2025 question paper

Bio MEMS

26 questions

1. Q1(a). Which of the following polymers is most commonly used in Soft Lithography for microfluidics? (i) PMMA (ii) PDMS (iii) Teflon (iv) Polycarbonate2025?m

   Module 2: Fundamentals of Microfluidic Systems

   Which of the following polymers is most commonly used in Soft Lithography for microfluidics?

   (i) PMMA
   (ii) PDMS
   (iii) Teflon
   (iv) Polycarbonate

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   Worked Solution

   Answer: (ii) PDMS

   PDMS (Polydimethylsiloxane) is the most widely used polymer in soft lithography for microfluidics because it is transparent, flexible, biocompatible, gas-permeable, and easy to mold into microchannels.

2. Q1(b). SU-8 is an example of: (i) Positive Photoresist (ii) Negative Photoresist (iii) Electron Beam Resist (iv) Inorganic Resist2025?m

   Module 3: Fabrication Techniques

   SU-8 is an example of:

   (i) Positive Photoresist
   (ii) Negative Photoresist
   (iii) Electron Beam Resist
   (iv) Inorganic Resist

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   Worked Solution

   Answer: (ii) Negative Photoresist

   SU-8 is an epoxy-based negative photoresist. The exposed regions polymerize and become resistant to the developer, allowing high-aspect-ratio microstructures to be formed.

3. Q1(c). In microfluidic channels, the fluid flow is predominantly: (i) Turbulent (ii) Transitional (iii) Laminar (iv) Inviscid2025?m

   Module 2: Fundamentals of Microfluidic Systems

   In microfluidic channels, the fluid flow is predominantly:

   (i) Turbulent
   (ii) Transitional
   (iii) Laminar
   (iv) Inviscid

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   Worked Solution

   Answer: (iii) Laminar

   Microfluidic flows generally have low Reynolds numbers because channel dimensions and flow velocities are small. Therefore, viscous forces dominate inertial forces and the flow is predominantly laminar, with little turbulent mixing.

4. Q1(d). The LIGA process utilizes which type of radiation for lithography? (i) Ultraviolet (UV) (ii) X-ray (iii) Infrared (iv) Visible Light2025?m

   Module 3: Fabrication Techniques

   The LIGA process utilizes which type of radiation for lithography?

   (i) Ultraviolet (UV)
   (ii) X-ray
   (iii) Infrared
   (iv) Visible Light

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   Worked Solution

   Answer: (ii) X-ray

   LIGA uses deep X-ray lithography to create high-aspect-ratio microstructures. The X-rays expose a thick resist, traditionally PMMA, through a mask.

5. Q1(e). Which of the following is an example of an Active Microvalve? (i) Check Valve (ii) Piezoelectric Valve (iii) Flap Valve (iv) Ball Valve2025?m

   Module 5: Microfluidic Actuation Systems: Micropumps and Valves

   Which of the following is an example of an Active Microvalve?

   (i) Check Valve
   (ii) Piezoelectric Valve
   (iii) Flap Valve
   (iv) Ball Valve

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   Worked Solution

   Answer: (ii) Piezoelectric Valve

   A piezoelectric valve is an active microvalve because an external electrical signal produces mechanical deformation of the piezoelectric actuator, which opens or closes the fluid path.

6. Q1(f). The term μTAS stands for: (i) Micro Thermal Analysis System (ii) Micro Total Analysis System (iii) Micro Tissue Actuation System (iv) Micro Transport and Sensing2025?m

   Module 4: Microfluidic Integration and Lab-on-Chip Systems

   The term μTAS stands for:

   (i) Micro Thermal Analysis System
   (ii) Micro Total Analysis System
   (iii) Micro Tissue Actuation System
   (iv) Micro Transport and Sensing

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   Worked Solution

   Answer: (ii) Micro Total Analysis System

   μTAS stands for Micro Total Analysis System. It integrates several laboratory operations such as sample preparation, mixing, separation, reaction and detection on a miniaturized platform.

