Development of a Microwave Sensor for Solid and Liquid Substances Based on Closed Loop Resonator

In this work, a compact dielectric sensor for the detection of adulteration in solid and liquid samples using planar resonators is presented. Six types of filter prototypes operating at 2.4 GHz are presented, optimized, numerically assessed, fabricated and experimentally validated. The obtained experimental results provided an error less than 6% with respect to the simulated results. Moreover, a size reduction of about 69% was achieved for the band stop filter and a 75% reduction for band pass filter compared to standard sensors realized using open/short circuited stub microstrip lines. From the designed filters, the miniaturised filter with Q of 95 at 2.4 GHz and size of 35 mm × 35 mm is formulated as a sensor and is validated theoretically and experimentally. The designed sensor shows better sensitivity, and it depends upon the dielectric property of the sample to be tested. Simulation and experimental validation of the designed sensor is carried out by loading different samples onto the sensor. The adulteration detection of various food samples using the designed sensor is experimentally validated and shows excellent sensing on adding adulterants to the original sample. The sensitivity of the sensor is analyzed by studying the variations in resonant frequency, scattering parameters, phase and Q factor with variation in the dielectric property of the sample loaded onto the sensor.

Assessment of Hypercoagulable State in Whole Blood in Sepsis Patients Using a Novel Microfluidic Dielectric Sensor

Background: There is an intimate link between inflammation and thrombosis, and patients with pro-inflammatory/infectious disorders develop a hypercoagulable state. Extant coagulation assays are unable to distinguish the pro-coagulant state of a patient's blood, require 2-3 mL of blood, and take 2-3 hours for processing. These assays are also typically examined in plasma and do not represent the contribution of blood cellular elements that participate in thrombosis in vivo. Thus, a point-of-care device for rapid, comprehensive assessment of whole blood coagulation is crucial to ensure appropriate and timely evaluation in critically ill patients. We have introduced a microfluidic sensor (ClotChip) that uses dielectric spectroscopy to provide such an assessment in a handheld platform. We have shown in clinical studies in patients with a hypocoagulable state that ClotChip is sensitive to both coagulation factor and platelet defects, allowing for a global assessment of blood coagulation status using <10 µL of whole blood and in <30 min. In this study, we optimized ClotChip to assess the blood coagulation status in patients with a hypercoagulable state. Methods: Citrated blood samples from 12 patients with a diagnosis of sepsis and 11 healthy donors as controls were obtained under an IRB-approved protocol and tested with ClotChip within 2 hours of collection. ClotChip readout curve was calculated as the temporal variation of blood dielectric permittivity at 1 MHz, and the time to reach a permittivity peak (T peak) was taken as an indicator of coagulation time based on our prior studies. To increase the sensitivity of the ClotChip T peak parameter to a hypercoagulable state, we used two different anticoagulants, recombinant thrombomodulin (rTM) and activated protein C (APC). To optimize the anticoagulant concentration, whole blood samples from healthy donors were treated in vitro with lipopolysaccharide to mimic a pro-coagulant state of blood and tested with ClotChip after adding various concentrations of rTM and APC. We concluded that a concentration of 5 µg/mL for rTM and 10 µg/mL for APC would result in an optimal change in T peak for detecting the pro-coagulant state. Since heparin (or lovenox) is routinely used in hospitalized patients, sepsis and control samples were pretreated with hepzyme at a final concentration of 2 IU/mL to reverse the heparin effect. The T peak parameter was measured and compared in (i) hepzyme only-, (ii) rTM-, and (iii) APC-treated samples. Data are reported as mean ± standard deviation. Two-tailed t test is used to test for statistical significance between groups, and P < 0.05 is considered statistically significant. In box-and-whiskers plots, the box represents the range from the first to the third quartile, the horizontal line represents the median, plus sign (+) represents mean of the data; whiskers extend to the maximum and minimum data values, and dots represent individual subject data. Results: In hepzyme only-treated samples, T peak was significantly prolonged at 478±137 sec in sepsis samples, as compared to 357±58 sec in controls (Figs. 1A, 1B). rTM treatment resulted in T peak of 503±128 sec for sepsis samples and 443±81 sec for controls, whereas APC treatment resulted in T peak of 1,095±850 sec for sepsis samples and 477±71 sec for controls (Figs. 1A, 1B). Although T peak was prolonged at baseline in hepzyme only-treated sepsis samples, no further prolongation was noted with rTM treatment (difference in T peak of 24±94 sec; Fig. 1C), as compared to rTM-treated controls (difference in T peak of 85±40 sec; Fig. 1C). However, with a difference in T peak of 616±804 sec, the APC-treated sepsis samples exhibited T peak prolongation when compared to hepzyme only-treated sepsis samples, whereas the APC-treated controls did not (difference in T peak of 119±64 sec; Fig. 1D). A comparison between the APC- and rTM-treated samples revealed a significant prolongation of T peak in sepsis samples (difference in T peak of 591±815 sec) when compared to controls (difference in T peak of 30±66 sec; Fig. 1E). Conclusions: Our studies identify a unique coagulation profile in sepsis patient blood using a microfluidic dielectric sensor. These data suggest that the addition of rTM or APC can enhance the sensitivity of the ClotChip T peak parameter for detecting the pro-coagulant state in whole blood. Ongoing studies are examining the coagulation profile in other pro-inflammatory and infectious states. Figure 1 Figure 1. Disclosures Suster: XaTek Inc.: Consultancy, Current holder of stock options in a privately-held company, Patents & Royalties, Research Funding. Mohseni: XaTek Inc.: Consultancy, Current holder of stock options in a privately-held company, Patents & Royalties, Research Funding. Nayak: BioChip Labs: Current Employment.

