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  • 1.
    Fernández Schrunder, Alejandro D.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Design of a hand-held reader for implantable applications2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Internet of Medical Things (IoMT) has rightfully motivated a surge of personal healthcare technological solutions in the form of wearable and implantable devices. Implantable biomedical devices are an attractive personal healthcare solution when physical limitations related to the interactions of electrical signals in the body restrict the reliability of wearable devices. For instance, retinal and cochlear implants, pacemakers, and neural recording interfaces, are among the many applications of implantable devices. However, implantable devices have stringent limitations in terms of size, weight, power consumption, heat dissipation, biocompatibility, and power independence. In many applications, using batteries to power the implantable device is not a feasible solution, and wireless communication is generally preferred. Therefore, a suitable solution for implantable systems is an external reader, which transfers power and communicates through a single RF link.This master thesis presents the design, implementation/assembly, and characterization of a hand-held reader for implantable applications. More specifically, this work addresses the design of an inductive link for wireless power transfer (WPT) and communication using an analytical modeling design flow, and electromagnetic (EM) simulations. The resulting link’s electrical parameters and performance metrics from analytical modeling and EM simulations are presented and compared. Moreover, this work includes the design of the associated powering and communication hardware of the reader, including its final integration on a printed circuit board (PCB) and respective packaging. The hand-held reader has been electrically characterized over a distance range below its nominal working distance, and its functionality has been demonstrated, in conjunction with a sensor prototype, at 20 mm separation between the reader and sensor coils. However, the electrical characterization of the reader shows that the performance of the inductive link is heavily degraded in terms of itsvoltage gain ( A=1.22V / V ), as compared to the results of analytical modeling ( A=6.108V /V ), EM simulations ( A=9.421V /V ), and circuit simulations ( A=10V /V ). This is believed to be caused by the power amplifier non-idealities, as well as load mismatches and a lower Q-factor of the primary coil, due to PCB parasitics and passive components tolerances. Nevertheless, The measurement results demonstrate that the implemented reader fulfills the specifications imposed by the targeted implantable device. This project was carried out at KTH’s Circuits and Systems Group in collaboration with OnabLab AB

  • 2.
    Fernández Schrunder, Alejandro
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Huang, Yu-Kai
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Rodriguez, Saul
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Rusu, Ana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    A Bioimpedance Spectroscopy Interface for EIM Based on IF-Sampling and Pseudo 2-Path SC Bandpass ΔΣ ADC2024In: IEEE Transactions on Biomedical Circuits and Systems, ISSN 1932-4545, E-ISSN 1940-9990, p. 1-13Article in journal (Refereed)
    Abstract [en]

    This paper presents a low-noise bioimpedance (bio-Z) spectroscopy interface for electrical impedance myography (EIM) over the 1 kHz to 2 MHz frequency range. The proposed interface employs a sinusoidal signal generator based on direct-digital-synthesis (DDS) to improve the accuracy of the bio-Z reading, and a quadrature low-intermediate frequency (IF) readout to achieve a good noise-to-power efficiency and the required data throughput to detect muscle contractions. The readout is able to measure baseline and time-varying bio-Z by employing robust and power-efficient low-gain IAs and sixth-order single-bit bandpass (BP) ΔΣ ADCs. The proposed bio-Z spectroscopy interface is implemented in a 180 nm CMOS process, consumes 344.3 - 479.3 μ W, and occupies 5.4 mm 2 area. Measurement results show 0.7 mΩ/√Hz sensitivity at 15.625 kHz, 105.8 dB SNR within 4 Hz bandwidth, and a 146.5 dB figure-of-merit. Additionally, recording of EIM in time and frequency domain during contractions of the bicep brachii muscle demonstrates the potential of the proposed bio-Z interface for wearable EIM systems.

