Integration Of Multiple Materials Research Articles

4D Printing in Biomedical Engineering: Advancements, Challenges, and Future Directions.

4D printing has emerged as a transformative technology in the field of biomedical engineering, offering the potential for dynamic, stimuli-responsive structures with applications in tissue engineering, drug delivery, medical devices, and diagnostics. This review paper provides a comprehensive analysis of the advancements, challenges, and future directions of 4D printing in biomedical engineering. We discuss the development of smart materials, including stimuli-responsive polymers, shape-memory materials, and bio-inks, as well as the various fabrication techniques employed, such as direct-write assembly, stereolithography, and multi-material jetting. Despite the promising advances, several challenges persist, including material limitations related to biocompatibility, mechanical properties, and degradation rates; fabrication complexities arising from the integration of multiple materials, resolution and accuracy, and scalability; and regulatory and ethical considerations surrounding safety and efficacy. As we explore the future directions for 4D printing, we emphasise the need for material innovations, fabrication advancements, and emerging applications such as personalised medicine, nanomedicine, and bioelectronic devices. Interdisciplinary research and collaboration between material science, biology, engineering, regulatory agencies, and industry are essential for overcoming challenges and realising the full potential of 4D printing in the biomedical engineering landscape.

Single-trigger dual-modal nanoplatform for in situ switch on cancer diagnosis imaging

Tumor markers in situ switch on nanoplatform is of great significance for disease early diagnosis and accurate treatment. It has significant advantages to realize simultaneous detection of multiple signals through single signal triggering. However, traditional nanoplatform often needs complex modification and integration of multiple materials. Herein, to achieve “one stone for two birds” and simplify nanoplatform structure, a dual-modal system was developed for glutathione (GSH)-triggered in situ switch on imaging of cancer. The transition metal oxide FeOOH shell was generated around CuInZnS quantum dots (CIZS QDs), and the near-infrared (NIR) fluorescence of QDs could be quenched. After being reduced to Fe2+ by GSH which normally overexpressed in cancer cells, CIZS QDs with fluorescence will generate. Therefore, the GSH-triggered fluorescence recovery could be used for in situ switch on cancer diagnostic imaging of cells and tumor-bearing mice. Furthermore, the reaction product Fe2+ enabled followed chemodynamic therapy (CDT) and magnetic resonance (MR) imaging properties to realize dual-modal diagnosis imaging. Compared with other FeOOH nanostructures, our method was more simple and efficient. Hence, this study provided a new attempt to construct versatile nanoplatform, which integrated cancer diagnosis imaging capability and may be applied in subsequent therapeutics.

Monitoring of hand function enabled by low complexity sensors printed on textile

Development of inexpensive, disposable, use-at-home, personalised health wearables can revolutionise clinical trial design and clinical care. Recent approaches have focused on electronic skins, which are complex systems of sensors and wiring produced by integration of multiple materials and layers. The requirement for high-end clean room microfabrication techniques create challenges for the development of such devices. Drawing inspiration from the ancient art of henna tattoos, where an artist draws designs directly on the hand by extruding a decorative ink, we developed a simple strategy for direct writing (3D printing) of bioelectronic sensors on textile. The sensors are realised using a very limited set of low-cost inks composed only of graphite flakes and silicone. By adapting sensor architectures in two dimensions, we produced electromyography (EMG), strain and pressure sensors. The sensors are printed directly onto stretchable textile (cotton) gloves and function as an integrated multimodal monitoring system for hand function. Gloves demonstrated functionality and stability by recording simultaneous readings of pinch strength, thumb movement (flexion) and EMG of the abductor pollicis brevis muscle over 5 days of daily recordings. Our approach is targeted towards a home based monitoring of hand function, with potential applications across a range of neurological and musculoskeletal conditions.

