dr. M.R. Venkatesh

1. Functional materials for MEMS based gas sensors
   Manjunath Ramachandrappa Venkatesh;
   PhD thesis, Delft University Technology, 2022. DOI: 10.4233/uuid:5bef3e79-1cab-411d-86dd-b9a518628824

2. A Low-Power MEMS IDE Capacitor with Integrated Microhotplate: Application as Methanol Sensor using a Metal-Organic Framework Coating as Affinity Layer
   Venkatesh, Manjunath R; Sachdeva, Sumit; El Mansouri, Brahim; Wei, Jia; Bossche, Andre; Bosma, Duco; de Smet, Louis CPM; Sudhölter, Ernst JR; Zhang, Guo Qi;
   Sensors,
   Volume 19, Issue 4, pp. 888, 2019.
   
   Abstract: ...

   Capacitors made of interdigitated electrodes (IDEs) as a transducer platform for the sensing of volatile organic compounds (VOCs) have advantages due to their lower power operation and fabrication using standard micro-fabrication techniques. Integrating a micro-electromechanical system (MEMS), such as a microhotplate with IDE capacitor, further allows study of the temperature dependent sensing response of VOCs. In this paper, the design, fabrication, and characterization of a low-power MEMS microhotplate with IDE capacitor to study the temperature-dependent sensing response to methanol using Zeolitic imidazolate framework (ZIF-8), a class of metal-organic framework (MOF), is presented. A Titanium nitride (TiN) microhotplate with aluminum IDEs suspended on a silicon nitride membrane is fabricated and characterized. The power consumption of the ZIF-8 MOF-coated device at an operating temperature of 50 °C is 4.5 mW and at 200 °C it is 26 mW. A calibration methodology for the effects of temperature of the isolation layer between the microhotplate electrodes and the capacitor IDEs is developed. The device coated with ZIF-8 MOF shows a response to methanol in the concentration range of 500 ppm to 7000 ppm. The detection limit of the sensor for methanol vapor at 20 °C is 100 ppm. In situ study of sensing properties of ZIF-8 MOF to methanol in the temperature range from 20 °C to 50 °C using the integrated microhotplate and IDE capacitor is presented. The kinetics of temperature-dependent adsorption and desorption of methanol by ZIF-8 MOF are fitted with double-exponential models. With the increase in temperature from 20 °C to 50 °C, the response time for sensing of methanol vapor concentration of 5000 ppm decreases by 28%, whereas the recovery time decreases by 70%.

3. A Low-Power MEMS IDE Capacitor with Integrated Microhotplate: Application as Methanol Sensor using a Metal-Organic Framework Coating as Affinity Layer
   Venkatesh, M.R.; Sachdeva, S.; El Mansouri, B.; Wei, J.; Bossche, A.; Bosma, D.; de Smet; L. C. P. M.; Sudhölter, E. J. R.; GuoQi Zhang;
   Sensors (Basel, Switzerland),
   2019. DOI: 10.3390/s19040888

4. Sensitive and Reversible Detection of Methanol and Water Vapor by In Situ Electrochemically Grown CuBTC MOFs on Interdigitated Electrodes
   S. Sachdeva; M.R. Venkatesh; B.E. Mansouri; J. Wei; A. Bossche; F. Kapteijn; G.Q. Zhang; J. Gascon; L.C.P.M. de Smet; E.J.R. Sudhölter;
   Small,
   Volume 13, Issue 29, 08 2017. DOI: 10.1002/smll.201604150
   
   Abstract: ...

   The in situ electrochemical growth of Cu benzene-1,3,5-tricarboxylate (CuBTC) metal-organic frameworks, as an affinity layer, directly on custom-fabricated Cu interdigitated electrodes (IDEs) is described, acting as a transducer. Crystalline 5-7 µm thick CuBTC layers are grown on IDEs consisting of 100 electrodes with a width and a gap of both 50 µm and a height of 6-8 µm. These capacitive sensors are exposed to methanol and water vapor at 30 °C. The affinities show to be completely reversible with higher affinity toward water compared to methanol. For exposure to 1000 ppm methanol, a fast response is observed with a capacitance change of 5.57 pF at equilibrium. The capacitance increases in time followed diffusion-controlled kinetics (k = 2.9 mmol s-0.5 g-1CuBTC ). The observed capacitance change with methanol concentration follows a Langmuir adsorption isotherm, with a value for the equilibrium affinity Ke = 174.8 bar-1 . A volume fraction fMeOH = 0.038 is occupied upon exposure to 1000 ppm of methanol. The thin CuBTC affinity layer on the Cu-IDEs shows fast, reversible, and sensitive responses to methanol and water vapor, enabling quantitative detection in the range of 100-8000 ppm.

5. Sensitive and Reversible Detection of Methanol and Water Vapor by In Situ Electrochemically Grown CuBTC MOFs on Interdigitated Electrodes
   Sumit Sachdeva; Manjunath R. Venkatesh; Brahim El Mansouri; Jia Wei; Andre Bossche; Freek Kapteijn; GuoQi Zhang; Jorge Gascon; Louis C. P. M. de Smet; Ernst J. R. Sudhölter;
   Small,
   Volume 13, Issue 29, pp. 1604150, 2017.

6. Smart Systems Integration in the era of Solid State Lighting
   GuoQi Zhang; H. van Zeijl; W.D. van Driel; R. Poelma; Z.K. Esfahani; M.R. Venkatesh; L. Middelburg; B. El Mansouri;
   In Smart System Integration conference (SSI),
   2017.

7. Electro-thermal analysis and design of a combined MEMS impedance and micro hotplate device for gas sensing applications
   M.R. Venkatesh; B. El Mansouri; J. Wei; A. Bossche; G.Q. Zhang;
   In 2016 17th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE),
   IEEE, pp. 1-9, 2016.

8. Modeling and simulation of monolithic integration of rectifiers for solid state lighting applications
   Venkatesh, MR; Liu, P; van Zeijl, HW; GuoQi Zhang;
   In Proceedings - 15th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems,
   pp. 1-6, 2014.

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