Piezoelectric Microfluidic Device for Continuous Ink Ejection
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Solution Overview
Problem
Continuous-jet microfluidic devices for inkjet printing face limitations due to the requirement for inks with varying viscosity and surface tension, which restricts the types of inks that can be used and may lead to nozzle clogging.
Innovation Solution
A MEMS-based microfluidic device with a piezoelectric actuator system that controls the ejection of a steady ink stream, allowing for the generation of droplets by varying the pressure and voltage applied to the chamber, reducing the risk of clogging and enabling the use of a wider range of inks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous jet microfluidic devices are used to maintain steady ink flow through nozzles, then nozzle clogging risk is reduced, but the device requires inks with specific viscosity and surface tension properties that vary with temperature
Solution Approach 1:
The patent employs a piezoelectric actuator that changes the physical state of ink at the nozzle by applying mechanical stress through voltage, causing rapid compression and expansion cycles that eject ink droplets. This parameter change approach allows continuous operation with various ink types without requiring specific viscosity-temperature characteristics, resolving the contradiction between reliability and adaptability.
Solution Approach 2:
The invention replaces the thermal actuation mechanism (heating) with a piezoelectric mechanical actuation system. Instead of relying on thermal effects that require ink properties to change with temperature, the piezoelectric actuator directly applies mechanical deformation to the ink chamber, enabling versatile ink compatibility while maintaining continuous jet operation and preventing clogging.
2Productivity
If drop-on-demand microfluidic devices are used with actuators to eject droplets only when needed, then ink is used efficiently for specific print areas, but nozzles remain idle for long periods leading to encrustation formation
Solution Approach 1:
The patent implements a continuous jet mode where ink flows continuously through the nozzles rather than stopping between droplet ejections. The piezoelectric actuator modulates this continuous flow to create droplets on demand while maintaining constant ink movement through the nozzle system. This continuous action prevents encrustation formation by ensuring ink always traverses the nozzle, while still achieving efficient ink usage through controlled droplet ejection timing.
3Ease of operation
If thermal actuators are used to heat ink streams for viscosity reduction and droplet generation, then droplet formation is achieved, but the system is limited to inks that exhibit appreciable viscosity variations with temperature
Solution Approach 1:
The invention substitutes the thermal field (heating) with a mechanical field (piezoelectric actuation). The piezoelectric actuator generates mechanical stress and strain in the ink chamber through voltage application, causing rapid compression and expansion that ejects droplets. This mechanical approach works with a broad range of ink types regardless of their thermal response characteristics, eliminating the limitation of requiring inks with specific temperature-dependent viscosity properties while maintaining effective droplet generation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device effectively manages ink ejection, reducing clogging risks and allowing for flexible ink usage, while maintaining a stable printing process independent of image type and speed.
Implementation Method 1
each cell has a piezoelectric actuator, which transforms electrical energy to mechanical energy in order to control ejection of a droplet from the chamber through the nozzle
Implementation Method 2
the thermal actuator heats part of the stream so as to locally reduce the viscosity and the surface tension, thus causing generation, starting from the stream of ink, of a succession of droplets
Data Source
AI summary
A microfluidic device for continuous ejection of fluids includes: a semiconductor body that laterally delimits chambers; an intermediate structure which forms membranes each delimiting a top of a corresponding chamber; and a nozzle body which overlies the intermediate structure. The device includes, for each chamber: a corresponding piezoelectric actuator; a supply channel which traverses the intermediate structure and communicates with the chamber; and a nozzle which traverses the nozzle body and communicates with the supply channel. Each actuator is configured to operate i) in a resting condition such that the pressure of a fluid within the corresponding chamber causes the fluid to pass through the supply channel and become ejected from the nozzle as a continuous stream, and ii) in an active condition, where it causes a deformation of the corresponding membrane and a consequent variation of the pressure of the fluid, causing a temporary interruption of the continuous stream.