Nanometric Hydroxyapatite Particles as Active Ingredient for Bioinks: A Review

Edilberto Ojeda,África García-Barrientos,Nagore Martínez de Cestafe,José María AlonsoORCID,Raúl Pérez-González andVirginia Sáez-Martínez *

Additive manufacturing (AM), frequently cited as three-dimensional (3D) printing, is a relatively new manufacturing technique for biofabrication, also called 3D manufacture with biomaterials and cells. Recent advances in this field will facilitate further improvement of personalized healthcare solutions. In this regard, tailoring several healthcare products such as implants, prosthetics, and in vitro models, would have been extraordinarily arduous beyond these technologies. Three-dimensional-printed structures with a multiscale porosity are very interesting manufacturing processes in order to boost the capability of composite scaffolds to generate bone tissue. The use of biomimetic hydroxyapatite as the main active ingredient for bioinks is a helpful approach to obtain these advanced materials. Thus, 3D-printed biomimetic composite designs may produce supplementary biological and physical benefits. Three-dimensional bioprinting may turn to be a bright solution for regeneration of bone tissue as it enables a proper spatio-temporal organization of cells in scaffolds. Different types of bioprinting technologies and essential parameters which rule the applicability of bioinks are discussed in this review. Special focus is made on hydroxyapatite as an active ingredient for bioinks design. The goal of such bioinks is to reduce the constraints of commonly applied treatments by enhancing osteoinduction and osteoconduction, which seems to be exceptionally promising for bone regeneration.

Physical, mechanical, and microstructural characterization of novel, 3D-printed, tunable, lab-grown plant materials generated from Zinnia elegans cell cultures

Ashley L. Beckwith, Jeffrey T. Borenstein, Luis F. Velásquez-García

To date, wood has been viewed as an attractive commodity because of its low relative cost and widespread availability. However, supply is increasingly strained, and, in many ways, trees make a non-ideal feedstock—with slow, climate and seasonally dependent growth, low yields of high-value products, and susceptibility to pests and disease. Recent research offered an approach to generate plant-based materials in vitro without needing to harvest or process whole plants, thereby enabling: localized, high-density production, elimination of energy-intensive collection and hauling, reduced processing, and inherent climate resilience. This work reports the first physical, mechanical, and microstructural characterization of 3-D printed, lab-grown, and tunable plant materials generated with Zinnia elegans cell cultures using such methodology. The data show that the properties of the resulting plant materials vary significantly with adjustments to hormone levels present in growth medium. In addition, configuration of the culture environment via bioprinting and casting enables the production of net-shape materials in forms and scales that do not arise naturally in whole plants. Finally, new comparative data on cell development in response to hormone levels in culture medium demonstrates the repeatability of growth trends, clarifies the relationship between developmental pathways, and helps to elucidate the relationships between cellular-level culture characteristics and emergent material properties.

Shape Memory Polymer Composites for 4D Printing of Wearable Devices

Kyra McLellan

In recent years, 3D printing techniques have provided new opportunities for the fast and custom fabrication of high-quality parts. New developments in 4D printing looks to create structures which change their shape over time. Through the design of new shape memory polymer composites (SMPCs) and the application of new printing methods and techniques, the current state of additive manufacturing technologies is being advanced. Herein, three primary studies are conducted: 1) a literature review on the potential of 4D printing custom, wearable devices for biomedical applications, 2) the material development and characterization of a new SMPC featuring 2D MXene flakes and the design of large-scale deformation 4D printed structures, and 3) the optimization and characterization of a new porous printing technique for the development of a hybrid 4D printed actuating/sensing wearable device. Through these studies, a holistic view of 3D printing is provided, including material development and manufacturing, with the intention of continued innovation in 4D printing

Facile Fabrication of Injectable Alginate and Poly(3,4-ethylenedioxythiophene)-Based Soft Electrodes toward the Goal of Neuro-Regenerative Applications

Ivana Perkucin, Kylie S. K. Lau, Tianhao Chen, Stephanie N. Iwasa, Hani E. Naguib, Cindi M. Morshead

Resident brain neural precursor cells (NPCs) are electrosensitive cells that respond to electric field application by proliferating, differentiating, and undergoing rapid and directed cathodal migration. Harnessing NPC potential is a promising strategy to facilitate neural repair following injury or disease. The use of electric fields to activate NPCs is limited by current electrode designs which are typically made of conductive metals that are stiff and can lead to neuroinflammation following implantation, in part due to the mechanical mismatch between physiological conditions and material. Herein, the design of a novel, injectable biobased soft electrode with properties suitable for electrical stimulation in vivo is explored. The recent interest in using biologically derived polymers which are relatively abundant and afford economic feasibility have been built upon. Sodium alginate is utilized to form soft hydrogels, thereby addressing the issue of mechanical mismatch, and the conductive polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), to generate an innovative new material. It is demonstrated that the optimized alginate PEDOT blend matches the modulus of the brain and is suitable for injection and is not cytotoxic to neural cells. Furthermore, in vivo studies demonstrate minimal activation of inflammatory cells upon implantation in the brain compared to classically used platinum-based electrodes.

