Space-resolved stimulation of active hydrogel layers can be achieved for example by using a micro-heater array. In the current work, we present the interaction of (i) such a rigid array of heating elements that can be selectively activated and (ii) an active thermo-responsive hydrogel layer that responds to the local stimulus change. Due to the respective local actuation, (iii) the surface form of a passive top-layer can be manipulated. We present continuum-based simulative predictions based on the Temperature Expansion Model and compare them to experimental outcomes for the system.

Recently, there has been an increasing interest in the electronics world for those aspects related to semiconducting gas sensor (SGS) materials. In view of the increasingly strict legal limits for pollutant gas emissions, there is a great interest in developing high performance gas sensors for applications such as controlling air pollution and exhaust gases in automotive industry. In this way, semiconductor gas sensors offer good advantages with respect to other gas sensor devices, due to their simple implementation, low cost and good stability and sensitivity. The first part of the thesis is dedicated to the synthesis, film structural and sensitivity study of the Tin Oxide film deposited by RF sputtering, doped with noble metal Palladium (Pd). Effects on the Gas Sensitivity due to the deposition parameters like thickness of the film, Substrate temperature, Ar /O2 ratio of the sputtering environment, annealing temperature and duration and doping metal weight % into the Tin Oxide films are studied and the results are shown in detail. The sensitivity and selectivity of the gas sensing film is decided by the operating temperature i.e. the temperature of the gas sensing film while it is in the target gas ambience, Microheaters happen to be the very important component in the gas sensor especially with wide band gap semiconducting metal oxides films such as tin oxide, gallium oxide or indium oxides. Other than gas sensing microheater also finds applications in many areas like thermal dip pen nanolithography, polymerase chain reaction (PCR), fluid pumping with bubbles, in vitro fertilization etc. So in this report due importance was given for the design and fabrication of the microheater. Microheaters are the most power consuming element of the integrated Gas sensors. This is also an important reason for the extensive microheater work in this research. Six different heater patterns were simulated by considering low power and temperature uniformity as an important goals. Among them the best three patterns named Double spiral, “Fan” Shape and “S” shape were chosen for fabrication and both thermal and electrical characterization results of them were presented in detail in the Microheater section of the thesis. It is believed that the intelligent design and integration of the electronic circuitry (for drive, signal conditioning/compensation, and read-out) with the gas sensing element can mitigate some of the significant issues inherent in solid-state gas sensors, such as strong temperature and humidity dependence, signal drift, aging, poisoning, and weak selectivity. The sensitivity of the gas sensors which has been indicated as the dynamic change of resistance in wide range should be read out properly. Towards this aim a low cast high efficient readout circuit is designed and implemented. Temperature monitoring and controlling is a key phenomenon in the metal Oxide based gas sensors since the selectivity mainly depends on the operating temperature of the sensing film. So focus was also shown on the design and implementation of the temperature monitoring and control unit, which been presented in the last part of this thesis.

Current gas sensor technology, although meeting the minimum requirements in many instances, suffers for a number of limitations. Hence, there is currently a considerable volume of research being undertaken at many laboratories of different countries. In the past, all chemical sensors and catalyst were optimized empirically by a trial and error method. Today, however, systematic research and development is becoming increasingly important in order to improve sensors and to find new sensing principles. Obtaining a long term stable gas sensor with improved sensitivity, selectivity, and low cost for mass production passes through fundamental research and material characterization to build new chemically sensitive devices or to improve existing ones. The bottom line in the design and manufacture of modern gas sensors is the transfer from ceramic(of Figaro type) to thin film gas sensors(TFGs). This transfer provides new opportunities for further microminiaturization, power consumption and cost reduction of gas sensors. Therefore, at the present time, thin film gas sensors are the basis for the design of the modern gas sensitive multi-parameter microsensor systems. Applications of these systems include environment, security, home systems, smart buildings, transportation, discrete manufacturing, process industries and so on. Microelectromechanical systems(MEMS) based integrated gas sensors present several advantages for these applications such as ease of array fabrication, small size, and unique thermal manipulation capabilities. MEMS based gas sensors; which are usually produced using a standard CMOS(Complimentary Metal Oxide Semiconductor) process, have the additional advantages of being readily realized by commercial foundries and amenable to the inclusion of on-chip electronics. In order to speed up the design and optimization of such integrated sensors, microheater designs for gas sensor applications have been presented as first part of the present thesis. As heater design is the key part for a gas sensor operation. So 3D simulations have been used to optimize micro-heater geometry. The application of MEMS Design Tool(COVENTORWARE) has been presented to the design and analysis of micro-hotplate (MHP) structures. Coupled Electro-thermal analysis provided an estimation of thermal losses and temperature distribution on the hotplate for realistic geometrical and material parameters pertinent to fabrication technology. Five microheater designs have been proposed in terms of different sizes and shapes in order to optimize the microhotplate structure to be used for gas sensor operation for the specified range of temperature and power consumption. To produce a gas sensor, which is able to detect LPG leak, thin films of tin oxide have been developed. FR sputtering has been used to deposit gas sensitive tin oxide thin filmls under various deposition conditions. Four different values of pressure in the range from high pressure(5 X 10-2 mbar) to lower pressure (2 X 10-3 mbar), three RF power values 50, 75, 100 W and varied oxygen percentage in sputtering atmosphere (0-18%) have been used to optimize the material properties of tin oxide thin films to study the sensitivity towards LPG. All the samples have been analyzed using various macro and microscopic characterization techniques. Extensive studies have been done on the sensor response for the samples deposited under different conditions. Finally the sample film deposited at 5 x 10-3 mbar, with applied power of 75 W in the presence of 8% oxygen, showed maximum sensitivity towards LPG.