High-resolution multiceramic additive manufacturing based on digital light processing

High-precision ceramic components with the integration of multiple materials and structures have excellent prospects in the applications of microelectronics, biomedical engineering, aerospace, etc. However, previous additive manufacturing technologies are challenging to use or can only achieve multiceramic distribution among different layers. In this paper, we proposed a novel multiceramic additive manufacturing technology based on digital light processing. Considering the high viscosity characteristic of ceramic slurry, a multiceramic additive manufacturing system was set up with the cyclic process of “coating - exposure - cleaning - drying”. By designing a typical multimaterial pattern, the exposure sequence of different materials in a single layer was studied. In addition, we focused on the interface quality in the printed parts, including the XY and ZX(Y) interfaces. The generation mechanism of the “staggered layers effect” at the XY interface was revealed. To improve the ZX(Y) interface precision, the relationship between the designed width and the actual cure width is demonstrated, which is determined by the UV light scattering in ceramic slurry and the “edge loss effect” at the ZX(Y) interface. Based on this relationship, we presented an error compensation method for ensuring interface precision together with interface bonding. The results show that high-precision and defect-free multiceramic components can be obtained by this technology. This novel multimaterial printing system also shows great potential for photocurable slurries loaded with other particles, such as metal particles.

Modular 4D Printing Assisted by Dynamic Chemical Bonds

Modular 4D printing is achieved by assembling and welding the modules of printed self-folding structures containing dynamic chemical bonds, enabling multifunctional shape-shifting structures and devices. Modular 4D printing is achieved by assembling and welding the modules of printed self-folding structures containing dynamic chemical bonds, enabling multifunctional shape-shifting structures and devices. Nature abounds many plants with delicate geometries that can change their shapes under external stimuli. Inspired by this, many human-made shape-shifting materials, including shape memory polymers (SMPs), hydrogels, and liquid crystal elastomers (LCEs), have been developed for on-demand shape programming for multifunctionality.1Lendlein A. Trask R.S. Multifunctional materials: concepts, function-structure relationships, knowledge-based design, translational materials research.Multifunctional Materials. 2018; 1: 010201Crossref Scopus (63) Google Scholar Recently, the emerging technique of additive manufacturing (or 3D printing) has offered unprecedented opportunities for sophisticated shape control. The merging of 3D printing and shape-shifting materials gives birth to the concept of 4D printing—the as-printed structure can change its shape under external stimuli with time (the fourth dimension).2Ge Q. Qi H.J. Dunn M.L. Active materials by four-dimension printing.Appl. Phys. Lett. 2013; 103: 131901Crossref Scopus (517) Google Scholar,3Raviv D. Zhao W. McKnelly C. Papadopoulou A. Kadambi A. Shi B. Hirsch S. Dikovsky D. Zyracki M. Olguin C. et al.Active printed materials for complex self-evolving deformations.Sci. Rep. 2014; 4: 7422Crossref PubMed Scopus (376) Google Scholar The interdisciplinary research, including the development of smart/functional materials and design strategies for 3D printing, has driven 4D printing toward even faster, more complex geometry control and enhanced functionalities. In this issue of Matter, Xie and colleagues report a 4D printing method called modular 4D printing, which is done via the assembly of the 3D-printed self-folding SMPs through dynamic exchange reaction-based interface welding toward geometry-dictated functions.4Fang Z. Song H. Zhang Y. Jin B. Wu J. Zhao Q. Xie T. Modular 4D Printing via Interfacial Welding of Digital Light-Controllable Dynamic Covalent Polymer Networks.Matter. 2020; 2 (this issue): 1187-1197Scopus (54) Google Scholar Among the various 3D printing methods, the digital light processing (DLP) method, based on digital micro-mirror devices (DMDs), emerges as a fast printing approach.5Tumbleston J.R. Shirvanyants D. Ermoshkin N. Janusziewicz R. Johnson A.R. Kelly D. et al.Continuous liquid interface production of 3D objects.Science. 2015; 347: 1349-1352Crossref PubMed Scopus (1347) Google Scholar More recently, grayscale DLP (gDLP) has been developed to print shape-shifting multi-material for 4D printing. For example, a two-stage cure resin has been developed for gDLP printing of graded multi-materials with widely tunable mechanical property gradients and thermomechanical properties for 4D printing.6Kuang X. Wu J. Chen K. Zhao Z. Ding Z. Hu F. et al.Grayscale digital light processing 3D printing for highly functionally graded materials.Sci. Adv. 2019; 5: v5790Crossref Scopus (201) Google Scholar However, direct 3D printing of shape-shifting structures with on-demand shapes usually requires the sophisticated design of functional resins. It is also time-consuming for large-size object printing because of the intrinsic layer-by-layer fabrication process. An alternative approach to access 3D structures is by self-folding from 2D precursors, which is also one type of 4D printing. Much progress in the digitally controlled 2D-to-3D transformation has been reported by using different shape-shifting mechanisms, including non-uniform swelling/deswelling and local stress relaxation/generation. However, shape shifting from flat films suffers from a narrow range of accessible 3D configurations. Xie and colleagues introduced a concept of modular 4D printing by using the DLP-printed self-folding structures as modules for devices assembly/welding assisted by dynamic chemical bonds.4Fang Z. Song H. Zhang Y. Jin B. Wu J. Zhao Q. Xie T. Modular 4D Printing via Interfacial Welding of Digital Light-Controllable Dynamic Covalent Polymer Networks.Matter. 