3D-Printed Carrageenan-Based Nanocomposites for Force-Sensing Applications

Vera M. Macedo, Nelson Pereira, Carmen R. Tubio, Pedro Martins, Carlos M. Costa, Senentxu Lanceros-Mendez

Technological development is leading to an exponential growth in the implementation of sensors and actuators where the concern about environmental problems is also focusing on electronic waste (e-waste), which is composed of hazardous materials, corresponding to a large part of urban waste, and has a strong environmental impact. Therefore, more environmentally friendly electronic components are required, natural polymers being a suitable approach to solve or attenuate those problems. This work reports on a bio-based polymer, carrageenan, embedded with dielectric barium titanate (BTO) nanoparticles to tailor the electrical response. The inclusion of the filler induces slight modifications in the thermal characteristics and on the physicochemical properties of the polymer matrix. On the other hand, the mechanical and dielectric properties improve with the addition of BTO and a high dielectric constant of ε′ ≈13 000 is obtained for the composite with 20 wt% BTO content. The increase of the dielectric constant is accompanied by a high AC electrical conductivity, leading to a high-ε′–high-loss material. The 20 wt% BTO composite is used to produce a force measuring sensor, due to the highest dielectric response. The functional response of the sensing system shows good stability over cycling.

3D-printed EVA-based patches manufactured by direct powder extrusion for personalized transdermal therapies

Giorgia Maurizii , Sofia Moroni, Shiva Khorshid, Annalisa Aluigi, Mattia Tiboni a, Luca Casettari

In recent years, 3D printing has attracted great interest in the pharmaceutical field as a promising tool for the on-demand manufacturing of patient-centered pharmaceutical forms. Among the existing 3D printing techniques, direct powder extrusion (DPE) resulted as the most practical approach thanks to the possibility to directly process excipients and drugs in a single step. The main goal of this work was to determine whether different grades of ethylene vinyl acetate (EVA) copolymer might be employed as new feedstock materials for the DPE technique to manufacture transdermal patches. By selecting two model drugs with different thermal behavior, (i.e., ibuprofen and diclofenac sodium) we also wanted to pay attention to the versatility of EVA excipient in preparing patches for customized transdermal therapies. EVA was combined with 30 % (w/w) of each model drugs. The physicochemical composition of the printed devices was investigated through Fourier-transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analyses. FT-IR spectra confirmed that the starting materials were effectively incorporated into the final formulation, and thermal analyses demonstrated that the extrusion process altered the crystalline morphology of the raw polymers inducing the formation of crystals at lower thicknesses. Lastly, the drug release and permeation profile of the printed systems was evaluated for 48 h and showed to be dependent on the VA content of the EVA grade (74.5 % of ibuprofen released from EVA 4030AC matrix and 12.6 % of diclofenac sodium released from EVA1821A matrix). Hence, this study demonstrated that EVA and direct powder extrusion technique could be promising tools for manufacturing transdermal patches. By selecting the EVA grade with the appropriate VA content, drugs with dissimilar melting points could be printed preserving their thermal stability. Moreover, the desired drug release and permeation profile of the drug can be achieved, representing an important advantage in terms of personalized medicine.

