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Fernández Schrunder, AlejandroORCID iD iconorcid.org/0000-0001-7549-0858
Publications (6 of 6) Show all publications
Fernández Schrunder, A., Huang, Y.-K., Rodriguez, S. & Rusu, A. (2024). A Bioimpedance Spectroscopy Interface for EIM Based on IF-Sampling and Pseudo 2-Path SC Bandpass ΔΣ ADC. IEEE Transactions on Biomedical Circuits and Systems, 1-13
Open this publication in new window or tab >>A Bioimpedance Spectroscopy Interface for EIM Based on IF-Sampling and Pseudo 2-Path SC Bandpass ΔΣ ADC
2024 (English)In: IEEE Transactions on Biomedical Circuits and Systems, ISSN 1932-4545, E-ISSN 1940-9990, p. 1-13Article in journal (Refereed) Epub ahead of print
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.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2024
Keywords
Bioimpedance spectroscopy, electrical impedance myography, analog front-end, sinusoidal signal generator, instrumentation amplifier, bandpass sigma-delta modulator, low-noise.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Medical Engineering
Research subject
Electrical Engineering; Medical Technology
Identifiers
urn:nbn:se:kth:diva-345246 (URN)10.1109/tbcas.2024.3370399 (DOI)2-s2.0-85186995458 (Scopus ID)
Funder
Swedish Foundation for Strategic Research, ITM17-0079
Note

QC 20240411

Available from: 2024-04-10 Created: 2024-04-10 Last updated: 2024-04-11Bibliographically approved
Ollmar, S., Fernández Schrunder, A., Birgersson, U., Kristoffersson, T., Rusu, A., Thorsson, E., . . . Rodriguez, S. (2023). A battery-less implantable glucose sensor based on electrical impedance spectroscopy. Scientific Reports, 13(1), Article ID 18122.
Open this publication in new window or tab >>A battery-less implantable glucose sensor based on electrical impedance spectroscopy
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2023 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 13, no 1, article id 18122Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Springer Nature, 2023
National Category
Medical Equipment Engineering
Research subject
Technology and Health
Identifiers
urn:nbn:se:kth:diva-338925 (URN)10.1038/s41598-023-45154-8 (DOI)001087271600078 ()37872272 (PubMedID)2-s2.0-85174690457 (Scopus ID)
Funder
Swedish Foundation for Strategic Research, ITM17-0079
Note

This work was partially funded by D.T.R.  Dermal Therapy Research Inc of Canada and the Swedish Foundation for Strategic Research (SSF) under project number ITM17-0079. 

QC 20240102

Available from: 2023-10-30 Created: 2023-10-30 Last updated: 2024-01-02
Fernández Schrunder, A. & Rusu, A. (2023). A Low-Distortion Current-Mode Signal Generator for Wide-Range Bioimpedance Spectroscopy. In: ISCAS 2023: 56th IEEE International Symposium on Circuits and Systems, Proceedings. Paper presented at 56th IEEE International Symposium on Circuits and Systems (ISCAS), Monterey, California, May 21-25, 2023. IEEE
Open this publication in new window or tab >>A Low-Distortion Current-Mode Signal Generator for Wide-Range Bioimpedance Spectroscopy
2023 (English)In: ISCAS 2023: 56th IEEE International Symposium on Circuits and Systems, Proceedings, IEEE, 2023Conference paper, Published 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.

Place, publisher, year, edition, pages
IEEE, 2023
Keywords
bioimpedance spectroscopy, sinusoidal signal generator, current-mode, programmable gain, programmable low-pass filter, low-distortion.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-328912 (URN)10.1109/ISCAS46773.2023.10181880 (DOI)001038214602012 ()2-s2.0-85167652994 (Scopus ID)
Conference
56th IEEE International Symposium on Circuits and Systems (ISCAS), Monterey, California, May 21-25, 2023
Funder
Swedish Foundation for Strategic Research, ITM17-0079
Note

