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Low-cost, fast and accurate antibody detection is important for viral infection testing, especially for in cases of epidemics or pandemics. Currently, most rapid antibody detection methods are based on lateral flow immunoassay tests. [1] Beads offer a convenient way to capture and concentrate antigens, antibodies, and other biological molecules but determining the concentration or number can be a challenge, in particular at lower concentration levels. What we would like to achieve is the ability to detect much lower concentration levels, and in principle count individual molecules or a bound complex labelled with the magnetic bead using a micro-solenoid. In this paper, a three-dimensional, hollow channel, micro-solenoid is investigated to improve sensitivity, with antibody testing using magnetic microbeads bound to the target antigen. Previous work has shown the use of magnetic microbeads for microfluidic devices [2]. The micro-solenoid is simulated using COMSOL multiphysics to test various geometric parameters such as bead size, coil size, and bead velocity for the goal of detecting and counting antibodies bound to the beads. A time dependent model was constructed in COMSOL using the magnetic fields and moving mesh modules. In order to simplify the simulation, a 2D axisymmetric model was used and the model was first solved using a stationary step. The bead is represented by a short cylinder, and the solenoid as a uniform diameter annular cylinder, 390 um in length. The coil was simulated through the coil interface under the magnetic fields module allowing it to be represented as single uniform object with variable number of turns, conductivity, and cross-sectional area. For several sets of constant bead size, coil size, and bead magnetization, the maximum voltage reached was found to be a linear function with respect to velocity. In terms of coil radius, the simulated voltage response decreased quadratically with increasing radius however this was only significant when the bead size was appreciable to the coil size for simulations featuring coil radii of 15, 25, 35, and 50 um with 2, 5, 10, and 12.5 um radii beads. The data is presented in figure 1A and 1B. The results for 10 and 12.5 um radius bead are the only ones with appreciable curvature. The simulated voltage response increased quadratically with increasing bead size and the curvature of the underlying quadratic fit increased with decreased coil radius. Future avenues of study include 3 dimensional designs and simulations and fabrication using microfabricated coils. [1] D. A. Mistry, J. Y. Wang, M.-E. Moeser, T. Starkey, and L. Y. W. Lee, “A systematic review of the sensitivity and specificity of lateral flow devices in the detection of SARS-CoV-2.,” BMC Infect. Dis., vol. 21, no. 1, p. 828, Aug. 2021, doi: 10.1186/s12879-021-06528-3. [2] Kyu Sung Kim and Je-Kyun Park, “Magnetic force-based immunoassay using superparamagnetic nanoparticles in microfluidic channel,” in The 13th International Conference on Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS ’05., Jun. 2005, vol. 1, pp. 81-84 Vol. 1. doi: 10.1109/SENSOR.2005.1496364. Figure 1

Gas chromatography is a common technique for the separation and analysis of mixtures of volatile organic compounds (VOCs). In many applications, such as breath analysis and room air sampling, the concentration of analytes is so low that preconcentration is necessary to selectively trap VOCs over a longer period of time, before analysis. The goal of this project is to develop an energy efficient, compact vapor preconcentrator for air sampling. We present thin-film preconcentrators (PCF) with integrated heaters and temperature sensors that were coated with polydimethylsiloxane (OV-1), poly(2,6-diphenylphenylene oxide) (Tenax-TA) and a mixture of OV-1 and Tenax-TA. The polymer thin-films were fabricated using a dynamic coating method with 20mg/ml OV-1 in a 1:1 mixture of DCM and pentane, 10mg/ml of OV-1 and 5mg/ml of Tenax-TA in chloroform, or 20 mg/ml of Tenax-TA in chloroform. The OV-1 and OV-1/ Tenax-TA PCFs were initially tested by connecting them to the inlet and FID of a gas chromatograph with 1 m of 50um guard column. A volume of 0.2 µl of an alkane was injected via the heated inlet 175 oC at 1 psi, after any breakthrough had passed, the GC was pressurized to 8 psi and the PCFs were heated using an integrated platinum film heater. The GC was kept at a constant temperature of 40°C during these tests while the PCF was independently heated outside of the GC oven. The adsorption ratio of