2020; 2 (this issue): 1187-1197Scopus (54) Google Scholar To achieve this goal, they first synthesized a diacrylate crosslinker with a semi-crystalline polycaprolactone (PCL) backbone and dynamic hindered urea linkages. Then they formulated various photopolymers for DLP printing. The location-specific exposure using digital light pattern and light attenuation across the thickness by photo absorbers allows precise heterogeneous curing in terms of in-plane and thickness direction, respectively. Upon removal of the residual monomers via dissolution treatment, the cured 2D films could bend and fold into predetermined 3D geometries. Because the cured material is an SMP, a smart material that can be programmed into a temporary shape and recover the initial shape in the presence of external stimuli, post-shape programming of the 4D-printed self-folding structures can also be achieved. Owing to the thermally reversible exchange reaction by the dynamic hindered urea linkage, the printed materials possess the attributes of robust interface weldability and reshaping capability at elevated temperatures. Xie and colleagues could, therefore, use the printed structures as modules for complex shape manipulation by a two-step assembly and welding approach (Figure 1). For example, four pieces of printed SMP films were first transformed into a Miura-ori module by monomer removal and then were assembled and welded into a folding-based lattice cylinder. Moreover, the obtained cylindercould be further reprogrammed into different meta-structures and permanent shape via the shape memory effect and dynamic exchange reaction, respectively. It was demonstrated that assembled structures could be programmed into different permanent configurations for shape-shifting devices with tunable Poisson’s ratio. Besides, multimaterial modular assembly can be achieved by using modules with distinct mechanical and thermomechanical properties. One of the advantages of the current approach is the versatile monomer choice to enable tailorable material properties. Xie and colleagues were able to prepare an elastomer and two semi-crystalline plastics with different glassy transition temperatures by altering monomer ratios and types. As an example, a Kresling-patterned model was then assembled into a three-layer multi-material cylinder using different materials in each layer. This modular cylinder shows functional properties, including rotation and sequential deformation upon tension and compression. The work of Xie and colleagues provide a versatile approach to access functional shape-shifting structures and devices with on-demand complex geometry. Notably, the vibrant interdisciplinary research of developing multi-stimuli-responsive materials, including various shape-programmable materials and the emerging covalent adaptive network polymers containing dynamic chemical bonds,7Podgórski M. Fairbanks B.D. Kirkpatrick B.E. McBride M. Martinez A. Dobson A. Bongiardina N.J. Bowman C.N. Toward Stimuli-Responsive Dynamic Thermosets through Continuous Development and Improvements in Covalent Adaptable Networks (CANs).Adv. Mater. 2020; : e1906876Crossref Scopus (169) Google Scholar will play an increasingly critical role in 4D printing. Toward dedicated geometries and multifunctional properties of 4D printing, a parallel advance in stimuli-responsive functional materials, 3D printing techniques, and design across multiple length scales are under development.8Kuang X. Roach D.J. Wu J. Hamel C.M. Ding Z. Wang T. Dunn M.L. Qi H.J. Advances in 4D Printing: Materials and Applications.Adv. Funct. Mater. 2018; 0: 1805290Google Scholar This invocation is shifting 4D printing from simple shape changing to the next generation of integrated structure-functionality evolution with enhanced sustainability. In addition to welding, the merit of dynamic chemical bonds also allows other properties, including self-healing, recycling, and reprocessing, for 4D printing.9Zhang B. Kowsari K. Serjouei A. Dunn M.L. Ge Q. Reprocessable thermosets for sustainable three-dimensional printing.Nat. Commun. 2018; 9: 1831Crossref PubMed Scopus (200) Google Scholar Moreover, we believe multifunctional properties, including mechanical, optical, electrical, and magnetic properties evaluation, can also be accommodated and integrated into 4D printing by using the modular concept. This rapid progress is laying the foundation for this exciting field, which can find broad applications in aerospace, electronics, biomedical devices, and more. Modular 4D Printing via Interfacial Welding of Digital Light-Controllable Dynamic Covalent Polymer NetworksFang et al.MatterMarch 9, 2020In BriefThe concept of modular 4D printing is put forward with the introduction of dynamic covalent bonds. The activation of dynamic bonds at a contact interface permits the assembly of different modules with tailorable materials properties. Intriguingly, the intrinsic dynamic nature of modules allows further manipulation of the permanent shapes. With the integration of multiple materials and geometric structures, we demonstrate the fabrication of shape-shifting devices with geometry-dictated functions. Full-Text PDF Open Archive

