Wireless, battery-free, subdermally implantable platforms for transcranial and long-range optogenetics in freely moving animals

Abstract

Wireless, battery-free, and fully subdermally implantable optogenetic tools are poised to transform neurobiological research in freely moving animals. Current-generation wireless devices are sufficiently small, thin, and light for subdermal implantation, offering some advantages over tethered methods for naturalistic behavior. Yet current devices using wireless power delivery require invasive stimulus delivery, penetrating the skull and disrupting the blood–brain barrier. This can cause tissue displacement, neuronal damage, and scarring. Power delivery constraints also sharply curtail operational arena size. Here, we implement highly miniaturized, capacitive power storage on the platform of wireless subdermal implants. With approaches to digitally manage power delivery to optoelectronic components, we enable two classes of applications: transcranial optogenetic activation millimeters into the brain (validated using motor cortex stimulation to induce turning behaviors) and wireless optogenetics in arenas of more than 1 m2 in size. This methodology allows for previously impossible behavioral experiments leveraging the modern optogenetic toolkit.

Wireless, fully implantable cardiac stimulation and recording with on-device computation for closed-loop pacing and defibrillation

“…3B. The capacitor bank stores up to 2.76 mJ of energy when fully charged to 5.6 V. As energy is consumed for stimulation, the capacitor bank voltage drops to 3.5 V (∆2.1 V), the digital system operation voltage, resulting in 1.7 mJ of usable energy ( 40 ). The device relies on wireless power harvesting, which is maximized empirically by varying secondary antenna turns to enable maximum power output at the operation voltage of 3.5 to 5.6 V shown in Fig.…”

“…Wireless control of the device is accomplished using a custom simplex protocol as described previously ( 40 , 41 ) to set parameters such as duty cycle, frequency, and the number of μ-ILEDs activated. Figure 3E shows a diagram of the wireless communication scheme used for pacing and electrophysiological recording state selection.…”

“…This is enough energy to operate -ILEDs at 101 mW/mm 2 for 1.5 s at a 100% duty cycle, which is far beyond the required on-time needed for high-powered stimulation events such as defibrillation (23). Wireless control of the device is accomplished using a custom simplex protocol as described previously (40,41) to set parameters such as duty cycle, frequency, and the number of -ILEDs activated. Figure 3E shows a diagram of the wireless communication scheme used for pacing and electrophysiological recording state selection.…”

“…Pulses of 100 (t 1 ), 200 (t 2 ), 300 (t 3 ), and 400 ms (t 4 ) (representing logic bits 0, 1, 2, and 3) with 50 ms between pulses are used in this scheme. This configuration enables an increase of transmission speed of 500% and parameter space of 200% over our previous work (40). See Materials and Methods for more information on wireless communication.…”

Thermal Analysis on Active Heat Dissipation Design with Embedded Flow Channels for Flexible Electronic Devices

“…In recent years, electronic products have emphasized intelligence and miniaturization, which require higher performance at the integration level. In particular, flexible electronic devices represent a rapidly developing branch, which has enabled many new applications such as curvilinear electronics and bio-integrated electronics [1][2][3][4][5][6] due to their unique advantages of stretchability and flexibility [7][8][9][10]. Furthermore, hybrid flexible systems have been investigated, such as electrophysiology [11], multimodal [12], large-area pressure [13] and other functions [14]; such functions may lead to overheating in the system.…”