Microheater

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

Micromachined convective accelerometers in standard integrated circuits technology

Abstract: This letter describes an implementation of micromachined accelerometers in standard complimentary metal–oxide–semiconductor technology. The devices operate based on heat convection and consist of microheaters and thermocouple or thermistor temperature sensors separated by a gap which measure temperature difference between two sides of the microheater caused by the effect of acceleration on free gas convection. The devices show a small linearity error of <0.5% under tilt conditions (±90°), and <2% under acceleration to 7g(g≡9.81 m/s2). Sensitivity of the devices is a nearly linear function of heater power. For operating power of ∼ 100 mW, a sensitivity of 115 μV/g was measured for thermopile configuration and 25 μV/g for thermistor configurations. Both types of devices are operable up to frequencies of several hundred Hz.

Thermally mediated control of liquid microdroplets at a bifurcation

Abstract: The ability to precisely control the motion of droplets is essential in droplet-based microfluidics. It serves as the basis for various droplet-based devices. This paper presents a thermal control technique for microdroplets at a bifurcation. Control was achieved using an integrated microheater that simultaneously induces a reduction in fluidic resistance and thermocapillarity. The temperature of the heater was monitored by an integrated temperature sensor. At a bifurcation with symmetric branches, a droplet can be split into two daughter droplets of controllable sizes or entirely switched into a desired branch. The physics of this phenomenon was investigated with the help of a numerical model. Splitting and switching were demonstrated within an operational temperature range 25‐38 ◦ C. The relatively low operational temperature range allows this technique to be used for droplets containing biological samples. The present control concept is not limited to bifurcations, but can be employed in other geometries.

Micromachined thin-film sensors for SOI-CMOS co-integration

Abstract: Co-integration of sensors with their associated electronics on a single silicon chip may provide many significant benefits regarding performance, reliability, miniaturization and process simplicity without significantly increasing the total cost. Micromachined Thin-Film Sensors for SOI-CMOS Co-integration covers the challenges and interests and demonstrates the successful co-integration of gas-flow sensors on dielectric membrane, with their associated electronics, in CMOS-SOI technology. We firstly investigate the extraction of residual stress in thin layers and in their stacking and the release, in post-processing, of a 1 µm-thick robust and flat dielectric multilayered membrane using Tetramethyl Ammonium Hydroxide (TMAH) silicon micromachining solution. The optimization of its selectivity towards aluminum is largely demonstrated. The second part focuses on sensors design and characteristics. A novel loop-shape polysilicon microheater is designed and built in a CMOS-SOI standard process. High thermal uniformity, low power consumption and high working temperature are confirmed by extensive measurements. The additional gas flow sensing layers are judiciously chosen and implemented. Measurements in the presence of a nitrogen flow and gas reveal fair sensitivity on a large flow velocity range as well as good response to many gases. Finally, MOS transistors suspended on released dielectric membranes are presented and fully characterized as a concluding demonstrator of the co-integration in SOI technology.

Microhotplates with TiN heaters

Abstract: Titanium nitride (TiN) has been investigated as a heater material for microhotplates and microreactors. TiN is available in many CMOS processes, unlike many other microheater materials. In addition, TiN has a very high melting point (2950 ◦C) meaning that it is stable up to higher temperatures than platinum (Pt) and polysilicon. For the first time, TiN is tested inside a conventional membrane of LPCVD silicon nitride (SiN). Two types of sputtered TiN are considered: high stress and low stress. Their performance is compared with that of e-beam evaporated Pt. The maximum average temperature of TiN heaters is 11% higher than those of Pt, and reaches over 700 ◦C. Failure of the TiN heaters is due to rupture of the membrane. Failure of the Pt heater is due to electro-stress migration. For high-stress TiN, the temperature coefficient of resistance is almost constant and close to that of Pt, making the material very suitable for temperature sensing. In the case of low-stress TiN the temperature coefficient of resistance (TCR) becomes nonlinear and changes sign. The large differences between the materials are explained by the grain structure. The different grain structures are related to the sputtering parameters according to the Thornton model.

Design, fabrication and characterization of a conducting PDMS for microheaters and temperature sensors

Abstract: In this paper, we present the design and fabrication procedure of a conducting polydimethylsiloxane (PDMS) and then evaluate its potential uses for heating and temperature sensing. The conducting PDMS was made up of a mixture of a PDMS prepolymer and metallic powder. Depending on purpose, i.e. heater or sensor, different weight ratios of the powder and geometric shapes were considered. Characterization of both the microheaters and the temperature sensors includes stability, repeatability, durability and time response. The results suggest that the microheater is feasible for constantly heating at a fixed temperature instead of running thermal cycles. The optimal heating range was estimated below 100 °C under the current setup and a power consumption of 210 ± 12 mW was needed for 92 °C. Hysteresis and time lag were observed in the temperature sensor. Accordingly, the sensor is recommended to be used for long-term monitoring instead of rapid temperature detections.