Direct Printing Method Research Articles

High‐Precision Drop‐on‐Demand Printing of Charged Droplets on Nonplanar Surfaces with Machine Learning

Direct printing methods are widely recognized as efficient techniques for manufacturing printed electronics. However, several challenges arise when printing on nonplanar surfaces, especially using the drop‐on‐demand (DoD) approach. These challenges include ink flow due to gravity, precise ink deposition, and reproducibility. This study introduces an innovative method for highly accurate DoD material jetting on nonplanar 3D conductive surfaces, enabling precise production and trajectory control of charged droplets. The technique involves using a grounded 3D substrate as the target, where in‐flight droplets are subjected to an external electric field generated by gate electrode installed on a piezo activated droplet dispenser. Individual droplets are generated and controlled using a complex trigger system that relays variable‐voltage signals to the gate electrode. Moreover, a predictive model for droplet deposition, exhibiting an accuracy of 87%, is developed utilizing supervised machine learning (ML). This approach significantly improves the accuracy and repeatability of droplet deposition. Overall, this study presents an effective method of integrating piezoelectric and electrohydrodynamic printing technologies, complemented by ML. It addresses the challenges associated with printing on nonplanar surfaces using the DoD material jetting technique and shows considerable promise for enhancing efficiency, accuracy, and repeatability in the manufacturing of printed electronics.

Mechanical, thermal, and microstructure analysis of 3D printed polyolefin elastomer-acrylonitrile butadiene styrene blends for tunable mechanical properties

Fused Deposition Modeling (FDM) has emerged as a cost-effective and user-friendly technique that has garnered significant attention in recent years. However, challenges persist when printing soft materials using FDM technology. This study proposes a solution by blending a soft polyolefin elastomer (POE) with a stiffer material, acrylonitrile butadiene styrene (ABS). A comprehensive experimental investigation utilizing a direct pellet printing method was conducted to 3D print POE-ABS blends in various ratios (10%, 30%, and 50% ABS content). The study encompassed material preparation, 3D printing, SEM (Scanning Electron Microscopy) analysis, Dynamic Mechanical Thermal Analysis (DMTA), uniaxial tensile testing, and compression testing to assess the mechanical properties and energy absorption capabilities of the 3D printed blends. The results of the DMTA showed that the blends with a higher amount of ABS have a larger area under the Tan δ curve, indicating their ability to absorb more energy. The SEM images revealed that as the proportion of ABS increases, the gaps between layers and beads become smaller. The mechanical properties of the pure printed POE, such as its elongation at break and tensile strength, were 2138% and 2.83 MPa, respectively. However, as the ABS content increased, the samples exhibited more rigid behavior, with a final transition to 50/50 ratio resulting in 9.4 MPa tensile strength and 160% elongation at break. The energy absorption test demonstrated that the sample with 30% ABS content has the highest energy absorption capability among all the tested samples. This research underscores the potential of blending soft and stiff materials to tailor properties for additive manufacturing applications, emphasizing the significance of material composition in achieving desired mechanical performance, printability, and functionality in printed objects.

Direct Printing of Disperse Dye Inks to Polyester Fabrics without Chemical Pretreatment.

Direct inkjet digital printing is a relatively green and environmentally friendly textile printing method with a wide range of applications in the textile printing and dyeing industry. However, pretreatment of the fabric is required before digital printing, which will generate certain energy consumption and wastewater. In this study, a digital direct inkjet printing method was developed to improve the printing accuracy of poly(ethylene terephthalate) (PET) fabrics without any pretreatment. A kind of direct inkjet printing ink was prepared by the response change in temperature viscosity. The increase in viscosity inhibits ink bleeding on the fabric, thereby improving printing accuracy. A thermosensitive direct inkjet printing disperse dye ink was prepared by adding cetyltrimethylammonium bromide (CTAB) and 3-methylsalicylic acid (3MS) to the ink. By evaluating the changes in the ink particle size, shear viscosity, and temperature viscosity, it was found that this thermosensitive ink has an excellent average particle size and special changes in viscosity with increasing temperature. When this heat-sensitive ink is printed on a polyester fabric, the fabric does not need pretreatment to improve the clarity of printing, and the printed fabric has satisfactory color fastness to friction and washing.

