Session: 01-04 Multifunctional Composites/Nanocomposites

Paper Number: 171629

171629 - Nanostructural Effects of Conjugated Polymers on the Airbrushing-Manufactured Mechano-Optoelectronic Thin Films 

In this study, we investigate how nanostructures of conjugated poly(3-hexylthiophene) (P3HT) polymers are related to mechano-optoelectronic (MO) properties of an airbrushing-manufactured thin-films. Understanding the interplay between nanoscale morphology and optoelectronic performance under mechanical deformation is critical for designing self-powered MO thin film-based strain sensors suitable for health monitoring wearables. To enhance both mechanical resilience and optoelectronic responsiveness under strain, multi-walled carbon nanotubes (MWCNTs) are incorporated into the P3HT:[6,6] phenyl-C61-butyric acid methyl ester (PCBM) matrix. MWCNTs are selected due to their outstanding mechanical properties and their unique ability to facilitate charge transport and promote molecular alignment within polymeric systems. This alignment arises from π–π stacking non-covalent interactions between the nanotube surface and the conjugated P3HT backbone, promoting local chain ordering and greater crystallinity within the active layer. 

The role of MWCNTs in promoting crystalline alignment and improving structural order is investigated using a suite of characterization techniques. Ultraviolet visible (UV-Vis) spectroscopy is used to evaluate peak absorbance ratios and determine dichroic ratios, giving insight into the degree of molecular orientation within the films. Grazing-incidence wide-angle X-ray scattering (GIWAXS) offers complementary information on molecular packing and crystallinity, while optical microscopy gives insight of macroscale film uniformity and morphology. To further probe the nanoscale structure, atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used to qualitatively assess surface texture, alignment, and MWCNT dispersion within the matrix. Two types of thin-film strain sensors are fabricated: one with MWCNTs dispersed in the P3HT:PCBM photoactive layer, and one without. Each sensor is deposited onto a flexible substrate made of polydimethylsiloxane (PDMS), using airbrushing.

In addition to the active sensing layer, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is employed as a transparent conductive electrode layer. Since PEDOT:PSS must balance high optical transparency with good electrical conductivity and adhesion to the substrate, we systematically investigate the effect of UV ozone surface treatment on its wettability and transmittance. Contact angle measurements are performed at various exposure durations to quantify surface energy, and UV-Vis transmittance data is collected to evaluate the impact on light throughput. These optimizations are crucial to ensuring that light emitted or transmitted through the sensor reaches the active layer efficiently.

The comparative performance of the two sensor types – P3HT:PCBM with and without MWCNTs – is evaluated to determine how nanostructure tuning affects sensor response to strain as an MO property. The expected data can be used to learn how MWCNT integration improves crystallinity and alignment under mechanical deformation, likely enhancing charge mobility and mechanical coupling in the thin films. The combination of airbrushing, nanostructure tuning, and surface engineering of PEDOT:PSS represents a promising pathway for scalable, high-performance thin-film sensor development.

This work contributes to the broader goal of understanding how material composition and processing methods influence the optoelectronic and mechanical behavior of MO devices. By combining nanomaterial integration with process optimization, we envision to give insight into designing next-generation MO sensors capable of functioning in health monitoring systems.

Presenting Author: Cason Jones New Mexico Tech

Presenting Author Biography: Cason Jones is a graduate student in the Department of Mechanical Engineering at New Mexico Tech, conducting research under the advisement of Dr. Donghyeon Ryu. His work focuses on the fabrication and characterization of mechano-optoelectronic (MO) thin films, specifically poly(3-hexylthiophene) (P3HT)-based composites. Using airbrushing techniques for thin film deposition, he investigates how processing conditions influence nanoscale morphology and device performance. He employs a suite of characterization methods including atomic force microscopy (AFM), scanning electron microscopy (SEM), UV-Vis spectroscopy, and grazing incidence wide-angle X-ray scattering (GIWAXS) to establish processing-structure-property (PSP) relationships in these functional materials. His research contributes to a larger project funded by NASA and the National Science Foundation (NSF), which aims to develop flexible, self-powered strain sensors for use in wearable electronics and health monitoring applications.