Extremely Sensitive Microwave Microfluidic Dielectric Sensor Using a Transmission Line Loaded with Shunt LC Resonators

In this paper, a very high sensitivity microwave-based planar microfluidic sensor is presented. Sensitivity enhancement is achieved and described theoretically and experimentally by eliminating any extra parasitic capacitance not contributing to the sensing mechanism. The sensor consists of a microstrip transmission line loaded with a series connected shunt LC resonator. A microfluidic channel is attached to the area of the highest electric field concentration. The electric field distribution and, therefore, the resonance characteristics are modified by applying microfluidic dielectric samples to the sensing area. The sensor performance and working principle are described through a circuit model analysis. A device prototype is fabricated, and experimental measurements using water/ethanol and water/methanol solutions are presented for validation of the sensing mathematical model.

Detecting Phase-Inversion Region of Surfactant-Stabilized Oil/Water Emulsions Using Differential Dielectric Sensors

Summary An experimental and theoretical investigation of surfactant-stabilized oil/water emulsion characteristics was carried out under water sweep (WS) and oil sweep (OS) conditions. Both hydrophilic and hydrophobic surfactants were used, with concentrations less than and more than the critical micelle concentration (CMC). Experimental data were acquired for detection of the phase-inversion region, which was measured simultaneously by several independent methods. These include a circular differential dielectric sensor (C-DDS), a rectangular differential dielectric sensor (R-DDS) (both sensors accurately detect the phase-inversion region), a pressure transducer, and a mass flowmeter. The addition of an emulsifier surfactant to an oil/water mixture generated a stable emulsion, which resulted in a phase-inversion delay. For water-continuous to oil-continuous flow, a hydrophilic surfactant was a better emulsifier, while for oil-continuous to water-continuous flow, a hydrophobic surfactant was a better emulsifier for creating more stable emulsions. The surfactant/oil/water emulsion resulted in an increase of the dispersed-phase volume fraction required for phase inversion, as compared to the case of oil/water dispersions without surfactant. For emulsions with surfactant concentrations above CMC, the presence of micelles contributed to further delay of the phase inversion, as compared to those with surfactant concentrations below CMC. The phase-inversion region exhibits a hysteresis between the OS and WS runs, below CMC and above CMC, which was due to the difference in droplet sizes caused by different breakup and coalescence processes for oil-continuous and water-continuousflow. This research shows that the DDS is an efficient instrumentation that can be used to detect the region where the emulsion phase inversion is expected to occur. Moreover, the experimental results and the pertinent analysis and discussion provide useful insights for a more informed design of surface facilities (including emulsion separators) in oil and gas production operations.