A 2 mm × 2 mm battery-free neural interface achieving 72-channel wireless simultaneous recording by dual overlapped on-chip antennas

Yili Shen; Yunshan Zhang; Changgui Yang; Yuxuan Luo; Bo Zhao

doi:10.1088/1674-4926/25120027

J. Semicond. > Just Accepted

ARTICLES

A 2 mm × 2 mm battery-free neural interface achieving 72-channel wireless simultaneous recording by dual overlapped on-chip antennas

Yili Shen^{1, §}, Yunshan Zhang^{1, §}, Changgui Yang¹, Yuxuan Luo¹ and Bo Zhao^{1, 2, 3,}

+ Author Affiliations

1. College of Integrated Circuits, Zhejiang University, Hangzhou 310000, China
2. Nanhu Brian-Computer Interface Institute, Hangzhou 310000, China
3. The State Key Lab of Brain-Machine Intelligence, Zhejiang University, Hangzhou 310000, China
^§Yili Shen and Yunshan Zhang contributed equally to this work and should be considered as co-first authors.

Author Bio:

Yili Shen received the B.Eng. degree in Microelectronic Science and Technology from Zhejiang University, Hangzhou, China, in 2021, where he is currently pursuing the Ph.D. degree in Electronic Science and Technology. His current research interests include analog/mixed-signal IC design, biomedical sensor interface, and wireless power/data transmission circuits design for implantable medical devices.

Bo Zhao received the Ph.D. degree from the Department of Electronic Engineering, Tsinghua University, Beijing, China, in 2011. He was a Research Fellow with the National University of Singapore, Singapore, from 2013 to 2015. From 2015 to 2018, he was an Assistant Project Scientist with Berkeley Wireless Research Center (BWRC), Department of Electrical Engineering and Computer Sciences, University of California at Berkeley, Berkeley, CA, USA. Since 2018, he has been a Professor with the Institute of VLSI Design, Zhejiang University, Hangzhou, China. He has authored or coauthored more than 60 articles and book chapters, and he holds more than 30 Chinese patents. His research interests include IoT radios, wireless power transfer, and wearable/implantable radios. He was a recipient of the 2017 IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS Darlington Best Paper Award and the Design Contest Award of the 2013 IEEE International Symposium on Low Power Electronics and Design. He serves as an Associate Editor for the IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS, as well as an Associate Editor for the IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I: Regular Papers. He also serves as a Committee Member of IEEE/C/SM. He was the Publication Chair of the 2016 IEEE Biomedical Circuits and Systems Conference. In 2022, he was elected to be the Chair Elect of Biomedical and Life Science Circuits and Systems Society.

Corresponding author: Bo Zhao, zhaobo@zju.edu.cn

DOI: 10.1088/1674-4926/25120027CSTR: 32376.14.1674-4926.25120027

Abstract: Battery-free radio systems utilizing wireless power transfer (WPT) further facilitate the miniaturization of neural implants. However, simultaneous monitoring of multiple neuronal activities is required to obtain high-fidelity neural signals. Consequently, the integration of numerous channels on a single chip and the wireless transmission of massive multi-channel data pose significant challenges for implantable battery-free neural interfaces. This work introduces dual overlapped on-chip antennas to eliminate the need for a battery in the neural implants and enable high-data-rate backscatter for transmitting the massive data acquired simultaneously from 72 channels. Additionally, an orthogonal coding and sampling technique is employed to reduce both power consumption and area per channel. Fabricated in a 65 nm CMOS process, the proposed chip integrates 72 neural recording channels within a 2 mm × 2 mm area and achieves a backscatter data rate of 18 Mbps.