Fabrication of micro-ultrasonic phased array electrode via electric field-driven printing method

The electrode is an important part of a micro-ultrasonic phased array, commonly fabricated by magnetron sputtering technology. However, with the expansion of the application field, the structures of the phased arrays are becoming more complex, making the traditional magnetron sputtering method no longer applicable, and the realization of micro-scale phased array electrodes by direct printing technology still faces great challenges. Herein, an electric field-driven direct printing method was proposed to fabricate micro-ultrasonic phased array electrodes. The influence of sintering parameters on the resistivity and the effect of printing parameters on the geometric size and surface morphology of the electrode were comprehensively explored, and the mathematical model between the electrode line width and the printing parameters was established. The final printed electrodes exhibit superior properties with a resistivity of 2.4 × 10−7 Ω⋅m , a surface roughness range of 460–550 nm, and a line width range of 125–480 µm. Additionally, a micro-scale electrode was printed on the piezoelectric ceramic with PZT-5 as the material, and after polarization treatment, the piezoelectric coefficient can reach 405 pC N−1, which proves that this method can be applied in the field of fabricating phased array electrodes.

Thread-analogous elastic fibers with liquid metal core by drawing at room temperature for multifunctional smart textiles

Stretchable and elastic conductive fibers with liquid metal core are appealing for integration into electronic fabrics and clothing, owing to their inherent electrical conductivity even under strain. Previously, injecting liquid metal into core of hollow elastic fiber has been utilized to fabricate conductive fibers, however, hydrodynamics limits the extent to which metals can be injected, thus limiting length and cross-sectional area. Although direct printing and spinning methods using coaxial needles have been utilized to fabricate long and thin polymer-encased liquid metal fibers via single step, various parameters including extrusion rate along with viscosity and surface tension of liquid metal and polymeric shell, needs to be considered. Herein, we introduce a simple and facile method for fabricating thread analogous conductive fibers by plastically deforming liquid metal injected polymeric shell via drawing at room temperature. This simple yet effective process generates long conductive fibers with narrow cross-sectional area of the liquid metal wire continuously formed along its length. The obtained fiber can withstand deformation arising from daily activities while maintaining excellent electrical performance, thus can be used for fabricating smart textiles serving multitude of purposes.

Direct printing of graphene terahertz closed-ring resonator array from periodic single droplets via enhanced coffee-ring effect

Graphene terahertz (THz) devices have emerged as a pivotal player in the THz area, and drop-on-demand (DOD) printing technology enables cost-effective patterning of THz microstructures. However, fast printing of THz microstructures and devices suffers from low efficiency owing to the drop-by-drop overlapping process. Here, we have developed a facile direct printing method to fabricate graphene THz closed-ring resonator (CRR) arrays from periodic single droplets ascribing to the enhanced coffee-ring effect. The construction of a complete graphene micro-ring was achieved using small reduced graphene oxide sheets, enabling the strategy of a graphene CRR from one single droplet. We attributed the mechanism of strengthened coffee-ring effect to the swift pinning, gapless between the contact line and the solute line, and close packing. Finally, we prepared a graphene THz CRR array featuring fine rings with widths of ∼12.3 μm, a high THz extinction ratio of 66.9%, and the highest measurement λ (relative THz response) of 9.8 documented so far for graphene-based THz microstructures and devices. Such an array from the expeditious DOD printing process exhibits a pronounced THz response and possible fast switching speed, which suggests new possibilities in building graphene THz microstructures, benefiting the future development of graphene THz devices.

Variasi Jenis Diluent terhadap Mutu Fisik Tablet Temu Putih (Curcuma zedoaria) menggunakan Metode Cetak Langsung

White Tumeric (Curcuma zedoaria) is a plant that contains curcuminoid compounds and essential oils on its rhizomes, which are helpful as an anticancer. This study aims to determine which filling material (diluent) is good as a filler for white meeting tablets (Curcuma zedoaria). Tablets are made using the direct printing method with the types of fillers (diluent) used are ludipress, starch 1500, and Spray Dried Lactose. The resulting tablets were carried out still angle and flow properties tests, compression index tests, weight uniformity tests, size uniformity tests, tablet hardness tests, tablet brittleness tests, and crush time tests. In the test of stationary angle and flow properties and compression index in ludipress filler materials, the flow property value was 10.42 g/s, the stationary angle value was 27.77º, and the compression index was 10%. In the starch filler material 1500 obtained a flow property value of 4.17 g/s, a stationary angle of 34.40º, and a compression index of 30%; in the formulation of Spray Dried Lactose obtained a flow property value of 10.18 g/s, a stationary angle of 27.74º, and a compression index of 5%. Variations of the diluent Spray Dried Lactose type show optimal results for white temu tablet filler (Curcuma zedoaria).

