Miniaturized, Battery‐Free Optofluidic Systems with Potential for Wireless Pharmacology and Optogenetics

Abstract

Combination of optogenetics and pharmacology represents a unique approach to dissect neural circuitry with high specificity and versatility. However, conventional tools available to perform these experiments, such as optical fibers and metal cannula, are limited due to their tethered operation and lack of biomechanical compatibility. To address these issues, a miniaturized, battery-free, soft optofluidic system that can provide wireless drug delivery and optical stimulation for spatiotemporal control of the targeted neural circuit in freely behaving animals is reported. The device integrates microscale inorganic light-emitting diodes and microfluidic drug delivery systems with a tiny stretchable multichannel radiofrequency antenna, which not only eliminates the need for bulky batteries but also offers fully wireless, independent control of light and fluid delivery. This design enables a miniature (125 mm ), lightweight (220 mg), soft, and flexible platform, thus facilitating seamless implantation and operation in the body without causing disturbance of naturalistic behavior. The proof-of-principle experiments and analytical studies validate the feasibility and reliability of the fully implantable optofluidic systems for use in freely moving animals, demonstrating its potential for wireless in vivo pharmacology and optogenetics.

Biodegradable Frequency‐Selective Magnesium Radio‐Frequency Microresonators for Transient Biomedical Implants

“…The geometry of the microheaters, shown in Figure b, is commonly referred to as spiral resonator (SR). Such a design enables the maximization of the capacitance and thus the minimization of the resonance frequency for a given diameter, or, alternatively, the reduction of the size compared to similar devices working in the same frequency range reported in the literature . Figure b also shows that by adding a meander to the design, the current density locally increases by one to two orders of magnitude, which creates a local hot spot at a specific location.…”

“…Details about the dimensions of the SRs used in Section are summarized in Table S2 in the Supporting Information. The ability to selectively power and heat up microresonators made of biodegradable materials is a significant step toward the use of such devices as heating and triggering elements in implantable biodegradable devices, in particular for controlled drug release and thermal therapy . In comparison, our device has 4–24 times smaller coil area, and its fabrication complexity is much reduced since it consists of only a single metal layer.…”

“…When implementing multiple resonators with distinct resonance frequencies in one or several implants, each RLC circuit can be selectively addressed by matching the frequency of the external excitation magnetic field to that of the resonator of interest. Selective drug delivery or differentiating drug delivery and optical stimulation in an implantable optofluidic system were demonstrated using such a technique …”

Injectable Biomedical Devices for Sensing and Stimulating Internal Body Organs

“…The most mature technology for recording and stimulating the brain is conducting metal electrodes, owing to their superior biocompatibility, manufacturing easiness, and electrical characteristics 39,102. Furthermore, the advent of optogenetics103 generated extensive developments in optical systems for the brain, such as optical fibers,104,105 thin film waveguides,50,106,107 and microscale inorganic light emitting diodes (LED)27,48,108–110 to efficiently deliver light to targeted neurons. Microfluidic channels embedded into the optoelectronics also enabled simultaneous photostimulation and delivery of liquid drugs in site‐specific areas 52,111.…”

“…Electronic and optoelectronic components such as micro‐LEDs can be extracted from their host wafers to yield ultrathin devices (approximately several micrometers) 138–140. Together with semiconductor printing and flexible electronics fabrication technologies, ultrathin probes consisting of micro‐LEDs, along with several other thin‐film devices could be created for the brain 27,52,108–110. Figure 5g represents a multifunctional recording and stimulation brain probe, which consisted of micro‐LEDs for optogenetics stimulation, temperature sensor for heat monitoring, thin‐film photodiodes for light intensity measurement and metal‐based microelectrodes for electrophysiological (EP) recording and electrical stimulation 27.…”