Thermal Measurement Techniques in Analytical Microfluidic Devices

Davaji, Benyamin; Lee, Chung Hoon

doi:10.3791/52828

Cited by 6 publications

(4 citation statements)

References 8 publications

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“…The achievable temperature resolution of our RTD is measured using a thermal bath setup to be 0.002 K 38,39 , which is higher compared to the thermal noise limit (Noise Equivalent Temperature) in RTD sensor (NET ~ 0.5 mK) and the resolution of our measurement system (SMU resolution ~ 0.4 mK). The resistance change of the sensor was measured in the 4-wire configuration using a Keithley 2600 source/measure unit (SMU) 40,41 . The measurements were performed at room temperature mainly to reduce the evaporation effect.…”

Section: Microscale Direct Measurement Of Localized Photothermal Heatmentioning

confidence: 99%

Microscale direct measurement of localized photothermal heating in tissue-mimetic hydrogels

Davaji

Richie

Lee

2019

Sci Rep

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Photothermal hyperthermia is proven to be an effective diagnostic tool for cancer therapy. The efficacy of this method directly relies on understanding the localization of the photothermal effect in the targeted region. Realizing the safe and effective concentration of nano-particles and the irradiation intensity and time requires spatiotemporal temperature monitoring during and after laser irradiation. Due to uniformities of the nanoparticle distribution and the complexities of the microenvironment, a direct temperature measurement in micro-scale is crucial for achieving precise thermal dose control. In this study, a 50 nm thin film nickel resistive temperature sensor was fabricated on a 300 nm SiN membrane to directly measure the local temperature variations of a hydrogel-GNR mixture under laser exposure with 2 mK temperature resolution. The chip-scale approach developed here is an effective tool to investigate localization of photothermal heating for hyperthermia applications for in-vitro and ex-vivo models. Considering the connection between thermal properties, porosity and the matrix stiffness in hydrogels, we present our results using the interplay between matrix stiffness of the hydrogel and its thermal properties: the stiffer the hydrogel, the higher the thermal conductivity resulting in lower photothermal heating. We measured 8.1, 7.4, and 5.6 °C temperature changes (from the room temperature, 20 °C) in hydrogel models with stiffness levels corresponding to adipose (4 kPa), muscle (13 kPa) and osteoid (30 kPa) tissues respectively by exposing them to 2 W/cm 2 laser (808 nm) intensity for 150 seconds.

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Section: Microscale Direct Measurement Of Localized Photothermal Heatmentioning

confidence: 99%

Microscale direct measurement of localized photothermal heating in tissue-mimetic hydrogels

Davaji

Richie

Lee

2019

Sci Rep

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“…The resistance change of the sensor due to temperature and strain is measured by the 4-wire measurement using a SMU. The details of the fabrication process and resistance measurement method are presented elsewhere [ 20 , 31 ].…”

Section: Principle Of Operationmentioning

confidence: 99%

On-chip detection of gel transition temperature using a novel micro-thermomechanical method

et al. 2017

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We present a new thermomechanical method and a platform to measure the phase transition temperature at microscale. A thin film metal sensor on a membrane simultaneously measures both temperature and mechanical strain of the sample during heating and cooling cycles. This thermomechanical principle of operation is described in detail. Physical hydrogel samples are prepared as a disc-shaped gels (200 μm thick and 1 mm diameter) and placed between an on-chip heater and sensor devices. The sol-gel transition temperature of gelatin solution at various concentrations, used as a model physical hydrogel, shows less than 3% deviation from in-depth rheological results. The developed thermomechanical methodology is promising for precise characterization of phase transition temperature of thermogels at microscale.

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“…In turn, the measurement of pressure at specific locations in a microfluidic device allows us to determine the permeability of the pattern [22] as well as correlate pressure changes with visual observations at the microscale in order to explain processes that govern subsurface systems (e.g., hydrocarbon reservoirs) [23]. Local measurements of thermal conductivity and electrical impedance can also be useful, e.g., to detect cellular response during culture [24], assess blood samples [25], count particles [26], determine the sample position in a microfluidic channel [27], or differentiate fluids in multi-phase fluid flow experiments [28].…”

Section: Introductionmentioning

confidence: 99%

“…When sensors are integrated within a microfluidic device, they increase the functionality and value of the device. Unfortunately, the fabrication of bespoke microfluidic devices with integrated sensors can be difficult, time consuming, and expensive because this requires advanced know-how and specialized equipment e.g., to develop a sensor, perform its accurate deposition and patterning, and seal the microfluidic chip without damaging the sensor [23][24][25][26][27][28][29][30]. Such microfluidic devices may also impose some limitations in conducting experiments.…”

Section: Introductionmentioning

confidence: 99%

Manufacturing of Microfluidic Devices with Interchangeable Commercial Fiber Optic Sensors

Wlodarczyk

MacPherson

Hand

et al. 2021

Sensors

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In situ measurements are highly desirable in many microfluidic applications because they enable real-time, local monitoring of physical and chemical parameters, providing valuable insight into microscopic events and processes that occur in microfluidic devices. Unfortunately, the manufacturing of microfluidic devices with integrated sensors can be time-consuming, expensive, and “know-how” demanding. In this article, we describe an easy-to-implement method developed to integrate various “off-the-shelf” fiber optic sensors within microfluidic devices. To demonstrate this, we used commercial pH and pressure sensors (“pH SensorPlugs” and “FOP-MIV”, respectively), which were “reversibly” attached to a glass microfluidic device using custom 3D-printed connectors. The microfluidic device, which serves here as a demonstrator, incorporates a uniform porous structure and was manufactured using a picosecond pulsed laser. The sensors were attached to the inlet and outlet channels of the microfluidic pattern to perform simple experiments, the aim of which was to evaluate the performance of both the connectors and the sensors in a practical microfluidic environment. The bespoke connectors ensured robust and watertight connection, allowing the sensors to be safely disconnected if necessary, without damaging the microfluidic device. The pH SensorPlugs were tested with a pH 7.01 buffer solution. They measured the correct pH values with an accuracy of ±0.05 pH once sufficient contact between the injected fluid and the measuring element (optode) was established. In turn, the FOP-MIV sensors were used to measure local pressure in the inlet and outlet channels during injection and the steady flow of deionized water at different rates. These sensors were calibrated up to 140 mbar and provided pressure measurements with an uncertainty that was less than ±1.5 mbar. Readouts at a rate of 4 Hz allowed us to observe dynamic pressure changes in the device during the displacement of air by water. In the case of steady flow of water, the pressure difference between the two measuring points increased linearly with increasing flow rate, complying with Darcy’s law for incompressible fluids. These data can be used to determine the permeability of the porous structure within the device.

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Thermal Measurement Techniques in Analytical Microfluidic Devices

Cited by 6 publications

References 8 publications

Microscale direct measurement of localized photothermal heating in tissue-mimetic hydrogels

Microscale direct measurement of localized photothermal heating in tissue-mimetic hydrogels

On-chip detection of gel transition temperature using a novel micro-thermomechanical method

Manufacturing of Microfluidic Devices with Interchangeable Commercial Fiber Optic Sensors

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