Key words: neural interface, wireless power transfer (WPT), backscatter, on-chip antennas

References

[1]	Lee C, Kim B, Kim J, et al. A miniaturized wireless neural implant with body-coupled data transmission and power delivery for freely behaving animals. 2022 IEEE International Solid-State Circuits Conference, 2022: 1
[2]	Sanni A, Vilches A, and Toumazou C. Inductive and ultrasonic multi-tier interface for low-power, deeply implantable medical devices. IEEE Trans Biomed Circuits Syst, 2012, 6(4): 297 doi: 10.1109/TBCAS.2011.2175390
[3]	ElAnsary M, Xu J X, Filho J S, et al. Bidirectional peripheral nerve interface with 64 second-order opamp-less ΔΣ ADCs and fully integrated wireless power/data transmission. IEEE J Solid-State Circuits, 2021, 56(11): 3247 doi: 10.1109/JSSC.2021.3113354
[4]	Buzsáki G. Large-scale recording of neuronal ensembles. Nat Neurosci, 2004, 7(5): 446 doi: 10.1038/nn1233
[5]	Csicsvari J, Henze D A, Jamieson B, et al. Massively parallel recording of unit and local field potentials with silicon-based electrodes. J. Neurophysiol, 2003, 90(2): 1314 doi: 10.1152/jn.00116.2003
[6]	Lopez C M, Andrei A, Mitra S, et al. An implantable 455-active-electrode 52-channel CMOS neural probe. IEEE J Solid-State Circuits, 2014, 49(1): 248 doi: 10.1109/JSSC.2013.2284347
[7]	Lee S B, Lee H M, Kiani M, et al. An inductively powered scalable 32-channel wireless neural recording system-on-a-chip for neuroscience applications. 2010 IEEE International Solid-State Circuits Conference, 2010: 120
[8]	Ng K A, Yuan C, Rusly A, et al. A wireless multi-channel peripheral nerve signal acquisition system-on-chip. IEEE J Solid-State Circuits, 2019, 54(8): 2266 doi: 10.1109/JSSC.2019.2909158
[9]	Zhang Y S, Yang C G, Chang Z Y, et al. An 8-shaped antenna-based battery-free neural-recording system featuring 3 cm reading range and 140 pJ/bit energy efficiency. IEEE J Solid-State Circuits, 2023, 58(11): 3194 doi: 10.1109/JSSC.2023.3276174
[10]	Lo Y K, Chang C W, Kuan Y C, et al. A 176-channel 0. 5cm3 0. 7g wireless implant for motor function recovery after spinal cord injury. 2016 IEEE International Solid-State Circuits Conference, 2016: 382
[11]	Yang C G, Zhang Z H, Zhang L, et al. A 128-channel 2mm×2mm battery-free neural dielet merging simultaneous multi-channel transmission through multi-carrier orthogonal backscatter. 2023 IEEE International Solid-State Circuits Conference, 2023: 30
[12]	Yang C G, Zhang Y S, Chang Z Y, et al. A 0. 4mm3 battery-less crystal-less neural-recording SoC achieving 1. 6cm backscattering range with 2mm×2mm on-chip antenna. 2022 IEEE Symposium on VLSI Technology and Circuits, 2022: 164
[13]	Cheng C H, Tsai P Y, Yang T Y, et al. A fully integrated 16-channel closed-loop neural-prosthetic CMOS SoC with wireless power and bidirectional data telemetry for real-time efficient human epileptic seizure control. IEEE J Solid-State Circuits, 2018, 53(11): 3314 doi: 10.1109/JSSC.2018.2867293
[14]	Chang Z Y, Yang C G, Zhang Y S, et al. A battery-less crystal-less 49. 8µW neural-recording chip featuring two-tone RF power harvesting. 2022 IEEE Custom Integrated Circuits Conference, 2022: 1
[15]	Muller R, Le H P, Li W, et al. A minimally invasive 64-channel wireless μECoG implant. IEEE J Solid-State Circuits, 2015, 50(1): 344 doi: 10.1109/JSSC.2014.2364824

Fig. 1. (Color online) Conventional architectures for wireless multi-channel neural-recording systems: (a) Active radio method. (b) Passive radio method, such as backscatter.

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Fig. 2. (Color online) System architecture of the proposed battery-free wireless neural-recording chip.

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Fig. 3. (Color online) Operation principle of the proposed dual overlapped on-chip antennas.

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Fig. 4. (Color online) Overlapped antennas of WPT and communication: (a) Conventional topology. (b) Proposed topology.

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Fig. 5. (Color online) Simulated isolation between the dual overlapped on-chip antennas.