7. Q1(g). Dielectrophoresis (DEP) is a technique commonly used in BioMEMS for: (i) Etching silicon (ii) Cell manipulation and separation (iii) Polymer curing (iv) Optical detection2025?m

   Module 6: BioMEMS and Microscale Techniques for Biomedical Applications

   Dielectrophoresis (DEP) is a technique commonly used in BioMEMS for:

   (i) Etching silicon
   (ii) Cell manipulation and separation
   (iii) Polymer curing
   (iv) Optical detection

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   Worked Solution

   Answer: (ii) Cell manipulation and separation

   Dielectrophoresis (DEP) uses a non-uniform electric field to exert a force on polarizable particles such as cells. By controlling the field and frequency, different cells can be trapped, moved, concentrated or separated.

8. Q1(h). Which etching process is isotropic in nature? (i) Wet Chemical Etching (ii) Deep Reactive Ion Etching (DRIE) (iii) Plasma Etching (iv) Ion Beam Milling2025?m

   Module 1: MEMS Overview

   Which etching process is isotropic in nature?

   (i) Wet Chemical Etching
   (ii) Deep Reactive Ion Etching (DRIE)
   (iii) Plasma Etching
   (iv) Ion Beam Milling

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   Worked Solution

   Answer: (i) Wet Chemical Etching

   Wet chemical etching is generally isotropic, meaning material is removed at approximately similar rates in different directions. This can cause lateral undercutting beneath a mask. Some wet etchants can be crystal-orientation dependent, but in the standard classification used in this question, wet etching is treated as isotropic.

9. Q1(i). The dominant force scaling advantage in MEMS at the micro-scale is: (i) Gravity (ii) Inertia (iii) Surface Tension (iv) Magnetic Force2025?m

   Module 1: MEMS Overview

   The dominant force scaling advantage in MEMS at the micro-scale is:

   (i) Gravity
   (ii) Inertia
   (iii) Surface Tension
   (iv) Magnetic Force

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   Worked Solution

   Answer: (iii) Surface Tension

   At the microscale, surface-area-to-volume ratio becomes very large. As a result, surface-related forces such as surface tension and adhesion become much more significant compared with body forces such as gravity.

10. Q1(j). A Lab-on-a-Chip integrates: (i) Only sensors (ii) Only actuators (iii) Multiple laboratory functions on a single chip (iv) Only data processing units2025?m

    Module 4: Microfluidic Integration and Lab-on-Chip Systems

    A Lab-on-a-Chip integrates:

    (i) Only sensors
    (ii) Only actuators
    (iii) Multiple laboratory functions on a single chip
    (iv) Only data processing units

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    Worked Solution

    Answer: (iii) Multiple laboratory functions on a single chip

    A Lab-on-a-Chip (LoC) miniaturizes and integrates laboratory operations such as sample preparation, transport, mixing, separation, reaction and detection onto a small chip.

12. Q2(a). Define MEMS. Discuss the history of MEMS development and highlight the salient features of MEMS technology.20257m

    Module 1: MEMS Overview

    Define MEMS. Discuss the history of MEMS development and highlight the salient features of MEMS technology.

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    Worked Solution

    MEMS: Definition, History and Salient Features

    MEMS (Micro-Electro-Mechanical Systems) are miniaturized systems that integrate mechanical structures, sensors, actuators and electronic circuits, generally fabricated using microfabrication techniques on a small substrate such as silicon.

    Brief history

    • 1950s–60s: Development of semiconductor fabrication and silicon technology provided the foundation for miniaturized devices.
    • 1960s: Early silicon pressure sensors and micromachined structures demonstrated practical MEMS concepts.
    • 1970s–80s: Surface and bulk micromachining developed rapidly; accelerometers and other sensors became feasible.
    • 1990s: MEMS accelerometers entered automotive airbag systems, while micromachined optical and fluidic devices expanded applications.
    • 2000s onward: MEMS became widespread in smartphones, medical devices, inertial sensors, microphones, microfluidics and biomedical systems.

    Salient features

    1. Very small size and low mass.
    2. Low power consumption.
    3. Batch fabrication enables high-volume production.
    4. Integration of mechanical and electronic functions.
    5. High sensitivity and fast response.
    6. Low material consumption.
    7. Ability to integrate sensors, actuators and signal processing.
    8. Applications across automotive, aerospace, healthcare, consumer electronics and industrial systems.

    Conclusion: MEMS combines mechanical and electronic engineering at the microscale to create compact, sensitive and multifunctional devices.