Poly(3-hydroxybutyrate): A potential biodegradable excipient for direct 3D printing of pharmaceuticals

Sofia Moroni, Shiva Khorshid, Annalisa Aluigi, Mattia Tiboni, Luca Casettari

During the past decades, 3D printing has revolutionised different areas of research. Despite the considerable progress achieved in 3D printing of pharmaceuticals, the limited choice of suitable materials remains a challenge to overcome. The growing search for sustainable excipients has led to an increasing interest in biopolymers. Poly(3-hydroxybutyrate) (PHB) is a biocompatible and biodegradable biopolymer obtained from bacteria that could be efficiently employed in the pharmaceutical field. Here we aimed to demonstrate its potential application as a thermoplastic material for personalised medicine through 3D printing. More specifically, we processed PHB by using direct powder extrusion, a one-step additive manufacturing technique. To assess and denote the feasibility and versatility of the process, a 3D square model was manufactured in different dimensions (sidexheight: 12x2 mm; 18x2 mm; 24x2 mm) and loaded with increasing percentages of a model drug (up to 30% w/w). The manufacturing process was influenced by the drug content, and indeed, an increase in the amount of the drug determined a reduction in the printing temperature, without affecting the other parameters (such as the layer height). The composition of the model squares was investigated using Fourier-transform infrared spectroscopy, the resulting spectra confirmed that the starting materials were successfully incorporated into the final formulations. The thermal behaviour of the printed systems was characterized by differential scanning calorimetry, and thermal gravimetric analysis. Moreover, the sustained drug release profile of the formulations was performed over 21 days and showed to be dependent on the dimensions of the printed object and on the amount of loaded drug. Indeed, the formulation with 30% w/w in the dimension 24x2 mm released the highest amount of drug. Hence, the results suggested that PHB and direct powder extrusion technique could be promising tools for the manufacturing of prolonged release and personalised drug delivery forms.

Lignin−Zein Composite: Synthesis, Three-Dimensional Printing, and Microbial Degradation

Jin Gyun Lee,∥ Yusheng Guo,∥ Jorge A. Belgodere, Ahmed Al Harraq, Aubry A. Hymel, Amber J. Pete, Kalliat T. Valsaraj, Michael G. Benton, Mary G. Miller, Jangwook P. Jung, and Bhuvnesh Bharti*

Worldwide use and disposal of plastics have reached a dramatic saturation point, polluting lands, oceans, and air across the globe. Responding to such a challenge requires, among other environmental remediation measures, the manufacture of alternative sustainable plastics. Recent studies in the area have enabled the development of degradable plastics; however, the rate and conditions required for the degradation of such materials remains under scrutiny. Here, we introduce a new class of fully plant-based, rapidly degradable lignin and zein composite blend that can be transformed into macroscopic structures using extrusion three-dimensional (3D) printing. Corn-derived zein forms the polymeric solution, while insoluble lignin granules act as a binder for enhanced printability and facile degradation. The blend showcases a shear-thinning behavior that is ideal for rapid extrusion printing into desired 3D structures, from cuvette caps to circuit boards. Biodegradation studies show that common bacteria readily found in soil and compost are able to decompose structures made with the lignin−zein composite in shorter time frames compared to a known biodegradable plastic, viz., polylactic acid. The rapid biodegradability and enhanced processability highlight the potential of lignin−zein composites to decrease our dependence on petroleum oil-based plastics.

Tunable plant-based materials via in vitro cell culture using a Zinnia elegans model

Ashley L. Beckwith, Jeffrey T. Borenstein, Luis F. Velasquez-García

Current systems for plant-based biomaterial production are inefficient and place unsustainable demands on environmental resources. This work proposes a novel solution to these shortcomings based on selective cultivation of tunable plant tissues using scalable, land-free techniques unconstrained by seasonality, climate, or local resource availability. By limiting biomass cultivation to only desirable plant tissues, ex planta farming promises to improve yields while reducing plant waste and competition for arable land. Employing a Zinnia elegans model system, this work provides the first proof-of-concept demonstration of isolated, tissue-like plant material production in vitro by way of gel-mediated cell culture. Parameters governing cell development and morphology including hormone concentrations, medium pH, and initial cell density are optimized and implemented to demonstrate the tunability of cultured biomaterials at cellular and macroscopic scales. Targeted deposition of cell-doped, nutrient-rich gel scaffolds via casting and 3D bioprinting enable biomaterial growth in near-final form, reducing downstream processing requirements. These investigations demonstrate the implementation of plant cell culture in a new application space, propose novel methods for quantification and evaluation of cell development, and characterize morphological developments in response to critical culture parameters illustrating the feasibility and potential of the proposed techniques.