Part of ISBN 978-1-6654-5109-3

QC 20231002

Available from: 2023-06-13 Created: 2023-06-13 Last updated: 2023-10-02Bibliographically approved
Fernández Schrunder, A. & Rusu, A. (2023). A Mixer-First Analog Front-End for Dry-Electrode Bioimpedance Spectroscopy. In: BioCAS 2023 - 2023 IEEE Biomedical Circuits and Systems Conference, Conference Proceedings: . Paper presented at 2023 IEEE Biomedical Circuits and Systems Conference, BioCAS 2023, Toronto, Canada, Oct 19 2023 - Oct 21 2023. Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>A Mixer-First Analog Front-End for Dry-Electrode Bioimpedance Spectroscopy
2023 (English)In: BioCAS 2023 - 2023 IEEE Biomedical Circuits and Systems Conference, Conference Proceedings, Institute of Electrical and Electronics Engineers (IEEE) , 2023Conference paper, Published 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%.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2023
Keywords
analog front-end, bioimpedance spectroscopy, dry electrodes, high input impedance, low-distortion, low-noise, passive mixer, programmable gain
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-343702 (URN)10.1109/BioCAS58349.2023.10388966 (DOI)2-s2.0-85184898068 (Scopus ID)
Conference
2023 IEEE Biomedical Circuits and Systems Conference, BioCAS 2023, Toronto, Canada, Oct 19 2023 - Oct 21 2023
Note

QC 20240223

Part of ISBN 979-8-3503-0026-0

Available from: 2024-02-22 Created: 2024-02-22 Last updated: 2024-02-23Bibliographically approved
Fernández Schrunder, A. & Rusu, A. (2023). A Mixer-First Analog Front-End or Dry-electrode Bioimpedance Spectroscopy. In: : . Paper presented at IEEE Biomedical Circuits and Systems Conference (BioCAS), Toronto, Canada, October 19-21, 2023.
Open this publication in new window or tab >>A Mixer-First Analog Front-End or Dry-electrode Bioimpedance Spectroscopy
2023 (English)Conference paper, Published 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%.

Keywords
Bioimpedance spectroscopy, high input impedance, dry electrodes, analog front-end, passive mixer, low-noise, low-distortion, programmable gain.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-338923 (URN)
Conference
IEEE Biomedical Circuits and Systems Conference (BioCAS), Toronto, Canada, October 19-21, 2023
Funder
Swedish Foundation for Strategic Research, ITM17-0079
Note

QC 20231101

Available from: 2023-10-30 Created: 2023-10-30 Last updated: 2023-11-01Bibliographically approved
Fernández Schrunder, A., Rodriguez, S. & Rusu, A. (2022). A Finite Element Analysis and Circuit Modelling Methodology for Studying Electrical Impedance Myography of Human Limbs. IEEE Transactions on Biomedical Engineering, 69(1), 244-255
Open this publication in new window or tab >>A Finite Element Analysis and Circuit Modelling Methodology for Studying Electrical Impedance Myography of Human Limbs
2022 (English)In: IEEE Transactions on Biomedical Engineering, ISSN 0018-9294, E-ISSN 1558-2531, Vol. 69, no 1, p. 244-255Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2022
Keywords
Bioimpedance, Muscle, Electrical Impedance Myography, Finite Element Analysis, Circuit Simulation, Muscles, Electrodes, Integrated circuit modeling, Impedance, Biological system modeling, Dielectrics, Biomedical measurement
National Category
Engineering and Technology Medical and Health Sciences
Research subject
Electrical Engineering; Medical Technology
Identifiers
urn:nbn:se:kth:diva-300157 (URN)10.1109/TBME.2021.3091884 (DOI)000733943200029 ()34161236 (PubMedID)2-s2.0-85112454304 (Scopus ID)
Projects
Implantable Bioimpedance
Funder
Swedish Foundation for Strategic Research, ITM17-0079
Note

QC 20230125

Available from: 2021-08-26 Created: 2021-08-26 Last updated: 2023-01-25Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7549-0858

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