Jeong, J.-W. et al. Cell 162, 662–674 (2015).

Pharmacological and optogenetic manipulations of neurons are two approaches for interrogating circuit function in the brain that are usually performed in separate experiments. Jeong et al. have now developed a device that can deliver both light and fluids in vivo. The device consists of an array of inorganic light-emitting diodes (μ-ILEDs) and four fluid-delivery channels connected to independent reservoirs. The device is wirelessly controlled by an infrared sensor that enables light delivery or a heating element that triggers fluid pumping via heat-sensitive expandable microspheres. The researchers used these devices to optogenetically activate and pharmacologically inhibit dopamine neurons in the ventral tegmental area of mice, causing a modulation of place preference behavior in freely moving animals.