these experiments is summarized in table 1. Alkanes above decane such as dodecane proved difficult to desorb, even with the integrated heater reaching temperatures of approximately 260°C. The air sampling experiments for each PCF were performed for decane and benzene using a dynamic headspace sampling method with a constant flow of nitrogen induced by a mass flow controller at a rate of 0.3 ml/min. at a pressure of 5psi. A six-way valve connected the PCF to the GC for desorption at a pressure of 15psi, after a set period of time. Analysis with Agilent 5890GC using a 20 m Rxi-1ms column, temperature ramp from 40°C to 180°C at a rate of 20°C/min, and FID detector. The results for the headspace sampling are summarized in figure 1. For benzene the thin-films with Tenax-TA saturate much more quickly than the OV-1 film and the pure Tenax-TA film which has the lowest capacity. For decane, the thin films with Tenax-TA still saturate faster but the largest capacity was observed for the mix of OV-1 and Tenax-TA over this limited range of sampling times. The authors would like to thank the Georgia Tech Research Institute for funding this research out of Independent Research and Development (IRAD) funds. Figure 1

Hydrogen sulfide, Nitrogen Dioxide, and sulfur dioxide are highly toxic gases with health effects at ppb and ppm levels in air. These compounds occur in industrial operations as well as in environmental atmospheric polluted air. Traditionally, microfabricated electrochemical gas sensors use photolithography processes for patterning of the electrodes and defining the electrode geometry for high surface area to increase the sensor gas sensitivity. We present herein a series of gas sensor designs fabricated via laser ablation of sputtered Au films. For these sensors, the laser ablation step itself takes less than two hours to pattern up to 60 sensors. The sensors are fabricated on a porous hydrophobic substrate made of layers of a Teflon woven mesh, and the 400 nm gold film was sputtered onto a 100 nm tungsten adhesion layer. A total of 60 sensors was patterned in a 6 by 10 grid per substrate with each sensor having a footprint of 15 mm x 15 mm. An image of some of the sensors and their corresponding designs are illustrated in figure 1. Laser ablation was performed by an Optec WS-Flex USP femtosecond 1030 nm laser. The pulse frequency was set to 400 kHz and both the speed and jump speed were set to 200 mm/s. The laser power is nominally 4 W and the power percentage setting was determined for each substrate by patterning a test array onto the substrate in increments of 2%. From this test array, the lowest power that completely ablated the gold could be determined and that was used for the remaining sensor ablation. Images of the etched surface area shown in the figure 1. Surface analysis with EDS using SEM microscope indicated the composition of the layers and effective removal of the gold from the Teflon sheet without damage to the Teflon porosity in the woven mesh, figure 2. The sensor electrodes were assembled by lamination between several plastic layers and then an electrolyte was added. The assembled sensors were diced from the assembled 10x6 sensor wafer and individual sensors were connected to a potentiostat and tested via exposure to the various pollutant gases. The current response of these amperometric sensors was measured and found to be linear with respect to concentration in the low ppm range. This work illustrates an alternative to photolithography for the preparation of thin film gas porous electrodes for use in amperometric gas sensors. Figure 1

This article provides measurements of thermal conductivity carried out on a microelectromechanical system (MEMS) structure for the application of selective gas sensing. MEMS thermal conductivity based gas sensors work by measuring the interaction of a heated polysilicon bridge with an ambient gas and sensing temperature changes. The tiny MEMS element provides an ability to measure noble gases and is especially applicable to binary mixtures. In this work we conducted experiments on the KWJ Engineering nano-powered thermal conductivity detector (TCD) elements to investigate the sensitivity of the sensor transient responses to gas composition. Measurements are made at constant power, constant resistance, and constant energy. By introducing feedback to maintain constant sensor temperature, the relative change of gas thermal conductivity with respect to temperature can be estimated and provide information about the concentration as well as insight into the composition of the gas mixture.

