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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
Huang, Y.-K., Rusu, A. & Rodriguez, S. (2023). A Current Monitoring and Over-Current Detection Circuit for Safe Electrical Stimulation. IEEE Transactions on Circuits and Systems - II - Express Briefs, 70(5), 1684-1688
Open this publication in new window or tab >>A Current Monitoring and Over-Current Detection Circuit for Safe Electrical Stimulation
2023 (English)In: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 70, no 5, p. 1684-1688Article in journal (Refereed) Published
Abstract [en]

This brief presents an integrated solution to over-current protection in neuromuscular stimulators. The proposed approach provides fast detection of a single-fault condition, i.e., unintentional electrode short circuit or malfunction of the stimulator, thereby preventing prolonged high-intensity currents from flowing into tissues. In addition, a programmable current threshold enables the system to be also used for monitoring the stimulation intensity. The proposed solution was designed in a 180 nm high-voltage CMOS technology, and its functionality was verified by post-layout simulations in which the safety mechanisms were tested under fault conditions. The implementation only occupies an area of 0.286 mm2, making it feasible to be embedded in fully integrated NMES stimulators while providing the required patient safety.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2023
Keywords
Neuromuscular electrical stimulation, current monitoring, over-current detection, safe electrical stimulation, HV CMOS process
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-327012 (URN)10.1109/tcsii.2023.3252804 (DOI)000988497300004 ()2-s2.0-85149865731 (Scopus ID)
Funder
Swedish Foundation for Strategic Research, ITM17-0079
Note

QC 20230630

Available from: 2023-05-16 Created: 2023-05-16 Last updated: 2023-06-30Bibliographically approved
Huang, Y.-K. & Rodriguez, S. (2023). An Inductorless 40.5V High-Voltage Generator for Integrated Neuromuscular Electrical Stimulators. In: Proceedings 2023 IEEE Biomedical Circuits and Systems Conference (BioCAS): . Paper presented at 2023 IEEE Biomedical Circuits and Systems Conference (BioCAS), Oct 19-21 2023, Toronto, Canada. Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>An Inductorless 40.5V High-Voltage Generator for Integrated Neuromuscular Electrical Stimulators
2023 (English)In: Proceedings 2023 IEEE Biomedical Circuits and Systems Conference (BioCAS), Institute of Electrical and Electronics Engineers (IEEE) , 2023Conference paper, Published paper (Refereed)
Abstract [en]

Neuromuscular electrical stimulation (NMES) requires voltages exceeding several tens of volts which are typically obtained by using DC-DC boost converters. However, these converters incorporate a large external inductor, which hinders integration and severely restricts the minimum size of the stimulator. This paper presents a charge pump (CP) high-voltage generator particularly designed for NMES applications. The proposed hybrid CP comprises a low-voltage latched CP followed by a high-voltage Dickson CP with boosted pumping clocks. This architecture generates an output voltage of 40.5 V from a 3.3 V supply, enabling the delivery of up to 30 mA stimulation pulses at a maximum frequency of 50 Hz. The circuit is designed in a 180 nm HV CMOS process and occupies a silicon area of 2.7 mm 2 . By eliminating the inductor and requiring only one external storage capacitor, this design has the potential of being used in compact stimulators for wearable medical applications.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2023
Keywords
high-voltage generator, charge pump, step-up DC-DC converter, neuromuscular electrical stimulator, switched capacitor voltage converter, HV CMOS process
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-342434 (URN)10.1109/BioCAS58349.2023.10389156 (DOI)2-s2.0-85184874143 (Scopus ID)
Conference
2023 IEEE Biomedical Circuits and Systems Conference (BioCAS), Oct 19-21 2023, Toronto, Canada
Funder
Region Stockholm, HMT FoUI-979040
Note

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

QC 20240119

Available from: 2024-01-19 Created: 2024-01-19 Last updated: 2024-02-22Bibliographically approved
Juthberg, R., Flodin, J., Guo, L., Rodriguez, S., Persson, N. K. & Ackermann, P. W. (2023). Neuromuscular electrical stimulation in garments optimized for compliance. European Journal of Applied Physiology, 123(8), 1739-1748
Open this publication in new window or tab >>Neuromuscular electrical stimulation in garments optimized for compliance
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2023 (English)In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 123, no 8, p. 1739-1748Article in journal (Refereed) Published
Abstract [en]

