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The objective of this study was to assess the performance of a capacitive sensor in measuring moisture content of cotton within the moisture range of 6-13%. The assessment was conducted in two phases: static and dynamic. During the static phase, models to predict moisture content were created and a 95% Confidence Interval of [-0.619,0.619], Percent Residual Accuracy of 97.586%, and a mean error of 4.396% were achieved. The Bland-Altman plot yielded a curve with a slight positive trend, suggesting the data could be modeled more appropriately by multiple models. The dynamic phase saw similar results as the static tests in overall trends, however the predicted values tended to be less accurate than static testing. Static testing had a RMSE of 0.313 compared to the dynamic testing having a RMSE of 0.737 [MC%]. Future work should increase the number of data points in the dynamic environment to improve these statistical markers.

This research presents a novel capacitive-sensing-based method to measure fluid velocity for microfluidics devices. To illustrate the importance of fluid velocity measurement, a case study was first conducted for a split and recombine micromixer. The study underscored the influence of fluid velocity on micromixer efficiency and mixing quality. The proposed fluid velocity measurement method employs two capacitance sensing electrodes placed along the fluid channel, capable of detecting small capacitance changes as fluid passing through the sensing area. The relation between capacitance changes and fluid velocity in the proposed sensing structures was developed and hence used to estimate fluid velocity. The proposed technique does not require extensive bench equipment and is suitable for point-of-care applications. To validate our approach, we implemented a two-step 3D printing process, creating a Polylactic acid (PLA) micro platform with embedded graphene–PLA composite electrodes. The accuracy of the developed method was investigated by cross-verifying the obtained velocities with an optical measurement method. Most absolute percentage discrepancies between the results from the proposed method and the optical method are under 12%, validating the precision of the proposed method. Future research will focus on integrating this velocity measurement method into microfluidic devices produced using advanced microfabrication technologies.

The notion of designing circuits based on charge sensing, charge adaptation, and charge programming is explored in this research. This design concept leads to a low-power capacitive sensing interface circuit that has been designed and tested with a MEMS microphone and a capacitive micromachined ultrasonic transducer. Moreover, by using the charge programming technique, a designed floating-gate based large-scale field-programmable analog array (FPAA) containing a universal sensor interface sets the stage for reconfigurable smart sensory systems. Based on the same charge programming technique, a compact programmable analog radial-basis-function (RBF) based classifier and a resultant analog vector quantizer have been developed and tested. Measurement results have shown that the analog RBF-based classifier is at least two orders of magnitude more power-efficient than an equivalent digital processor. Furthermore, an adaptive bump circuit that can facilitate unsupervised learning in the analog domain has also been proposed. A projection neural network for a support vector machine, a powerful and more complicated binary classification algorithm, has also been proposed. This neural network is suitable for analog VLSI implementation and has been simulated and verified on the transistor level. These analog classifiers can be integrated at the interface to build smart sensory systems.