Advances in 3D bioprinting for the biofabrication of tumor models

Monica Gabriela Sanchez-Salazar, Mario Moises Alvarez, G. Trujillo-de Santiago

Cancer research depends on the challenging task of producing representative and reliable models of human disease; these have largely been limited to mouse models or human cancer cell lines cultured in monolayers. Three-dimensional (3D) cell culture offers more realistic options, but conventional 3D models still fail to recreate the human tumor microenvironment. One biofabrication technique that has emerged as a powerful tool is 3D bioprinting, which can generate tumor constructs with increasing complexity. By incorporating factors like stromal cells, vasculature, hydrogels, and functional molecules into the bioprinting process, researchers are now able to create human tumor models that quite realistically represent human glioblastoma, breast, cervical, ovarian, hepatoma, lung, colon, and oral cancers. The obtained structures range from coaxially extruded fibers and monolayered grids to cylinders, cubes, discs, beads, and even mini-organs. Here, we discuss recent advances in cancer research based on 3D bioprinting. Our aim is to provide a broad perspective of the possibilities provided by this biofabrication technique for the generation of complex tumor models. We also review the different structures and characterization techniques used with these models. The use of 3D bioprinted tumors is increasing in areas like tumor biology, migration, invasion, and metastasis, as well as in pharmaceutical testing and even personalized medicine. Future work will involve improvement of the mechanical properties and chemical cues provided to the cells within the 3D constructs. The inclusion of several cell types within a single construct will upgrade current recapitulations of real tumor tissues. Bioprinting of cells cultured from patients’ own biopsies will generate personalized models of the tumor niche.

Experimental Study and Analytical model of Shear Thinning in 3D Bioprinting of Gelatin

Busarac, N.; Jovanović, Ž.; Njezić, S.; Živić, F.; Grujović, N.; Adamović, D.

This paper presented extrusion-based 3D bioprinting of gelatin hydrogel and optimisation of material properties and process parameters, in order to improve printability of hydrogel. Gelatin hydrogel was prepared by mixing it with water in concentration of 13.04 wt%. Dimensional accuracy of the bioprinting was studied and significant changes in comparison with designed geometry were noted. Gelatin hydrogel made only with water showed inadequate thixotropy for extrusion based bioprinting and poor mechanical properties of the printed sample, and needs additional constituents to enable good printability with satisfying dimensional accuracy. We presented parameter optimisation index (POI), shear thinning model and friction factor of gelatin hydrogel by using analytical approach. Friction factor of the gelatin hydrogel during bioprinting was 0.268? 10-5. Analytical models of shear thinning and friction factor were in consistence with experimental data, and indicated that such approach can be used in optimisation of bioprinting parameters and material properties.

IMPLEMENTATION OF BIOPRINTING IN THE HEALTH AREA OF ECUADOR

Rodríguez Daniela, Fuentes Mauricio, Flor Omar, Correa Melissa, Villalobos Andrea

A feasibility study of the implementation of 3D bioprinting technology is presented, presenting aspects of interest to health institutions. These types of projects promote improvements in the quality of life of citizens, offering effective and effective solutions to different skin ailments, more specifically to burn problems. The work was carried out at the Eugenio Espejo Hospital in the city of Quito, Ecuador, for its important medical demand in the metropolitan area. This work deals with the development of the technology necessary to carry out the bioprinting service, taking into account the economic and feasibility aspects and relevant for its implementation so that this service is optimal and responds adequately to the social needs in the problems associated health.

Human Oral Motion-Powered Smart Dental Implant (SDI) for In Situ Ambulatory Photo-biomodulation Therapy

Moonchul Park, Sayemul Islam, Hye-Eun Kim, Jonathan Korostoff, Markus B. Blatz, Geelsu Hwang,* and Albert Kim*

Peri-implant disease is an inflammatory condition affecting the soft and hard tissues surrounding a dental implant. However, current preventative methods are insufficient due to the limited bioactivity on the dental implant and poor patient compliance. Recently, photo-biomodulation (PBM) therapy that can recover and regenerate peri-implant soft tissue has attracted considerable attention in dentistry. In this paper, a seamless human oral motion-powered dental implant system (called Smart Dental Implant or SDI) is presented as an ambulatory PBM therapy modality. SDI allows the in situ light delivery, which is enabled by the energy harvesting from dynamic human oral motions (chewing and brushing) via an engineered piezoelectric dental crown, an associated circuit, and micro light emitting diodes (LEDs). The SDI also offers adequate mechanical strength as the clinical standards. Using primary human gingival keratinocytes (HGKs) as a model host organism and Pseudomonas aeruginosa lipopolysaccharides (LPS) as a model inflammatory stimulus, effective SDI-mediated PBM therapy is demonstrated. A new class of dental implants could be an ambulatory PBM therapy platform for the prevention of peri-implant disease without patient dependency, warranting long-lasting dental implants.

