Electrospun composite poly(lactic acid)/polyaniline nanofibers from low concentrations in CHCl 3 : Making a biocompatible polyester electro-active William Serrano, Anamaris Mel  endez, Idalia Ramos, Nicholas J. Pinto * Department of Physics and Electronics, University of Puerto Rico at Humacao, Humacao, PR 00792, USA article info Article history: Received 11 July 2014 Received in revised form 28 August 2014 Accepted 6 September 2014 Available online 16 September 2014 Keywords: Electrospinning Nanofibers Diode abstract Nanofibers of poly(lactic acid) (PLA) blended with polyaniline (PANi) were fabricated via electrospinning at much lower PLA concentrations (~1wt%) in CHCl 3 than reported before using a more efficient tech- nique of preparing the solutions. The polymer nanofibers had diameters in the range 10 nme300 nm. Nanofibers prepared with a 3 wt% PLA/PANi solution were conducting and were used to fabricate a diode which was electrically characterized and exhibited a low turn-on voltage and a rectification ratio of 500. The device characteristics were analyzed using the standard thermionic emission model of a Schottky junction and yielded an ideality factor of 1.6 and a barrier height of 0.49 eV. Using a simple circuit, the diode was able to rectify a low frequency alternating current signal with an efficiency of 10%. The ability to engineer insulating PLA into nanofibers that are electro-active extends the range of applications of this biocompatible and biodegradable polyester to include electronic devices that have reduced toxicity. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction The design of degradable and electrically conductive polymers is an important field of study for biomedical applications [1]. Poly(- lactic acid)ePLA is a thermoplastic aliphatic polyester that is biocompatible and biodegradable, with lactic acid being a typical harmless byproduct of decomposition. PLA can be produced via processing starch and although it is an electrical insulator, it is mechanically robust and environmentally stable and has therefore attracted interest in passive electrical applications such as biomedical implants (screws), controlled drug delivery, kitchen variety commodity products and 3-D printing [2]. Commercial PLA has a hard grainy morphology, but is readily soluble in organic solvents and can be cast into thin films, fibers, foams or other forms. Fibers typically have a larger surface to volume ratio compared to films and are thus technologically advantageous for sensor appli- cations. One common technique of making PLA fibers is using electrospinning [3e7]. Composite fibers of PLA blended with con- ducting polymers have also been fabricated via this technique [8,9]. In all of these experiments however, the PLA concentration in so- lution was 8wt% or higher, reducing the possibility of obtaining PLA fibers that are electrically conducting to be used in devices and sensors. The motivation for the present work is therefore to fabri- cate nanofibers of this biodegradable polymer that are electrically conducting so that they can be used in active electronic devices such as diodes, sensors and in 3D printing of PLA based products. In this work we have used the electrospinning technique to fabricate nanofibers of PLA blended with the conducting polymer polyaniline doped with camphor-sulfonic acid (PANi-CSA) at con- centrations as low as 1 wt% of PLA in chloroform (CHCl 3 ). PANi-CSA is a common conducting polymer that is easy to synthesize and is also soluble in CHCl 3 in the doped conducting form. By controlling the evaporation of the solvent in the blend solution prior to elec- trospinning, while keeping the amount of PANi-CSA fixed, extremely fine fibers of the blend could be produced at low PLA concentrations than previously reported and that were electrically conducting. Electrospinning nanofibers of PLA at low concentra- tions increased the probability of making them conducting, used less material and made the fabrication of devices economical. The fibers were used to fabricate a diode, and represent the first use of these composite fibers as the active material in an electronic device, where PLA provides the mechanical stability of the fibers and PANi- CSA provides the conducting pathway. A diode was selected as a prototype device as it forms the basic building block in complex electronic circuits, especially in power supplies. The standard thermionic emission model of a Schottky junction was applied to * Corresponding author. Tel.: þ1 787 850 9381. E-mail address: nicholas.pinto@upr.edu (N.J. Pinto). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer http://dx.doi.org/10.1016/j.polymer.2014.09.015 0032-3861/© 2014 Elsevier Ltd. All rights reserved. Polymer 55 (2014) 5727e5733