| 1. |
- Cavallaro, Sara, et al.
(författare)
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Label-Free Surface Protein Profiling of Extracellular Vesicles by an Electrokinetic Sensor
- 2019
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Ingår i: ACS Sensors. - : AMER CHEMICAL SOC. - 2379-3694. ; 4:5, s. 1399-1408
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Tidskriftsartikel (refereegranskat)abstract
- Small extracellular vesicles (sEVs) generated from the endolysosomal system, often referred to as exosomes, have attracted interest as a suitable biomarker for cancer diagnostics, as they carry valuable biological information and reflect their cells of origin. Herein, we propose a simple and inexpensive electrical method for label-free detection and profiling of sEVs in the size range of exosomes. The detection method is based on the electrokinetic principle, where the change in the streaming current is monitored as the surface markers of the sEVs interact with the affinity reagents immobilized on the inner surface of a silica microcapillary. As a proof-of-concept, we detected sEVs derived from the non-small-cell lung cancer (NSCLC) cell line H1975 for a set of representative surface markers, such as epidermal growth factor receptor (EGFR), CD9, and CD63. The detection sensitivity was estimated to be similar to 175000 sEVs, which represents a sensor surface coverage of only 0.04%. We further validated the ability of the sensor to measure the expression level of a membrane protein by using sEVs displaying artificially altered expressions of EGFR and CD63, which were derived from NSCLC and human embryonic kidney (HEK) 293T cells, respectively. The analysis revealed that the changes in EGFR and CD63 expressions in sEVs can be detected with a sensitivity in the order of 10% and 3%, respectively, of their parental cell expressions. The method can be easily parallelized and combined with existing microfluidic-based EV isolation technologies, allowing for rapid detection and monitoring of sEVs for cancer diagnosis.
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| 2. |
- Gatty, Hithesh K., et al.
(författare)
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A Miniaturized Amperometric Hydrogen Sulfide Sensor Applicable for Bad Breath Monitoring
- 2018
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Ingår i: Micromachines. - : MDPI. - 2072-666X. ; 9:12
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Tidskriftsartikel (refereegranskat)abstract
- Bad breath or halitosis affects a majority of the population from time to time, causing personal discomfort and social embarrassment. Here, we report on a miniaturized, microelectromechanical systems (MEMS)-based, amperometric hydrogen sulfide (H2S) sensor that potentially allows bad breath quantification through a small handheld device. The sensor is designed to detect H2S gas in the order of parts-per-billion (ppb) and has a measured sensitivity of 0.65 nA/ppb with a response time of 21 s. The sensor was found to be selective to NO and NH3 gases, which are normally present in the oral breath of adults. The ppb-level detection capability of the integrated sensor, combined with its relatively fast response and high sensitivity to H2S, makes the sensor potentially applicable for oral breath monitoring.
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| 3. |
- Gatty, Hithesh K, et al.
(författare)
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A wafer level liquid cavity integrated amperometric gas sensor with ppb leve nitric oxide gas sensitivity
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Tidskriftsartikel (refereegranskat)abstract
- A miniaturized amperometric nitric oxide (NO) gas sensor based on wafer-level fabrication of electrodes and a liquid electrolyte chamber is reported in this paper. The sensor is able to detect NO gas concentrations of the order of parts per billion (ppb) levels and has a measured sensitivity of 0.04 nA ppb−1 with a response time of approximately 12 s. A sufficiently high selectivity of the sensor to interfering gases such as carbon monoxide (CO) and to ammonia (NH3) makes it potentially relevant for monitoring of asthma. In addition, the sensor was characterized for electrolyte evaporation which indicated a sensor operation lifetime allowing approximately 200 measurements.
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| 4. |
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| 5. |
- Gatty, Hithesh K., et al.
(författare)
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An amperometric nitric oxide sensor with fast response and ppb-level concentration detection relevant to asthma monitoring
- 2015
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 209, s. 639-644
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Tidskriftsartikel (refereegranskat)abstract
- A MEMS-based amperometric nitric oxide (NO) gas sensor is reported in this paper. The sensor is designed to detect NO gas for the purpose of asthma monitoring. The unique property of this sensor lies in the combination of a microporous high-surface area electrode that is coated with Nafion (TM), together with a liquid electrolyte. The sensor is able to detect gas concentrations of the order of parts-per-billion (ppb) and has a measured NO sensitivity of 0.045 nA/ppb and an operating range between 25 and 65% relative humidity. The settling time of the sensor is measured to 8s. The selectivity to interfering gases such as ammonia (NH3) and carbon monoxide (CO) was high when placing an activated carbon fiber filter above the sensor. The ppb-level detection capability of this sensor combined with its relatively fast response, high selectivity to CO and NH3 makes the sensor potentially applicable in gas monitoring for asthma detection.
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| 6. |
- Gatty, Hithesh K., et al.
(författare)
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Design and Analysis of General Purpose MEMS Accelerometer
- 2007
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Ingår i: International Conference on Sensors and Related Networks (SENNET’07).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Inertial sensors including accelerometers and gyroscopes play an important role in vibration sensing, health monitoring, automotive applications etc. Here we design, fabricate and characterize the set of accelerometers with natural frequencies varying from 8 to 18 kHz. The design is compatible with PolyMUMPs process and has an ease of integrability with the electronic circuits. The operating voltage of the sensor is less than 3.5 V and both the structural and electrode layers are in polysilicon. The user is given an option of choosing the accelerometer in terms of sensitivity and the working range of g (acceleration due to gravity) based on the need of the application. Analytical, Numerical and experimental studies are carried out to determine the sensitivity, frequency range, maximum measurable acceleration and the pull-in voltage of each device. Effect of residual stress on the static and dynamic response characteristics of the accelerometer has been explored and the effect of same on its sensitivity.