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  • 3.
    Fernández Schrunder, Alejandro
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Rodriguez, Saul
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Rusu, Ana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    A Finite Element Analysis and Circuit Modelling Methodology for Studying Electrical Impedance Myography of Human Limbs2022In: IEEE Transactions on Biomedical Engineering, ISSN 0018-9294, E-ISSN 1558-2531, Vol. 69, no 1, p. 244-255Article in journal (Refereed)
    Abstract [en]

    Objective: Electrical impedance myography (EIM) measures bioimpedance over muscles. This paper proposes a circuit-based modelling methodology originated from finite element analysis (FEA), to emulate tissues and effects from anthropometric variations, and electrode placements, on EIM measurements. The proposed methodology is demonstrated on the upper arms and lower legs. Methods: FEA evaluates impedance spectra (Z-parameters), sensitivity, and volume impedance density for variations of subcutaneous fat thickness (tf), muscle thickness (tm), and inter-electrode distance (IED), on limb models over 1Hz-1MHz frequency range. The limbs models are based on simplified anatomical data and dielectric properties from published sources. Contributions of tissues to the total impedance are computed from impedance sensitivity and density. FEA Z-parameters are imported into a circuit design environment, and used to develop a three Cole dispersion circuit-based model. FEA and circuit model simulation results are compared with measurements on ten human subjects. Results: Muscle contributions are maximized at 31.25kHz and 62.5kHz for the upper arm and lower leg, respectively, at 4cm IED. The circuit model emulates variations in tf and tm, and simulates up to 89 times faster than FEA. The circuit model matches subjects measurements with RMS errors < 36.43 and < 17.28, while FEA does with < 36.59 and < 4.36. Conclusions: We demonstrate that FEA is able to estimate the optimal frequencies and electrode placements, and circuit-based modelling can accurately emulate the limbs bioimpedance. Significance: The proposed methodology facilitates studying the impact of biophysical principles on EIM, enabling the development of future EIM acquisition systems.

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  • 4.
    Fernández Schrunder, Alejandro
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Rusu, Ana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    A Low-Distortion Current-Mode Signal Generator for Wide-Range Bioimpedance Spectroscopy2023In: ISCAS 2023: 56th IEEE International Symposium on Circuits and Systems, Proceedings, IEEE, 2023Conference paper (Refereed)
    Abstract [en]

    This paper presents a low-distortion current-mode sinusoidal signal generator for bioimpedance spectroscopy measurements. The proposed full current-mode operation enables linearity enhancement and potential savings in silicon area and power consumption. Programmability in the low-pass filter and current driver enables impedance measurements from 0.2 Ω to10 kΩ over a wide frequency range from 1 kHz to 1 MHz.The current generator, designed in a 0.18 μm CMOS process, consumes between 736 μW at the lowest frequency and gain, and 1.70 mW at the highest frequency and gain, and occupies 1.76 mm2 silicon area. Post-layout simulation results show a spurious-free dynamic range larger than 40 dBc over the entire frequency range, which enables bioimpedance measurements with errors below 1%, as it is required for wearable devices evaluating neuromuscular disorders.

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  • 5.
    Fernández Schrunder, Alejandro
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Rusu, Ana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    A Mixer-First Analog Front-End for Dry-Electrode Bioimpedance Spectroscopy2023In: BioCAS 2023 - 2023 IEEE Biomedical Circuits and Systems Conference, Conference Proceedings, Institute of Electrical and Electronics Engineers (IEEE) , 2023Conference paper (Refereed)
    Abstract [en]

    This paper presents a high input impedance, low-noise, and low-distortion analog front-end (AFE) for bioimpedance (bio-Z) spectroscopy measurements targeting neuromuscular health assessments. The proposed 8-phase quadrature mixer-first architecture achieves a high input impedance through passive mixers driven by non-overlapping clocks. The 8-phase signals are recombined to extract the real and imaginary parts of the bio-Z, while rejecting unwanted harmonics to improve linearity. Programmability of the AFE enables accurate bio-Z measurements up to 10 kΩ for 11 logarithmically spaced frequencies, in the 1 kHz to 1 MHz frequency range. The AFE, designed in a 0.18 μm CMOS process, consumes 245.99 μW at the lowest gain and 300.56 μW at the highest gain, and occupies 2.4 mm2 silicon area. Post-layout simulation results show that the input impedance is always higher than the electrode impedance by more than 10x. The AFE achieves a sensitivity of 7.7 mΩrms, and a maximum SNDR of 103.87 dBFS over a 61 Hz bandwidth. These results demonstrate that the proposed AFE enables bio-Z measurements, using dry electrodes, with errors below 1%.

