Self-sensing of temperature rises on light emitting diode based optrodes

Abstract

Objective. This work presents a method to determine the surface temperature of microphotonic medical implants like LEDs. Our inventive step is to use the photonic emitter (LED) employed in an implantable device as its own sensor and develop readout circuitry to accurately determine the surface temperature of the device. Approach. There are two primary classes of applications where microphotonics could be used in implantable devices; opto-electrophysiology and fluorescence sensing. In such scenarios, intense light needs to be delivered to the target. As blue wavelengths are scattered strongly in tissue, such delivery needs to be either via optic fibres, two-photon approaches or through local emitters. In the latter case, as light emitters generate heat, there is a potential for probe surfaces to exceed the 2 °C regulatory. However, currently, there are no convenient mechanisms to monitor this in situ. Main results. We present the electronic control circuit and calibration method to monitor the surface temperature change of implantable optrode. The efficacy is demonstrated in air, saline, and brain. Significance. This paper, therefore, presents a method to utilize the light emitting diode as its own temperature sensor.

Opto‐electro‐thermal optimization of photonic probes for optogenetic neural stimulation

“…The internal junction temperature will be higher giving rises to questions about effects on longevity. In other work on this topic , we have explored such effects which typically amount to 15°C above ambient (ie, 52°C). This is actually much less than the 80°C operating temperature for lighting LEDs which have operational lifetimes of 20 000 hours.…”

Closed-loop optogenetic control of normal and pathological network dynamics

“…Long-term protection of active electronic components within brain tissue is a challenge but the silicone encapsulation technique we used here has proven to be highly reliable in accelerated lifetime testing of insulators (Lamont, 2020). We are currently developing array implants that combine multiple forks with multiple LEDs on each prong to deliver uniform or patterned illumination to a large volume of cortex, together with custom CMOS circuitry (Ramezani et al, 2018) to process LFP recordings, supply drive current and monitor LED temperature (Dehkhoda et al, 2018). The cell-specific control enabled by optogenetics has applications in many neurological disorders, and we hope these technologies will help translate the promise of optogenetic therapies to the human brain.…”

Physical Sensors for Biomedical Applications

“…Thermal sensors are utilized to measure the on-body temperature measurements, which is a vital indicator of person's health [12][13][14]. A vide variety of sensor devices are available that record oral, skin, tympanic, and rectal mucosa temperatures.…”