Micro-fluid Ejection Head Thermal Management for High Viscosity Fluids
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Solution Overview
Problem
Micro-fluid ejection devices face challenges in reliably jetting high viscosity fluids due to clogging and initial ejection issues when the jet head is uncapped or idle, especially when viscosities exceed 20 mPa-sec, requiring maintenance procedures like wipers or suction to clear nozzles.
Innovation Solution
Applying a heat signal to pre-heat the ejection head to a temperature 20°C above the steady state ejection temperature, followed by a firing signal with specific pulse durations to initiate and maintain fluid ejection, eliminating the need for thermal wipers or elaborate maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the jet head is left uncapped for relatively short periods without wiping or maintenance, then operation simplicity is improved, but fluid ejection reliability deteriorates due to clogging
Solution Approach 1:
The system performs preliminary heating of the jet head before fluid ejection to prevent clogging during idle periods. By maintaining the jet head at an elevated temperature (heating to a first temperature that is about 20°C above steady state ejection temperature), the fluid viscosity is reduced and prevent solidification or excessive thickening that would cause clogging, thereby eliminating the need for wiping maintenance while ensuring reliable ejection.
Solution Approach 2:
The system dynamically changes the temperature parameter of the jet head based on operational state. During idle periods, the jet head is heated to a higher first temperature to prevent clogging. During active ejection, the temperature is maintained at a lower steady state ejection temperature. This parameter change allows the system to operate without maintenance while maintaining reliability.
2Reliability
If the jet head is heated to high temperature continuously, then fluid viscosity is reduced improving ejection reliability, but energy consumption increases
Solution Approach 1:
The system applies heating periodically rather than continuously. A heat signal is applied to heat the jet head to the first elevated temperature during idle periods or initial stages. Once the fluid is flowing or after a certain period, the heating is reduced to maintain only the steady state ejection temperature. This periodic heating approach ensures reliable ejection while minimizing energy consumption.
Solution Approach 2:
The system applies excessive heating (heating to a first temperature about 20°C above steady state) only when necessary - specifically during initial operation or after idle periods when clogging risk is highest. During normal continuous operation, only the minimum necessary heating (steady state ejection temperature) is applied. This partial excessive action ensures reliability when needed while reducing energy consumption during normal operation.
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
Ensures reliable and repeatable ejection of high viscosity fluids without nozzle clogging, maintaining ejection head functionality for extended periods without maintenance, and adapting for fluids transitioning from solid to liquid phases.
Implementation Method 1
applying a heat signal to the ejection head for a first period of time to heat the ejection head to a first temperature that is about 20°C above a steady state fluid ejection temperature
Implementation Method 2
heating the ejection head to a first temperature that is about 20°C above a steady state fluid ejection temperature for continuous or intermittent fluid ejection
Data Source
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AI summary
Methods for ejecting fluids having a viscosity ranging from about 20 mPa-sec to about 100 mPa-sec at 22° C from a micro-fluid ejection head. The methods include the steps of applying a heat signal to the ejection head for a first period of time to heat the ejection head to a first temperature that is about 20 °C above a steady state fluid ejection temperature for continuous or intermittent fluid ejection from the ejection head; and subsequently, applying a firing signal to ejection heaters on the ejection head during which fluid ejection from the ejection head occurs.