Abstract MEMS fabrication technology has been applied to build micro-GC systems for portable analysis and detection of volatile organic compounds for environmental monitoring, medical diagnostics and food safety and security (1). Pioneering work at Sandia National Laboratories developed - these miniature systems (2). Novel designs for pre-concentrators have been developed to provide efficient sample injection into these systems (3). We have integrated a 6m length micro-GC column with an ion trap mass spectrometer (4). To inject the sample into the column, our initial method was to use a syringe injection into a heated septum with Agilent 6890. However, for automated operation and method of sampling, pre-concentration of the volatile organic compounds is required, followed by rapid heating, for sample injection for analysis. A microfabricated pre-concentrator can fulfill this function by providing a high surface area in a compact platform with reduced thermal mass, compared to commercial desorption tubes. The design has an integrated platinum heater and was fabricated using standard photolithography, deep reactive ion etching and wafer bonding. To evaluate the performance, the pre-concentrator is mounted inside a commercial Agilent 6890 GC system. Liquid injections 0.02uL, using a syringe, with a 100:1 split, at a helium flow rate of 0.005 ml/min. The flow rate was increased during the desorption cycle, and the preconcentrator was heated by electrical current of providing approx. 5W to enable rapid heating to 180°C. This miniature pre-concentrator provides a small thermal mass design and was capable of fast desorption of several analytes with detection by FID. References [1] M. Akbar, M. Restaino, M. Agah, “Chip-scale gas chromatography: From injection through detection,” Microsystems Nanoengineering, Vol. 1, pg. 15938 (2015). [2] in J. J. Whiting, E. B. Myers, R. P. Manginell, M. W. Moorman, K. Pfeifer, J. M. Anderson, C. S. Fix, C. Washburn, A. Staton, D. Porter, D. Graf, D. R. Wheeler, J. Richards, K. E. Achuythan, M. Roukes, R. J. Simonson, "μChem Lab: twenty years of developing CBRNE detection systems with low false “μChemLab: twenty years of developing CBRNE detection systems with low false alarm rates”Proceedings of SPIE, Vo.l. 11010, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XX, 1101012 (17 May 2019); doi: 10.1117/12.2518778. [3] Tian, Wei-Chang, H. K. L. Chan, Chia-Jung Lu, S. W. Pang, E. T. Zellers, “ Multiple-stage microfabricated preconcentrator-focuser for micro gas chromatography system,” J. Microelectromachanical Systems, Vol. 14, No. 3, pp 498-507 (2005). [4] Tzu-Hsuan Chang, D. Struk, M. Navaei, V. M. Doroshenko; V. Laiko; E. Moskovets; K. Novoselov, J. D. Dimandja, Peter J. Hesketh, “Separation of Volatile Organic Compounds using of MEMS-GC Integrated Heater for Ion Trap Mass Spectrometer,” Sensors and Actuators B, Vol. 307, pg. 127588 (2020).