13. Q2(b). Explain the standard Photolithography process flow with the help of neat diagrams.20257m

    Module 1: MEMS Overview

    Explain the standard Photolithography process flow with the help of neat diagrams.

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    Worked Solution

    Standard Photolithography Process Flow

    Photolithography transfers a geometric pattern from a mask onto a photoresist-coated substrate.

    Steps

    1. Wafer cleaning: Remove particles, organic contamination and moisture from the substrate.
    2. Dehydration/bake: Heat the wafer to remove residual moisture.
    3. Photoresist coating: Spin-coat a uniform layer of photoresist.
    4. Soft bake: Remove solvent and stabilize the resist film.
    5. Mask alignment: Align the photomask with existing wafer features.
    6. UV exposure: Expose selected resist regions through the mask.
    7. Development: Developer removes the soluble portion of the resist. In a positive resist the exposed area is removed; in a negative resist the exposed area remains.
    8. Rinse and dry: Remove developer residues.
    9. Hard bake: Improve adhesion and mechanical stability where required.
    10. Etching/deposition: Transfer the resist pattern into the underlying material or use it as a mask for subsequent fabrication.
    11. Resist stripping: Remove the remaining resist after pattern transfer.

    Simplified flow

    Clean wafer → Coat resist → Soft bake → Align mask → UV exposure → Develop → Rinse → Etch/deposit → Strip resist

    Photolithography provides precise pattern definition and is fundamental to MEMS and microelectronic fabrication.

14. Q3(a). Compare and contrast Wet Etching and Dry Etching. Explain the significance of Anisotropic Etching in MEMS fabrication.20257m

    Module 1: MEMS Overview

    Compare and contrast Wet Etching and Dry Etching. Explain the significance of Anisotropic Etching in MEMS fabrication.

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    Worked Solution

    Wet Etching vs Dry Etching and Importance of Anisotropy

    Parameter	Wet Etching	Dry Etching
    Medium	Liquid chemical etchant	Plasma/reactive gas or ions
    Nature	Often isotropic; some crystal-dependent etchants are anisotropic	Can be controlled for anisotropic profiles
    Equipment	Relatively simple	More complex vacuum/plasma equipment
    Selectivity	Often high	Can be engineered through plasma chemistry
    Feature control	Lateral undercut may occur	Better control of vertical sidewalls is possible
    Waste/safety	Chemical waste and handling issues	Gas/plasma safety requirements

    Anisotropic etching

    Anisotropic etching removes material preferentially in one direction, producing steep or well-defined sidewalls rather than equal lateral and vertical removal.

    It is important in MEMS because it enables:

    • high-aspect-ratio structures,
    • accurate microchannels and cavities,
    • vertical sidewalls,
    • precise dimensions and better device performance.

    Example: DRIE can produce deep silicon structures with nearly vertical sidewalls.

15. Q3(b). Discuss the motivation for developing Microfluidic Systems. Explain how the Surface-to-Volume ratio influences micro-scale phenomena.20257m

    Module 2: Fundamentals of Microfluidic Systems

    Discuss the motivation for developing Microfluidic Systems. Explain how the Surface-to-Volume ratio influences micro-scale phenomena.

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    Worked Solution

    Motivation for Microfluidic Systems and Surface-to-Volume Ratio

    Microfluidics deals with controlling very small volumes of fluids, typically in channels with dimensions from micrometres to hundreds of micrometres.

    Motivation

    1. Very small sample and reagent consumption.
    2. Low operating cost.
    3. Rapid analysis and reaction times.
    4. High-throughput parallel processing.
    5. Integration of sample preparation, reaction and detection.
    6. Portable point-of-care diagnostic systems.
    7. Precise control of fluid transport and cellular environments.

    Surface-to-volume ratio

    For a characteristic length $L$, surface area scales approximately as $L^2$ while volume scales as $L^3$. Therefore, surface-to-volume ratio scales as $1/L$ and increases strongly as dimensions decrease.

    Consequences include:

    • surface forces and adhesion become important,
    • heat transfer becomes rapid,
    • diffusion can dominate mass transport,
    • capillary forces become significant,
    • wall interactions strongly influence fluid behavior.

    Thus, the high surface-to-volume ratio is one of the main reasons microfluidic systems behave differently from conventional fluidic systems.

