Non-Contact Thermistor Level Detection in Microplate Washers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for monitoring the filling level in microtiter plates during washing processes are unreliable due to contamination risks, dependence on fluid properties, and indirect measurement methods, which limit accurate fluid volume determination and increase complexity and costs.
Innovation Solution
A non-contact filling level sensor system using temperature-dependent PTC resistors placed outside the receiving body of microtiter plates, allowing for indirect temperature transition and resistance changes to indicate filling levels without contamination, with each channel monitored separately using a measurement bridge for accurate volume verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical methods are used to monitor filling level by observing fluid columns with photoelectric sensors, then fluid volume can be determined indirectly, but the measurement reliability deteriorates due to dependence on fluid properties, flow rate, foaming, channel condition, and media transparency
Solution Approach 1:
A thermistor is placed inside an insulating seal (intermediary component) that is inserted into the piston rod. The thermistor measures temperature changes of the piston rod caused by fluid contact, rather than directly contacting the fluid itself. This intermediary arrangement allows reliable filling level detection without the measurement being affected by fluid optical properties, foaming, or channel conditions.
Solution Approach 2:
The patent replaces optical measurement methods with a thermal-based measurement system. Instead of using photoelectric sensors to observe fluid columns optically, the system uses a thermistor to detect temperature changes in the piston rod that occur when fluid contacts it during filling. This substitution eliminates dependence on fluid transparency and optical properties.
2Measurement precision
If conductivity methods with electrically conductive contacts are used to determine fluid volume, then volume can be measured through short-circuiting contacts, but measurement reliability deteriorates due to foam formation, conductive crystal bridge development, and fluid metallic components causing contamination
Solution Approach 1:
The thermistor is enclosed within an insulating seal that acts as an intermediary barrier between the sensor and the fluid. This prevents direct electrical contact between the measurement system and the fluid, eliminating problems associated with conductive crystal bridges, foam formation, and metallic component contamination while still allowing temperature-based volume measurement.
Solution Approach 2:
The patent replaces electrical conductivity-based measurement with thermal-based measurement. Instead of using conductive contacts that short-circuit when fluid reaches them, the system uses a thermistor to detect temperature changes in the piston rod. This substitution eliminates all reliability issues associated with conductive measurement methods.
3Measurement precision
If individual pumps are used for each channel instead of a single pump distributing fluid to multiple channels, then fluid flow can be monitored per channel, but device complexity and tubing complexity increase significantly
Solution Approach 1:
The insulating seal with the embedded thermistor acts as an intermediary measurement point in the common fluid line. This allows the system to maintain a simple single-pump architecture with minimal tubing while still enabling per-channel monitoring through the thermistor's detection of temperature changes when fluid reaches the piston rod.
4Measurement precision
If thermistors are placed inside pipettes to detect filling levels, then solid-gaseous and gaseous-solid changes of state can be detected, but the thermistor becomes contaminated by direct contact with the fluid
Solution Approach 1:
The insulating seal serves as an intermediary structure that houses the thermistor while preventing direct fluid contact. The seal is inserted into the piston rod, and the thermistor measures temperature changes of the piston rod itself rather than contacting the fluid directly. This eliminates contamination while preserving filling level detection capability.
Solution Approach 2:
The insulating seal acts as a protective shell enclosing the thermistor. This shell allows the thermistor to be positioned in the fluid path for accurate measurement while preventing direct contact between the thermistor and the fluid, thus avoiding contamination.
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
Enables reliable, non-contact monitoring of fluid levels and volumes in microtiter plates, reducing contamination risks and complexity, while improving process control and accuracy in microplate washers.
Implementation Method 1
at least one thermistor (15) extending along an outside of the wall (13a) of the receiving body (13), in particular without contact with the liquid, is used as the filling level sensor
Implementation Method 2
temperature-dependent PTC resistors placed outside the receiving body of microtiter plates, allowing for indirect temperature transition and resistance changes to indicate filling levels
Data Source
AI summary
A device and a method are used for measuring the filling level of a fluid for monitoring a dispense/aspirate process in reaction vessels, including at least one cavity for dispensing and aspirating the fluid, where the cavity is provided with a filling level sensor whose signals, transmitted to an evaluation unit, are evaluated to determine the filling level, the at least one cavity is assigned a receiving body which is closed at the bottom and is separated from the cavity for receiving the fluid, the filling level sensor is at least one thermistor extending along the outside of a wall of the receiving body without coming in contact with the fluid, the evaluation unit evaluates the temperature influence of the thermistor in dispensing, aspirating and in retention of the fluid in the receiving body to detect the filling level, in this way the process monitoring in washing the reaction vessels is improved.