Sensors are extremely valuable to this world. Without sensors, we would not be able to live as we do in this data-driven environment. Therefore, finding new ways to measure the matter around us is a continuous process. In this work, an addition to the new sensors is attempted, using materials that can withstand the most extreme circumstances. This work describes the process of designing, simulating, producing, measuring and validating a pressure sensor based on LPCVD Silicon Carbide.
The created sensor should be modular and back-end-of-line compatible. In addition, the sensor should measure pressures from 80Pa up to 1MPa at temperatures from room temperature to 600°C. Because of a favourable reaction to high temperatures, a capacitive sensor type that uses a sealed membrane for absolute pressure measurements is chosen.
Due to the large pressure range, the design has been split into three distinct parts, each with its specialised pressure range. A low-range for 80Pa to 100kPa, a mid-range sensor for 100kPa to 300kPa and a high-range sensor for 300kPa to 1MPa. To compensate for the nonlinearity in the device, two approaches are taken. One method splits the bottom electrodes, generating a more linear output with the correct division. This approach is used for low-and-mid-pressure devices. The other approach uses touch mode to decrease nonlinearity. After the membrane touches the bottom contact, a linear range is found. This approach is taken for the high-pressure device.
A flowchart has been developed based on the necessary layers to create the sensors. Using this flowchart, masks have been designed. During production, the process was adjusted, as delamination of the dielectric layer was observed. In addition, because of difficulty with sealing, the membrane is thicker than the original design.
During production, buckling of the membranes was observed. This causes the sensors to behave differently compared to the simulations. One effect the buckling may have caused is the reaction to temperature. This is opposite to the simulations. In addition, subjecting the sensors to a vacuum also causes behaviour opposite to what was intended. When high pressure is applied, the sensors do work as intended. Due to the design alterations and buckling effect, the sensors are less sensitive to pressure than intended. The best sensor has a sensitivity of 0.025 f F/100Pa compared to the designed 0.3 f F/100Pa. However, the output of the sensor is linear without needing the designed compensation techniques.

The goal of this Bachelor graduation project is to make an electrical stimulator that can be used to help people empty their urinary bladder. Patients that are unable to relax the urethral sphincter are most commonly treated by mechanically emptying the bladder or by sacral root stimulation where the roots are selectively cut.

The stimulator to be made must send a high-frequency signal that cancels the blocking of the urethral sphincter. This method should be able to empty the bladder without the use of mechanical devices or selectively cutting nerves.

The whole project is divided into three parts: Control and Interface, Arbitrary Waveform Generator and Safety Module. These parts have been performed by three different subgroups. In this report, the Arbitrary Waveform Generator is discussed. The other parts are explained in the respective reports [1, 2].

The requirements for this waveform are to generate a biphasic pulse with frequencies ranging from 1 to 15 kHz. The amplitude range of this pulse should be adjustable between 0 and 10 mA and the pulse width and interphase delay should be fully adjustable. In order to generate this signal, a power management system was necessary. In addition to the power management system, the LPC1343 microcontroller was chosen to control the system. One of its functions is to control a DAC by communication using the SPI protocol. The DAC can linearly control the output voltages between 0 and the offered reference voltage, in this case 3.3 V by sending 10 bits of data. Using a voltage to current converter, made by the Interface and Control subgroup, the output voltage is converted to a current between 0 and 10 mA [1]. Three additional signals from the microcontroller operate an H-bridge. This is a switching circuit that is able to direct the generated current through a load. Using a timer and four interrupt moments, the three signals are generated that can make a cathodic pulse, anodic pulse and can disconnect the current source.

The chosen DAC has a close to ideal behavior. Therefore, the conversion from the microcontroller to the voltage to current converter is very precise. The H-bridge works best at low frequencies. At 1 kHz, around 2% of a total pulse of 127.2 μs is needed to reach 63% of the cathodic or anodic amplitude. At high frequencies, the time increases. At 15 kHz, 24% of a total pulse of 8.4 μs is needed to reach the amplitude.