Microactuator : Design, Working, Types & Its Applications

Generally, an actuator uses an energy source for moving or controlling mechanical components. These are frequently found in various machines and electric motors. For many years, different types of mechanical devices have been miniaturized, although this procedure normally needs the individual’s very smaller components. In the 21st century, microactuators were developed where Industrial processes like micromachining & lithography are mainly used to make a microactuator.  This article discusses an overview of a microactuator – working with applications.

Microactuator Definition

A microscopic servomechanism used to supply & transmit a measured amount of energy for the system or another mechanism operation is known as a microactuator. Like a general actuator, a microactuator has to meet these standards like fast switching, large travel, high precision, less power consumption, etc. These actuators are available in different sizes which vary from millimeters to micrometers, but once they are packaged they can achieve the whole size in centimeters,

Once the mechanical motion of solids is generated, then these actuators’ typical displacements range from nanometers to millimeters. Similarly, the typical flow rates generated for these actuators range from picoLiter or minute to microLiter or minute ranges. The Microactuator diagram is shown below.


Micro Actuator Construction

The following figures show three thermal microactuator designs biomaterial actuator, bent-beam actuator & flexure actuator. The design of thermal actuators with a single material is symmetric which is known as bent-beam or V-shaped.

Microactuator Design
                                     Microactuator Design

The bi-material actuator includes materials with different thermal expansion coefficients & works equally to a bimetallic thermostat. Whenever the temperature changes because of an embedded heater in the actuator, the microactuator can move because of the variation within the expansion associated with the variation within the temperature.

The bent-beam actuator includes angled legs which are helpful in expanding once heated and provide force and displacement output. The flexure actuator is asymmetric which includes a hot arm & a cold arm. These actuators include asymmetric legs that bend to the surface due to differential expansion once heated.


Working of Microactuator

The working principle of a Microactuator is to generate mechanical motion of fluids or solids where this motion is generated via changing one form of energy to another energy like from thermal, electromagnetic, or electrical into kinetic energy (K.E) of movable components. For most of the actuators, different force generation principles are used like the piezo effect, bimetal effect, electrostatic forces & shape memory effect. Like a general actuator, a microactuator has to meet these standards like fast switching, large travel, high precision, less power consumption, etc.

The mechanical actuator includes a power supply, transduction unit, actuating element, and output action.

Microactuator Working
                                          Microactuator Working
  • The power supply is Electrical current/voltage.
  • The transduction unit converts the right form of the power supply into the preferred form of actions of the actuating element.
  • Actuating element is a component or material that moves through the power supply.
  • Output action is generally in a prescribed motion.

Microactuator Types

Microactuators are available in different types which are discussed below.

  • Thermal Microactuator
  • MEMS Microactuator
  • Electrostatic Micro Actuator
  • Piezoelectric

Thermal Microactuator

A thermal microactuator is a standard component that is used in Microsystems. These components are electrically powered through Joule heating otherwise optically activated by using a laser. These actuators are used in MEMS designs which include nanopositioners & optical switches. The main benefits of thermal microactuators mainly include less operating voltages, high generation of force, and less vulnerability to adhesion failures as compared to electrostatic actuators. These actuators need more power & their switching speeds are limited through cooling times.

Thermal Micro Actuator
Thermal Micro Actuator

For designing and testing these microactuators, a wide range of work has to be done. So these microactuators are designed with different microfabrication methods like silicon-on-insulator processing & surface micromachining. The applications of microactuators mainly include tunable impedance RF networks, micro-relays, very accurate medical instrumentation, and many more.

MEMS Microactuator

MEMS microactuator is one kind of Micro Electro Mechanical System and its main function o this is to change the energy into motion. These actuators combine electrical & mechanical components with micrometer dimensions. So, the typical motions attained by these actuators are micrometers. MEMS microactuators are mainly used in different applications like ultrasonic emitters, optical beam deflection micromirrors & camera focus systems. So these types of microactuators are mainly used to produce a controlled deflection.


Electrostatic Micro Actuator

A microactuator driving units which are driven through electrostatic force is known as an electrostatic microactuator. The electrostatic microactuator is becoming the most significant building block within computing systems & optical signal processing because of its high density, small size, low power consumption & high speed. In general, the operation principle within these systems can be explained as electrostatic attractive energy causing a mechanical revolution, conversion or mirror plate deformation, controlling the phase, power, or light beam direction when it transmits throughout some free space or medium.

Electrostatic Micro Actuator
Electrostatic Micro Actuator

In this type of microactuator, each driving unit includes wave-like electrodes where these electrodes are pulled & insulated from each other through the electrostatic force. This type of actuator deformation mainly depends on the electrostatic force, the external force & the structure’s elasticity.

This actuator’s motion was simply analyzed through the FEM (finite-element method) & this actuator’s macro model was fabricated to verify its motion. So, it was confirmed that the actuator’s apparent compliance can be controlled by a feedback control system using capacitive displacement sensing and electrostatic driving.

Piezoelectric Micro Actuator

Piezoelectric microactuators are very famous and most frequently used in different fields. These are designed by mounting piezoelectric elements on top of each other. Once a voltage is given to both sides of these elements, then they can expand. But it has a complicated structure so it is complex to assemble. Piezoelectric micro-actuator is used in different servo control systems to provide ultra-precise positioning & compensation with the potential.

Piezoelectric Type
Piezoelectric Type

Please refer to this link to know about a Piezoelectric Actuator.

Advantages and Disadvantages

The advantages of microactuators include the following.

  • The thermal microactuators’ benefits are less operating voltages, generation of force is high, and less susceptibility to adhesion failures when compared to electrostatic actuators.
  • The microactuators are available in a smaller size, with less power consumption & faster response system.

The disadvantages of microactuators include the following.

  • Thermal microactuators need more power.
  • The switching speed of thermal microactuators is limited by cooling times.

Microactuator Applications

The applications of microactuators include the following.

  • Microactuator is a small active device used to produce mechanical motion of fluids/ solids. Here motion is produced by changing one form of energy to another form.
  • Microactuators are applicable in microfluidics for Lab-on-a-Chip & Implantable Drug Delivery Systems.
  • It is a microscopic servomechanism that transmits & supplies a measured amount of energy for another system/mechanism operation.
  • Microactuators are used for building small mirrors for projectors & displays.
  • MEMS microactuators are mainly used in different applications like ultrasonic emitters, camera focus systems & optical beam deflection micromirrors.
  • The force produced by an electric microactuator is mainly utilized to generate mechanical deformations within the material of interest.

Thus, this is all about an overview of the Microactuator which is capable of performing the conventional tool’s tasks within the macroworld, however, they are very smaller in size & allow greater precision. Micro actuator examples mainly include an optical matrix switch collected with torsional micromirrors which are driven through electrostatic force, a microactuator used for microwave antenna scanning, a microactuator with thin film memory alloy & 3-dimensional microstructure self-assembly with scratch drive microactuators. Here is a question for you, what is MEMS?