16. Q4(a). Describe the different types of microfluidic channels and their working principles.20257m

    Module 2: Fundamentals of Microfluidic Systems

    Describe the different types of microfluidic channels and their working principles.

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    Worked Solution

    Types of Microfluidic Channels and Working Principles

    Microfluidic channels can be classified according to geometry and function.

    1. Straight channels

    A simple rectangular or circular passage transports fluid from inlet to outlet. At low Reynolds number, flow is mainly laminar and pressure-driven.

    2. Serpentine channels

    The channel contains repeated bends. The longer path increases residence time and can enhance mixing through repeated deformation of fluid streams.

    3. T-junction channels

    Two streams meet at a T-shaped junction. They are commonly used for controlled mixing and droplet generation.

    4. Y-junction channels

    Two inlet streams merge at an angle into one channel. They are useful for controlled co-flow and diffusion-based mixing.

    5. Flow-focusing channels

    A central stream is squeezed by side streams, allowing controlled formation of droplets or particles.

    6. Microchambers

    Expanded regions connected to channels provide space for reactions, cell trapping, sensing or incubation.

    Working principle

    Fluid movement is produced by pressure-driven flow, electroosmotic flow or other microscale actuation methods. Because flow is generally laminar, mixing is often achieved by diffusion or deliberate channel geometry rather than turbulence.

17. Q4(b). What are biocompatible polymers? Discuss the properties and applications of PDMS (Polydimethylsiloxane) in BioMEMS.20257m

    Module 2: Fundamentals of Microfluidic Systems

    What are biocompatible polymers? Discuss the properties and applications of PDMS (Polydimethylsiloxane) in BioMEMS.

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    Worked Solution

    Biocompatible Polymers and PDMS in BioMEMS

    Biocompatible polymers are polymeric materials that can perform their intended function in contact with biological tissues, cells or fluids without causing unacceptable adverse biological responses.

    Important properties of PDMS

    • Biocompatibility for many laboratory and diagnostic applications.
    • Optical transparency, useful for microscopy.
    • Flexible and elastomeric.
    • Easy replication by soft lithography.
    • Low cost and rapid prototyping.
    • Good gas permeability, especially oxygen and carbon dioxide.
    • Low surface energy and easy molding.
    • Can be bonded to glass or other substrates after surface treatment.

    Applications

    1. Microfluidic channels.
    2. Cell culture and cell manipulation platforms.
    3. Lab-on-Chip devices.
    4. Drug delivery research.
    5. Micropumps and valves.
    6. Diagnostic and biological analysis devices.

    Limitation

    PDMS can absorb some small hydrophobic molecules and its surface properties can change with treatment, so material selection must match the biomedical application.

18. Q5(a). Explain the fabrication steps for high-aspect-ratio structures using SU-8 photoresist and Ultraviolet (UV) lithography.20257m

    Module 3: Fabrication Techniques

    Explain the fabrication steps for high-aspect-ratio structures using SU-8 photoresist and Ultraviolet (UV) lithography.

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    Worked Solution

    SU-8 High-Aspect-Ratio Structures Using UV Lithography

    SU-8 is a negative epoxy-based photoresist capable of forming thick, high-aspect-ratio structures.

    Fabrication steps

    1. Substrate preparation: Clean and dehydrate the silicon/glass substrate.
    2. SU-8 coating: Dispense SU-8 and spin coat it to the required thickness. For very thick layers, multiple coating steps may be used.
    3. Soft bake: Heat the coated wafer to remove solvent.
    4. Mask alignment: Place the patterned photomask over the wafer.
    5. UV exposure: Expose the SU-8 through the mask. Exposed regions undergo cross-linking.
    6. Post-exposure bake: Further cross-link the exposed regions.
    7. Development: Developer removes the unexposed SU-8, leaving the patterned high-aspect-ratio structures.
    8. Rinse and dry: Remove developer residue.
    9. Hard bake, if required: Improves stability and mechanical robustness.

    Why SU-8 is suitable

    It provides thick films, high aspect ratios, good chemical resistance, good mechanical strength and relatively high resolution, making it useful for microchannels, molds and microstructures.

19. Q5(b). Write a detailed note on X-ray lithography and the LIGA process. What are its advantages?20257m

    Module 3: Fabrication Techniques

    Write a detailed note on X-ray lithography and the LIGA process. What are its advantages?