Enhanced corrosion resistance of Mg and Mg alloys with fs-laser printed hydrophobic and periodically microrippled surface for armor application

Magnesium (Mg) and its alloys have properties such as high strength-to-weight ratio and good castability, which make them quite promising in industrial applications. Future widespread application of them needs to overcome the limitations such as the fast corrosion rate of Mg and Mg alloys. In this study, an anticorrosion armor with was printed using femtosecond (fs) laser direct writing method. This protective armor is covered with controllable micro-nano structures. Thus, it has a controllable water contact angle ranged from 68° to 158°. In addition, due to the fs laser energy deposition, a grain refined layer less than 15 μm consisting of nanocrystals forms on the surface. Under the synergistic effects of the superhydrophobic surface and nanocrystal layer, Mg and Mg alloys (AZ91D) exhibit significantly enhanced corrosion voltage and exponentially decreased corrosion current density. In particular, pitting on the surface is largely improved, and the corrosion pits on the surface after laser-treatment are approximately 200 times smaller in depth (<2.5 μm) than those of the pristine surface (531 μm). Therefore, the armor on Mg and Mg alloys with enhanced corrosion resistance can be successfully fabricated by the fs-laser direct printing method, extensively used in Mg and Mg alloys applications.

Direct Manufacturing Technology for High‐Precision Follow‐the‐Shape Circuits on Complex, Hard, Curved Surfaces

Abstract3D curved electronics are a trend in the microelectronics industry, but conformal printing of circuits on complex curved surfaces remains challenging, especially for electronics comprising concave surfaces with large curvature. In this study, a new manufacturing method is proposed for follow‐the‐shape circuits, using high‐precision direct printing technology to print circuits on hard, arbitrarily curved surfaces. A circuit with any complex curved surface can be directly digitized and programmed for fully autonomous and controlled printing without indirect transfer or pad printing processing. The proposed direct printing method begins with using unique 3D projection technology to map a 2D planar functional circuit onto a 3D digital curved surface. The next step is directly printing the integrated circuit on a complex surface by controlled planning of the spatial motion trajectory, high‐frequency drive control of the precision nozzle, and precise switching control of the heterogeneous functional material. Optimal printing parameters are obtained by exploring the main factors affecting molding quality and electrical conductivity of curved surface circuits. Simple examples, such as an acoustic‐optic touch time‐delay three‐control multifunction system, demonstrate the feasibility and broad potential of the proposed technology.

Methods of Evaluating Adaptation and Accuracy of Additive Manufactured Removable Partial Dentures: A Scoping Review

This study aimed to provide a comprehensive review of various recent methods that can be used to assess the fit and accuracy of additive-manufactured removable partial dentures (RPDs), focusing on 3D-printed RPDs. An electronic search of the English language literature from January 2000 to February 2022 was performed using four databases: Medline/PubMed, Scopus, Web of Science, and EBSCOhost, using relevant keywords. The parameters of interest were extracted and tabulated. Of 936 retrieved studies, 26 studies were included. Most of the studies were laboratory studies, conducted between 2011 and 2022, did not include control group, used stone cast model as reference, used direct 3D printing method, and polished the final RPD framework. Methods of assessment can be divided into two categories: 1) qualitative assessment which is based mainly on visual inspection or tactile sense, and 2) quantitative assessment which includes optical assessment (with or without a registration material) and computerized assessment based on surface-matching software programs. In conclusion, computerized assessment using different surface matching software provides more accurate and precise quantitative assessment of denture fit and allows researcher and practitioner to detect minute dimensional changes that cannot be detected visually.