Purpose: Physical inactivity is associated with muscle atrophy and venous thromboembolism, which may be prevented by neuromuscular electrical stimulation (NMES). This study aimed to investigate the effect on discomfort, current amplitude and energy consumption when varying the frequency and phase duration of low-intensity NMES (LI-NMES) via a sock with knitting-integrated transverse textile electrodes (TTE). Methods: On eleven healthy participants (four females), calf-NMES via a TTE sock was applied with increasing intensity (mA) until ankle-plantar flexion at which point outcomes were compared when testing frequencies 1, 3, 10 and 36 Hz and phase durations 75, 150, 200, 300 and 400 µs. Discomfort was assessed with a numerical rating scale (NRS, 0–10) and energy consumption was calculated and expressed in milli-Joule (mJ). Significance set to p ≤ 0.05. Results: 1 Hz yielded a median (inter-quartile range) NRS of 2.4 (1.0–3.4), significantly lower than both 3 Hz with NRS 2.8 (1.8–4.2), and 10 Hz with NRS 3.4 (1.4–5.4) (both p ≤.014). Each increase in tested frequency resulted in significantly higher energy consumption, e.g. 0.6 mJ (0.5–0.8) for 1 Hz vs 14.9 mJ (12.3–21.2) for 36 Hz (p =.003). Longer phase durations had no significant effect on discomfort despite generally requiring significantly lower current amplitudes. Phase durations 150, 200 and 400 µs required significantly lower energy consumption compared to 75 µs (all p ≤.037). Conclusion: LI-NMES applied via a TTE sock produces a relevant plantar flexion of the ankle with the best comfort and lowest energy consumption using 1 Hz and phase durations 150, 200 or 400 µs.

Place, publisher, year, edition, pages
Springer Nature, 2023
Keywords
Electric stimulation therapy, Pain, Patient comfort, Patient compliance
National Category
Physiology
Identifiers
urn:nbn:se:kth:diva-333870 (URN)10.1007/s00421-023-05181-9 (DOI)000982817500001 ()37010623 (PubMedID)2-s2.0-85165608495 (Scopus ID)
Note

Correction in DOI 10.1007/s00421-023-05211-6

QC 20230815

Available from: 2023-08-15 Created: 2023-08-15 Last updated: 2023-11-16Bibliographically approved
Huang, Y.-K. & Rodriguez, S. (2023). Noise Analysis and Design Methodology of Chopper Amplifiers With Analog DC-Servo Loop for Biopotential Acquisition Applications. IEEE Transactions on Very Large Scale Integration (vlsi) Systems, 1-13
Open this publication in new window or tab >>Noise Analysis and Design Methodology of Chopper Amplifiers With Analog DC-Servo Loop for Biopotential Acquisition Applications
2023 (English)In: IEEE Transactions on Very Large Scale Integration (vlsi) Systems, ISSN 1063-8210, E-ISSN 1557-9999, p. 1-13Article in journal (Refereed) Published
Abstract [en]

Biopotential acquisition chopper instrumentation amplifiers require a dc-servo loop (DSL) in order to filter electrode dc offsets. However, the noise performance degradation due to the addition of the DSL is often overlooked despite that it can be very detrimental at the frequencies of interest. This article presents an in-depth noise analysis of biopotential acquisition chopper instrumentation amplifiers with analog DSLs. Analytical expressions that predict the noise of different DSL implementations are found and a design flow to minimize their noise contribution is proposed. The design methodology is demonstrated with example circuits targeting biopotential recording systems. These circuits are implemented using a standard 180 nm CMOS technology, and their performance is verified through postlayout simulations. The findings of this work provide a comprehensive understanding of the noise characteristics of a DSL, its impact on noise performance, and design strategies for noise optimization.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2023
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Signal Processing
Identifiers
urn:nbn:se:kth:diva-339178 (URN)10.1109/tvlsi.2023.3315417 (DOI)001085421000001 ()2-s2.0-85174847996 (Scopus ID)
Funder
Swedish Foundation for Strategic Research, ITM17-0079Region Stockholm, 979040
Note

QC 20231106

Available from: 2023-11-03 Created: 2023-11-03 Last updated: 2023-11-06Bibliographically 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
Huang, Y.-K. & Rodriguez, S. (2022). Noise Analysis of Current-Feedback DC-Servo Loop in Current-Balancing Chopper Amplifiers. In: Nurmi, J Wisland, DT Aunet, S Kjelgaard, K (Ed.), 2022 IEEE NORDIC CIRCUITS AND SYSTEMS CONFERENCE (NORCAS): . Paper presented at 8th IEEE Nordic Circuits and Systems Conference (NorCAS), OCT 25-26, 2022, Oslo, NORWAY. Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>Noise Analysis of Current-Feedback DC-Servo Loop in Current-Balancing Chopper Amplifiers
2022 (English)In: 2022 IEEE NORDIC CIRCUITS AND SYSTEMS CONFERENCE (NORCAS) / [ed] Nurmi, J Wisland, DT Aunet, S Kjelgaard, K, Institute of Electrical and Electronics Engineers (IEEE) , 2022Conference paper, Published paper (Refereed)
Abstract [en]