  • 6.
    Fernández Schrunder, Alejandro
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Rusu, Ana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    A Mixer-First Analog Front-End or Dry-electrode Bioimpedance Spectroscopy2023Conference paper (Refereed)
    Abstract [en]

    This paper presents a high input impedance,low-noise, and low-distortion analog front-end (AFE) forbioimpedance (bio-Z) spectroscopy measurements targeting neu-romuscular health assessments. The proposed 8-phase quadra-ture mixer-first architecture achieves a high input impedancethrough passive mixers driven by non-overlapping clocks. The 8-phase signals are recombined to extract the real and imaginaryparts of the bio-Z, while rejecting unwanted harmonics toimprove linearity. Programmability of the AFE enables accuratebio-Z measurements up to 10 kΩ for 11 logarithmically spacedfrequencies, in the 1 kHz to 1 MHz frequency range. The AFE,designed in a 0.18 μm CMOS process, consumes 245.99 μW atthe lowest gain and 300.56 μW at the highest gain, and occupies2.4 mm2 silicon area. Post-layout simulation results show that theinput impedance is always higher than the electrode impedanceby more than 10x. The AFE achieves a sensitivity of 7.7 mΩrms,and a maximum SNDR of 103.87 dBFS over a 61 Hz bandwidth.These results demonstrate that the proposed AFE enables bio-Zmeasurements, using dry electrodes, with errors below 1%.

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  • 7.
    Ollmar, Stig
    et al.
    Department of Clinical Science, Intervention and Technology, Karolinska Institute, Stockholm, Sweden.
    Fernández Schrunder, Alejandro
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Birgersson, Ulrik
    Department of Clinical Science, Intervention and Technology, Karolinska Institute, Stockholm, Sweden.
    Kristoffersson, Tomas
    Prevas AB, Stockholm, Sweden.
    Rusu, Ana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Thorsson, Elina
    Pathology Unit, Department of Biomedical Science and Veterinary Public Health, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Hedenqvist, Patricia
    Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Manell, Elin
    Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden..
    Rydén, Anneli
    Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden..
    Jensen-Waern, Marianne
    Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Rodriguez, Saul
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    A battery-less implantable glucose sensor based on electrical impedance spectroscopy2023In: Scientific Reports, E-ISSN 2045-2322, Vol. 13, no 1, article id 18122Article in journal (Refereed)
    Abstract [en]

    The ability to perform accurate continuous glucose monitoring without blood sampling has revolutionised the management of diabetes. Newer methods that can allow measurements during longer periods are necessary to substantially improve patients’ quality of life. This paper presents an alternative method for glucose monitoring which is based on electrical impedance spectroscopy. A battery-less implantable bioimpedance spectroscope was designed, built, and used in an in vivo study on pigs. After a recovery period of 14 days post surgery, a total of 236 subcutaneous bioimpedance measurements obtained from intravenous glucose tolerance tests, with glucose concentration ranges between 77.4 and 523.8 mg/dL, were analyzed. The results show that glucose concentrations estimated by subcutaneous bioimpedance measurements correlate very well to the blood glucose reference values. The pigs were clinically healthy throughout the study, and the postmortem examinations revealed no signs of adverse effects related to the sensor. The implantation of the sensor requires minor surgery. The implant, being externally powered, could in principle last indefinitely. These encouraging results demonstrate the potential of the bioimpedance method to be used in future continuous glucose monitoring systems.

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1 - 7 of 7
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