Introduction Microfabricated gas chromatography systems based upon MEMS fabrication technology are under development for portable chemical vapor analysis and chemical detection. In particular, Sandia National Laboratories has pioneered development of these miniature systems (1). Current methods for coating microfabricated gas chromatography columns are based upon deposition from a saturated mixture of siloxanes in a solvent, which are adapted from techniques developed for coating of open-tubular capillary columns (2). This static method is more successful with silica open tube columns which have a uniform cross-section area, however in a microfabricated column, a rectangular cross-section is produced in the channel. The square corners tend to have a thicker layer of material deposited using this process and hence these thicker layers provide a different retention time for the analytes which results in peak broadening and reduction in resolution and peak capacity of the column. Alternative stationary phases have been investigated (3), and using chemical vapor deposition (CVD) they can be grown with uniform thickness, for example carbon nanotubes (CNTs) (4) The CNTs have high surface area and are stable at high temperatures. Method A silicon substrate is used for the fabrication of a microfabricated spiral column, 6m in length using standard photolithography and deep reactive ion etching fabrication processes (5). An ultra-thin layer of iron catalyst is deposited by sputtering into the etched silicon channel. Using a Black Magic plasma enhanced CVD growth a layer of CNTs are formed thickness 0.5 to 1 micrometer. Figure 1 shows an SEM micrograph of the deposited CNTs layer which coats the sides of channel and base with uniform thickness. Next a layer of gold is deposited for eutectic bonding of the silicon lid in order to enclose the channel making the column. Finally high temperature annealing is carried out at 450 oC to increase bond strength. Results The column is mounted inside a commercial Agilent 6890 GC system oven with a short length of guard column, approximately 0.5m length, connect between the split injector and the flame ionization detector. A liquid injection of three compounds, hexane, octane and decane, volume of 0.02uL, was carried out with a 100:1 split and injector temperature of 275°C. The helium carrier gas flow rate was 0.1 ml/min. A typical chromatogram is shown in Figure 2. The McReynolds probes for polarity were also injected, and the Kovats indices were evaluated for comparison with OV-1 (Ohio Valley, OH) polymer stationary phase. Conclusions The use of CNT’s for a stationary phase may offer some advantages with micro-GC column fabrication because the quality of the layer can be inspected prior to bonding. We can observe the low polarity of the CNT stationary phase compared to the poly-siloxane However, it may be possible to chemically functionalize the surface for the CNTs for more polar compound separation and analysis. References [1] in J. J. Whiting, E. B. Myers, R. P. Manginell, M. W. Moorman, K. Pfeifer, J. M. Anderson, C. S. Fix, C. Washburn, A. Staton, D. Porter, D. Graf, D. R. Wheeler, J. Richards, K. E. Achuythan, M. Roukes, R. J. Simonson, "μChem Lab: twenty years of developing CBRNE detection systems with low false “μChemLab: twenty years of developing CBRNE detection systems with low false alarm rates” Proceedings of SPIE, Vo.l. 11010, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XX, 1101012 (17 May 2019); doi: 10.1117/12.2518778. [2] C. F. Poole, The Essence of Chromatography, Elsevier, 2003. [3] I. Azzouz, J. Vial, D. Thiébaut, R. Haudebourg, K. Danaie, P. Sassiat, J. Breviere, “Review of stationary phases for microelectromechanical systems in gas chromatography: feasibility and separations,” Analytical and Bioanalytical Chemistry, Vol. 406, pp. 981–994 (2014). [4] W. Intrchom, S. Mitra, “Analytical sample preparation, preconcentration and chromatographic separation on carbon nanotubes,” Current Opinion in Chemical Engineering, Vol. 16, pp. 102-114 (2017). [5] M. Navaei, A. Mahdavifar, J.-M. Dimandja, G. McMurray, P. J. Hesketh “All silicon micro GC column temperature programming using axial heating,” Micromachines, Vol 6, pp. 865-878 (2015). Figure 1

