A method for preparing microsensors (e.g., microelectrodes) suitable for use in electrophysiology and electrochemistry studies in vitro and in vivo is described. The method can involve preparing a polymeric resin-insulated electron conducting fiber using a 3D printed mold comprising one or more channels, wherein each of the channels includes a tapered section. An electron conducting fiber partially enclosed within a metal or glass support can be laid in a channel; and a polymeric resin can be poured into the channel and cured, providing a polymer-insulated electron conducting fiber having a tapered section in proximity to a polymer-free electroactive tip area. For example, the method can be used to provide a polyimide-insulated carbon fiber microsensor. The mold can be used for the batch fabrication of the microsensors. The microsensors themselves, the molds for making the microsensors, and methods of using the microsensors are also described.