Hollow Micro String Calorimeter for Heat Loss Reduction
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Solution Overview
Problem
Current micron-scale calorimeters face challenges due to heat loss and measurement errors caused by conductive metal layers, which complicate the detection of exothermic reactions and bio-cell activity, especially in micro or nano volume ranges.
Innovation Solution
A micron-scale calorimeter employing a vibrating micro-string as a temperature sensor, utilizing acoustical means to oscillate the string at resonance frequency and optical means to detect these frequencies, thereby avoiding the use of thermopiles and minimizing heat loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If metal electrodes and thermopile are used for heating and temperature measurement, then electrical heating and resistance-based thermometry can be implemented, but heat loss occurs through conductive metal layers and measurement errors are introduced
Solution Approach 1:
The patent replaces the electrical heating system (metal electrodes) with an acoustic heating system using surface acoustic waves (SAW). The SAW device generates heat through acoustic energy dissipation in the piezoelectric substrate, eliminating the need for conductive metal electrodes that cause heat loss. This substitution maintains heating functionality while removing the harmful thermal conduction path.
Solution Approach 2:
The patent replaces the electrical resistance-based thermometry (thermopile with metal layers) with a quality factor-based temperature sensing method. The temperature is determined by measuring changes in the quality factor (Q-factor) of the acoustic resonator, which varies with temperature. This eliminates the need for metal electrodes used for electrical resistance measurement, thereby removing the source of heat loss and measurement error.
2Measurement precision
If metal layer resistance is monitored for temperature detection, then temperature information can be obtained, but the metal layer becomes a source of heat conduction away from the measurement site
Solution Approach 1:
The patent replaces the electrical resistance-based temperature sensing mechanism with an acoustic resonance-based sensing mechanism. The temperature is inferred from changes in the resonant frequency and quality factor of the SAW resonator, which are temperature-dependent. This substitution eliminates the metal layer that causes harmful heat conduction, as the sensing is performed through acoustic properties of the piezoelectric substrate rather than electrical properties of metal electrodes.
3Device complexity
If steady state measurement is attempted, then simplified analysis is possible, but transient state and unsteady heat transfer behavior must be considered in practice
Solution Approach 1:
The patent employs periodic acoustic excitation at the resonant frequency of the SAW device to maintain steady-state oscillation. This periodic action allows the system to operate in a stable, repeatable state where the quality factor can be reliably measured. The continuous acoustic excitation ensures that the resonator remains in steady-state vibration, enabling consistent temperature measurements even during transient thermal conditions of the sample.
Solution Approach 2:
The patent uses feedback control to maintain the acoustic resonator at its resonant frequency by monitoring the quality factor and adjusting the excitation frequency accordingly. This feedback mechanism ensures that the system remains in optimal operating conditions, allowing for reliable temperature measurements during transient states. The feedback loop compensates for frequency drift and maintains measurement accuracy throughout the measurement process.
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
This approach allows for accurate identification of substances and monitoring of bio-cell activities by correlating oscillating frequencies with heat generation, providing a more reliable and efficient method for calorimetric measurements in micro or nano volumes.
Implementation Method 1
acoustical means adapted to oscillate the string at its resonance frequency by emitting sound waves in the vicinity of the string
Implementation Method 2
emitting sound waves in the vicinity of the string
Implementation Method 3
optical means adapted to detect oscillating frequencies of the string
Implementation Method 4
Heat produced in by the substances gives rise to a temperature change in the material surrounding the void
Implementation Method 5
As there exist a correlation between the oscillating frequency of the string and the heat generated in the micron-scale calorimeter
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The present invention relates to a micron-scale calorimeter and a calorimetry method utilizing the micron-scale calorimeter. In accordance with the invention, there is provided a micron-scale calorimeter comprising a micro-channel string, being restrained at at least two longitudinally distanced positions so as to form a free released double clamped string in-between said two longitudinally distanced positions said micro-channel string comprising a microfluidic channel having a closed cross section and extending in the longitudinal direction of the hollow string, acoustical means adapted to oscillate the string at different frequencies by emitting sound waves towards the string, optical means adapted to detect oscillating frequencies of the string, and controlling means controlling the strength and frequency of the sound wave emitted by the acoustical means and receiving a signal from the optical means representing the detected oscillating frequencies.