An Implantable, Battery-Powered, Wireless, Stimulator

ELAINE 2020, Rostock, Germany, 29-SEP-20



Kevan Hashemi
Open Source Instruments Inc.
www.opensourceinstruments.com

Introduction

• Open Source Instruments Inc. is a small business in Massachusetts, USA.
• We have been making implantable telemetry devices for mice and rats since 2010.
• We ship around 500 Subcutaneous Transmitters (SCTs) each year.
• Most of our SCTs are used in epilepsy and pain research.
• Developed Implantable Sensor with Lamp (ISL) for rats from 2013-2016.
• The ISL is a combined optogenetic stimulator and electroencephalogram (EEG) sensor.
• Funding for rat-sized ISL from Wellcome Trust via Institute of Neurology, UCL, UK.
• The ISL was successful in all ways but one: stimulation artifact often corrupted sensor signal.
• Developed Mouse-Sized Implantable Stimulator-Transponder (IST) 2019-2020.
• Developed Mouse-Sized Implantable Stimulator-Sensor (ISS) 2020.
• Funding 2020: SBIR Phase I Grant, National Institute of Mental Health, USA.
• Primary Collaborator: Schaffer-Nishimura Laboratory, Cornell University.
• These devices can provide optogenetic or electrical stimulation.

Implantable Stimulator-Transponder (IST)

IST Type A3036B Specification

• Volume: 0.9 ml.
• Animal Welfare: operates in freely-moving, cohabiting mice.
• Power Supply: 19-mAhr lithium polymer battery.
• Maximum Inactive Life while Implanted: 16 weeks.
• Maximum Stimulation Duration: 120 hrs.
• Maximum Lamp Full Power Duration: 1.9 hrs at 10 mA
• Stimulus Voltage: 3.7 V with 50-Ω source resistance.
• Operating Range: 50 cm for 95% reception while implanted.
• Stimulus Programming: single command for n pulses of d ms with period T ms.
• Command Confirmation: transmits command acknowledgements upon request.
• Synchronization: data transmission of shows pulses.
• Recharging: after explantation, recharge through lamp leads.

Separate Sensor and Stimulator

Implant stimulator and sensor. Sensor inputs X+ and X−. Stimulator outputs L+ and L−. Stimulator and sensor batteries isolated. Stimulus current does not flow into sensor. Stimulus artifact in sensor <5 μV. Permits external closed-loop control. No internal closed-loop control.

Implantable Stimulator-Sensor (ISS)

ISS Type A3037A Specification

• Volume: 1.5 ml.
• Animal Welfare: operates in freely-moving, cohabiting mice.
• Power Supply: Two isolated 10-mAhr lithium polymer batteries.
• Maximum Inactive Life: 8 weeks.
• Maximum Stimulation Duration: 200 hrs.
• Maximum Lamp Full Power Duration: 1.0 hrs at 10 mA
• Stimulus Voltage: 3.7 V with 50-Ω source resistance.
• Operating Range: 50 cm for 95% reception while implanted.
• Stimulus Programming: single command for n pulses of d ms with period T ms.
• Command Confirmation: transmits command acknowledgements.
• Stimulus artifact in sensor <5 μV.
• Closed-Loop Control: on-board amplitude-triggered stimulus initiation.
• Maximum Internal Closed-Loop Control Duration: 200 hrs.
• Recharging: after explantation, recharge through lamp and sensor leads.

Conclusion

• Collaborating with Cornell University, University College London, and University of Edinburgh.
• Dozens of implantations performed for optogenetic pilot studies.
• Lamp power and command reception are sustained for weeks of implantation.
• Recharging through leads with custom chargers works well.
• Careful tuning of command receiver gives reliable command reception.
• Submitted application for SBIR Phase II funding 8-SEP-20.

• Reduce ISS volume to 1.3 ml.
• Implement microprocessor in ISS logic chip.
• Set up on-board EEG and electrocardiogram (EKG) event detection.
• Expand variety of implantable lamps for use in optogenetics.
• Expand library of stimulus patterns.
• Develop, test, and publish implantation protocols.

Appendix: Rat-Sized IST (Added After First Day of Conference)

Specification of Rat-Sized Device Equip the IST with a 1000-mA-hr lithium primary cell. Same battery as our SCT version A3028L for rats. Volume: 6.5 ml, well-tolerated by adult rats. Animal Welfare: freely-moving, cohabiting mice. Maximum Inactive Life: 16 years. Maximum Stimulation Duration: 400 days. Maximum Stimulus Current: 1 mA Stimulus Voltage: 2.7 V. Operating Range: 50 cm. Control: single command for a regular stimulus. Confirmation: transmits command acknowledgements. Synchronization: data signal shows pulses. Recharging: none.

SCT with Same Battery