A high-performance 8 nV/root Hz 8-channel wearable and wireless system for real-time monitoring of bioelectrical signals

Background: It is widely accepted by the scientific community that bioelectrical signals, which can be used for the identification of neurophysiological biomarkers indicative of a diseased or pathological state, could direct patient treatment towards more effective therapeutic strategies. However, the design and realisation of an instrument that can precisely record weak bioelectrical signals in the presence of strong interference stemming from a noisy clinical environment is one of the most difficult challenges associated with the strategy of monitoring bioelectrical signals for diagnostic purposes. Moreover, since patients often have to cope with the problem of limited mobility being connected to bulky and mains-powered instruments, there is a growing demand for small-sized, high-performance and ambulatory biopotential acquisition systems in the Intensive Care Unit (ICU) and in High-dependency wards. Finally, to the best of our knowledge, there are no commercial, small, battery-powered, wearable and wireless recording-only instruments that claim the capability of recording electrocorticographic (ECoG) signals. Methods: To address this problem, we designed and developed a low-noise (8 nV/√Hz), eight-channel, battery-powered, wearable and wireless instrument (55 × 80 mm2). The performance of the realised instrument was assessed by conducting both ex vivo and in vivo experiments. Results: To provide ex vivo proof-of-function, a wide variety of high-quality bioelectrical signal recordings are reported, including electroencephalographic (EEG), electromyographic (EMG), electrocardiographic (ECG), acceleration signals, and muscle fasciculations. Low-noise in vivo recordings of weak local field potentials (LFPs), which were wirelessly acquired in real time using segmented deep brain stimulation (DBS) electrodes implanted in the thalamus of a non-human primate, are also presented. Conclusions: The combination of desirable features and capabilities of this instrument, namely its small size (~one business card), its enhanced recording capabilities, its increased processing capabilities, its manufacturability (since it was designed using discrete off-the-shelf components), the wide bandwidth it offers (0.5 – 500 Hz) and the plurality of bioelectrical signals it can precisely record, render it a versatile and reliable tool to be utilized in a wide range of applications and environments

Mems teknolojisi ile yüzey mikroişlenmiş kapasitif ivme ölçerler

Micromachined accelerometers have found large attention in recent years due to their low-cost and small size. There are extensive studies with different approaches to implement accelerometers with increased performance for a number of military and industrial applications, such as guidance control of missiles, active suspension control in automobiles, and various consumer electronics devices. This thesis reports the development of various capacitive micromachined accelerometers and various integrated CMOS readout circuits that can be hybrid-connected to accelerometers to implement low-cost accelerometer systems. Various micromachined accelerometer prototypes are designed and optimized with the finite element (FEM) simulation program, COVENTORWARE, considering a simple 3-mask surface micromachining process, where electroplated nickel is used as the structural layer. There are 8 different accelerometer prototypes with a total of 65 different structures that are fabricated and tested. These accelerometer structures occupy areas ranging from 0.2 mm2 to 0.9 mm2 and provide sensitivities in the range of 1-69 fF/g. Various capacitive readout circuits for micromachined accelerometers are designed and fabricated using the AMS 0.8 æm n-well CMOS process, including a single-ended and a fully-differential switched-capacitor readout circuits that can operate in both open-loop and close-loop. Using the same process, a buffer circuit with 2.26fF input capacitance is also implemented to be used with micromachined gyroscopes. A single-ended readout circuit is hybrid connected to a fabricated accelerometer to implement an open-loop accelerometer system, which occupies an area less than 1 cm2 and weighs less than 5 gr. The system operation is verified with various tests, which show that the system has a voltage sensitivity of 15.7 mV/g, a nonlinearity of 0.29 %, a noise floor of 487 HzMikroişlenmiş ivmeölçerler, düşük maliyetleri ve küçük boyutları sebebiyle son yıllarda büyük ilgi görmektedir. Füzelerde güdüm kontrolü, otomobillerde aktif süspansiyon kontrolü, ve çeşitli tüketici elektronik aygıtları gibi askeri ve endüstriyel uygulamalarda, daha yüksek performanslı ivmeölçerler yapabilmek için farklı açılardan, geniş çaplı araştırmalar yürütülmektedir. Bu tez çeşitli ivmeölçer yapılarını ve düşük maliyetli ivmeölçer sistemleri oluşturabilmek için ivmeölçerlere hibrit bağlanabilecek çeşitli entegre CMOS okuma devrelerini rapor etmektedir. Çeşitli mikroişlenmiş ivmeölçerler COVENTORWARE sonlu eleman simulatorü ile elektro kaplanmış nikelin yapısal kaptan olarak kullanıldığı, 3 maskeli yüzey mikroişleme üretimine göre tasarlanmış ve optimize edilmiştir. Üretilmiş ve test edilmiş 65 değişik yapıdan oluşan 8 farklı ivmeölçer prototipi bulunmaktadır. Bu ivmeölçer yapıları, 0.2 mm2 ile 0.9 mm2 arasında değişen alanları vi kaplamaktadırlar ve 1-69 fF/g aralığında değişen kapasite hassasiyeti sağlamaktadırlar. Açık döngü ve kapalı döngü olarak çalışabilen, bir tek çıkışlı ve bir tamamiyle fark gösteren anahtarlamalı kapasitör okuma devrelerini içeren çeşitli kapasitif okuma devreleri AMS 0.8 µm CMOS işleme ile dizayn edilip üretilmiştir. Aynı işlemeyi kullanarak, mikroişlenmiş jiroskoplarda kullanılmak üzere giriş kapasitesi 2.26 fF olan bir tampon devresi de oluşturulmuştur. 1 cm2 den daha az alan kaplayan ve 5 gr. dan daha hafif olan açık döngülü bir ivmeölçer sistemi oluşturmak için tek çıkışlı okuma devresi, üretilen bir ivmeölçere hibrit bağlanmıştır. Sistemin 5 V kaynaktan 20 mW’dan daha az güç tüketirken, 15.7 mV/g orantı katsayısı, % 0.29 orantı katsayısı hatası, 487 µg Hz gürültü seviyesi, ve 13.9 mg bias kararsızlığı olduğunu gösteren çeşitli testlerle sistemin çalışması onaylanmıştır. Bu araştırmada sunulan sistem Türkiye’de geliştirilen ilk ivmeölçer sistemidir, ve ivmeölçerler ve dönüölçerlerden oluşan düşük maliyetli ulusal ataletsel ölçüm birimi üzerine yapılan araştırmanın bir parçasıdır.M.S. - Master of Scienc