Fabrication of Injectable Micro-Scale Opto- Electronically Transduced Electrodes (MOTEs) for Physiological Monitoring

Abstract

In vivo, chronic neural recording is critical to understand the nervous system, while a tetherless, miniaturized recording unit can render such recording minimally invasive. We present a tetherless, injectable micro-scale opto-electronically transduced electrode (MOTE) that is ∼60µm × 30µm × 330µm, the smallest neural recording unit to date. The MOTE consists of an AlGaAs micro-scale light emitting diode (µLED) heterogeneously integrated on top of conventional 180nm complementary metal-oxide-semiconductor (CMOS) circuit. The MOTE combines the merits of optics (AlGaAs µLED for power and data uplink), and of electronics (CMOS for signal amplification and encoding). The optical powering and communication enable the extreme scaling while the electrical circuits provide a high temporal resolution (<100µs). This paper elaborates on the heterogeneous integration in MOTEs, a topic that has been touted without much demonstration on feasibility or scalability. Based on photolithography, we demonstrate how to build heterogenous systems that are scalable as well as biologically stable-the MOTEs can function in saline water for more than six months, and in a mouse brain for two months (and counting). We also Manuscript

Injectable wireless microdevices: challenges and opportunities

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Fig. 2 State-of-the-art fully injectable wireless microdevices: a an OWIC (Cortese et al 2020 ), b a wireless temperature sensor (Shi et al 2021 ), c a wireless glucose sensor (Mujeeb-U-Rahman et al 2019 ), d a Microbead (reprinted with permission from [X], Copyright 2019, IEEE), and e a MOTE (S. Lee et al 2020 )

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“…The MOTE is a neural recording microdevice that has an AlGaAs μLED integrated on 180 nm CMOS (Fig. 2 (e)) (S. Lee et al 2020 ). By utilizing light as power and communication media, the MOTE achieves an impressive scaling: 330 μm × 80 μm × 30 μm, less than a single nanoliter.…”

A conceptual advance that gives microrobots legs

“…The second strategy is to try to build fully autonomous devices free of any tethers. Microrobots have been made that combine energy-storage technology, or methods for scavenging energy from the environment, with on-board logic circuits and sensors to produce controlled outputs, without tethers [10][11][12] . Such autonomy will probably be needed for many practical applications of microrobots.…”

“…The authors' robots, although not autonomous in their current form, can be seen as a platform to which 'brains' and a battery can be attached. Untethered, submillimetre-sized chips with sensors and integrated circuits are an active area of research [10][11][12] , and so the hurdle of developing autonomous programmability for microrobots will soon be overcome. The integration of microscale actuators with submillimetre circuit boards and sensors will undoubtedly bring us closer to Feynman's vision.…”

Tracking the Migration of Injectable Microdevices in the Rodent Brain Using a 9.4T Magnetic Resonance Imaging Scanner

“…Fully injectable wirelessly powered devices, or microdevices, play a major role in many emerging biomedical applications including neural monitoring (Lee et al, 2020;Sigurdsson et al, 2020;Zhang et al, 2020), neural stimulation (Freeman et al, 2017;Khalifa et al, 2019), and temperature sensing (Cortese et al, 2020;Shi et al, 2021). Microdevices in this case should not be confused with micro/nanoparticles (Chen et al, 2018;Le et al, 2019;Kozielski et al, 2021) as the latter does not include integrated circuitry.…”