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    Worked Solution

    X-ray Lithography and LIGA

    X-ray lithography uses short-wavelength, high-energy X-rays to transfer a mask pattern into a thick resist. The short wavelength provides low diffraction and enables high-resolution, high-aspect-ratio structures.

    LIGA

    LIGA is a German acronym derived from Lithographie, Galvanoformung, Abformung (lithography, electroplating and molding).

    Process

    1. Coat a conductive substrate with a thick X-ray-sensitive resist such as PMMA.
    2. Align a patterned X-ray mask.
    3. Expose the resist using deep X-rays.
    4. Develop the resist to form deep cavities/columns.
    5. Electroplate metal into the resist mold.
    6. Remove the resist to obtain a metal microstructure.
    7. The metal structure can also serve as a mold for replication.

    Advantages

    • Very high aspect ratio.
    • Nearly vertical sidewalls.
    • High dimensional accuracy.
    • Excellent replication capability.
    • Suitable for relatively thick microstructures.
    • Useful for microgears, nozzles, molds and other precision MEMS structures.

    Limitation

    The process requires specialized X-ray sources and masks, making it expensive and less accessible than conventional UV lithography.

20. Q6(a). Define Micro Total Analysis Systems (μTAS). Discuss the concept and major applications of Lab-on-Chip (LoC) devices.20257m

    Module 4: Microfluidic Integration and Lab-on-Chip Systems

    Define Micro Total Analysis Systems (μTAS). Discuss the concept and major applications of Lab-on-Chip (LoC) devices.

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    Worked Solution

    μTAS and Lab-on-Chip

    μTAS (Micro Total Analysis System) is a miniaturized analytical system in which several laboratory operations are integrated on a microfluidic platform.

    Concept

    A typical LoC/μTAS can integrate:
    sample introduction → preparation → mixing → reaction → separation → detection → data processing.

    The small channel dimensions reduce sample and reagent volumes and can make analysis rapid and portable.

    Major applications

    1. Point-of-care medical diagnostics.
    2. Blood and cell analysis.
    3. DNA/RNA analysis and PCR-related workflows.
    4. Drug screening and pharmaceutical research.
    5. Environmental and chemical analysis.
    6. Food and pathogen detection.
    7. Personalized and rapid diagnostic testing.

    Advantages

    • Low sample consumption.
    • Fast analysis.
    • Small device size.
    • Potential for automation and portability.
    • Reduced reagent cost.
    • High-throughput parallel processing.
21. Q6(b). Discuss the various microfluidic strategies used for mixing and separation in LoC platforms.20257m

    Module 4: Microfluidic Integration and Lab-on-Chip Systems

    Discuss the various microfluidic strategies used for mixing and separation in LoC platforms.

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    Worked Solution

    Microfluidic Mixing and Separation Strategies in LoC

    Mixing strategies

    Because microfluidic flow is usually laminar, turbulence is weak. Mixing is therefore achieved using:

    1. Passive mixing: Channel geometry such as serpentine, herringbone, split-and-recombine, T-junction and chaotic advection structures increases interfacial area and diffusion.
    2. Droplet-based mixing: Small droplets provide short diffusion distances and can be transported through channels.
    3. Active mixing: External energy such as acoustic, magnetic, electric or pneumatic actuation disturbs the streams and enhances mixing.

    Separation strategies

    1. Filtration: Microstructures physically retain particles larger than a selected size.
    2. Hydrodynamic separation: Channel geometry and flow conditions separate particles according to size or trajectory.
    3. Dielectrophoresis: Non-uniform electric fields manipulate particles according to electrical properties.
    4. Electrophoresis: Charged particles migrate under an electric field at different rates.
    5. Magnetic separation: Magnetically labeled cells or particles are captured or deflected using magnetic fields.
    6. Centrifugal/inertial methods: Curved or specially shaped channels create forces that alter particle trajectories.

    These methods allow LoC systems to perform automated sample preparation and analysis with very small volumes.

23. Q7(a). Classify micropumps. Explain the working principle and design of a Piezoelectric Micropump.20257m

    Module 5: Microfluidic Actuation Systems: Micropumps and Valves

    Classify micropumps. Explain the working principle and design of a Piezoelectric Micropump.