Modular 4D Printing via Interfacial Welding of Digital Light-Controllable Dynamic Covalent Polymer Networks

Summary Advanced multifunctional devices increasingly rely on challenging complex shapes for their functions. 3D printing offers a solution but is often limited by the fabrication speed and/or material diversity. 4D printing based on digitally controlled 2D-to-3D transformation is advantageous in speed, but the accessible shapes are limited and integration of multiple materials is difficult. We report herein a concept that significantly extends the technological scope by combining 4D printing with modular assembly. Specifically, 4D photo-printed structures based on dynamically crosslinked polymers can be assembled in a modular fashion by interfacial bond exchange. Complex 3D objects with tailorable multiple materials can consequently be produced. This allows the fabrication of sophisticated shape-memory devices including a 3D Miura-patterned structure with zero Poisson's ratio and a Kresling-patterned cylindrical structure with superior mechanical stability. Our approach extends the possibilities for the future development of multifunctional devices with seamless integration of material, structure, and function.

Stereolithographic 3D Printing for Deterministic Control over Integration in Dual-Material Composites.

This work introduces a rapid and facile approach to predictably control integration between two materials with divergent properties. Programmed integration between photopolymerizable soft and stiff hydrogels was investigated for their promise in applications such as tissue engineering where heterogeneous properties are often desired. Spatial control afforded by grayscale 3D printing was leveraged to define regions at the interface that permit diffusive transport of a second material in-filled into the 3D printed part. The printing parameters (i.e., effective exposure dose) for the resin were correlated directly to mesh size to achieve controlled diffusion. Applying this information to grayscale exposures led to a range of distances over which integration was achieved with high fidelity. A prescribed finite distance of integration between soft and stiff hydrogels led to a 33% increase in strain to failure under tensile testing and eliminated failure at the interface. The feasibility of this approach was demonstrated in a layer-by-layer 3D printed part fabricated by stereolithography, which was subsequently infilled with a soft hydrogel containing osteoblastic cells. In summary, this approach holds promise for applications where integration of multiple materials and living cells is needed by allowing precise control over integration and reducing mechanical failure at contrasting material interfaces.

Experimental and analytical investigation of mechanical behavior of laser-sintered diamond-lattice structures

Typically, additive manufacturing (AM) processes are limited to a single material per build while many products benefit from the integration of multiple materials with varied properties. To achieve the benefits of multiple materials, the geometric freedom of AM could be used to build internal structures that emulate a range of different material properties such as stiffness, Poisson’s ratio, and elastic limit using only a single build material. This paper examines a wide range of properties that can be achieved using diamond lattice structures manufactured from Nylon 12 with a commercial laser sintering (LS) process. Stiffness and energy absorption were measured for all lattices and the stiffness response was compared to finite element analysis (FEA). Simulation shows agreement with experimental results over a stiffness range of four orders of magnitude once a correction factor is applied. Experimental results also show a wide range of energy absorption for diamond lattice structures and a significant increase in the effective elastic limit of the build material, which compensates for the low ductility of many AM materials. The elastic limit decreases with an increasing t/L ratio meanwhile the degradation under cyclic loading is relatively independent of the t/L ratio. Extrapolating this data into lattice structures made from metal, these same structures could mimic a wide range of “fully” dense and porous materials with just the use of a single material. Since the diamond lattice is a cellular structure, the voids can also be filled with other materials or structures to add secondary control of embedded functions such as energy storage and sensing.

