Single Polymer Composites Research Articles

Improving dynamic energy absorption performance and stability loss prediction of an all-PET sandwich structure through artificial neural networks

Abstract One key characteristic that is frequently studied in composite sandwich structure mechanics is low-velocity impact performance. Single polymer composites present higher ductility when compared to traditional glass fibre and carbon fibre reinforced plastic composites (GFRP, CFRP), which makes them strong candidates for impact energy absorption. These lightweight structures are also fully recyclable due to their all-PET constituents, an important aspect when considering possible applications. In this paper an existing second order composite SrPET and PET foam sandwich structure (self-reinforced poly-ethylene terephthalate matrix and fibre) is numerically investigated for optimal structural design configuration under out-ofplane, low velocity, dynamic loading. The study explores the parametric geometry interdependencies of the structure’s configuration with respect to its energy absorption potential. The results are then compared to the quasi-static loading performance behaviour studied by M.N. Velea et all [1]. This work provides a deeper understanding of how geometry configurations can influence energy absorption capabilities highlighting structural strengths and weaknesses while exploring non-equilateral triangle configurations. The Design Space Exploration (DSE) is carried out by using an optimization algorithm for a dynamic out of plane 3D impact simulation based on the finite element (FE) method software. The synergy between DSE and FE generates a guided simulation loop that can successfully be used to train a neural network to predict the dynamic behaviour of different geometric configurations from the exploration space. Based on the data samples obtained, an artificial neural network (ANN) is built to predict the energy absorption capacity for a given set of structural design parameters, useful in experimental validation test cases.

Design of interconnected graphene loaded thermoplastic elastomeric blend composite films for minimizing electromagnetic radiation and efficient heat management

AbstractIn this work, electrically conductive thermoplastic elastomeric blend composite films based on polystyrene (PS)/ethylene‐co‐methyl acrylate (EMA) filled with functionalized graphene were developed via the solution mixing technique. Morphological analysis revealed that selective localization of amine‐functionalized reduced graphene oxide (G‐ODA) sheets in the EMA phase of co‐continuous binary blend formed a well‐connected dense conductive pathway by graphene sheets ultimately facilitating the double percolation phenomenon. The electrical percolation threshold was achieved at ~2 wt% of G‐ODA loading which was much lower than that for both single polymer composites. An electrical conductivity of 0.9 S/cm was obtained for blend composite film with 10 wt% of graphene concentration whereas for the same filler loading, PS and EMA composites exhibited electrical conductivity of 1.9 × 10−1 and 2.3 × 10−1 S/cm, respectively. The obtained thermal conductivity of the blend composite with 10 wt% of G‐ODA loading was 0.95 W/m K with 400% enhancement compared to the neat blend system. The same composite exhibited increased real and imaginary permittivity of 92 and 83, respectively. The electrical percolation threshold is well‐correlated with the percolation concentration found from storage modulus and thermal conductivity data. The fabricated PS/EMA blend composite film exhibited absorption‐dominant electromagnetic interference SE of −25 and − 35 dB in X‐band frequency (8.2–12.4 GHz) for 10 wt% of graphene loading with a sample thickness of 0.5 and 1 mm, respectively.

SUPERHYDROPHOBIC ALL-CELLULOSE COMPOSITE VIA HEXADECYLTRIMETHOXYSILANE AND HDTMS/SILICA

All-cellulose composite (ACC) is a novel single polymer composite (SPC) that consists of cellulose for both reinforcing fiber and matrix phases. ACC has good mechanical, thermal, and optical properties due to compatibility of reinforcing fiber and matrix phases. However, abundant hydroxyl (OH) groups in the cellulose structures resulted in higher hydrophilicity of ACC, thus limiting the potential use in outdoor applications. In this study, ACC was fabricated using solvent infusion processing (SIP) from rayon textile with sodium hydroxide (NaOH)/urea solution to partially dissolve the cellulose fibers, followed by regeneration and drying processes. Subsequently, ACC was treated using two different coating solutions: (i) hexadecyltrimethoxysilane (HDTMS) and (ii) HDTMS/SiO2 (silica). As a result, an efficient water repellency for HDTMS/SiO2-treated ACC was observed, showing a water contact angle of 159.3∘, as compared to HDTMS-treated ACC with a water contact angle of 144.1∘. However, a slightly higher water absorption of 52% was observed for HDTMS/SiO2-treated ACC, as compared to only 44% for HDTMS-treated ACC. Both treated ACCs showed smooth and homogeneous structures upon completion of the treatment.