Design, Characterization, and Additive Manufacturing of Shape Memory Composites

Sleeper, Weston

Direct Ink Writing (DIW) is an additive manufacturing method that utilizes a reservoir of fluid that is precisely extruded to construct 3-Dimensional (3D) structures from layering 2-Dimensional (2D) patterns. Fluids used in DIW printing can vary from in-situ, UV-cured resins to thermosetting epoxies that are solidified following the printing process. This thesis explores the latter fluid, specifically those epoxies which possess shape memory abilities. The shape memory function allows a solid, printed component to deform elastically when its temperature exceeds the glass transition temperature (T_g). However, shape memory epoxies traditionally lack the necessary fluid qualities for printing. By forming a composite ink and integrating a network of multiwalled carbon nanotubes (MWCNTs) or carbon black within the uncured fluid profile, the resulting multiphase ink can possess the requisite fluid rheology to facilitate 3D printing through the DIW process. This thesis examines the development and characteristics of two novel DIW inks, one supported by carbon black and the other supported by MWCNTs. In both cases, the composite ink, made printable by either its carbon black or MWCNT content, is further reinforced with VMX24 carbon short fibers. The varying short fiber content revealed various trends in conductivity and mechanical characteristics of the finished 3D printed samples. For the carbon-black based ink, the resulting prints proved themselves to be potential candidates for strain sensors, given their strong electromechanical response at low strain. For both MWCNT- and carbon black-based epoxy inks, the shape memory effect of the base epoxy was retained, resulting in novel DIW inks that are both functional and mechanically resilient.

Bioprinted Three-Dimensional Cell-Laden Hydrogels to Evaluate Adipocyte-Breast Cancer Cell Interactions

Sarah Chaji, Jenna Al-Saleh, and Cheryl T. Gomillion *

Three-dimensional (3D) bioprinting, although still in its infancy as a fabrication tool, has the potential to effectively mimic many biological environments. Cell-laden 3D printed structures have demonstrated to be an improvement from the widely used monolayer platforms, largely because of recapitulation of native tissue architecture with the 3D structures. Thus, 3D in vitro models have been increasingly investigated for improved modeling of cell and disease systems, such as for breast cancer. In the present work, multicellular cell-laden hydrogels comprised of adipocytes and breast cancer cells were bioprinted and evaluated. An ideal bioink of 3:2 5% alginate was determined to mimic the tissue stiffness observed in a physiological breast cancer tumor environment. Rheological characterization and degradation studies were performed to verify the stability of the artificial breast hydrogel environment. It was found that both the breast cancer cells and adipocytes remained viable directly after printing and throughout the 10-day culture period within the printed hydrogels. Direct printing of the cells in co-culture resulted in morphology changes and variations in cell localization within printed structures. Overall, the feasibility of efficiently fabricating multicellular cell-laden bioprinted models of the breast tumor microenvironment was established.

Formation of highly elastomeric and property-tailorable poly(glycerol sebacate)- co-poly(ethylene glycol) hydrogels through thiol-norbornene photochemistry

Yu-Ting Tsai, Chun-Wei Chang, and Yi-Cheun Yeh

Poly(glycerol sebacate) (PGS) is a synthetic biorubber that presents good biocompatibility, excellent elasticity and desirable mechanical properties for biomedical applications; however, the inherent hydrophobicity and traditional thermal curing of PGS restrict its fabrication of hydrogels for advanced bioapplications. Here, we designed a new class of hydrophilic PGS-based copolymer that allows hydrogel formation through thiol-norbornene chemistry. Poly(glycerol sebacate)-co-polyethylene glycol (PGS-co-PEG) macromers were synthesized through a stepwise polycondensation reaction, and then the norbornene functional groups were introduced to PGS-co-PEG structure to form norbornene-functionalized PGS-co-PEG (Nor_PGS-co-PEG). Nor_PGS-co-PEG macromers can be crosslinked using dithiols to prepare hydrogels in the presence of light and photoinitiator. The mechanical, swelling and degradation properties of Nor_PGS-co-PEG hydrogels can be controlled by altering the crosslinker amount. In particular, the elongation of Nor_PGS-co-PEG hydrogels can be modulated up to 950%. Nor_PGS-co-PEG can be processed using electrospinning and 3D printing techniques to generate microfibrous scaffolds and printed structures, respectively. In addition, the cytocompatibility of Nor_PGS-co-PEG was also demonstrated using in vitro cellular viability studies. These results indicate that Nor_PGS-co-PEG is a promising biomaterial with definable properties for scaffold manufacturing, presenting a great potential for biomedical applications.

