thermal-measurement-techniques-in-analytical-microfluidic-devices

Thermal Measurement Techniques in Analytical Microfluidic Devices

Thermal measurement techniques have been used for many applications such as thermal characterization of materials and chemical reaction detection. ...

Marquette University

We have developed an ultrasonic PZT/tapered glass capillary resonant actuator that can eject a single droplet every acoustic cycle without also generating satellite droplets. The mechanism of the actuation is resonant longitudinal motion-induced squeezing of a tapered volume. The actuator is driven at 160 kHz and requires voltages less than 2 Vpp to operate. In this paper, the droplet generation of isopropanol and water mixtures, which have different densities, viscosities, and surface tensions, is investigated. It is determined that the geometrical squeezing mechanism and the ejected jet breakup makes the droplet size independent of frequency, but more a function of the ejecting orifice diameter that is much smaller than the capillary wavelength.

Single microdroplet ejection using an ultrasonic longitudinal mode with a PZT/tapered glass capillary.

Integrated freestanding single-crystal silicon nanowires with typical dimension of 100 nm × 100 nm × 5 µm are fabricated by conventional 1:1 optical lithography and wet chemical silicon etching. The fabrication procedure can lead to wafer-scale integration of silicon nanowires in arrays. The measured electrical transport characteristics of the silicon nanowires covered with/without SiO(2) support a model of Fermi level pinning near the conduction band. The I-V curves of the nanowires reveal a current carrier polarity reversal depending on Si-SiO(2) and Si-H bonds on the nanowire surfaces.

Integrated freestanding single-crystal silicon nanowires: conductivity and surface treatment.

Direct growth of a suspended single nanostructure (SSN) at a specific location is presented. The SSN is grown across a metallic nanoscale gap by migration in air at room temperature. The nanogap is fabricated by industrial standard optical lithography and anisotropic wet chemical silicon etching. A DC current bias, 1 nA, is applied across the metallic gap to induce nanoscale migration of Zn or ZnO. The history of the voltage drop across the gap as a function of time clearly indicates the moment when migration begins. The shape of SSNs grown across the nanogap by the migration is asymmetric at each electrode due to the asymmetric electric field distribution within the nanogap. An SSN can be used as the platform for two-terminal active or passive nanoscale electronics in optoelectronics, radio frequency (RF) resonators, and chemical/biological sensors.

Suspended and localized single nanostructure growth across a nanogap by an electric field.

In this report, a paper-based micro-calorimetric biochemical detection method is presented. Calorimetric detection of biochemical reactions is demonstrated as an extension of current colorimetric and electrochemical detection mechanisms of paper-based biochemical analytical systems. Reaction and/or binding temperature of glucose/glucose oxidase, DNA/hydrogen peroxide, and biotin/streptavidin, are measured by the paper-based micro-calorimeter. Commercially available glucose calibration samples of 0.05, 0.15 and 0.3% wt/vol concentration are used for comparing the device performance with a commercially available glucose meter (electrochemical detection). The calorimetric glucose detection demonstrates a measurement error less than 2%. The calorimetric detection results of DNA concentrations from 0.9 to 7.3 mg/mL and temperature changes in biotin and streptavidin reaction are presented to demonstrate the feasibility of integrating the calorimetric detection method with paper based microfluidic devices.

A paper-based calorimetric microfluidics platform for bio-chemical sensing.

A microfabricated calorimeter (μ-calorimeter) with an enclosed reaction chamber is presented. The 3D micromachined reaction chamber is capable of analyzing liquid samples with volume of 200 nl. The thin film low-stress silicon nitride membrane is used to reduce thermal mass of the calorimeter and increase the sensitivity of system. The μ-calorimeter has been designed to perform DC and AC calorimetry, thermal wave analysis, and differential scanning calorimetry. The μ-calorimeter fabricated with an integrated heater and a temperature sensor on opposite sides of the reaction chamber allows to perform thermal diffusivity and specific heat measurements on liquid samples with same device. Measurement results for diffusivity and heat capacitance using time delay method and thermal wave analysis are presented.

A novel on-chip three-dimensional micromachined calorimeter with fully enclosed and suspended thin-film chamber for thermal characterization of liquid samples.

Article	Year
Single microdroplet ejection using an ultrasonic longitudinal mode with a PZT/tapered glass capillary. IEEE transactions on ultrasonics, ferroelectrics, and frequency control\| PubMed ID: 15600097	2004
Integrated freestanding single-crystal silicon nanowires: conductivity and surface treatment. Nanotechnology\| PubMed ID: 21178224	2011
Suspended and localized single nanostructure growth across a nanogap by an electric field. Nanotechnology\| PubMed ID: 21911928	2011
A paper-based calorimetric microfluidics platform for bio-chemical sensing. Biosensors & bioelectronics\| PubMed ID: 24713542	2014
A novel on-chip three-dimensional micromachined calorimeter with fully enclosed and suspended thin-film chamber for thermal characterization of liquid samples. Biomicrofluidics\| PubMed ID: 24926386	2014

Chung Hoon Lee

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