Multifunctional AIEgens for Future Theranostics.

The combination of diagnosis and therapeutics into one theranostics system has attracted great interest in life science and biomedical fields. The current theranostic platform largely relies on the integration of multiple materials with different functionalities. The all-in-one approach has the risk of high complicity with reduced reproducibility. Smart design of simple molecules born with multifunctions should represent one of the future directions in theranostics. Fluorogens with aggregation-induced emission (AIEgens) are one type of such smart materials, which have attracted increasing attentions in recent years. In this concept, the key frontier developments of simple AIEgens with multifunctions for imaging and therapy are presented, which include fluorescence-photoacoustic imaging, fluorescence-magnetic resonance imaging, fluorescence image-guided photodynamic therapy, fluorescence image-guided chemotherapy and photoacoustic image-guided photothermal therapy. The smart molecular design to endow each AIEgen with strong capability to simultaneously offer two or more theranostic functions should attract more scientists into this exciting research direction.

High-performance ternary blend polymer solar cells involving both energy transfer and hole relay processes.

The integration of multiple materials with complementary absorptions into a single junction device is regarded as an efficient way to enhance the power conversion efficiency (PCE) of organic solar cells (OSCs). However, because of increased complexity with one more component, only limited high-performance ternary systems have been demonstrated previously. Here we report an efficient ternary blend OSC with a PCE of 9.2%. We show that the third component can reduce surface trap densities in the ternary blend. Detailed studies unravel that the improved performance results from synergistic effects of enlarged open circuit voltage, suppressed trap-assisted recombination, enhanced light absorption, increased hole extraction, efficient energy transfer and better morphology. The working mechanism and high device performance demonstrate new insights and design guidelines for high-performance ternary blend solar cells and suggest that ternary structure is a promising platform to boost the efficiency of OSCs.

Broken Band Alignment in EuS-CdS Nanoheterostructures

Integration of multiple materials in a controllably programmed manner on the nanoscale has led to the evolution of the next generation of nanoparticles. We have explored the formation of bifunctional europium sulfide − cadmium chalcogenide composite nanostructures, as both of the semiconductor materials exhibit intriguing physical characteristics, suggesting that architectural tunability of these hybrid structures could have interesting effects on their collective properties. A two step synthetic procedure has been devised, where CdSe or CdS nanorods were used as a platform for the growth of the secondary material domains. An eight-coordinate lanthanide based single-source precursor, Eu(Ddtc)3(Bipy), was implemented as the material source for the selective growth of spherical EuS nanocrystals on the tips of cadmium chalcogenide nanorods. The composition and structure of these hybrid particles have been analyzed by high-resolution TEM. The nanoheterostrucutre has a type III, or broken band alignment, which...

Materials for Devices in Life Science Applications

The unprecedented technology advancements in miniaturizing integrated circuits, and the resulting plethora of sophisticated, low cost electronic devices demonstrate the impact that micro/nano scale engineering can have when applied only to the area of electrical and computer engineering. Current research efforts in micro/nano fabrication technology for implementing integrated devices hope to yield similar revolutions in life science fields. The integrated life chip technology requires the integration of multiple materials, phenomena, technologies, and functions at micro/nano scales. By cross linking the individual engineering fields through micro/nano technology, various miniaturized life chips will have future impacts in the application markets such as medicine and healthcare.

Materials for Devices Applications in Life Sciences

The unprecedented technology advancements in miniaturizing integrated circuits, and the resulting plethora of sophisticated, low cost electronic devices demonstrate the impact that micro/nano scale engineering can have when applied only to the area of electrical and computer engineering. Current research efforts in micro/nano fabrication technology for implementing integrated devices hope to yield similar revolutions in life science fields. The integrated life chip technology requires the integration of multiple materials, phenomena, technologies, and functions at micro/nano scales. By cross linking the individual engineering fields through micro/nano technology, various miniaturized life chips have been developed at UCI that will have future impacts in the application markets such as medicine and healthcare.