical transmission
Low mechanical strength
Explanation - High dielectric strength prevents short‑circuits between high‑voltage components.
Correct answer is: High dielectric strength
Q.110 Which material is favored for the electrode contacts of a cochlear implant because of its balance between conductivity and biocompatibility?
Platinum‑iridium alloy
Copper
Aluminum
Nickel
Explanation - Pt‑Ir offers excellent conductivity and resists corrosion while being well tolerated by tissue.
Correct answer is: Platinum‑iridium alloy
Q.111 A biodegradable sensor that monitors intracranial pressure should degrade via:
Oxidation
Hydrolysis
Photodegradation
Thermal degradation
Explanation - Water in cerebrospinal fluid drives hydrolytic breakdown of polymers like PLGA.
Correct answer is: Hydrolysis
Q.112 Which of the following is a common method to improve the adhesion of metal films to polymer substrates in flexible medical devices?
Surface roughening
Applying a magnetic field
Cooling to cryogenic temperatures
Increasing humidity
Explanation - Roughening increases surface area and mechanical interlocking, enhancing adhesion.
Correct answer is: Surface roughening
Q.113 The use of a shape‑memory polymer (SMP) in a stent allows:
Self‑expansion when exposed to body temperature
Permanent rigidity
Magnetic navigation
Optical signaling
Explanation - SMPs recover a preset shape at physiological temperatures, enabling minimally invasive deployment.
Correct answer is: Self‑expansion when exposed to body temperature
Q.114 Which property is essential for the encapsulant of an implantable RF telemetry module?
Low dielectric constant and loss
High magnetic permeability
High electrical conductivity
Optical transparency
Explanation - Low dielectric loss preserves RF signal strength for reliable wireless communication.
Correct answer is: Low dielectric constant and loss
Q.115 A major benefit of using a carbon‑based nanomaterial (e.g., graphene) as an electrode in a glucose sensor is:
Increased magnetic susceptibility
Large surface area for enzyme immobilization
High optical reflectivity
Low electrical conductivity
Explanation - Graphene's high surface area enhances enzyme loading, improving sensor sensitivity.
Correct answer is: Large surface area for enzyme immobilization
Q.116 Which material is often chosen for the outer shell of an implantable cardioverter‑defibrillator (ICD) because it provides both strength and biocompatibility?
Titanium
Aluminum
Copper
Polystyrene
Explanation - Titanium offers high strength, corrosion resistance, and excellent biocompatibility for device housings.
Correct answer is: Titanium
Q.117 In an implantable drug‑delivery pump, the valve membrane should be made of a material that:
Is highly permeable to water
Has predictable mechanical properties and biostability
Is magnetic
Is electrically conductive
Explanation - Consistent valve performance over time requires a stable, non‑degrading material.
Correct answer is: Has predictable mechanical properties and biostability
Q.118 What is the main function of a biocompatible adhesive in the assembly of a retinal prosthesis?
To provide electrical insulation
To bond components without toxic leaching
To generate heat for stimulation
To increase magnetic field strength
Explanation - Medical adhesives create reliable joints while meeting strict biocompatibility standards.
Correct answer is: To bond components without toxic leaching
Q.119 Which property of a polymeric material is most critical for a skin‑mounted pulse oximeter that must stay comfortable for days?
High Young's modulus
Low water vapor transmission rate
High flexibility and breathability
High magnetic susceptibility
Explanation - Comfort requires a soft, breathable material that conforms to skin movements.
Correct answer is: High flexibility and breathability
Q.120 A conductive polymer coating on a neural electrode reduces the impedance mainly because:
It increases the electrode's surface roughness and effective area
It makes the electrode magnetic
It reduces the electrode's thickness
It increases the electrode's hardness
Explanation - Roughness and higher surface area lower interfacial impedance, improving signal quality.
Correct answer is: It increases the electrode's surface roughness and effective area
Q.121 Which material is often selected for the flexible interconnects of a wearable EEG cap because of its stretchability and conductivity?
Silver nanowire‑embedded silicone
Copper foil
Aluminum wire
Stainless steel mesh
Explanation - Silver nanowire networks within silicone provide conductive pathways that stretch with the skin.
Correct answer is: Silver nanowire‑embedded silicone
Q.122 In an implantable pressure sensor that uses a capacitive principle, the dielectric material must have:
High dielectric constant and low loss
Magnetic permeability
High thermal conductivity
Optical opacity
Explanation - A high‑k, low‑loss dielectric maximizes capacitance change with pressure while preserving signal integrity.
Correct answer is: High dielectric constant and low loss
Q.123 Which of the following is a key advantage of using a biodegradable polymer such as PLGA for temporary neural probes?
Permanent electrical conductivity
Elimination of surgical removal after functional period
High magnetic susceptibility
Optical transparency
Explanation - PLGA degrades safely, allowing the probe to disappear after data collection is complete.