Effect of coarse aggregate content on the rheological and buildability properties of 3D printable concrete

Additive manufacturing in construction industry is gaining attention among both researchers and industries. The present study deals with the effect of coarse aggregate (CA) content on the performance of 3D printable concrete. The fresh and rheological properties of the designed concrete with 8 mm down sized CA were assessed. The rheological parameters for the material with varying coarse aggregate (CA) volume fraction from 0% to 50% were studied. There is limited literature on the effect of large sized CA on the printability of the concrete. The rheological properties were measured using in-house developed rheometer designed for concrete with CA. The concrete mix with CA content percentage 10%, 20%, 30%, 40% and 50% were compared with control mix (CA content 0%). The static and dynamic yield stress values for 20% and 30% CA content followed decreasing trend and when increased more than threshold limit of 30%, the yield stress values increased. It was observed that the mortar volume ratio, fine aggregate ratio with respect to CA influences the rheological properties and slump flow. Relationship between the slump flow value and static yield stress was fixed for the designed concrete. Extrusion based layer by layer printing of cementitious material without the support of form-work makes the material more prone to failure and qualitative approach to resist the failure of the material while printing is a key aspect in 3D concrete printing and this quality is termed as ‘buildability’. The challenge lies in designing a material which is flowable with minimum dynamic yield stress and increased structuration rate confirming that the material attains the yield strength once the printing is initiated. The concrete mix with flowability 180 mm to 190 mm was having good buildability and smooth extrusion. The buildability of the designed concrete mix was calculated using Kruger’s analytical model in terms of number of layers and validated the model by direct printing method. The printing parameters like printing speed and resting time was fixed for the concrete with 8 mm down sized aggregate. The concrete mix with 40% CA content showed better buildability with optimum static and dynamic yield stress values.

Lasing by Template‐Assisted Self‐Assembled Quantum Dots

AbstractMiniaturized laser sources with low threshold power are required for integrated photonic devices. Photostable core/shell nanocrystals are well suited as gain material and their laser properties can be exploited by direct patterning as distributed feedback (DFB) lasers. Here, the 2nd‐order DFB resonators tuned to the photoluminescence wavelength of the QDs are used. Soft lithography based on template‐assisted colloidal self‐assembly enables pattern resolution in the subwavelength range. Combined with the directional Langmuir–Blodgett arrangement, control of the waveguide layer thickness is further achieved. It is shown that a lasing threshold of 5.5 mJ cm−2 is reached by a direct printing method, which can be further reduced by a factor of ten (0.6 mJ cm−2) at an optimal waveguide thickness. Moreover, it is discussed how one can adjust the DFB geometries to any working wavelength. This colloidal approach offers prospects for applications in bioimaging, biomedical sensing, anti‐counterfeiting, or displays.

Direct 3D printed biocompatible microfluidics: assessment of human mesenchymal stem cell differentiation and cytotoxic drug screening in a dynamic culture system

BackgroundIn vivo-mimicking conditions are critical in in vitro cell analysis to obtain clinically relevant results. The required conditions, comparable to those prevalent in nature, can be provided by microfluidic dynamic cell cultures. Microfluidics can be used to fabricate and test the functionality and biocompatibility of newly developed nanosystems or to apply micro- and nanoelectromechanical systems embedded in a microfluidic system. However, the use of microfluidic systems is often hampered by their accessibility, acquisition cost, or customization, especially for scientists whose primary research focus is not microfluidics.ResultsHere we present a method for 3D printing that can be applied without special prior knowledge and sophisticated equipment to produce various ready-to-use microfluidic components with a size of 100 µm. Compared to other available methods, 3D printing using fused deposition modeling (FDM) offers several advantages, such as time-reduction and avoidance of sophisticated equipment (e.g., photolithography), as well as excellent biocompatibility and avoidance of toxic, leaching chemicals or post-processing (e.g., stereolithography). We further demonstrate the ease of use of the method for two relevant applications: a cytotoxicity screening system and an osteoblastic differentiation assay. To our knowledge, this is the first time an application including treatment, long-term cell culture and analysis on one chip has been demonstrated in a directly 3D-printed microfluidic chip.ConclusionThe direct 3D printing method is tested and validated for various microfluidic components that can be combined on a chip depending on the specific requirements of the experiment. The ease of use and production opens up the potential of microfluidics to a wide range of users, especially in biomedical research. Our demonstration of its use as a cytotoxicity screening system and as an assay for osteoblastic differentiation shows the methods potential in the development of novel biomedical applications. With the presented method, we aim to disseminate microfluidics as a standard method in biomedical research, thus improving the reproducibility and transferability of results to clinical applications.Graphical

