3D printed dopamine microfluidic sensor based on thermally induced graphitic electrodes on diamond.

Dopamine (DA) is a neurotransmitter that regulates diverse physiological operations in the brain, whereas malfunctions of the dopaminergic system are associated with many diseases. Therefore, detecting the concentration of DA $in vitro$ from neuroendocrine cell is relevant for drug screening investigations or early diagnosis of sickness. In this contribution, we intend to merge the electrochemical properties of the thermally induced graphite on artificial diamond and the capabilities of a stereolithography 3D printer to produce a droplet-based microfluidic biosensor capable of detecting DA in physiological solutions. The solution under analysis is confined into micro-drop directly created into the microfluidic sensor taking advantage of its immiscibility into the oil stream which works as carrier. Each micro-drop can be considered as a single micro Petri dish and can be individually analysed by the diamond biosensor. The detection process takes advantage of the proportionality between the DA concentration and the generated amperometric current intensity. Our approach relies on developing a versatile method, assuring a time-effective and simple fabrication method with reasonable sensitivity.