Introduction Micro GC systems based upon MEMS fabrication technology have been developed for portable analysis systems to enable detection and quantification of volatile organic compounds over the past twenty years (1). In particular, work at Sandia National Laboratories, has pioneered development of these miniature systems (2). Novel designs for pre-concentrators have also been developed to assist with sample injection into these low flow rate systems (3). We have studied micro-GC columns made by silicon to silicon direct bonding (4), and integrated a micro-GC column 6m length, with an ion trap mass spectrometer for this purpose (5). To inject the sample into the column, our initial method was to use a syringe injection into a heated septum with Agilent 6890. However, for automated operation and method of sampling, pre-concentration of the volatile organic compounds is required, followed by rapid heating for sample injection for analysis. A microfabricated pre-concentrator can fulfill this function by providing a high surface area and a compact platform with reduced thermal mass, compared to commercial desorption tubes. Method We designed a pre-concentrator (MPC) with an integrated platinum heater. The MPC is fabricated using standard photolithography, deep reactive ion etching and wafer bonding. The layout of the geometry in the preconcentrator is shown in Figure 1. Pillars 50 um in diameter are located in the channel to provide a high surface area. The silicon surface is liquid coated with Tenax TA (Tenax 60-80 mesh from Supelco) and PDMS (OV-1 from Ohio Valley Specialty) in an organic solvent, dichloromethane, typically a dozen times to build up a layer of approximate thickness less than a micrometer. Results Sample collection from air flow was modelled with COMSOL and indicates the pressure drop for an air flow of 600sccm a pressure drop of less than 3 psi at room temperature. Figure 3 shows results of the model with a channel depth of 350 um. To evaluate the performance, the pre-concentrator it is mounted inside a commercial Agilent 6890 GC system. A 2m length of Guard Column, 50 um ID was selected to minimize the dead-volume in the fluidic connections between the sample injection port, MPC and the flame ionization detector. Liquid injection of decane at volume of 0.02uL, using a syringe into Agilent 6890 heated injector at 275°C, with a 100:1 split, at a helium flow rate of 0.005 ml/min. Typical results, shown in Figure 4A for heating profile, indicate complete absorption, and no break-through, followed by rapid desorption with heating Figure 4B. The flow rate could be increased at the outlet during the desorption cycle using electrical current of 130 mA to the heater approx.180 ohms, provided rapid heating to 180°C, based upon resistance temperature calibration of the heater and temperature sensor, located on the lid of the MPC. Conclusions This miniature pre-concentrator provided the opportunity to build a small thermal mass designs using silicon microfabrication. With an integrated platinum heater, rapid heating at low power consumption of 5W was achieved, capable of desorption of the captured analyte to detection with FID in GC system. References [1] M. Akbar, M. Restaino, M. Agah, “Chip-scale gas chromatography: From injection through detection,” Microsystems Nanoengineering, Vol. 1, pg. 15938 (2015). [2] in J. J. Whiting, E. B. Myers, R. P. Manginell, M. W. Moorman, K. Pfeifer, J. M. Anderson, C. S. Fix, C. Washburn, A. Staton, D. Porter, D. Graf, D. R. Wheeler, J. Richards, K. E. Achuythan, M. Roukes, R. J. Simonson, "μChem Lab: twenty years of developing CBRNE detection systems with low false “μChemLab: twenty years of developing CBRNE detection systems with low false alarm rates”Proceedings of SPIE, Vo.l. 11010, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XX, 1101012 (17 May 2019); doi: 10.1117/12.2518778. [3] Tian, Wei-Chang, H. K. L. Chan, Chia-Jung Lu, S. W. Pang, E. T. Zellers, “ Multiple-stage microfabricated preconcentrator-focuser for micro gas chromatography system,” J. Microelectromachanical Systems, Vol. 14, No. 3, pp 498-507 (2005). [4] M. Navaei, A. Mahdavifar, J.-M. Dimandja, G. McMurray, P. J. Hesketh “All silicon micro GC column temperature programming using axial heating,” Micromachines, Vol 6, pp. 865-878 (2015). [5] Tzu-Hsuan Chang, D. Struk, M. Navaei, V. M. Doroshenko; V. Laiko; E. Moskovets; K. Novoselov, J. D. Dimandja, Peter J. Hesketh, “Separation of Volatile Organic Compounds using of MEMS-GC Integrated Heater for Ion Trap Mass Spectrometer,” revised, Sensors and Actuators B, 2020. Figure 1

This paper describes an ultra-thin, low cost 3D glass sensor packaging platform for near-hermeticity with novel feedthrough and encapsulation technologies. Glass panels of thicknesses ranging from 50 µm to 300 µm are used which limits overall form factor to 10 MPa) and Dow Chemical's Benzocyclobutene (BCB) 14-P005 is found to be the best candidate for panel level glass-glass bonding. Modelling of the proposed three-layer glass packaging platform was performed in COMSOL Multiphysics. Results show a maximum deformation of about 2.3 µm - 2.5 µm in the BCB and GX-92 bonded package and the least average internal stress of 6.40 MPa in the BCB bonded package. The complete manufacturing cycle starting from cavity formation on bare glass to final 3D assembly to form the lidded/open cavity package including singulation is panel based, enabling significant cost reduction (depending on die dimensions and panel size) compared to ceramic and other substrate technologies.