Study on the influence of in-mold sequential injection molding process parameters on mechanical properties of self-reinforced single composites

Abstract In this paper, the self-reinforced single polymer composites (SR-SPCs) with different mechanical properties were obtained by compound injection molding technology, and the micro-morphology of these samples was observed. Then, using structured statistical methods, analysis of variance, and response surface methodology, study the effects of various molding variables on material morphology and properties and determine the most important molding variables and their interactions. Finally, the associated experimental data are fitted by the least squares minimization program, and the relevant dimensionless equations are obtained. The purpose is to objectively analyze the influence mechanism of molding parameters on SR-SPCs and establish a mechanism model. It was found that temperature change was the most important factor affecting the morphology and mechanical properties. The degree of molecular orientation is the most important factor to determine the tensile strength and elastic modulus of the sample. The change of crystallinity is the most important factor related to the elongation at break. By establishment relevant dimensionless equations, the influence of molding parameters on the mechanical properties of SR-SPCs, such as tensile strength and elastic modulus, was preliminarily studied.

Single Component Polymers, Polymer Blends, and Polymer Composites for Interventional Endovascular Embolization of Intracranial Aneurysms.

Intracranial aneurysm is the abnormal focal dilation in brain arteries. When untreated, it can enlarge to rupture points and account for subarachnoid hemorrhage cases. Intracranial aneurysms can be treated by blocking the flow of blood to the aneurysm sac with clipping of the aneurysm neck or endovascular embolization with embolics to promote the formation of the thrombus. Coils or an embolic device are inserted endovascularly into the aneurysm via a micro-catheter to fill the aneurysm. Many embolization materials have been developed. An embolization coil made of soft and thin platinum wire called the "Guglielmi detachable coil" (GDC) enables safer treatment for brain aneurysms. However, patients may experience aneurysm recurrence because of incomplete coil filling or compaction over time. Unsatisfactory recanalization rates and incomplete occlusion are the drawbacks of endovascular embolization. So, the fabrication of new medical devices with less invasive surgical techniques is mandatory to enhance the long-term therapeutic performance of existing endovascular procedures. For this aim, the current article reviews polymeric materials including blends and composites employed for embolization of intracranial aneurysms. Polymeric materials used in embolic agents, their advantages and challenges, results of the strategies used to overcome treatment, and results of clinical experiences are summarized and discussed.

Development of nanoparticle-filled polypropylene-based single polymer composite foams

In this study, our focus was on developing and investigating nanoparticle-filled polypropylene-based single polymer composite foams. These composites had porous and nanotube-reinforced matrices, with plain woven polypropylene (PP) fabric as reinforcement. Our main objective was to enhance the energy absorption and stiffness of the single polymer composites (SPCs) by modifying their matrices. We produced SPCs with two different matrices: one of amorphous poly-alpha-olefin (APAO) and one of thermoplastic elastomer (TPE) blended with APAO. We observed that the APAO matrix exhibited better impregnation of the fabric due to its low viscosity, while the composites with the TPE matrix showed significantly better tensile properties. The foaming process applied to the matrices resulted in a substantial increase in energy absorption for the SPCs, while preserving their tensile properties relative to their density. Scanning electron microscope images confirmed that foaming of the APAO matrix was notably more effective, primarily due to its low viscosity. Furthermore, we successfully enhanced the stiffness and tensile properties of the SPCs by nano-reinforcing the matrices with multi-wall carbon nanotubes (MWCNTs). Due to the size of the nanotubes, this reinforcement did not compromise the impact properties of the SPCs. Scanning electron microscope images also demonstrated improved dispersion of the nanotubes within the APAO matrices.

