Implantable Stimulators




Overview

We offer a variety of wireless, implantable stimulators. They may be used to power implantable light sources, to provide direct electrical stimulation of the brain, or to operate another electrically-activated device, such as a chemical pump. Our Implantable Stimulator-Transponders (IST) provides stimulation as well as wireless command acknowledgement, battery measurement, and a stimulus synchronizing signal. Our Implantable Stimulator-Sensors (ISS) include amplifier and transmitter to monitor a biometric signal. We provide a variety of implantable lamps for use with our stimulators in optogenetic experiments, as well as provide bipolar electrodes for direct stimulation of neurons and nerves with electrical current. Our newest stimulators are the Implantable Stimulator-Sensor (A3037), which provides a biometric sensor as well as optogenetic stimulation, and the Implantable Stimulator-Transponder (A3036), which provides optogenetic stimulation only. Our newest light sources are those of our Implantable Lamp (A3036IL) series, which include fiber-coupled LEDs and epoxy-dome LEDs for deep brain and organ surface illumination.

Glossary

Implantable Stimulator-Transponder (IST): A device that applies a voltage to its stimulus electrodes after receiving a radio-frequency command, and which also transmits acknowledgements, battery measurements, and synchronization signals. An example IST is the A3036A.

Implantable Stimulator-Sensor (ISS): A device that applies a voltage to its stimulus electrodes after receiving a radio-frequency command, transmits acknowledgements, battery measurements, and in addition provides continuous monitoring of a biometric signal with wireless transmission. An example ISS is the A3037A.


Figure: Implantable Stimulator-Transponder (A3036A). Volume 0.9 ml, length 21 mm, leads 45-mm each 28 Ω, suitable for mice. The pins at the ends of the leads mate with sockets on an implantable lamp.

Implantable Light-Emitting Diode (ILED): A light-emitting diode designed to illuminate the surface of light-sensitive tissue. The LED is equipped with sockets that accept the pins at the end of stimulator leads. And example ILED is the blue A3036IL-A.


Figure: Implantable LED (A3036IL-C). A blue EZ5290 LED for surface illumination, equipped with mounting tube. Socket connections on back side.

Fiber-Coupled Light-Emitting Diode (FC-LED): An LED with a fiber-optic light guide glued to its surface, which carries roughly half its light a to a tapered glass tip, where the light is emitted in all directions. The light guide is six to ten millimeters long, and allows us to deliver optical stimulation to tissue several millimeters below the surface. An example FC-LED is the A3036IL-A8. Another example is the A3024HF-B, which provides a guide cannula in addition to the light guide.


Figure: Fiber-Coupled Implantable LED (FC-LED). A blue EZ500 LED coupled to an 8-mm, 450-μm diameter fiber for depth illumination. Note thinning of mounting tube to ease cutting after implantation.

Subcutaneous Transmitter (SCT): A device that amplifiers and filters one or more biometric signals, samples them, and transmits the samples wirelessly to an external data receiver. An example SCT is the A3028B single-channel 0.3-160 Hz transmitter for mice.


Figure: The Implantable Stimulator-Sensor (A3037A). Volume 1.7 ml, mass 2.7 g. Leads by insulation color. Clear: transmit and receive antenna. Orange: positive stimulus. Purple: negative stimulus. Red: positive sensor input. Blue: negative sensor input.

Implantable Sensor with Lamp (ISL): A two-part device consisting of a implant body, which we implant in the abdomen of a host animal, and a head fixture, which we implant over the tissue we want to illuminate. Together, the sensor and the lamp provide continuous, wireless monitoring of a biometric signal, and generate optical stimuli in response to radio-frequency commands. Our Mouse-Sized ISL (MS-ISL) is under development with funding from the NIH, and will be available in late 2020.


Figure: Implantable Stimulator-Sensor (ISS) Connections to Optical Stimulator and Local Field Potential Sensor.

Closed-Loop Control: When we have both a sensor and a stimulator implanted in an animal, we can generate stimuli in response to events in the sensor signal. This real-time response to sensor data with a stimulus is what we call closed-loop control. Watching for seizure onset in EEG, and responding to seizure onset with twenty seconds of electrical pulses applied to the brain, is an example of a closed-loop system.