3D printing of step-gradient nanocomposite hydrogels for controlled cell migration

Andisheh Motealleh, Betul Celebi-Saltik, Naihal Ermis, Sacha Nowak, Ali Khademhosseini, Nermin Seda Kehr

In this study, we report the step-gradient nanocomposite (NC) hydrogel generated easily by spatial connection of different nanocomposite hydrogel pastes varying in the concentrations of nanomaterials with the aid of a 3Dprinting technique. The prepared 3D printed gradientNChydrogel has selfadhesive properties and is used to direct the migration of fibroblast cells towards the higher concentration of biopolymer-coated silica-based nanomaterials (NMs) within the 3D network of the hydrogel. Furthermore, we demonstrate the potential application of our gradientNChydrogel in migration and subsequent enhanced osteogenic differentiation of human bone marrow derived mesenchymal stem cells (hBMMSC). The osteogenic differentiation ofhBMMSCis achieved in the absence of osteogenic differentiation medium due to the silica-based NMs. The increase in the NM content in the gradient construct promoteshBMMSCmigration and results in higher Ca2+ deposition.

Photoactivated polymeric bilayer actuators fabricated via 3D printing

Daniel Hagaman, Steven Leist, Jack Zhou, Hai-Feng Ji

4D printing is an emerging additive manufacturing technology that combines the precision of 3D printing with the versatility of smart materials. 4D printed objects can change their shape over time with the application of a stimulus (i.e., heat, light, moisture). Light driven smart materials are attractive because light is wireless, remote, and can induce a rapid shape change. Herein, we present a method for fabricating polymeric bilayer actuators via 3D printing which reversibly change their shape upon exposure to light. The photoactive layer consists of a poly(siloxane) containing pendant azobenzene groups. Two different photoactive polymers were synthesized, and the photomechanical effect displayed by the bilayers was evaluated. These bilayers exhibit rapid actuation with full cycles completed within seconds, and photo generated stresses ranging from 1.03 to 1.70 MPa.

Porous shape memory polymer nanocomposites: synthesis, characterization, and potential bio-application

Jishan Luo

Porous shape memory polymers (SMPs) are the smart materials which attract significant interests in the fields such as aerospace, civil engineering, electrical engineering, and biomedical device. Porous SMPs have low recover stress, excellent recover strain, low density, and biocompatibility, making it a great potential candidate in the treatment of Intracranial Aneurysms (ICAs). In this thesis, pristine SMP foams, CNT/SMP nanocomposite foams, and 3D printed CNT/SMP nanocomposite scaffolds are synthesized and characterized. The pristine SMP foams have a porosity of 85.7% and a shear fracture around 90% of the strain, which have significantly higher elastic deformation at the temperature above glass transition temperature. Compared with the pristine SMP foams, CNT/SMP nanocomposite foams have good conductivity, which enables it to use joule-heating method to trigger the compressed foams to recover to the original shape in much less time. Using 3D printing technique to fabricate the CNT/SMP nanocomposite scaffolds has greatly reduced the manufacturing time from 120 hours to 30 minutes and can personalize the geometry of printed complex structures. Designing tunable configuration of electroactive CNT/SMP nanocomposites enables this study advantageous for the potential medical device design for treating the ICAs.

Design of a 4D Printing System using Thermal Sensitive Smart Materials and Photoactivated Shape Changing Polymers

Steven Leist

4D printing is an emerging additive manufacturing technology that combines 3D printing with smart materials. Current 3D printing technology can print objects with a multitude of materials; however, these objects are usually static, geometrically permanent, and not suitable for multi-functional use. The 4D printed objects can change their shape over time when exposed to different external stimuli such as heat, pressure, magnetic fields, or moisture. In this research, heat and light reactive smart materials are explored as a 4D printing materials. Synthetization of a material that actuates when exposed to stimulus can be a very difficult process, and merging that same material with the ability to be 3D printed can be further difficult. A common 3D printing thermoplastic, poly(lactic) acid (PLA), is used as a shape memory material that is 3D printed using a fused deposition machine (FDM) and combined with nylon fabric for the exploration of smart textiles. The research shows that post printed PLA possesses shape memory properties depending on the thickness of the 3D printed material and the activation temperature. PLA can be thermomechanically trained into temporary shapes and return to its original shape when exposed to high temperatures. PLA can be 3D printed onto nylon fabrics for the creation of the smart textiles....