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| 7. |
- Gatty, Hithesh K, 1980-
(författare)
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MEMS-based electrochemical gas sensors and wafer-level methods
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes novel microel ectromechanical system (MEMS) based electrochemical gas sensors and methods of fabrication.This thesis presents the research in two parts. In the first part, a method to handle a thin silicon wafer using an electrochemically active adhesive is described. Handling of a thin silicon wafer is an important issue in 3D-IC manufacturing where through silicon vias (TSVs) is an enabling technology. Thin silicon wafers are flexible and fragile, therefore difficult to handle. In addressing the need for a reliable solution, a method based on an electrochemically active adhesive was developed. In this method, an electrochemically active adhesive was diluted and spin coated on a 100 mm diameter silicon wafer (carrier wafer) on which another silicon wafer (device wafer) was bonded. Device wafer was subjected to post processing fabrication technique such as wafer thinning. Successful debonding of the device wafer was achieved by applying a voltage between the two wafers. In another part of the research, a fabrication process for developing a functional nanoporous material using atomic layer deposition is presented. In order to realize a nanoporous electrode, a nanoporous anodized aluminum oxide (AAO) substrate was used, which was functionalized with very thin layers (~ 10 nm) of platinum (Pt) and aluminum oxide (Al2O3) using atomic layer deposition. Nanoporous material when used as an electrode delivers high sensitivity due to the inherent high surface area and is potentially applicable in fuel cells and in electrochemical sensing.The second part of the thesis addresses the need for a high performance gas sensor that is applicable for asthma monitoring. Asthma is a disease related to the inflammation in the airways of the lungs and is characterized by the presence of nitric oxide gas in the exhaled breath. The gas concentration of above approximately 50 parts-per-billion indicates a likely presence of asthma. A MEMS based electrochemical gas sensor was successfully designed and developed to meet the stringent requirements needed for asthma detection. Furthermore, to enable a hand held asthma measuring instrument, a miniaturized sensor with integrated electrodes and liquid electrolyte was developed. The electrodes were assembled at a wafer-level to demonstrate the feasibility towards a high volume fabrication of the gas sensors. In addition, the designed amperometric gas sensor was successfully tested for hydrogen sulphide concentration, which is a bio marker for bad breath.
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| 8. |
- Gatty, Hithesh K., et al.
(författare)
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Temporary wafer bonding and debonding by an electrochemically active polymer adhesive for 3D integration
- 2013
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Ingår i: Micro Electro Mechanical Systems (MEMS), 2013 IEEE 26th International Conference on. - New York : IEEE. - 9781467356541 ; , s. 381-384
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Konferensbidrag (refereegranskat)abstract
- Thin wafer handling is an important issue in 3D integration technologies. This paper reports on an efficient method for bonding a thin wafer and debonding it at room temperature from a carrier wafer. This method addresses the major problem of fragility and flexibility in handling of thin wafers used in TSV fabrication. In the presented method the carrier wafer is spin coated with an electrochemically active polymer adhesive. It is then bonded to a device wafer. The wafer stack is thinned and finally released from the carrier wafer by applying a voltage.
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| 9. |
- Gatty, Hithesh K., et al.
(författare)
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Temporary Wafer Bonding and Debonding for 3D Integration Using an Electrochemically Active Polymer Adhesive
- 2014
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Ingår i: ECS Journal of Solid State Science and Technology. - : The Electrochemical Society. - 2162-8769 .- 2162-8777. ; 3:5, s. P115-P121
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Tidskriftsartikel (refereegranskat)abstract
- The use of thin silicon wafers is an enabling technology for 3D integration in the semiconductor industry. However, thin silicon wafers are fragile to handle and reliable solutions are required for thin wafer handling. This paper reports a novel method of bonding and debonding a thin wafer (< 50 mu m) using an electrochemically active polymer adhesive. In the presented method the carrier wafer is first spin coated with the adhesive and then bonded to the device wafer by applying force and temperature. Debonding of the wafer is realized at room temperature by applying a voltage between the carrier and the device wafer, which substantially reduces the bond strength. The bonding and debonding properties of the adhesive show that temporary wafer bonding using electrochemically active adhesives has the potential to be an attractive approach for temporary wafer bonding for thin wafer handling in 3D integration processes.
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| 10. |
- Gatty, Hithesh K., et al.
(författare)
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Wafer-level fabrication of individual solid-state nanopores for sensing single DNAs
- 2020
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 31:35
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Tidskriftsartikel (refereegranskat)abstract
- For biomolecule sensing purposes a solid-state nanopore platform based on silicon has certain advantages as compared to nanopores on other substrates such as graphene, silicon nitride, silicon oxide etc Capitalizing on the developed CMOS technology, nanopores on silicon are scalable without any requirement for additional processing, the devices are low cost and the process can be repeatable with a high yield. One of the essential requirements in biomolecule sensing is the ability of the nanopore to interact with the analyte. In this work, we present a method for processing high aspect ratio, single nanopores in the range of 10-30 nm in diameter and approximately 700 nm in length on a silicon-on-insulator (SOI) wafer. The presented method of manufacturing the high aspect ratio individual nanopores combines optical lithography and anisotropic KOH etching with a final electrochemical etching step to form the nanopores and is repeatable and can be processed in batches. We demonstrate electrical detection of dsDNA translocation, where the characteristic time of the process is in the millisecond range. We also analyse the translocation parameters and correlate the enhanced length of the nanopore to a longer translocation time as compared to other substrates.
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