Study of frequency dependence properties of CCTO-BT/polymer composites

In the current study, the calcium copper titanate (CCTO)/polymer, barium titanate (BT)/polymer, and CCTO-BT/polymer composites with variable volume fractions of CCTO and BT are fabricated using hand lay-up and compression molding processes. The composites are characterized for the frequency dependence on dielectric properties, conductivity, impedance spectroscopy, and electrical modulus. X-ray diffraction (XRD) patterns of CCTO-BT/polymer composite samples confirmed the presence of both CCTO and BT ceramic samples separately. The dielectric properties of hybrid CCTO-BT/polymer composites with 10 vol% CCTO 10 vol% BT, 12 vol% CCTO 8 vol% BT, and 8 vol% CCTO 12 vol% BT was found relatively better than those of the single ceramic filler reinforced polymer composites. AC conductivity analysis shows a significant improvement in the results of hybrid filler-filled CCTO-BT/polymer composites in comparison with single filler-filled polymer composites. Thus, impedance analysis confirms higher insulating properties for 8 vol% CCTO 12 vol% BT and 12 vol% CCTO 8 vol% BT hybrid CCTO-BT/polymer composites with respect to the single and other hybrid ceramic polymer composites. The analysis suggests the hybrid CCTO-BT/polymer composites to be adopted as a possible dielectric material for energy storage devices and other electronic applications.

Development and Characterization of Supercooled Polyethylene Naphthalate

The utilization of undercooled or supercooled polymers presents a promising approach for the creation of single-polymer composites (SPCs), applicable not only to compaction processing but also to extrusion, injection molding, and 3D printing techniques. This study focuses on the development and characterization of supercooled polyethylene naphthalate (PEN) through differential scanning calorimetry (DSC) and rheological measurements. By employing predetermined conditions, a supercooling degree of 50 ˚C for PEN was achieved. The impact of maximum heating temperature, cooling rate, and shear rate on the supercooling degree was examined, revealing that higher supercooling degrees of PEN can be attained by increasing these factors. Additionally, the flow behavior of supercooled polymer melts at various temperatures was analyzed. The supercooling state of PEN exhibited remarkable stability for a minimum duration of half an hour at temperatures exceeding 250 ˚C.

<i>In Sit</i>u Surface Treatment on All-Cellulose Composites (ACCs) Using Alkyl Ketene Dimer (AKD) via Solvent Infusion Processing (SIP)

Water repellence all-cellulose composite (ACC) was developed using alkyl ketene dimer (AKD). ACC is a novel single polymer composite (SPC), consisting of cellulose for both reinforcing and matrix phases. However, a technical challenge was observed for ACCs due to hydrophilic characteristic of cellulose, contributing to a higher water absorption, instability and deterioration of its physical and mechanical properties. In this study, ACC was prepared using solvent infusion process (SIP) and AKD treatment was performed in-situ during SIP prior to the drying process. As the results, ACC changed from hydrophilic to hydrophobic behaviour upon completion of AKD treatment. Fourier Transform Infrared (FTIR) spectroscopy examination confirmed the presence of AKD moieties on the ACC surface after the treatment. In addition, microstructure images indicated the presence of continuous and cloud-like coating appearance on the treated ACC unlike the untreated ACC. The increasing water contact angle (WCA) was also observed with the increasing AKD concentration, showing a maximum WCA of 160˚. The water content (WC) dropped up to 43% for treated ACC, indicating a decreasing trend of water content with the increasing AKD concentration, as compared to the untreated ACC. It is envisaged that the successful treatment of AKD treated ACC may avoid the potential damage of ACC in outdoor applications.

The effect of the heat used during composite processing on the mechanical properties of fibrous reinforcement of polypropylene-based single-polymer composites

In this study, we investigated the effect of heat treatment on the mechanical properties of high-tenacity polypropylene (PP) fibers. An application field of versatile polypropylene as fibers and tapes is the reinforcement of single-polymer composites. During consolidation at an elevated temperature, typically near the melt temperature of PP, the heat causes molecular relaxation of the strongly oriented molecular chains, which impairs mechanical properties. We investigated the shrinkage of PP single fibers isothermally and anisothermally, and heat-treated PP single fibers and multifilament rovings in a temperature range of 120–190 °C for 5–20 min in a constrained and an unconstrained arrangement. The heat-treated fibers and rovings were then tensile tested and their residual mechanical properties were determined and compared to the as-received rovings. We analyzed the tensile characteristics mathematically, applying the statistical fiber-bundle-cell modeling method, and described the measured and averaged stress–strain curves with fitted E-bundles having fibers with nonlinear tensile characteristics. The tensile modulus of the constrained fibers treated for 5 min decreased less in the whole heat treatment temperature range but considerably decreased further with increasing treatment time. Conversely, their tensile strength decreased only slightly, and treatment time had a minor effect up to 180–190 °C (above the melting temperature of the fiber). The results proved that constraining is a useful tool for preserving the reinforcing ability of high-tenacity polymer fibers.

