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Perforated microelectrode arrays (pMEAs) have become essential tools for ex vivo retinal electrophysiological studies. pMEAs increase the nutrient supply to the explant and alleviate the accentuated curvature of the retina, allowing for long-term culture and intimate contacts between the retina and electrodes for electrophysiological measurements. However, commercial pMEAs are not compatible with in situ high-resolution optical imaging and lack the capability of controlling the local microenvironment, which are highly desirable features for relating function to anatomy and probing physiological and pathological mechanisms in retina. Here we report on microfluidic pMEAs (μpMEAs) that combine transparent graphene electrodes and the capability of locally delivering chemical stimulation. We demonstrate the potential of μpMEAs by measuring the electrical response of ganglion cells to locally delivered high K + stimulation under controlled microenvironments. Importantly, the capability for high-resolution confocal imaging of the retina tissue on top of the graphene electrodes allows for further analyses of the electrical signal source. The new capabilities provided by μpMEAs could allow for retinal electrophysiology assays to address key questions in retinal circuitry studies. 

Exploring ways to tune and improve the performance of graphene is of paramount importance in creating functional graphene-based electronic and optoelectronic devices. Recent advancements have shown that altering the morphology of graphene can have a pronounced effect on its properties. Here, we present a practical and facile method to manipulate the morphology of a suspended graphene ribbon using a laser to locally induce heating while monitoring its electrical and optoelectronic properties in situ . Electrical measurements reveal that the conductance of suspended graphene transistors can be tuned by modifying its morphology. Additionally, scanning photocurrent measurements show that laser-induced folded graphene ribbons display significantly enhanced localized photocurrent responses in comparison with their flat counterparts. Moreover, the localization of the laser-induced heating allows for a series of folds to be induced along the entire graphene ribbon, creating targeted photocurrent enhancement. Through further investigations, it is revealed that the photo-thermoelectric effect is the primary mechanism for the increased photocurrent response of the device. Our experimental results explore the mechanisms and consequences of the folding process as well as provide a strategy to manipulate morphology and physical properties of graphene for future engineering of electronics and optoelectronics.