External Closed-Loop Control: Closed-loop control where event detection and stimulus initiation are performed outside the animal. Suppose we have an Implantabl Stimulator-Transponder (IST) and a Subcutaneous Transmitter (SCT) implanted in the same animal. The SCT transmits EEG out of the animal to a data receiver. A computer downloads the EEG signal from the data receiver and looks for seizure onset. When it detects seizure onset, the computer instructs a command transmitter to send a stimulus command to the IST. When it receives the command, the IST generates a sequence of light pulses in the hope of stopping the seizure. In this example, event detection and stimulus initiation are external to the animal.


Figure: Implantable Stimulator and Subcutaneous Transmitter Systems Operating Together to Provide External Closed-Loop Control.

Internal Closed-Loop Control: Closed-loop control where event detection and stimulus initiation are performed inside the animal. Suppose we have an Implantabl Stimulator-Sensor (ISS) implanted in an animal. The ISS digitizes EEG and uses its on-board processor to detect seizure onset and decide when to generate a sequence of light pulses. In this example, event detecton and stimulus initiation are internal to the animal.

Ex-Vivo Recharging: Recharging the battery of an implantable stimulator before implantation or after explantation. If after explantation, the stimulus electrodes must be recovered and cleaned, perhaps by means of acetone to dissolve dental cement followed by two clean acetone washes. We connect the stimulus electrodes to the clips of a battery charger, having made sure the stimulator is inactive. An example battery charger is the IST Charger (A3033A).

System Details

Implantable Stimulators: Description of our implantable stimulation system, including the use of on-board sensors and implementation of closed-loop control.

Setup Instructions: How to set up an implantable stimulator system.

An Implantable, Battery-Powered, Wireless Stimulator: Presentation at ELAINE 2020 virtual conference. Fifteen-minute video here.

Stimulator Tool: The program that controls IST and ISS devices, available in the LWDAQ Tool Menu. Initiates stimuli, turns on data and synchronizing transmission, monitors acknowledgements, checks battery voltages.

Subcutaneous Transmitters: Description of the telemetry system upon which the ISL is based.

News Group: News group for optogenetics and telemetry users.

Parts and Prices: A list of devices and their prices.

Circuit Manuals

Command Transmitter (A3029): A 910-MHz transmitter for use with implantable stimulators.

Implantable Stimulator-Transponder (A3036): An implantable stimulator that acknowledges command reception.

Implantable Lamp (A3036IL): Implantable lamps for use with implantable stimulators.

Implantable Stimulator-Sensor (A3037): An implantable stimultor, transponder, and sensor that comes in a version small enough to fit in a mouse.

Battery Charger (A3033): Description of the simple battery chargers we offer for ex-vivo recharging.

Development Logbook: Account of the development of the original rat-sized ISL, presented in blog format.

Older Documents

Rat-Sized Implantable Sensor with Lamp (A3030): An implantable stimulator-sensor and implantable lamps for use in rats.

MS-ISL Application: Extract from our application to the National Institute of Health (NIH) Small Business Innovation Research (SBIR) program for development of mouse-sized implantable sensor with lamp, internal closed-loop control, and fiber-coupled LEDs, including demonstration of the system's abilit to carry out optogenetic experiments. We were awarded this grant on 16-SEP-19. We will be collaborating with our co-applicants at Cornell University duriomg the year-long development schedule.

IST Proposal:: Development proposal for the Implantable Stimulator-Transponder, a mouse-sized, general-purpose, implantable stimulator with no EEG monitor. Development began on 06-AUG-19 in collaboration with UCL's Department of Anatomy and Developmental Biology. Prototype ISTs completed 06-DEC-19. Further development of stimulators will be funded by our SBIR grant.

MS-ISL Technical Proposal: A proposal for development of a mouse-sized implantable sensor with lamp, without internal closed-loop control, and fiber-coupled LEDs small enough for implantation in mice, leading to a set of working prototypes. Now superceded by our SBIR grant. This proposal places the cost of performing animal studies upon the collaborating institutes, as well as incidental costs of purchasing command receivers, faraday enclosures, and subcutaneous transmitters.

Technical Proposal: Specification, Schedule, and Budget for development of the Implantable Sensor with Lamp in collaboration with ION, UCL.

Conceptual Design: Draft design to motivate development of the Implantable Sensor with Lamp.

Command Transmitter-Receiver (A3023): Prototype transmitter and micropower receiver.

Implantable Lamp (A3024): Prototype command receiver and lamp driver.

Lamp Controller (A2060L): A LWDAQ-based pulse generator for controlling optogenetic illumination.