A review of the fabrication methods and mechanical behavior of continuous thermoplastic polymer fiber–thermoplastic polymer matrix composites

AbstractThermoplastic polymer fiber–thermoplastic polymer matrix composites (PPCs or PRFPs), often recognized as self‐reinforced or single polymer composites, are potential candidates for future advanced polymer composites because of various advantages(e.g., recyclability, formability, low‐cost, ultra‐lightweight, environmental friendliness, etc.). The manufacturability and mechanical behavior of these composites compared to conventional carbon‐/glass‐/aramid‐fiber‐reinforced polymers is of great interest to the composites community, but there are a limited number of studies in this area. To this end, this paper reviewed fabrication methods with different processing parameters and mechanical behavior of uni‐/multi‐directional thermoplastic PPCs featuring continuous thermoplastic polymer fibers from limited data in the literature. It was shown that most specific behaviors (normalized by density) of these materials in various loading conditions (e.g., quasi‐static tension/shear/flexure, tension‐tension fatigue, and out‐of‐plane impacting, etc.) are comparable to or better than glass‐/aramid‐fiber‐reinforced polymers. Particularly, the specific ductility in the foregoing conditions outperforms all the carbon‐/glass‐/aramid‐fiber‐reinforced polymers. Thermoplastic PPCs with remarkable performance can be achieved through several uncomplicated methods (e.g., film stacking, hot compaction, powder and solution impregnations, matrix infusion and injection molding, additive manufacturing, etc.), which have some similarities to the methods used for carbon‐/glass‐/aramid‐fiber‐reinforced polymers. Moreover, several opportunities and challenging problems of thermoplastic PPCs were summarized at the end of this review paper. Efficient solutions may require countless efforts in the composites community to further strengthen the performance and understanding of thermoplastic PPCs for wide applications in various engineering fields in the future.

Investigation on the Mechanical Properties of Flax/False Banana Hybrid Fiber-Reinforced Polymer Composite

The intent of this research is to develop new material from flax and false banana fiber hybrid reinforced polymer composite using polyester resin as a matrix to replace synthetic fiber-reinforced polymer composites for automotive interior bodies. The composite samples were fabricated based on the weight percentage of fibers/matrix and the orientation of the fibers that were combined with Taguchi’s experimental design using the hand layup fabrication process. And also, single flax and single false banana fiber-reinforced polymer composite was fabricated with the same composition and orientation alone. The composite was tested for tensile and flexural strength properties, and it had been discussed and specimens were prepared according to ASTM standards. As a result, false banana showed better flexural strength than false banana fiber-reinforced composite for tensile strength, whereas the hybrid composites of 25% of flax, 15% of false banana, and unidirectional orientation have shown the maximum tensile and flexural strength with a value of 113.4 MPa and 167.88 MPa, respectively.

Effective thermo-viscoelastic behavior of short fiber reinforced thermo-rheologically simple polymers: An application to high temperature fiber reinforced additive manufacturing

This paper presents a procedure for the estimation of the effective thermo-viscoelastic behavior in fiber-reinforced polymer filaments used in high temperature fiber-reinforced additive manufacturing (HT-FRAM). The filament is an amorphous polymer matrix (PEI) reinforced with elastic short glass fibers treated as a single polymer composite (SPC) holding the assumption of thermo-rheologically simple matrix. Effective thermo-viscoelastic behavior is obtained by implementing mean-field homogenization schemes through the extension of the correspondence principle to continuous variations of temperature by using the time–temperature superposition principle and the internal time technique. The state of the fibers in the composite is described through the use of probability distribution functions. Explicit forms of the effective properties are obtained from an identification step, ensuring the same mathematical structure as the matrix behavior. The benchmark simulations are predictions of residual stress resulting from the cooling of the representative elementary volumes (REVs) characterizing the composite filament. The computation of the averaged stress in the benchmarking examples is achieved by solving numerically the stress–strain problem via the internal variables’ framework. Reference solutions are obtained from Fast Fourier Transform based full-field homogenization simulations. A comparative analysis is performed, showing the reliability of the proposed homogenization procedure to predict residual stress against extensive computations of the macroscopic behavior of a given microstructure.

