5.4 Microfluidic actuation and control systems

Microfluidic actuation and control systems are the backbone of tiny liquid-handling devices. They use clever tricks like electrowetting and pressure to move droplets around, making lab-on-a-chip tech possible. It's like having a mini science lab that fits in your pocket!

These systems include essential parts like microvalves and micropumps. They let us do cool stuff like mix tiny amounts of chemicals, manipulate individual droplets, and even analyze single cells. It's all about shrinking down lab processes to save time and materials.

Microfluidic Actuation Mechanisms

Electrowetting and Dielectrophoresis

Top images from around the web for Electrowetting and Dielectrophoresis

• 

  Automated Raman based cell sorting with 3D microfluidics - Lab on a Chip (RSC Publishing) DOI:10 ... View original

  Is this image relevant?

• 

  Frontiers | Deep learning with microfluidics for on-chip droplet generation, control, and analysis View original

  Is this image relevant?

• 

  Frontiers | Conquering the Tyranny of Number With Digital Microfluidics View original

  Is this image relevant?

• 

  Automated Raman based cell sorting with 3D microfluidics - Lab on a Chip (RSC Publishing) DOI:10 ... View original

  Is this image relevant?

• 

  Frontiers | Deep learning with microfluidics for on-chip droplet generation, control, and analysis View original

  Is this image relevant?

1 of 3

Top images from around the web for Electrowetting and Dielectrophoresis

• 

  Automated Raman based cell sorting with 3D microfluidics - Lab on a Chip (RSC Publishing) DOI:10 ... View original

  Is this image relevant?

• 

  Frontiers | Deep learning with microfluidics for on-chip droplet generation, control, and analysis View original

  Is this image relevant?

• 

  Frontiers | Conquering the Tyranny of Number With Digital Microfluidics View original

  Is this image relevant?

• 

  Automated Raman based cell sorting with 3D microfluidics - Lab on a Chip (RSC Publishing) DOI:10 ... View original

  Is this image relevant?

• 

  Frontiers | Deep learning with microfluidics for on-chip droplet generation, control, and analysis View original

  Is this image relevant?

1 of 3

• Electrowetting uses an applied electric field to modify the wetting properties of a surface
  • Allows precise control over the movement and manipulation of small liquid droplets on a surface
  • Commonly used in digital microfluidics for applications such as lab-on-a-chip devices and liquid lenses
• Dielectrophoresis employs non-uniform electric fields to induce a force on dielectric particles or droplets
  • Enables the manipulation, separation, and sorting of particles based on their size, shape, and dielectric properties
  • Finds applications in cell sorting, particle trapping, and micro-scale assembly

Pressure-Driven Actuation: Pneumatic and Hydraulic

• Pneumatic actuation utilizes compressed air or gas to control the movement of fluids in microfluidic devices
  • Offers fast response times and high force generation
  • Commonly used in microfluidic valves, pumps, and actuators for flow control and fluid manipulation
• Hydraulic actuation employs pressurized liquids to drive fluid movement and control in microfluidic systems
  • Provides precise control over flow rates and pressures
  • Finds applications in microfluidic systems requiring stable and continuous flow, such as in drug delivery and cell culture

Capillary Action

• Capillary action is the spontaneous movement of liquids through narrow spaces due to surface tension and adhesive forces between the liquid and the surface
  • Enables passive fluid transport in microfluidic devices without the need for external actuation
  • Widely used in paper-based microfluidics, lateral flow assays (pregnancy tests), and capillary-driven microfluidic systems

Microfluidic Components

Microvalves

• Microvalves are miniaturized valves used to control and regulate fluid flow in microfluidic devices
  • Can be actuated using various mechanisms, such as pneumatic, electrostatic, or piezoelectric actuation
  • Enable precise control over fluid routing, switching, and isolation in complex microfluidic networks
• Different types of microvalves include check valves, diaphragm valves, and pinch valves
  • Check valves allow fluid flow in only one direction, preventing backflow
  • Diaphragm valves use a flexible membrane to open or close a fluid channel
  • Pinch valves compress a flexible tube to stop or allow fluid flow

Micropumps

• Micropumps are miniaturized pumps used to generate and control fluid flow in microfluidic devices
  • Can be categorized into mechanical and non-mechanical pumps based on their actuation mechanism
  • Mechanical pumps include peristaltic pumps, diaphragm pumps, and rotary pumps
  • Non-mechanical pumps include electroosmotic pumps, magnetohydrodynamic pumps, and acoustic pumps
• Micropumps are essential components in microfluidic systems for applications such as drug delivery, cell culture, and chemical synthesis

Lab-on-a-Chip Devices

• Lab-on-a-chip devices integrate multiple laboratory functions on a single microfluidic chip
  • Enable miniaturization, automation, and parallelization of complex biological and chemical assays
  • Offer advantages such as reduced sample and reagent consumption, faster analysis times, and improved sensitivity and specificity
• Examples of lab-on-a-chip applications include point-of-care diagnostics, drug discovery, and environmental monitoring
  • Point-of-care diagnostic devices can perform rapid and accurate testing for diseases using small sample volumes
  • Drug discovery platforms can screen large numbers of compounds using microfluidic arrays and cell-based assays
  • Environmental monitoring devices can detect pollutants and contaminants in water and air samples using integrated sensors and microfluidic sample preparation

Microfluidic Manipulation Techniques

Microfluidic Mixing

• Microfluidic mixing is the process of combining and homogenizing fluids at the microscale
  • Challenging due to the laminar flow nature of microfluidics, where mixing occurs primarily through diffusion
  • Various mixing strategies have been developed to enhance mixing efficiency, such as passive and active mixing
• Passive mixing techniques rely on channel geometry and surface features to induce chaotic advection and improve mixing
  • Examples include serpentine channels, herringbone structures, and split-and-recombine mixers
• Active mixing techniques use external energy sources to generate perturbations and enhance mixing
  • Examples include acoustic mixing, electrokinetic mixing, and magnetic mixing

Droplet Manipulation

• Droplet manipulation involves the generation, control, and processing of discrete droplets in microfluidic devices
  • Enables the compartmentalization of reactions, high-throughput screening, and single-cell analysis
  • Droplets can be generated using various techniques, such as flow-focusing, T-junction, and co-axial devices
• Droplet manipulation techniques include droplet merging, splitting, sorting, and trapping
  • Droplet merging combines two or more droplets to initiate reactions or mix reagents
  • Droplet splitting divides a single droplet into multiple smaller droplets
  • Droplet sorting separates droplets based on their properties, such as size or fluorescence
  • Droplet trapping immobilizes droplets for long-term observation or analysis
• Applications of droplet microfluidics include single-cell sequencing, enzyme kinetics studies, and directed evolution experiments
  • Single-cell sequencing isolates individual cells in droplets for high-throughput genetic analysis
  • Enzyme kinetics studies use droplets as miniaturized reactors to measure reaction rates and optimize conditions
  • Directed evolution experiments employ droplets to screen large libraries of mutant enzymes or proteins for desired properties