Jonathon Oiler

Three-Dimensional Flexible Thermal Sensor for Intravascular Flow Monitoring

A novel design and assembly technology is developed for a three-dimensional (3-D) flexible thermal flow sensor based on convective heat transfer to reduce detection error caused by position variation of a sensor inside the flow of narrow and curved geometries, such as coronary artery. The 3-D sensor has three independent sensing elements equally distributed around the catheter tube. This arrangement introduces three independent information channels, and cross-comparisons are used to provide accurate flow measurement. The resistance of the sensing elements is measured at ~ 1-1.2 kΩ with the temperature coefficient of resistance at 0.086%/°C. Using a constant-current circuit, the three sensing elements are heated to ~ 10°C above ambient temperature. Flow testing is implemented in a pipe channel at two positions: on the wall and along the center line. Experimental results from these two positions are discussed and computational fluid dynamic simulation based on Newtonian fluid properties is implemented, showing comparable results within an acceptable range of experimental to simulation errors. Therefore, we demonstrate the capability of 3-D thermal flow sensor for detecting the position of the catheter in the flow channel, thereby providing an accurate flow measurement.

Molecular Electronic Transducer-Based Low-Frequency Accelerometer Fabricated With Post-CMOS Compatible Process Using Droplet as Sensing Body

This letter reports a low-frequency micro-accelerometer implementing a liquid-state sensing body, based on molecular electronic transducer (MET) in post-CMOS compatible microfabrication technology. The device employs a sub-microliter electrolyte droplet encapsulated in oil as the sensing body, and a MET electrode configuration as the sensing read-out mechanism. The promising and unique performance of the MET design allows the fabricated device to achieve 10.8 V/G(G=9.81 m/s2) sensitivity at 20 Hz with nearly flat response over the frequency range from 1 to 50 Hz, and a low noise floor of 75 μG/√(Hz) at 20 Hz.

Localized cell lysis by Self Focused Acoustic Transducers

This paper presents localized cell lysis using a Self Focused Acoustic Transducer (SFAT). The 18 MHz acoustic waves generated by the SFAT focus at a spot of around 100 µm in diameter with a peak intensity of 25 W/cm2, which is strong enough to produce acoustic cavitation at such high frequency. With the great pressure and temperature produced by the cavitation, cells are broken and detached in a tiny area from the substrate while leaving other ones intact. That is ideal for localized cell lysis and killing tumors. Moreover, the gene analysis is conducted to confirm that the lysis effect is due to the high intensity of focused acoustic waves.

Film Bulk Acoustic-wave Resonator (FBAR) based humidity sensor

This paper described relative humidity (RH) sensing with ZnO based Film Bulk Acoustic-wave Resonator (FBAR). The resonant frequency of the FBAR decreased in a two-stage manner as the RH increased in the environment. For low RH (RH<50%), a frequency shift of 2.2 kHz per 1% RH change was observed. This effect was attributed to water molecules replacing the adsorbed oxygen on the ZnO surface, thus increasing the density of the film. While for high RH (RH>50%), a frequency shift of 8.5 kHz per 1% RH change was obtained, which was due to the mass loading effect of the water layers formed on the ZnO surface. Ultraviolet (UV) light was applied to monitor its effects on the humidity sensing performance of the FBAR. UV can enhance the sensitivity at low RH (response increased to 3.4 kHz per 1 % RH change), while degrade the sensitivity at high RH (response decreased to 5.7 kHz per 1% RH change). This study has proven the feasibility of measuring relative humidity using ZnO film based FBAR.

Film Bulk Acoustic-wave Resonator (FBAR) based infrared sensor

This paper described an infrared (IR) radiation sensor based on Film Bulk Acoustic-wave Resonator (FBAR). The resonant frequency of FBAR sensor downshifts linearly when there is IR (peak wavelength at 780nm) illumination on the device. This effect attributed to the temperature sensitivity of the FBAR. The noise equivalent temperature difference (NETD) and the detection limit for 780 nm IR of the sensor is 25 mK at 25 °C and 19 μW/mm2, respectively. This study has proven the feasibility of detection of IR using ZnO film based FBAR.

A novel technique to cover microfluidic systems with Parylene-C

This paper describes a novel technique for covering microfluidic systems using Parylene-C. Microfluidic systems consisting of micro channels and reservoirs need to be covered to protect or isolate liquid samples from the environment. Thick photoresist and wax are employed as the sacrificial layers in the enclosed micro channels and reservoirs before Parylene-C sealing. The results show that the melted wax improves adherence on a flat and neat Parylene-C film cover and can greatly benefit the mass production. After removing the sacrificial layers, Parylene-C is heated to 120 °C to change the residual stress of Parylene-C film to strongly tensile for a flatter surface.

Film Bulk Acoustic-Wave Resonator based radiation sensor

This paper describes a high-energy electromagnetic wave radiation detection device using zinc oxide (ZnO) based Film Bulk Acoustic-Wave Resonator (FBAR). The resonant frequency of the FBAR decreased after gamma radiation, with the peak sensitivity of 9.3 kHz/krad and minimum detectable dosage of 218 rad occurring at the lowest experimental dose of 20 krad (all dosages are calibrated with ZnO), while the sensitivity decreased with increasing total ionizing dosage. The incident radiation generated charges that was trapped near the ZnO-silicon nitride (SiN) interface, which increased the plate capacitance of the FBAR, resulting in the decrease of resonant frequency.

Film Bulk Acoustic-Wave Resonator (FBAR) based ultraviolet sensor

This paper described ultraviolet (UV) radiation sensing using ZnO based Film Bulk Acoustic-wave Resonator (FBAR). The resonant frequency upshifted when there was UV illumination on the FBAR. For 365 nm UV light, the frequency upshift was 9.8 kHz with an intensity of 600 µW/cm2, and the detection limit of the sensor was 6.5 nW. The frequency increase of the FBAR UV sensor was proposed to be due to the density decrease of ZnO film upon UV illumination. When UV was incident on the ZnO film, it can cause oxygen desorption from the ZnO surface, resulting in density decrease of the film. This study has proven the feasibility of detection of low intensity UV using ZnO film based FBAR.

Thermoelectric Cool-Film Shear Stress Sensor

Hot-wire anemometers, being a robust and highly sensitive method for measuring flow properties, can be limited in sensitivity where locally increasing the temperature may induce measurement inaccuracy such as when used in near-boiling fluids. In this environment, locally decreasing the temperature allows for a larger temperature difference between the sensor and the ambient environment, thereby increasing device sensitivity while maintaining single-phase convection heat transfer physics. In this letter, we present the new capability of using thermoelectrically cooled sensors to measure wall shear stress. The power required to maintain a constant sensor temperature was increased as the wall shear stress in the channel was increased, providing proof of concept.

Ozone senosr using ZnO based film bulk acoustic resonator

This abstract describes room temperature ozone sensing using a ZnO based film bulk acoustic resonator (FBAR). The resonant frequency of the FBAR decreased upon ozone exposure due to the density increase of the ZnO film. Ozone can be adsorbed on the ZnO surface by capturing free electrons from the film, which increases the film density. The minimum detectable concentration is 21 ppb (parts per billion) with a response time of 12 s. An analytical model was developed to predict the relationship between resonant frequency and ozone concentration. In agreement with the experiment, a hyperbolic function was obtained.