Chopper amplifiers for biopotential acquisition commonly suppress differential electrode DC offsets by using a DC-servo loop (DSL). However, the noise contribution of the DSL is always neglected in noise analysis. The noise introduced by the DSL, in particular at low frequencies, is of great importance in biosensor applications. This work presents the noise modeling of a current-balancing chopper amplifier with DSL and describes the effect of the DSL on the noise performance. Two different DSL implementations are analyzed. It is found that the exact placement of the chopper in the DSL has a strong impact in the noise performance; therefore, its placement can not be arbitrarily selected. A circuit topology to minimize its noise contribution is then proposed and verified by simulation.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2022
Keywords
biopotential acquisition, low-noise chopper amplifier, dc-servo loop, noise analysis, noise modeling
National Category
Signal Processing
Identifiers
urn:nbn:se:kth:diva-322479 (URN)10.1109/NORCAS57515.2022.9934347 (DOI)000889469600007 ()2-s2.0-85142434913 (Scopus ID)
Conference
8th IEEE Nordic Circuits and Systems Conference (NorCAS), OCT 25-26, 2022, Oslo, NORWAY
Note

Part of proceedings: ISBN 979-8-3503-4550-6

QC 20221216

Available from: 2022-12-16 Created: 2022-12-16 Last updated: 2023-01-24Bibliographically approved
Huang, Y.-K., Rusu, A. & Rodriguez, S. (2021). A 4-Channel NMES IC for Wearable Applications. In: BioCAS 2021 - IEEE Biomedical Circuits and Systems Conference, Proceedings: . Paper presented at 2021 IEEE Biomedical Circuits and Systems Conference, BioCAS 2021, 6-9 October 2021, Virtual/Online. Institute of Electrical and Electronics Engineers Inc.
Open this publication in new window or tab >>A 4-Channel NMES IC for Wearable Applications
2021 (English)In: BioCAS 2021 - IEEE Biomedical Circuits and Systems Conference, Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2021Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents an integrated circuit solution for multi-channel neuromuscular electrical stimulation (NMES). The stimulation waveform is digitally controlled and supports monophasic pulses, and both symmetric and asymmetric biphasic pulses. In addition, the current intensity is programmable, ranging from 0 mA to 31 mA with 5-bit resolution. The integrated circuit occupies an area of 1 mm2and it is designed and simulated in a 180 nm high-voltage CMOS technology. The circuits are powered using standard 1.8 V and 3.3 V power supplies for the digital control and digital-to-analog converter, and a single 40 V power supply for the output drivers. The simulation results show that the design achieves a voltage compliance of up to 35 V, meeting the requirements for NMES applications while offering a very compact and scalable solution.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2021
Keywords
biomedical interface, current driver, electrical therapy, high-voltage CMOS process, neuromuscular electrical stimulation, wearable medical application, CMOS integrated circuits, Digital control systems, Electric power systems, Medical applications, Wearable technology, Circuit solution, Current drivers, Electrical stimulations, High voltage CMOS process, Power supply, Wearable applications, Timing circuits
National Category
Physiology Neurology Medical Engineering
Identifiers
urn:nbn:se:kth:diva-316369 (URN)10.1109/BioCAS49922.2021.9644966 (DOI)000837980700039 ()2-s2.0-85124195724 (Scopus ID)
Conference
2021 IEEE Biomedical Circuits and Systems Conference, BioCAS 2021, 6-9 October 2021, Virtual/Online
Note

Part of proceedings: ISBN 978-1-7281-7204-0

QC 20220912

Available from: 2022-08-16 Created: 2022-08-16 Last updated: 2023-01-24Bibliographically approved
Hussain, M. W., Elahipanah, H., Zumbro, J. E., Rodriguez, S., Malm, B. G., Mantooth, H. A. & Rusu, A. (2019). A SiC BJT-Based Negative Resistance Oscillator for High-Temperature Applications. IEEE Journal of the Electron Devices Society, 7(1), 191-195
Open this publication in new window or tab >>A SiC BJT-Based Negative Resistance Oscillator for High-Temperature Applications
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2019 (English)In: IEEE Journal of the Electron Devices Society, E-ISSN 2168-6734, Vol. 7, no 1, p. 191-195Article in journal (Refereed) Published
Abstract [en]

This brief presents a 59.5 MHz negative resistanceoscillator for high-temperature operation. The oscillator employs an in-house 4H-SiC BJT, integrated with the requiredcircuit passives on a low-temperature co-fired ceramic substrate. Measurements show that the oscillator operates from room-temperature up to 400 C. The oscillator delivers an output◦power of 11.2 dBm into a 50 Ω load at 25 C, which decreases to 8.4 dBm at 400 C. The oscillation frequency varies by 3.3% in the entire temperature range. The oscillator is biased witha collector current of 35 mA from a 12 V supply and has amaximum DC power consumption of 431 mW.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2019
Keywords
4H-SiC BJT, high-temperature, LTCC, negative resistance, oscillator
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-245068 (URN)10.1109/JEDS.2018.2889638 (DOI)000460753000029 ()2-s2.0-85059455428 (Scopus ID)
Note

QC 20190311

Available from: 2019-03-05 Created: 2019-03-05 Last updated: 2024-03-18Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0565-9907

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