3D-Branched Fe2O3 Nanorods on Micropillar Arrays Decorated with Co-Pi for Enhanced PEC Water Splitting

Photoelectrochemical(PEC) water splitting has gained great attention as a route for future hydrogen production owing to its sustainable and cost-effective properties. However, since PEC water splitting has limitations on efficiency and stability, research on materials, structures and catalysts are in progress to solve those problems. In our experiments, the nano-pattern structure is created using direct-printing to increase the photoanode efficiency.In this study, enlarged surface area is accomplished by micropillar structured FTO and Fe2O3 nanorods. We fabricated micropillar structure via direct printing method. The direct-printing method has advantages in not only simple process but also low price to form micro-nano size structures. To obtain micropillar structure, spin coating of hydrogen silsesquioxane(HSQ) was performed on micropillar patterned polydimethylsiloxane(PDMS) mold. Then, we applied glass substrate and pressure on it. Detachment of PDMS mold is followed by deposition of FTO layer. Hydrothermally synthesized Fe2O3 nanorods are formed on micropillar structured FTO and Co-Pi catalyst was electrodeposited on Fe2O3 nanorods to enhance surface water oxidation.Due to micropillar pattern, optical absorption of patterned Fe2O3 photoanode is higher than that of flat Fe2O3 photoanode in the whole range of optical wavelength. Also micropillar patterned Fe2O3 sample showed 2.6 times higher photocurrent at 1.23 VRHE than flat Fe2O3 sample. These results were confirmed that micropillar structure increased the surface area and light scattering effect. Furthermore, applying Co-Pi catalyst increased photocurrent at 1.23 VRHE for 2.0 times higher owing to the enhancement of surface water oxidation. As a result, photocurrent of the micropillar patterned, decorated with Co-Pi sample shows 1.51 mA/cm2, and that of flat, non-decorated sample shows 0.29 mA/cm2 at 1.23 VRHE. Figure 1

Encoding of direct 4D printing of isotropic single-material system for double-curvature and multimodal morphing

The ability to morph flat sheets into complex 3D shapes is extremely useful for fast manufacturing and saving materials while also allowing volumetrically efficient storage and shipment and a functional use. Direct 4D printing is a compelling method to morph complex 3D shapes out of as-printed 2D plates. However, most direct 4D printing methods require multi-material systems involving costly machines. Moreover, most works have used an open-cell design for shape shifting by encoding a collection of 1D rib deformations, which cannot remain structurally stable. Here, we demonstrate the direct 4D printing of an isotropic single-material system to morph 2D continuous bilayer plates into doubly curved and multimodal 3D complex shapes whose geometry can also be locked after deployment. We develop an inverse-design algorithm that integrates extrusion-based 3D printing of a single-material system to directly morph a raw printed sheet into complex 3D geometries such as a doubly curved surface with shape locking. Furthermore, our inverse-design tool encodes the localized shape-memory anisotropy during the process, providing the processing conditions for a target 3D morphed geometry. Our approach could be used for conventional extrusion-based 3D printing for various applications including biomedical devices, deployable structures, smart textiles, and pop-up Kirigami structures.

High‐Performance n‐Channel Printed Transistors on Biodegradable Substrate for Transient Electronics

AbstractInnovative methods to fabricate and integrate biodegradable high‐grade electronics on green substrates are needed for the next generation of robust high‐performance transient electronics. This is also needed to alleviate the growing problem of electronic waste (e‐waste). Herein, the authors present the n‐channel silicon (Si) nanoribbons‐based high‐performance transistors developed on biodegradable metal (magnesium) foils using the direct transfer printing method. The developed transistors present high effective mobility of &gt;600 cm2 V−1 s−1, high on/off current ratio (Ion/off) of &gt;104, negligible hysteresis, transconductance of 0.19 mS, and an on‐current of 1.6 mA at a bias of 2 V. Further, the transistors show stable device performance under temperature stress (5–50 °C), gate‐bias stress, continuous long‐term transfer scans for 24 h (&gt;3000 cycles), and aging test (up to 100 days) demonstrating the excellent potential for futuristic high‐performance robust transient devices and circuits. Finally, the effect of transience on the electrical functioning of devices on Mg foils (at pH 8) and degradation of Mg foils at different pH values is studied by hydrolysis. The outcome from these experiments demonstrates the potential of direct transfer printing for high‐performance transient electronics and also as the new avenue toward zero e‐waste.