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    Worked Solution

    Micropump Classification and Piezoelectric Micropump

    Classification of micropumps

    Micropumps can broadly be classified as:

    1. Mechanical/non-dynamic displacement pumps: diaphragm, peristaltic and reciprocating types.
    2. Dynamic or non-mechanical pumps: electroosmotic, electrohydrodynamic, magnetohydrodynamic and other field-driven pumps.

    They may also be described as externally actuated or self-actuated, depending on the actuation mechanism.

    Piezoelectric micropump

    A piezoelectric micropump uses a piezoelectric actuator bonded to or coupled with a flexible diaphragm.

    Basic structure:
    Piezo actuator → flexible diaphragm → pump chamber → inlet valve → outlet valve

    Working

    1. Applying an alternating voltage causes the piezoelectric element to expand/contract or bend.
    2. This deflects the diaphragm and changes the chamber volume.
    3. During one stroke, chamber expansion lowers pressure and draws fluid through the inlet valve.
    4. During the opposite stroke, chamber compression raises pressure and pushes fluid through the outlet valve.
    5. Repeated electrical excitation produces continuous pumping.

    Advantages

    • Small size.
    • Fast response.
    • Low power requirements in suitable designs.
    • Precise flow control.
    • Easy electrical control.

    Applications include drug delivery, microfluidic transport, cooling and Lab-on-Chip systems.

24. Q7(b). Differentiate between Active and Passive Microvalves. Explain the working of a Check Valve with a diagram.20257m

    Module 5: Microfluidic Actuation Systems: Micropumps and Valves

    Differentiate between Active and Passive Microvalves. Explain the working of a Check Valve with a diagram.

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    Worked Solution

    Active vs Passive Microvalves and Check Valve

    Feature	Active Microvalve	Passive Microvalve
    Actuation	Requires external energy/control	Operates mainly due to pressure/flow conditions
    Control	Can be actively opened/closed	Opening/closing depends on fluid conditions and geometry
    Examples	Piezoelectric, pneumatic, thermal valves	Check, flap, ball valves
    Complexity	Generally higher	Generally simpler

    Check valve working

    A check valve permits fluid flow primarily in one direction and prevents reverse flow.

    Simplified diagram:
    Inlet → [Valve seat / movable flap] → Outlet

    When inlet pressure exceeds the valve opening pressure, the movable element lifts away from the seat and fluid flows forward. When pressure reverses or falls, the element returns to the seat and blocks reverse flow.

    Advantages

    • Prevents backflow.
    • Simple construction.
    • Useful for directional fluid control in micropumps and microfluidic circuits.
25. Q8(a). Discuss the techniques used for microfabricated sample extraction and concentration in biomedical applications.20257m

    Module 6: BioMEMS and Microscale Techniques for Biomedical Applications

    Discuss the techniques used for microfabricated sample extraction and concentration in biomedical applications.

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    Worked Solution

    Microfabricated Sample Extraction and Concentration

    BioMEMS can miniaturize sample preparation so that small quantities of biological material are extracted and concentrated before analysis.

    Techniques

    1. Microfiltration: Membranes or microfabricated pores retain cells, particles or macromolecules according to size.
    2. Microfluidic trapping: Structures such as pillars, wells or chambers physically capture target particles or cells.
    3. Centrifugal/inertial concentration: Controlled fluid motion drives particles toward selected regions of a microchannel.
    4. Dielectrophoretic concentration: Non-uniform electric fields attract or repel polarizable cells and particles, concentrating them at electrode regions.
    5. Magnetic concentration: Magnetic beads bound to target molecules/cells are captured with magnetic fields.
    6. Electrophoretic methods: Electric fields transport charged molecules and can concentrate or separate them.
    7. Membrane-based extraction: Selective membranes can isolate target molecules or components from complex samples.

    Importance

    These techniques reduce sample volume, shorten preparation time and facilitate integration with downstream sensing and analysis on a Lab-on-Chip.

26. Q8(b). Explain the role of BioMEMS in cell manipulation. Describe the principle of Dielectrophoresis (DEP).20257m

    Module 6: BioMEMS and Microscale Techniques for Biomedical Applications

    Explain the role of BioMEMS in cell manipulation. Describe the principle of Dielectrophoresis (DEP).