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Fig. 6. (Color online) Simulated received power of dual overlapped antennas: (a) Communication antenna, (b) Power antenna.

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Fig. 7. (Color online) Simulated rectifier output voltage in conventional single-antenna design and proposed dual overlapped on-chip antennas design.

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Fig. 8. (Color online) Proposed orthogonal coding and sampling technique: (a) Schematic, (b) Timing diagram.

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Fig. 9. (Color online) Operation principle of the orthogonal coding and sampling technique: (a) On-chip modulation, (b) Off-chip demodulation.

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Fig. 10. (Color online) Simulated power gain from the external power antenna to the rectifier output.

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Fig. 11. (Color online) Die photograph of the proposed chip.

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Fig. 12. (Color online) Power breakdown.

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Fig. 13. (Color online) Measurement setup.

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Fig. 14. (Color online) Impedance matching strategies for WPT and communication link.

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Fig. 15. Measured WPT gain at different ranges.

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Fig. 16. (Color online) Measured backscatter signal with dual overlapped antennas: (a) Frequency spectrum, (b) Time-domain waveform.

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Fig. 17. (Color online) Measurement results of a single neural-recording channel: (a) Gain of CCIA, (b) IRN, (c) PSD of SAR ADC, (d) SNDR & SFDR of ADC in different input frequencies.

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Fig. 18. (Color online) PSD of four-channel reconstructed signals with 2 mV_PP inputs at different frequencies.

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Table 1. Performance summary and comparison.

Specifications		This Work	ISSCC’22 [1]	JSSC’21 [3]	JSSC’19 [8]	JSSC’23 [9]	ISSCC’16 [10]
System	CMOS Process (nm)	65	110	130	180	65	180
	# of Channels	72	4	64	10	1	16
	Chip Size (mm²)	2×2	1.4×2.8	2.34×3	3.4×2.3	2×2	4.4×5.7
	Area / Ch. (mm²)	0.06	0.98	0.11	0.78	4	1.6
	Total Power (μW)	743	644	810	4400	35	NA
	Power / Ch. (μW)	10.32	161	12.66	440	35	NA
	Off-chip Devices	NO	Electrode	NO	1 Coil, 1LED & 4 Caps	2 Coil	1 Coil & Caps
	Clock Recovery	YES	NO	NO	NO	YES	YES
WPT & Comm.	Wireless Link	Inductive	Body Coupled	Inductive	Inductive & Near Infrared	Inductive	Inductive
	Implanted Coil Size	2×2 mm² & 1.94×1.94 mm² (On-chip)	NA	2.3×2.3 mm² (On-chip)	Φ15 mm (Off-chip)	4.7×4.7 mm² (Off-chip)	Φ13.5 mm (Off-chip)
	WPT Freq. (MHz)	400	32	60	22	408	2
	Com. Method	Backscatter	Active	Active	Active	Backscatter	Backscatter
	Carrier Freq. (MHz)	700	40.96	600	NA	1180	2
	Data Rate (Mbps)	18	20.48	2	3	0.25	2
	Energy Per Bit (pJ/Bit)	42.3	32	405	1466	140	NA
Neural Recording	Architecture	Orthogonal Coding & Shared ADC	Dedicated CTDSM	Dedicated DSM	TMD & Shared ADC	Single Channel	TDM & Shared ADC
	Signal Bandwidth	1.3 Hz−10 kHz	10 kHz	10 kHz	0.1 Hz− 5.5 kHz	0.9 Hz− 6.9 kHz	5 Hz−7 kHz
	IRN (μV_rms)	8.62	6.6	24.7	1.9	6.77	7.68
	SNDR/SFDR (dB)	55.24/65.26	83/94.2	49.92/NA	50.5/NA	60.15/NA	52.93/NA

