Writing instruments, such as pens, are ubiquitous in the classroom, but their functionality is largely for one purpose: they are used to represent ideas and record information on paper. However, by replacing the conventional ink in a pen with easy-to-synthesize conducting polymer-based inks, it is possible to change a simple writing utensil into a materials processing tool that can create circuits, sensors, and potentially other optoelectronic devices. The Polysketch pen is a modified ballpoint pen that contains a conductive polyaniline ink that can be synthesized safely by high school and undergraduate students in a 1-3 hour laboratory setting. The synthesis and formulation of the ink and the construction of the pen expose students to nanomaterial synthesis, chemical/material purification, and functional design with a specific goal: producing an appropriately viscous, fast-drying ink with a suitable loading level of polyaniline for conductive properties. The Polysketch pen leaves conductive traces on paper, which can be used to draw simple circuits or construct sensors responding to mechanical strains or ambient chemical species. This activity has the objective of introducing materials-relevant polymer synthesis into high school and undergraduate laboratories while introducing concepts in conductive polymers such as doping/dedoping and percolation in conductive networks. The activity is constructed such that students have the opportunity to explore processing-structure-properties-performance relationships by optimizing ink formulation. Most importantly, students will ultimately arrive at a tangible, versatile product and tool that enables them to explore other types of interactive devices and art to "trace a line of their creation".