Many electronic products of today utilize some form of touch technology. Looking at everything from smartphone screens to ticket vending machines, it is obvious that the number of applications is big and the demand is huge. Touch technologies generally require no force to use, which reduces mechanical wear-and-tear and thus increases their lifespan. In this thesis, a touch system was constructed to control RGB LEDs. The sensor surface was made from a white, semi-clear plastic, through which the LEDs’ light should be visible. Since the plastic both needed to transmit visible light and act as a touch surface, a problem arose: how do you construct a transparent touch sensor that can control RGB LEDs in a reliable way? Firstly, this thesis describes and discusses many of the different available touch technologies and their strengths and weaknesses. From this information, a specific sensor technology was chosen, from which a prototype of the transparent touch sensor was built. The sensor prototype was a capacitive sensor, made from a thin metallic mesh, placed on the back of the plastic surface. Using an embedded system, based on a differential capacitance touch IC and a microcontroller, the capacitance of the sensor was measured and converted into signals which controlled the LEDs. In order to ensure the sensor’s reliability, the environmental factors which affected the sensor had to be determined and handled. To do this, measurements were performed on the sensor to see how its capacitance changed with environmental changes. It was concluded that moisture, temperature and frequency had negligible effect on the sensor’s dielectric properties. However, it was discovered that proximity to ground greatly affected the sensor and that the sensor was significantly dependent on its enclosure and grounding. / Många av de elektronikprodukter som produceras idag använder någon form av touchteknik. Då den används i allt från skärmar på smartphones till biljettautomater är det tydligt att användningsområdena är många och att efterfrågan är stor. Touchtekniker kräver i regel ingen kraft för att användas, vilket minskar mekaniskt slitage och därför ökar dess livslängd. I detta arbete skulle en touchstyrning till en uppsättning RGB-lysdioder byggas. Problemet var att sensorytan skulle vara en vit, halvgenomskinlig plast, genom vilken lysdioderna skulle lysa. Eftersom plasten både skulle släppa igenom ljus och agera touchyta uppstod problemet: hur konstruerar man en genomskinlig touchsensor som kan styra RGBlysdioder på ett pålitligt sätt? Denna rapport inleds med att beskriva och diskutera många av de touchtekniker som finns idag samt vilka föroch nackdelar de har. Utifrån denna information valdes en specifik sensorteknik, varifrån en prototyp på den genomskinliga touchsensorn byggdes. Sensorprototypen var en kapacitiv sensor uppbyggd av ett tunt metallnät placerat bakom plastpanelen. Med ett inbyggt system, bestående av en integrerad touchkrets för differentiell kapacitansmätning och en mikrokontroller, mättes sensorns kapacitans och en styrning till lysdioderna implementerades. För att säkerställa sensorns pålitlighet var det viktigt att analysera vilka miljöfaktorer som påverkade sensorn och hur de kunde hanteras. Mätningar utfördes därför på sensorn för att se hur dess kapacitans förändrades med avseende på dessa. Det kunde konstateras att fukt, temperatur och frekvens hade försumbar påverkan på sensorns dielektrum. Däremot kunde det visas att närhet till jordplan påverkade sensorn avsevärt och att sensorns tillförlitlighet berodde signifikant på dess inkapsling och jordning.

Nanotechnology offers great promise for the development of nanodevices. Hence it becomes important to study the mechanical behavior of nanostructures for their use in such systems. MEMS (Micro ElectroMechanical Systems) provide an effective and precise method for testing nanostructures. Consequently this study focuses on the development of a MEMS thermal nanotensile tester to investigate the mechanical behavior of one-dimensional nanostructures. Extensive characterization of these MEMS devices (structural, electrical and thermal behavior) was performed using experimental as well as finite element methods. Tensile testing of nanostructures requires manipulation of individual nanostructures on the MEMS device. The study involves the development of an efficient methodology for the manipulation of nanowires and nanobeams for nanoscale testing. Furthermore, two different sensing schemes for the developed devices, namely capacitive and resistive, have been extensively investigated and the advantages and various issues related to both have been discussed. Nanocrystalline (nc) Ni nanobeams (typical dimensions of 500 nm x 200 nm x 20 µm) have been tested to failure using the MEMS devices. Improvements in the design for the MEMS nanotensile tester have been suggested to significantly enhance the device performance and to resolve the various issues involved with nano scale tests. Differential capacitive sensing for stress-strain measurements has been suggested to improve the accuracy of strain measurements.