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    Worked Solution

    BioMEMS for Cell Manipulation and Dielectrophoresis

    BioMEMS provides precise microscale methods for transporting, trapping, sorting, counting and analyzing biological cells.

    Applications in cell manipulation

    • Cell trapping and positioning.
    • Cell sorting and separation.
    • Concentration of rare cells.
    • Controlled cell culture environments.
    • Cell counting and characterization.
    • Isolation of specific cell populations.

    Principle of DEP

    Dielectrophoresis (DEP) is the motion of a polarizable particle in a non-uniform electric field. A cell becomes polarized when subjected to the electric field. Because the field is non-uniform, the induced electrical forces do not cancel, producing a net DEP force.

    In simplified form:
    $F_{DEP} \propto r^3 \epsilon_m Re[K(\omega)]
    abla |E|^2$

    where $r$ is particle radius, $\epsilon_m$ is medium permittivity, $K(\omega)$ is the frequency-dependent Clausius-Mossotti factor, and $E$ is electric-field strength.

    • Positive DEP: cells move toward stronger electric-field regions.
    • Negative DEP: cells move toward weaker electric-field regions.

    By changing frequency, field strength and medium properties, different cell types can be manipulated or separated.

27. Q9(a). Present a case study on a BioMEMS device, detailing its working principle and impact.20257m

    Module 6: BioMEMS and Microscale Techniques for Biomedical Applications

    Present a case study on a BioMEMS device, detailing its working principle and impact.

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    Worked Solution

    Case Study: Lab-on-Chip Blood Cell Analysis Device

    A useful BioMEMS case study is a microfluidic blood-analysis Lab-on-Chip designed to prepare, separate and detect blood components.

    Working principle

    1. A small blood sample is introduced through a microfluidic inlet.
    2. Microchannels guide the sample under controlled laminar flow.
    3. Filters or microstructures separate cells according to size, deformability or other properties.
    4. Additional microfluidic regions can concentrate or mix the sample with reagents.
    5. Sensors or optical detection zones measure the target cells or analytes.
    6. Electronics process the signal and provide an analytical result.

    Impact

    • Requires only a small sample volume.
    • Can reduce analysis time.
    • Enables portable or point-of-care testing.
    • Reduces reagent consumption.
    • Integrates sample preparation and analysis.
    • Can support rapid screening in resource-limited settings.

    Conclusion

    The integration of microfluidics, sensing and electronics demonstrates how BioMEMS can convert laboratory procedures into compact, automated diagnostic platforms.

28. Q9(b). Discuss the challenges and future scope of integrating MEMS technology into medical implants.20257m

    Module 6: BioMEMS and Microscale Techniques for Biomedical Applications

    Discuss the challenges and future scope of integrating MEMS technology into medical implants.

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    Worked Solution

    MEMS in Medical Implants: Challenges and Future Scope

    Challenges

    1. Biocompatibility: Materials must not cause unacceptable tissue reactions or toxicity.
    2. Long-term reliability: The device must operate for years despite body fluids, mechanical loading and biological conditions.
    3. Packaging: MEMS structures and electronics must be protected while maintaining required sensing or actuation functions.
    4. Power: Implantable devices require very low power and, where possible, wireless power or energy harvesting.
    5. Wireless communication: Reliable communication through biological tissue is challenging.
    6. Miniaturization: The system must remain sufficiently small without sacrificing performance.
    7. Biofouling: Proteins and cells can accumulate on surfaces and change sensor performance.
    8. Mechanical compatibility: Stiffness and deformation must be compatible with surrounding tissue.
    9. Sterilization: Materials and packaging must withstand an appropriate sterilization process.
    10. Regulatory requirements: Medical implants require extensive safety, reliability and clinical validation.

    Future scope

    • Implantable pressure, temperature and biochemical sensors.
    • Smart drug-delivery systems.
    • Neural interfaces and stimulation devices.
    • Wireless and battery-free implants.
    • Energy harvesting from body motion or physiological sources.
    • Closed-loop systems that sense a condition and automatically provide therapy.
    • Integration with microfluidics and wireless electronics.

    Conclusion: MEMS can make medical implants smaller, smarter and more precise, but long-term biocompatibility, reliability, power and regulatory validation remain major engineering challenges.