Tag Archives: LED

Injectable optoelectronics with wireless control

The ability to wirelessly control neural circuitry has been a long-standing goal in neuroscience. Recent advances have put this goal in site using optogenetic approaches. In 2011, multiple groups presented the first attempts at making wireless light delivery application for optogenetics (Iwai et al., 2011; Wentz et al., 2011). These advances, however, were constrained to particular environments or apparatuses to power the devices. The radiofrequency power scavenging approach presented in Kim et al., 2013 frees the experimenter from these constraints. In the recent report, the Bruchas (Washington University at St. Louis) and Rogers (University of Illinois at Urbana-Champaign) labs present ultrathin, microscale optoelectronics and sensors that can be used for the optogenetic manipulations. Unlike other wireless approaches this system can be used with any behavioral apparatus or paradigm, which should allow researchers to explore more complex behaviors while perturbing neural circuitry.

The wireless µILED devices can incorporate wired cellular-scale components that can all be inserted into the brain using a combination of a silk-based biodissolvable adhesive (Kim et al., 2010) and an injection needle similar in concept to electrode delivery presented previously (Kozai and Kipke, 2009). These components include, but are presumably not limited to, temperature sensors, electrodes for … Continue reading

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Thermal and optical characterization of a micro-LED probe

Over the last few years, there has been a significant drive to improve light sources for in vivo optogenetic control of neuronal activity. In particular, recent work has focused on the design and microfabrication of compact devices that exhibit multiple optical stimulation sites in order to gain control over closely spaced regions within the brain (see here a list of posts related to this). In a recent Optics Letters paper, McAlinden, Massoubre and colleagues presented a novel microprobe device with integrated light sources. The probe produces sufficient light for optogenetic stimulation without causing significant heating in local brain tissue. The device (see figure below) consists of a 100 µm wide, 50-100 µm thick probe with 5 individually addressable microLEDs. Each LED has a diameter of 40 µm, but can be reduced to 10 µm if higher density probes are required. The LED probes are p-n diodes made from quantum well structures using GaN on Sapphire material. The spacing between LEDs is fixed to allow 1mm of neural tissue to be addressed.

The light output from the LEDs was measured, with scattering and absorption accounted for by experimentally measuring the light transmitted through varying thicknesses of brain tissue. The recorded light … Continue reading

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Micro-electrocorticogram electrodes for simultaneous recording and optical stimulation

Wen Li’s group at Michigan State University recently presented preliminary results on the development of an epidural micro-electrocorticogram (μECoG) array combining microelectrodes and light emitting diodes (LEDs) for optical neural stimulation. This work follows-up on a new line of research aiming at providing μECoG arrays with versatile optical stimulation capabilities (see for example the work of Ledochowitsch et al). The “Opto-μECoG” arrays developped in Wen Li’s group were especially designed to address three major limitations of current designs, in particular the limited cortical area and spatial resolution available for optical stimulation. The key features of these Opto-μECoG arrays are the following:

Untethered system: integration of surface mounted μ-LED light sources (220 × 270 ×50 μm3, wavelength peak at 460nm, Cree® TR2227TM) on the Opto-μECoG array allows the possibility to achieve a truly untethered system. Maximized target cortical area available for optical stimulation: optically transparent indium tin oxide (ITO) [2] epidural electrodes of the Opto-μECoG array allow maximum exposure of the target cortical area for optical stimulation. Maximized spatial resolution of optical stimulation: the embedded light sources, placed on top of the ITO electrodes, were preciously arranged based on a recent study of the optimal spacing of subdural, epidural, and scalp … Continue reading

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