Sensor interfaces are needed to communicate the measured real-world analog values to the base¬band digital processor. They are dominated by the presence of high accuracy, high resolution analog to digital converters (ADC) in the backend. On most occasions, sensing is limited to small range measurements and low-modulation sensors where the complete dynamic range of ADC is not utilized. Designing a subsystem that integrates the sensor and the interface circuit and that works with a low resolution ADC requiring a small die-area is a challenge. In this work, we present a CMOS based area efficient, integrated sensor interface for applications like capacitance, temperature and dielectric-constant measurement. In addition, potential applica-tions for this work are in Cognitive Radios, Software Defined Radios, Capacitance Sensors, and location monitoring. The key contributions in the thesis are: 1 High Sensitivity Frequency-domain CMOS Capacitance Interface: A frequency domain capacitance interface system is proposed for a femto-farad capacitance measurement. In this technique, a ring oscillator circuit is used to generate a change in time period, due to a change in the sensor capacitance. The time-period difference of two such oscillators is compared and is read-out using a phase frequency detector and a charge pump. The output voltage of the system, is proportional to the change in the input sensor capacitance. It exhibits a maximum sensitivity of 8.1 mV/fF across a 300 fF capacitance range. 2 Sensitivity Enhancement for capacitance sensor: The sensitivity of an oscillator-based differential capacitance sensor has been improved by proposing a novel frequency domain capacitance-to-voltage (FDC) measurement technique. The capacitance sensor interface system is fabricated in a 130-nm CMOS technology with an active area of 0.17mm2 . It exhibits a maximum sensitivity of 244.8 mV/fF and a measurement resolution of 13 aF in a 10-100 fF measurement range, with a 10 pF nominal sensor capacitance and an 8-bit ADC. 3 Frequency to Digital Converter for Time/Distance measurement: A new architecture for a Vernier-based frequency-to-digital converter (VFDC) for location monitoring is pre¬sented, in which, a time interval measurement is performed with a frequency domain approach. Location monitoring is a common problem for many mobile robotic applica¬tions covering various domains, such as industrial automation, manipulation in difficult areas, rescue operations, environment exploration and monitoring, smart environments and buildings, robotic home appliances, space exploration and probing. The proposed architecture employs a new injection-locked ring oscillator (ILR) as the clock source. The proposed ILR oscillator does not need complex calibration procedures, usually required by Phase Locked Loop (PLL) based oscillators in Vernier-based time-to-digital convert¬ers. It consumes 14.4 µW and 1.15 mW from 0.4 V and 1.2 V supplies, respectively. The proposed VFDC thus achieves a large detectable range, fine time resolution, small die size and low power consumption simultaneously. The measured time-difference error is less than 50 ps at 1.2 V, enabling a resolution of 3 mm/kHz frequency shift. 4 A bio-sensor array for dielectric constant measurement: A CMOS on-chip sensor is presented to measure the dielectric constant of organic chemicals. The dielectric constant of these chemicals is measured using the oscillation frequency shift of a current controlled os¬cillator (CCO) upon the change of the sensor capacitance when exposed to the liquid. The CCO is embedded in an open-loop frequency synthesizer to convert the frequency change into voltage, which can be digitized using an off-chip analog-to-digital converter. The dielectric constant is then estimated using a detection procedure including the calibration of the sensor. 5 Integrated Temperature Sensor for thermal management: An integrated analog temper¬ature sensor which operates with simple, low-cost one-point calibration is proposed. A frequency domain technique to measure the on-chip silicon surface temperature, was used to measure the effects of temperature on the stability of a frequency synthesizer. The temperature to voltage conversion is achieved in two steps i.e. temperature to frequency, followed by frequency to voltage conversion. The output voltage can be used to com¬pensate the temperature dependent errors in the high frequency circuits, thereby reduc¬ing the performance degradation due to thermal gradient. Furthermore, a temperature measurement-based on-chip self test technique to measure the 3 dB bandwidth and the central frequency of common radio frequency circuits, was developed. This technique shows promise in performing online monitoring and temperature compensation of RF circuits.

<p>There are no commercially available wearable shoe in-sole sensors that are capable of measuring and distinguishing between shear and compression forces. Companies have already developed shoe sensors that simply measure pressure and make general inferences on the collected data with elaborate software [2, 3, 4, 5]. Researchers have also attempted making sensors that are capable of measuring shear forces, but they are not well suited for biomedical applications [61, 62, 63, 64]. This work focuses on the development of a novel wearable sensor system that is capable of identifying and measuring shear and compression forces through the use of capacitive sensing. Custom hardware and software tools such as materials test systems and capacitive measurement systems were developed during this work. Numerous sensor prototypes were developed, characterized, and optimized during the scope of this project. Upon analysis of the data, the best capacitive measurement system developed in this work utilized the CAV444 IC chip, whereas the use of the Arduino-derived measurement system required data filtering using median and Butterworth zero phase low pass filters. The highest dielectric constant reported from optimization experiments yielded 9.7034 (+/- 0.0801 STD) through the use of 60.2% by weight calcium copper titanate and ReoFlex-60 silicone. The experiments suggest certain sensors developed in this work feasibly measure and distinguish between shear and compressional forces. Applications for such technology focus on improving quality of life in areas such as managing diabetic ulcer formation, preventing injuries, optimizing performance for athletes and military personnel, and augmenting the scope of motion capture in biomechanical studies.</p>