Correct answer is: Elimination of surgical removal after functional period
Q.124 A medical device that must transmit data through the body using ultrasound typically employs a matching layer made of:
Parylene‑C
Silicone rubber
Aluminum
Copper
Explanation - Silicone's acoustic impedance can be tuned to match tissue, improving ultrasound transmission.
Correct answer is: Silicone rubber
Q.125 Why is a low‑modulus material such as polyurethane preferred for the outer housing of a soft robotic prosthetic hand?
It provides high electrical conductivity
It allows the device to conform to the user's movements without causing pressure points
It is magnetic
It is highly radiopaque
Explanation - Flexibility improves comfort and reduces tissue irritation.
Correct answer is: It allows the device to conform to the user's movements without causing pressure points
Q.126 Which property of a polymeric encapsulant is most important for an implant that will be exposed to chronic electrical stimulation?
High dielectric strength
Low optical transmission
Magnetic permeability
High thermal expansion
Explanation - The encapsulant must withstand high voltages without breakdown.
Correct answer is: High dielectric strength
Q.127 What is the primary reason for using a thin titanium nitride (TiN) coating on micro‑electrode arrays?
To increase magnetic susceptibility
To improve charge injection capacity and reduce impedance
To make the electrodes biodegradable
To enhance optical reflectivity
Explanation - TiN provides a high surface area and stable electrochemical interface.
Correct answer is: To improve charge injection capacity and reduce impedance
Q.128 For a fully implantable optical stimulator, the window material must be:
Opaque to visible light
Transparent to the stimulation wavelength and biocompatible
Highly magnetic
Conductive
Explanation - Light must pass through the window without attenuation while remaining safe for tissue.
Correct answer is: Transparent to the stimulation wavelength and biocompatible
Q.129 Which material is most often used for the conductive traces of a flexible cardiac rhythm monitor?
Gold on polyimide
Aluminum on glass
Copper on steel
Nickel on ceramic
Explanation - Gold provides corrosion resistance and maintains conductivity on a flexible polyimide substrate.
Correct answer is: Gold on polyimide
Q.130 A critical design factor for an implantable antenna is its:
Mechanical stiffness
Dielectric loss tangent of the surrounding encapsulant
Magnetic permeability of surrounding tissue
Optical absorption
Explanation - Low loss maintains antenna efficiency and reliable wireless communication.
Correct answer is: Dielectric loss tangent of the surrounding encapsulant
Q.131 Which property of a biomaterial makes it suitable for use as a coating on a cardiac stent to reduce restenosis?
High electrical conductivity
Controlled drug release capability
Magnetic properties
Optical clarity
Explanation - Drug‑eluting coatings release antiproliferative agents, decreasing tissue growth that can re‑occlude the vessel.
Correct answer is: Controlled drug release capability
Q.132 The main advantage of using a bio‑inert ceramic (e.g., alumina) as an insulating layer in a neural stimulator is:
High magnetic permeability
Excellent electrical insulation and durability
Electrical conductivity
Optical transparency
Explanation - Ceramics resist corrosion and provide reliable isolation in harsh bodily environments.
Correct answer is: Excellent electrical insulation and durability
Q.133 Which characteristic of a material determines its suitability for a biodegradable scaffold that must support tissue growth before resorption?
High electrical conductivity
Controlled mechanical strength and degradation rate
Magnetic susceptibility
Optical reflectivity
Explanation - The scaffold must be strong enough initially, then degrade as new tissue takes over.
Correct answer is: Controlled mechanical strength and degradation rate
Q.134 A flexible implantable glucose sensor often incorporates a nanostructured metal surface. What is the primary benefit of nanostructuring?
Increasing magnetic field interaction
Reducing mechanical strength
Increasing surface area for enzyme immobilization
Changing optical color
Explanation - Nanostructures provide more sites for the enzyme, improving sensor sensitivity.
Correct answer is: Increasing surface area for enzyme immobilization
Q.135 Which polymer is commonly used as a soft, biocompatible matrix for embedding micro‑LEDs in an optogenetic implant?
Polydimethylsiloxane (PDMS)
Polyethylene terephthalate (PET)
Polystyrene
Polyvinyl chloride (PVC)
Explanation - PDMS is optically clear, flexible, and biocompatible, ideal for housing micro‑LEDs.
Correct answer is: Polydimethylsiloxane (PDMS)
Q.136 The use of a high‑k dielectric material such as hafnium oxide (HfO₂) in an implantable MEMS pressure sensor primarily improves:
Mechanical strength
Capacitive sensitivity
Magnetic shielding
Optical transparency
Explanation - Higher dielectric constant increases capacitance change per unit pressure, enhancing sensor resolution.
Correct answer is: Capacitive sensitivity
Q.137 Which property makes titanium alloy Ti‑6Al‑4V especially suitable for long‑term bone fixation devices?
High magnetic susceptibility
Low density and high corrosion resistance
Electrical conductivity
Optical reflectivity
Explanation - Ti‑6Al‑4V combines lightweight strength with a stable oxide surface that resists bodily fluids.
Correct answer is: Low density and high corrosion resistance