Development of single‐polypropylene composites interleaved with MWCNT‐doped melt‐blown fine fiber mats

AbstractIn this article, we demonstrate fabricating polypropylene (PP)/multiwalled carbon nanotube (MWCNT) nanocomposite fiber veils and use them as interleaves in single‐polymer composites (SPCs) to enhance their thermal and mechanical properties. With this regard, we produced a hierarchical composite structure made of a film, a woven fabric and a fine fiber mat made of the same polymer. The nanocomposite fiber mats were generated by melt‐blowing. Results implied that incorporating MWCNT increased the viscosity of the melt blowing grade PP resin. Increasing MWCNT content increased the average fiber diameter and pore size by 2.1‐fold and 2.5‐fold, respectively. Incorporating MWCNT enhanced the melt‐blown (MB) fiber mat's specific strength by 78% and improved the thermal stability. We generated multiscale SPCs by film‐stacking, for which we applied a PP film as a matrix, a PP‐woven fabric as the primary reinforcement, and the MB fiber mats as interleaves. The SPC's tensile modulus was improved by 37% by the interleaving. Our findings implied that the MWCNT‐doped PP fiber mat interleaving provides a robust interfacial adhesion and higher damage tolerance under tensile load. Master curves were constructed from dynamic mechanical analysis frequency sweep tests based on the time–temperature superposition principle. The storage modulus increased by 33%, while the tanδ decreased around 10% with PP/MWCNT fiber mat interleaving. The developed multiscale SPC with MWCNT fiber mat interleaving veils may be easily integrated into engineering composite applications due to its cost‐efficiency, fair recycling, straightforward processing, enhanced stiffness, and interfacial adhesion.

Melt-blown fiber mat interleaving enhances the performance of single-polypropylene composites

In this study, we demonstrate that integrating melt-blown fiber mat interleaves into single-polypropylene composites enhances several mechanical properties and influences the morphology positively. Polypropylene veils were generated by melt blowing. We then created single-polypropylene composites by film-stacking in which we applied a film as a matrix, a woven fabric as primary reinforcement, and the melt-blown fiber mats as interleaves. The tensile modulus was improved in the range of 20%–46%, and the interlaminar shear strength and the perforation energy at impact were increased by 17% and 14%, respectively, due to interleaving. Master curves were constructed from dynamic mechanical analysis frequency sweep tests based on the time–temperature superposition principle. The storage modulus significantly increased while the tanδ decreased. The interleaving considerably reduced the delamination by creating a net-like structure leading to superior interfacial adhesion. The interleaving demonstrated in this study can promote single-polymer composites’ utilization in various engineering applications where high toughness and impact resistance are required.

Effects of Injection Molding Parameters on Properties of Insert-Injection Molded Polypropylene Single-Polymer Composites

The reinforcement and matrix of a polymer material can be composited into a single polymer composite (SPC), which is light weight, high strength, and has easy recyclability. The insert injection molding process can be used to realize the multiple production of SPC products with a short cycle time and wide processing temperature window. However, injection molding is a very complicated process; the influence of several important parameters should be determined to help in the future tailoring of SPCs to specific applications. The effects of varying barrel temperature, injection pressure, injection speed, and holding time on the properties of the insert-injection molded polypropylene (PP) SPC parts were investigated. It was found that the sample weight and tensile properties of the PP SPCs varied in different rules with the variations of these four parameters. The barrel temperature has a significant effect, followed by the holding time and injection pressure. Suitable parameter values should be determined for enhanced mechanical properties. Based on the tensile strength, a barrel temperature of 260 °C, an injection pressure of 127.6 MPa, an injection speed of 0.18 m/s, and a holding time of 60 s were determined as the optimum processing conditions. The best tensile strength and peel strength were up to 120 MPa and 19.44 N/cm, respectively.