This paper describes advances in integrated ultra-thin wireless power module components for Internet of Things (IoT) and wireless sensor applications. A typical wireless module integrates both an inductive link for wireless power transfer, and supercapacitor as a storage element. The performance of the inductive link is enhanced with innovative high-permeability and low-loss magnetic films for improved inductive coupling between the receiver and the transmitter. Up to 4X enhancement in power transfer efficiency is demonstrated with the innovative magnetic films. Energy storage is achieved through a thinfilm micro fabricated supercapacitor layer with interdigitated graphene-based planar electrodes and solid-state electrolytes for easier integration. The component properties demonstrated through this work are projected to achieve high power levels with ultra-thin form-factors.

Miniature gas chromatography (GC) columns of length 6m were fabricated in silicon using eutectic bonding to achieve a column with improved temperature control. The micro GC column includes an integrated platinum thin film heater and temperature sensors for closed loop temperature programing. In order to achieve low power operation the GC column was mounted inside the vacuum chamber of an ion-trap mass spectrometer. This approach provides much lower power consumption than a laboratory instrument. The ion trap electronics were miniaturized and operate at lower power, to demonstrate a portable instrument able to operate at with less than 25W, including vacuum pumps. This instrument will have a range of applications from environmental monitoring, to food safety and medical diagnostics, including breath analysis. Static coating of the stationary phase in the microfabricated column was carried out by injection using a solvent and extraction at reduced pressure to improve resolution. This paper reports the results of different stationary phases investigated to separate mixtures of volatile organic compounds, specifically OV-1 and OV-215. The properties of the stationary phases where characterized using a novel probe mixture for microcolumn evaluation and six McReynolds probes to identify the Kovats indices and the polarity of the column. The dependence of polarity on the coating technique and temperature of the column during analysis was also investigated. Results are presented with both an FID and ion-trap mass spectrometer to achieve rapid temperature programmed analysis of mixtures of up to 18 organic compounds.

This paper reports on characterization and optimization of a low-noise Thermal Conductivity Detector (TCD) for detection of ammonia. Ammonia is a highly toxic agent and is widely produced by of chickens in a chicken farm. There are studies that show the presence of ammonia decreases the quality and quantity of egg and meat production, and may inhibit growth in cell lines. Research has shown that high level of ammonia will create about 5-10% runts in a flock [1]. Therefore, accurate detection ammonia is important issue for food quality control and also labor safety. The commercially available ammonia sensors on the market often have short battery life, baseline drift, selectivity problem, false alarms and need frequent recalibration. Currently most ammonia sensors rely on the chemical interaction of the gas and a specific material which chemical properties changed by the gas. The drawbacks of these sensors are the reliability of the sensors under different environmental conditions and limited life-time. On the other hand, gas sensors which primarily use physical properties of the gas to sense, such as Thermal Conductivity Detector (TCD) is potentially more stable [2]. The working principle of thermal conductivity detectors is based on relating bridge resistivity to its temperature, and bridge temperature depends on the heat loss to the surrounding gas. Here we present a comprehensive COMSOL model to study the effect of the micro-bridge geometry and the heat transfer phenomenal through the gas and substrate. The purpose of the geometry design is to reduce the heat loss to the substrate at the micro-bridge anchors, to improve the efficiency of the sensor, and increase the heat loss through the gas phase to improve the detection limit. For the purpose of this study, we investigated the effect of three differed designed depicted in figure 1. Based on the simulation data, the micro-bridge with the uniform cross-section shows the highest ratio of heat loss through the gas relative to total power of the sensor. This has improved the sensitivity