DownLoad: CSV

[1]	Lee C, Kim B, Kim J, et al. A miniaturized wireless neural implant with body-coupled data transmission and power delivery for freely behaving animals. 2022 IEEE International Solid-State Circuits Conference, 2022: 1
[2]	Sanni A, Vilches A, and Toumazou C. Inductive and ultrasonic multi-tier interface for low-power, deeply implantable medical devices. IEEE Trans Biomed Circuits Syst, 2012, 6(4): 297 doi: 10.1109/TBCAS.2011.2175390
[3]	ElAnsary M, Xu J X, Filho J S, et al. Bidirectional peripheral nerve interface with 64 second-order opamp-less ΔΣ ADCs and fully integrated wireless power/data transmission. IEEE J Solid-State Circuits, 2021, 56(11): 3247 doi: 10.1109/JSSC.2021.3113354
[4]	Buzsáki G. Large-scale recording of neuronal ensembles. Nat Neurosci, 2004, 7(5): 446 doi: 10.1038/nn1233
[5]	Csicsvari J, Henze D A, Jamieson B, et al. Massively parallel recording of unit and local field potentials with silicon-based electrodes. J. Neurophysiol, 2003, 90(2): 1314 doi: 10.1152/jn.00116.2003
[6]	Lopez C M, Andrei A, Mitra S, et al. An implantable 455-active-electrode 52-channel CMOS neural probe. IEEE J Solid-State Circuits, 2014, 49(1): 248 doi: 10.1109/JSSC.2013.2284347
[7]	Lee S B, Lee H M, Kiani M, et al. An inductively powered scalable 32-channel wireless neural recording system-on-a-chip for neuroscience applications. 2010 IEEE International Solid-State Circuits Conference, 2010: 120
[8]	Ng K A, Yuan C, Rusly A, et al. A wireless multi-channel peripheral nerve signal acquisition system-on-chip. IEEE J Solid-State Circuits, 2019, 54(8): 2266 doi: 10.1109/JSSC.2019.2909158
[9]	Zhang Y S, Yang C G, Chang Z Y, et al. An 8-shaped antenna-based battery-free neural-recording system featuring 3 cm reading range and 140 pJ/bit energy efficiency. IEEE J Solid-State Circuits, 2023, 58(11): 3194 doi: 10.1109/JSSC.2023.3276174
[10]	Lo Y K, Chang C W, Kuan Y C, et al. A 176-channel 0. 5cm3 0. 7g wireless implant for motor function recovery after spinal cord injury. 2016 IEEE International Solid-State Circuits Conference, 2016: 382
[11]	Yang C G, Zhang Z H, Zhang L, et al. A 128-channel 2mm×2mm battery-free neural dielet merging simultaneous multi-channel transmission through multi-carrier orthogonal backscatter. 2023 IEEE International Solid-State Circuits Conference, 2023: 30
[12]	Yang C G, Zhang Y S, Chang Z Y, et al. A 0. 4mm3 battery-less crystal-less neural-recording SoC achieving 1. 6cm backscattering range with 2mm×2mm on-chip antenna. 2022 IEEE Symposium on VLSI Technology and Circuits, 2022: 164
[13]	Cheng C H, Tsai P Y, Yang T Y, et al. A fully integrated 16-channel closed-loop neural-prosthetic CMOS SoC with wireless power and bidirectional data telemetry for real-time efficient human epileptic seizure control. IEEE J Solid-State Circuits, 2018, 53(11): 3314 doi: 10.1109/JSSC.2018.2867293
[14]	Chang Z Y, Yang C G, Zhang Y S, et al. A battery-less crystal-less 49. 8µW neural-recording chip featuring two-tone RF power harvesting. 2022 IEEE Custom Integrated Circuits Conference, 2022: 1
[15]	Muller R, Le H P, Li W, et al. A minimally invasive 64-channel wireless μECoG implant. IEEE J Solid-State Circuits, 2015, 50(1): 344 doi: 10.1109/JSSC.2014.2364824

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Received: 14 December 2025 Revised: 17 January 2025 Online: Accepted Manuscript: 09 February 2026

Article Navigation > Journal of Semiconductors > 2026 > Accepted Manuscript

Yili Shen, Yunshan Zhang, Changgui Yang, Yuxuan Luo, Bo Zhao. A 2 mm × 2 mm battery-free neural interface achieving 72-channel wireless simultaneous recording by dual overlapped on-chip antennas[J]. Journal of Semiconductors, 2026, In Press. doi: 10.1088/1674-4926/25120027 ****Y L Shen, Y S Zhang, C G Yang, Y X Luo, and B Zhao, A 2 mm × 2 mm battery-free neural interface achieving 72-channel wireless simultaneous recording by dual overlapped on-chip antennas[J]. J. Semicond., 2026, accepted doi: 10.1088/1674-4926/25120027

