Microheater

About: Microheater is a research topic. Over the lifetime, 814 publications have been published within this topic receiving 12478 citations.

Thermocapillary actuation of liquids using patterned microheater arrays

Abstract: We demonstrate a microfluidic actuation technique capable of directing nanoliter liquid samples on the surface of a glass substrate through the use of both electronically addressable heater arrays and chemical patterning. Pathways for liquid movement are delineated by the arrangement of microheaters, which also provide the thermocapillary actuating force. The drops are confined by selectively depositing a fluorinated monolayer to the surface, which defines the channel edges. Operating voltages in the range of 2-3V were used to move, split, and trap liquids. This fluid transportation technique enables direct access to liquid samples for handling and diagnostic purposes and offers a low power alternative to existing microfluidic systems.

Tunable high speed silicon microring modulator

Abstract: We present a 12.5 Gbps silicon micro-ring modulator achieved by carrier depletion in a lateral pn diode. Tunability of the resonant wavelength is accomplished by means of a microheater, with an efficiency of 2.36 mW/nm.

Development of the pipetting error sensor

Abstract: An air volume flow rate sensor with a resolution of nano-liter per second is developed to monitor the pipetting errors of the polymerase chain reaction (PCR) mixture dispense processes for DNA quantification experiments. Based on the CMOS and post-CMOS micromachining processes, the sensor which comprises microstructures and mixed signal processor in a die size of 2 mm square is fabricated and is set within a standard 200 μL pipette tip. The microstructures of the sensor consist of a polysilicon microheater and a thermopiles array. The centered microheater encircled by temperature sensors generates the heat plume. As the sensor is positioned against the flow, the thermal plume will be pushed towards to the temperature sensors array and the temperature difference can be converted into voltage to determine the air volume flow rate through the tip. The total volume of air movement can be correlated to liquid volumetric delivery and then the pipetting error can be tracked by the non-contact method. The DNA quantification experiments with hepatitis B virus (HBV) plasmid standard samples are performed on a real-time PCR machine as the pipetting error is monitored by the proposed sensor to reject large discrepancy in mean delivery volumes. The DNA quantification results for the serial samples with the initial template concentration ranging from 104 to 108 copies/mL give high linear standard curves, and the coefficient of variation (CV) of DNA quantification experiments for the three replicates intra-assay is less than 6%. These results indicate that accurate DNA quantification and high reproducibility of experiments can be obtained by the pipetting error sensor.

Capillary-driven microfluidic chips with evaporation-induced flow control and dielectrophoretic microbead trapping

Abstract: This work reports our efforts on developing simple-to-use microfluidic devices for point-of-care diagnostic applications with recent extensions that include the trapping of microbeads using dielectrophoresis (DEP) and the modulation of the liquid flow using integrated microheaters. DEP serves the purpose of trapping microbeads coated with receptors and analytes for detection of a fluorescent signal. The microheater is actuated once the chip is filled by capillarity, creating an evaporation-induced flow tuned according to assay conditions. The chips are composed of a glass substrate patterned with 50-nm-thick Pd electrodes and microfluidic structures made using a 20-μm-thick dry-film resist (DFR). Chips are covered/sealed by low temperature (50°C) lamination of a 50-μm-thick DFR layer having excellent optical and mechanical properties. To separate cleaned and sealed chips from the wafer, we used an effective chip singulation technique which we informally call the “chip-olate” process. In the experimental section, we first studied dielectrophoretic trapping of 10-μm beads for flow rates ranging from 80 pL s−1 to 2.5 nL s−1 that are generated by an external syringe pump. Then, we characterized the embedded microheater in DFR-covered chips. Flow rates as high as 8 nL s−1 were generated by evaporation-induced flow when the heater was biased by 10 V, corresponding to 270-mW power. Finally, DEP-based trapping and fluorescent detection of functionalized beads were demonstrated as the flow was generated by evaporation-induced flow after the microfluidic structures were filled by capillarity.