Implantable Sensor with Lamp (Obsolete)

Notice of Obsolescence

[26-JUL-22] The Implantable Sensor with Lamp (ISL) is obsolete. We have abandoned our attempts to combine sensor, stimulator, and light source into a single device, and instead have separated them into an Implantable Stimulator-Transponder (IST), an Implantable Light-Emitting Diode (ILED), and a Subcutaneous Transmitter (SCT). Separating the sensor and stimulator reduces lamp artifact, increases operating life, and improves animal health. The only disadvantage of separating the sensor and stimulator is that internal closed-loop control is no longer possible: the sensor cannot act as an event detector and activate a stimulus on its own. But closed-loop control is of little value in translational research studies: we always want to record the sensor output for later study, and we always want to know which stimulus has been issued, so it is no inconvenience for us to detect events and initiate stimuli using the external data acquisition system.


[25-JUL-22] The Implantable Sensor with Lamp (ISL) combines biometric sensor and optogenetic stimulator in one wireless device controlled by its own micro-power processor. By combining the sensor and stimulator, we make it possible to implement immediate response to the sensor signal with the generation of a suitable stimulus. But we also make it much harder to isolate the sensor signal from the stimulation signal, so that our sensor signal tends to be plagued by various forms of what we call lamp artifact. The Implantable Sensor with Lamp (A3037) reduces lamp artifact to a few tens of microvolts by powering the lamp and sensor from two separate batteries, and communicating the stimulus pulses from the sensor circuit to the stimulator circuit using an opto-isolator.

Figure: The Implantable Stimulator-Sensor (A3037A). Volume 1.7 ml, mass 2.7 g. Provides two stimulus leads and two sensor leads.

To generate light, we connect the stimulus leads of the ISL to one of our Implantable Light-Emitting Diodes (ILEDs). Our Surface-Mount Light-Emitting Diodes (SMLEDs) come in red, green, and blue. These are designed to be fastened to the surface of an organ and illuminate the tissue within. Our Fiber-Coupled Light-Emitting Diodes (FCLEDs) are designed to be anchored to the skull for illumination of deeper brain tissue.


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. Example ISTs are the new A3041 and the obsolete A3036.

Figure: The Obsolete Implantable Stimulator-Transponder (A3036C). Volume 0.75 ml, length 14 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.

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.

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. We no longer manufacture an ISS. Instead, we recommend implanting an IST with an SCT. Example ISSs are the obsolete A3037 and A3030.

Figure: Surface-Mount Light Emitting Diode (SMLED, OSI part number A3036IL-C). A blue EZ5290 LED die covered by a clear epoxy dome. For surface illumination, equipped with steel mounting tube. Sockets on back side.

Surface-Mount Light-Emitting Diode (SMLED): 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: Fiber-Coupled Implantable LED (FCLED). A blue EZ500 LED coupled to a 4-mm, 270-μm diameter fiber for depth illumination. Note thinning of mounting tube to ease cutting after implantation.

Fiber-Coupled Light-Emitting Diode (FCLED): A light-emitting diode 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: Implantable Stimulator-Transponder (IST) and Subcutaneous Transmitter (SCT) Connections to Optical Stimulator and Local Field Potential Sensor Respectively.

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.

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

Internal and External Closed-Loop Control: When we analyze the sensor signal and decide the response in a computer outside the animal, we call this external control. When we perform the same analysis and decision-making within the animal, we call it internal control. Separate IST and SCT implants provide reliable and long-lasting external closed-loop control. Only an ISL can provide internal closed-loop control.

System Details

Examples of Optogenetic Response: Examples of EEG recordings with synchronous video showing optogenetic response.

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

Stimulator Tool: The program that controls ISTs, 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 stimulators are based.

News Group: News group for optogenetics and telemetry users.

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

Circuit Manuals

Implantable Stimulator-Transponder (A3041): A non-rechargeable, long-life, implantable stimulator that acknowledges command reception, provides synchronizing signal, and monitors its battery voltage.

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

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

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

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

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

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

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

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

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

Older Documents

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

MS-ISL SBIR Phase I 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 ability to carry out optogenetic experiments. Grant number 1R43MH119880-01A1, awarded 16-SEP-2019.

MS-ISL SBIR Phase II Application: The Research Strategy section from our application to the NIH for SBIR Phase II funding to continue development of our MS-ISL. This application was declined twice and we have no plans to apply again.

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 superseded 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.