Citation:

Y L Shen, Y S Zhang, C G Yang, Y X Luo, and B Zhao, A 2 mm × 2 mm battery-free neural interface achieving 72-channel wireless simultaneous recording by dual overlapped on-chip antennas[J]. J. Semicond., 2026, accepted doi: 10.1088/1674-4926/25120027

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A 2 mm × 2 mm battery-free neural interface achieving 72-channel wireless simultaneous recording by dual overlapped on-chip antennas

DOI: 10.1088/1674-4926/25120027

CSTR: 32376.14.1674-4926.25120027

Yili Shen^{1, §},
Yunshan Zhang^{1, §},
Changgui Yang¹,
Yuxuan Luo¹,
Bo Zhao^{1, 2, 3,}

1.
College of Integrated Circuits, Zhejiang University, Hangzhou 310000, China
2.
Nanhu Brian-Computer Interface Institute, Hangzhou 310000, China
3.
The State Key Lab of Brain-Machine Intelligence, Zhejiang University, Hangzhou 310000, China

More Information

Yili Shen received the B.Eng. degree in Microelectronic Science and Technology from Zhejiang University, Hangzhou, China, in 2021, where he is currently pursuing the Ph.D. degree in Electronic Science and Technology. His current research interests include analog/mixed-signal IC design, biomedical sensor interface, and wireless power/data transmission circuits design for implantable medical devices
Bo Zhao received the Ph.D. degree from the Department of Electronic Engineering, Tsinghua University, Beijing, China, in 2011. He was a Research Fellow with the National University of Singapore, Singapore, from 2013 to 2015. From 2015 to 2018, he was an Assistant Project Scientist with Berkeley Wireless Research Center (BWRC), Department of Electrical Engineering and Computer Sciences, University of California at Berkeley, Berkeley, CA, USA. Since 2018, he has been a Professor with the Institute of VLSI Design, Zhejiang University, Hangzhou, China. He has authored or coauthored more than 60 articles and book chapters, and he holds more than 30 Chinese patents. His research interests include IoT radios, wireless power transfer, and wearable/implantable radios. He was a recipient of the 2017 IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS Darlington Best Paper Award and the Design Contest Award of the 2013 IEEE International Symposium on Low Power Electronics and Design. He serves as an Associate Editor for the IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS, as well as an Associate Editor for the IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I: Regular Papers. He also serves as a Committee Member of IEEE/C/SM. He was the Publication Chair of the 2016 IEEE Biomedical Circuits and Systems Conference. In 2022, he was elected to be the Chair Elect of Biomedical and Life Science Circuits and Systems Society
Corresponding author: zhaobo@zju.edu.cn
Received Date: 2025-12-14
Revised Date: 2025-01-17

Available Online: 2026-02-09

Abstract

Abstract

Battery-free radio systems utilizing wireless power transfer (WPT) further facilitate the miniaturization of neural implants. However, simultaneous monitoring of multiple neuronal activities is required to obtain high-fidelity neural signals. Consequently, the integration of numerous channels on a single chip and the wireless transmission of massive multi-channel data pose significant challenges for implantable battery-free neural interfaces. This work introduces dual overlapped on-chip antennas to eliminate the need for a battery in the neural implants and enable high-data-rate backscatter for transmitting the massive data acquired simultaneously from 72 channels. Additionally, an orthogonal coding and sampling technique is employed to reduce both power consumption and area per channel. Fabricated in a 65 nm CMOS process, the proposed chip integrates 72 neural recording channels within a 2 mm × 2 mm area and achieves a backscatter data rate of 18 Mbps.
- neural interface,
- wireless power transfer (WPT),
- backscatter,
- on-chip antennas

^§Yili Shen and Yunshan Zhang contributed equally to this work and should be considered as co-first authors.

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