Kaiyan Qiu

A Review of Fabrication and Applications of Bacterial Cellulose Based Nanocomposites

Bacterial cellulose (BC) is a unique nanofibrous biomaterial which can have applications in many engineering fields. BC possesses excellent mechanical properties and biocompatibility and can be engineered in various forms from nano to macro scales. BC based nanocomposites can be manipulated to improve their properties and/or functionalities. Such materials can be categorized as high-strength materials as well as materials for plant biomimicking, biomedical, electrically conductive, catalysis, optical, luminescent, proton conductive, separating, antimicrobial, thermo-responsive, and other applications. The review presented here focuses on various fabrication methods used and novel applications of BC based nanocomposites that are expected to be commercialized.

3D Printed Stretchable Tactile Sensors

The development of methods for the 3D printing of multifunctional devices could impact areas ranging from wearable electronics and energy harvesting devices to smart prosthetics and human-machine interfaces. Recently, the development of stretchable electronic devices has accelerated, concomitant with advances in functional materials and fabrication processes. In particular, novel strategies have been developed to enable the intimate biointegration of wearable electronic devices with human skin in ways that bypass the mechanical and thermal restrictions of traditional microfabrication technologies. Here, a multimaterial, multiscale, and multifunctional 3D printing approach is employed to fabricate 3D tactile sensors under ambient conditions conformally onto freeform surfaces. The customized sensor is demonstrated with the capabilities of detecting and differentiating human movements, including pulse monitoring and finger motions. The custom 3D printing of functional materials and devices opens new routes for the biointegration of various sensors in wearable electronics systems, and toward advanced bionic skin applications.

Bacterial cellulose-based membrane-like biodegradable composites using cross-linked and noncross-linked polyvinyl alcohol

Bacterial cellulose (BC)-based membrane-like biodegradable composites were produced by immersing wet BC pellicles in polyvinyl alcohol (PVA) solution. The BC content in the BC–PVA composites can be adjusted by varying the concentration of PVA solution. Chemical cross-linking of PVA was carried out using glutaraldehyde to increase the mechanical properties of the composites as well as to make the PVA partially to highly water insoluble. Examination by scanning electron microscopy indicated that the PVA not only penetrated the BC network, but also filled the pores within the BC pellicle. Attenuated total reflectance-Fourier transform infrared spectroscopy showed that acetal linkages could be formed in the BC–PVA composites by a cross-linking reaction. Sol–gel results indicated that cross-linking reaction increasingly made PVA insoluble in water resulting in higher gel (cross-linked fraction) content in the PVA. Wide-angle X-ray diffraction results showed decreased crystallinity in cross-linked BC and PVA, as expected. It was also found that crystal size was smaller in PVA after cross-linking. The BC–PVA composites had excellent tensile properties and cross-linking increased these properties further. Thermogravimetric analysis showed higher thermal stability for BC–PVA composites compared to PVA. The cross-linked specimens, especially the highly cross-linked ones, showed even higher thermal stability. The methods developed in this study make it possible to control the PVA content in the composites as well as the cross-linking level of PVA. These composites could be good candidates for replacing traditional non-biodegradable plastics.

3D Printed Organ Models with Physical Properties of Tissue and Integrated Sensors

The design and development of novel methodologies and customized materials to fabricate patient-specific 3D printed organ models with integrated sensing capabilities could yield advances in smart surgical aids for preoperative planning and rehearsal. Here, we demonstrate 3D printed prostate models with physical properties of tissue and integrated soft electronic sensors using custom-formulated polymeric inks. The models show high quantitative fidelity in static and dynamic mechanical properties, optical characteristics, and anatomical geometries to patient tissues and organs. The models offer tissue-mimicking tactile sensation and behavior and thus can be used for the prediction of organ physical behavior under deformation. The prediction results show good agreement with values obtained from simulations. The models also allow the application of surgical and diagnostic tools to their surface and inner channels. Finally, via the conformal integration of 3D printed soft electronic sensors, pressure applied to the models with surgical tools can be quantitatively measured.

3D Printed Organ Models for Surgical Applications

Medical errors are a major concern in clinical practice, suggesting the need for advanced surgical aids for preoperative planning and rehearsal. Conventionally, CT and MRI scans, as well as 3D visualization techniques, have been utilized as the primary tools for surgical planning. While effective, it would be useful if additional aids could be developed and utilized in particularly complex procedures involving unusual anatomical abnormalities that could benefit from tangible objects providing spatial sense, anatomical accuracy, and tactile feedback. Recent advancements in 3D printing technologies have facilitated the creation of patient-specific organ models with the purpose of providing an effective solution for preoperative planning, rehearsal, and spatiotemporal mapping. Here, we review the state-of-the-art in 3D printed, patient-specific organ models with an emphasis on 3D printing material systems, integrated functionalities, and their corresponding surgical applications and implications. Prior limitations, current progress, and future perspectives in this important area are also broadly discussed.

3D Printed Polymer Photodetectors

Extrusion-based 3D printing, an emerging technology, has been previously used in the comprehensive fabrication of light-emitting diodes using various functional inks, without cleanrooms or conventional microfabrication techniques. Here, polymer-based photodetectors exhibiting high performance are fully 3D printed and thoroughly characterized. A semiconducting polymer ink is printed and optimized for the active layer of the photodetector, achieving an external quantum efficiency of 25.3%, which is comparable to that of microfabricated counterparts and yet created solely via a one-pot custom built 3D-printing tool housed under ambient conditions. The devices are integrated into image sensing arrays with high sensitivity and wide field of view, by 3D printing interconnected photodetectors directly on flexible substrates and hemispherical surfaces. This approach is further extended to create integrated multifunctional devices consisting of optically coupled photodetectors and light-emitting diodes, demonstrating for the first time the multifunctional integration of multiple semiconducting device types which are fully 3D printed on a single platform. The 3D-printed optoelectronic devices are made without conventional microfabrication facilities, allowing for flexibility in the design and manufacturing of next-generation wearable and 3D-structured optoelectronics, and validating the potential of 3D printing to achieve high-performance integrated active electronic materials and devices.