Manufacturing and testing of single polymer polyamide 66 composites

In the last decades, a new class of polymer composites has attracted the attention of research activities and has driven the development of new materials with interesting potential in many industrial fields. The idea of these new materials, better known as single polymer composites (SPCs) or self-reinforced polymeric composites (SRPCs), arises from the observation that the same polymer shows different melting points depending on the form in which it is available (eg powder, fibre or film). In other words, it is possible to obtain innovative composites by combining matrices and reinforcements made of the same polymer ensuring, among other things, products with perfect interfacial adhesion and recyclability.In this work, self reinforced laminated samples based on a technical polyamide 66 (PA66) fabric were manufactured by hot-compaction technique and compared with compression molded plaques based on commercial polyamide 66, neat and filled with 30 wt% of glass fibres, taken as the reference materials. Preliminary calorimetric analyses made possible to establish the most appropriate process conditions. With the awareness of a narrow window of processability of the raw materials, plates from the PA66 fabric were produced by considering two cooling protocols. The calorimetric analysis and the mechanical tests carried out in quasi-static, dynamic and impulsive modalities have highlighted distinctions between the 2 types of self-reinforced composites essentially due to the different structural features promoted by the applied process conditions. The results were systematically validated with morphological investigations of the fractured surfaces coming from the impact tests. Analysis of micrographs, among other things, made it possible to identify the main damage mechanisms characterizing the failure of the new self reinforced materials.

Multi-Walled Carbon Nanotubes and Carbon Black Incorporated Heterogeneous Layered Polymer Composites with Enhanced Electrical Features

The present work is centered on the study of electrical properties of three different types of composites i.e. single layer carbon black (CB) and multi-walled carbon nanotubes (MWCNTs) based PMMA composites, CB/PMMA and MWCNTs/PMMA, and bilayer polymer composites CB/PMMA-MWCNTs/PMMA, prepared by solution mixing method using chloroform as dispersion medium. It is expected that two layers in bilayer polymer composites would show increased interfacial interactions resulting in improved electrical character especially dielectric properties. Prepared composites have been characterized by UV-Vis and FTIR spectroscopy for successful synthesis. Electrical properties, conductivity, dielectric constant and tangent loss of all composites were measured at frequency range of 40Hz to 1MHz by using LCR meter. Percolation threshold value was obtained by using data of electrical conductivity as a function of volume fraction of fillers. The obtained value of percolation threshold was much lower for bilayer polymer composites i.e. 0.01 vol% as compared to the single layer polymer composites. Observed data of dielectric constant encourages the synthesis of composites with this kind of structure.

Interface thermal resistance and thermal conductivity of polymer composites at different types, shapes, and sizes of fillers: A review

AbstractThe growing demand toward miniaturization and power device packaging required new die‐attach materials with high thermal conductivity (TC). Multitudinous attention is being paid to enhance the TC of thermally conductive polymer composites as it is easy to fabricate and environmentally friendly and has low‐cost processability. However, after years of extensive research, it can be concluded that reinforcing different morphologies of fillers (types, sizes, and shapes) into polymer composite creates interfacial thermal resistance (ITR) that greatly constrains the TC value. Thus, this article presents an exhaustive review in minimizing the ITR effect by optimizing the types, sizes, and shapes of the fillers used. This literature also seeks to review the use of different morphologies of fillers in single and hybrid polymer composites. It was found that hybridizing two different fillers shows remarkable TC enhancement due to its synergistic effect and formation of three‐dimensional network/conduction path. The size and shape of fillers used play a vital role in improving the TC of the polymer composite compared with the type of filler used due to more contact area created, which significantly reduces the ITR. The results presented here may facilitate improvement in the development of future work for new die attach of the thermally conductive polymer composite.

Multi-material multi-photon 3D laser micro- and nanoprinting

Three-dimensional (3D) laser micro- and nanoprinting based upon multi-photon absorption has made its way from early scientific discovery to industrial manufacturing processes, e.g., for advanced microoptical components. However, so far, most realized 3D architectures are composed of only a single polymeric material. Here, we review 3D printing of multi-materials on the nano- and microscale. We start with material properties that have been realized, using multi-photon photoresists. Printed materials include bulk polymers, conductive polymers, metals, nanoporous polymers, silica glass, chalcogenide glasses, inorganic single crystals, natural polymers, stimuli-responsive materials, and polymer composites. Next, we review manual and automated processes achieving dissimilar material properties in a single 3D structure by sequentially photo-exposing multiple photoresists as 3D analogs of 2D multicolor printing. Instructive examples from biology, optics, mechanics, and electronics are discussed. An emerging approach – without counterpart in 2D graphical printing – prints 3D structures combining dissimilar material properties in one 3D structure by using only a single photoresist. A controlled stimulus applied during the 3D printing process defines and determines material properties on the voxel level. Change of laser power and/or wavelength, or application of quasi-static electric fields allow for the seamless manipulation of desired materials properties.