Robust and adaptable sensor technology is essential for achieving meaningful structural health monitoring (SHM) and integrated nondestructive evaluation (NDE). Unfortunately, prevailing sensor technologies are most often pre-packaged and therefore lack much adaptability. In other words, sensors are rarely structure-specific or application-specific. Rather, an existing pre-packaged sensor must be retrofit to the component or structure under inspection. Multifunctional additive manufacturing (AM) has immense potential to overcome this limitation by permitting stimulus-responsive materials to be printed onto or directly embedded within structures for application-specific sensing. Herein, we explore this concept for strain sensors fabricated via multifunctional AM. Specifically, pelletized polylactic acid (PLA) is modified by the addition of carbon nanofibers (CNFs) at 7.5% by weight. This modification is done through a dry-mix process which is followed by multiple reclaiming and re-extrusion cycles through a single-screw filament extruder. Through this process, the CNFs form an electrically conductive network within the PLA structure. Because the electrical conductivity of the CNFmodified PLA is deformation-dependent (i.e. the material is piezoresistive), the sensors printed from CNF/PLA filament can be leveraged for strain sensing. In this work, we utilize a commercially available fused deposition modeling (FDM) printer to print the CNF-modified PLA into small and thin dog-bone shapes. These sensors then are adhered to a comparatively stiff substrate such that resistance changes across the sensor can be monitored as a function of strain as the substrate is deformed within a load frame. Our preliminary results show that AM-produced CNF-modified PLA strain gauges can indeed be used to track strains consistently. These successful preliminary results show that multifunctional AM has considerable potential for the development of highly adaptive, application-specific, and on-demand sensing technology.
Multi-functional additive manufacturing is a promising route to achieving exciting new rapid prototyping and in-the-field manufacturing capabilities. Ideally, multi-functionality could be imparted to materials that can be used with existing additive manufacturing hardware with little-to-no modification of the hardware. However, because much of the additive manufacturing hardware currently available is highly sensitive to the properties of the input material, it is important to understand the relationship among the processing/development of the input material, its physical properties, and quality and properties of the additively manufactured part. To that end, this project explores the effects of processing conditions on the electrical properties and printability of nanofiller-modified fused deposition modeling (FDM) filament. Specifically, pulverized polylactic acid (PLA) is dry mixed with carbon nanofibers (CNFs) and extruded through a commercially available single-screw filament extruder. Filament resistivity and diameter are then statistically characterized as a function of extrusion temperature and number of extrusions. Printability is also quantitatively and qualitatively characterized using a commercial FDM printer. Insights developed through this work could be of considerable significance to next-generation additively manufactured piezoresistive-based sensors, actuators, and electrical components.
Progress in developing optical imaging for biomedical applications requires customizable and often complex objects known as "phantoms" for testing, evaluation, and calibration. This work demonstrates that 3D printing is an ideal method for fabricating such objects, allowing intricate inhomogeneities to be placed at exact locations in complex or anatomically realistic geometries, a process that is difficult or impossible using molds. We show printed mouse phantoms we have fabricated for developing deep tissue fluorescence imaging methods, and measurements of both their optical and mechanical properties. Additionally, we present a printed phantom of the human mouth that we use to develop an artery localization method to assist in oral surgery.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.