of the sensor by 18% for gases with low thermal conductance such as ammonia. To improve the sensitivity of our TCD sensor by changing the working temperature, the temperature of the sensor has a tremendous effect on the noise level and, consequently, limit of detection (LOD). Ammonia and nitrogen have comparable thermal conductivity at room temperature, but the slope of change of their thermal conductivity is not equal. We have exploited of change in thermal conductivity of gases for different sensor operating temperatures by increasing the sensor power. As a result, the increase of working temperature of sensor has improved sensitivity and reduced the LOD. In conclusion, we have analyzed operation of micro-bridge for robust performance to detect ammonia, which has comparably similar thermal conductivity to the nitrogen. Robust sensitivity of gas detection is also being investigated by 3-Omega techniques, for read-out circuit, increase in the working temperature of the sensor and having better Signal-to-Noise Ratio (SNR). There is also more room in improvement of material properties including having higher thermal coefficient resistivity. Figure 1

MEMS gas sensors have the advantage of low power operation, fast response time, and have attracted a lot of interest because of their potential low cost. There is a need for monitoring of changes in the environment, in particular for carbon dioxide and methane. These gases can be detected using electro-thermal method based upon thermal conductivity changes. MEMS based micro-TCD which are ultra-low power, requiring less than 6 uJ per measurement and have a response time 100uS or less [1]. Because of their rapid response time they are also very suitable for MEMS-GC systems [2]. We have investigated different modes of pulsed operation for these sensors using constant current, constant resistance, constant power and constant energy. The detection of helium and hydrogen in nitrogen indicated a low level of detection less than 500ppm or better. A comparison of thermal time constants and resistance response for micro-thermal conductivity sensors with different aspect ratio, surface area to volume, operated at constant power density or at similar average temperatures will be discussed. Fitting a model based upon kinetic theory of gases to temperature dependent sensor response of gas mixtures has potential for evaluation of multi component mixtures. References [1]A. Mahdavifar, M. Findlay, J. R. Stetter, P. J. Hesketh, “Transient thermal response of micro-thermal conductivity detector for the identification of gas mixtures: An ultra-fast and low power method,” Nature Microsystems and Nanooengineering Vol. 1, pg. 15025 (2015). [2] A. Mahdavifar , M. Navaei , P. J. Hesketh , J. D. Dimandja , J. R. Stetter , G. McMurray, “Implementation of a polysilicon micro electro-thermal detector in gas chromatography system with applications in portable environmental monitoring,” Journal of Solid State Science and Technology, Vol. 4, No. 10, pp. S1-S5 (2015).

Chemoembolization, using a combination of embolic and chemotherapeutic agents, appears to be an effective treatment for hepatocellular carcinoma. Although the postulated mechanism of effectiveness hinges on a prolonged drug delivery, increasing evidence suggests that embolization mixtures are not stable. The objective of this study was to investigate examples of these mixtures.Dialysis techniques have been used to examine the pharmacokinetic properties of chemoembolization mixtures that contain doxorubicin, Lipiodol (Guerbet Products, Montreal, Quebec), and the embolizing agents Avitene (Alcon Laboratories Inc., Fort Worth, Texas), Gelfoam (Upjohn, Kalamazoo, MI), and Angiostat (Regional Therapeutic Inc., Pacific Palisades, CA).Lipiodol, Gelfoam, and Avitene, when combined with doxorubicin, had only a small effect on the diffusion of the drug when compared with the diffusion curve of doxorubicin alone. Gelfoam or Avitene produced a thrombus-like consistency when added to a doxorubicin/Lipiodol combination, and an additional decrease in the doxorubicin appearance rate was observed. However, after 6 hours, doxorubicin levels for these mixtures reached control values observed in 3 hours. Angiostat without Lipiodol produced a profound concentration-dependent decrease in the diffusion of doxorubicin. After 9 hours, only 23% of the doxorubicin had been released.The strong complexing ability of the embolic agent Angiostat may enable it to be a carrier for doxorubicin and surpass other mixtures currently employed for transcatheter chemoembolization.