On-demand direct printing of tin microdots by a piezoelectric microjet: design, simulation, and experimental evaluation

Metal microdot precision printing is widely applied in flexible circuit manufacturing, ball grid array and additive manufacturing, etc. Compared with indirect metal microdot printing, direct printing can realize high efficiency printing by directly ejecting hot-melt metal droplets. While, due to the compressibility of the driving gas, uniform printed microdots are hardly to be obtained by using the existing direct printing method. In this work, a piezoelectric microjet, which can print tin microdots directly by the drive of piezoelectric actuator without complex pneumatic system, is designed. Optimization analyses of the displacement amplifier are carried out to obtain high amplification efficiency for realizing hot-melt droplet ejection and effective heat insulation. The forming, spreading, and solidification processes of the ejected hot-melt tin droplets are discussed, and the printing mechanism is revealed. Based on experimental research, the influences of the excitation parameters and the target surface characteristics on the morphology and size of the printed tin microdots are studied, and the methods to meet different printing requirements are proposed. Tin microdot diameter of 340 μm can be printed on the surface with temperature of 120 °C when voltage pulse with amplitude of only 16 V is applied on the designed piezoelectric microjet with the nozzle diameter of 200 μm. The feasibility and controllability of the tin microdot printing methods are verified by two-dimensional printing and three-dimensional deposition printing test. This work can provide important reference for on-demand printing of metal microdots.

On‐Demand, Direct Printing of Nanodiamonds at the Quantum Level (Adv. Sci. 5/2022)

Nanodiamonds Diamond nanocrystals, namely nanodiamonds, hosting point defects such as nitrogen-vacancy (NV) centers have been emerging as one of the most promising quantum materials. In article number 2103598, Ji Tae Kim, Zhiqin Chu, and co-workers develop a direct printing method for nanodiamonds containing NV centers at the quantum level. The method developed here provides a high-precision, lithography-free route to place diamond defects directly on the universal substrate towards their further developments in many exciting quantum research areas and beyond.

EFFECT OF VARIATION OF LUBRICANT CONCENTRATION (MAGNESIUM STEARATE) ON THE PHYSICAL QUALITY OF METOCLOPRAMID HCl TABLETS WITH DIRECT PRINTING METHOD

Metoclopramide HCl is used to relieve nausea and vomiting. Market availability in the form of tablets, syrup and injection. The most preferred drug use by patients is oral medication because of its ease of use. Chewable tablets are a new product as an alternative for treatment in pediatric and adult patients who have difficulty swallowing drugs. This study aims to formulate the chewable tablet preparations of metoclopramide HCl using variations in lubricant concentrations. The variations of magnesium stearate with concentrations of 1%, 2%, and 3% using the direct printing method made to obtain a better physical quality test including organoleptics, weight uniformity, uniformity of size, tablet hardness, tablet brittleness, tablet crush time, uniformity of content. The results of the physical quality test were statistically analyzed using one way ANOVA to determine the effect of variations in the concentration of lubricants on the characteristics of chewable tablets. The results showed that variations in the concentration of magnesium stearate lubricant in the manufacture of metoclopramide HCl chewable tablets had an effect on the physical quality of metoclopramide HCl chewable tablets. The concentration of magnesium stearate which produces metoclopramide HCl chewable tablets with good physical properties is 2%.

Advances in Screen Printing of Conductive Nanomaterials for Stretchable Electronics.

Stretchable electronics have demonstrated tremendous potential in wearable healthcare, advanced diagnostics, soft robotics, and persistent human–machine interfaces. Still, their applicability is limited by a reliance on low-throughput, high-cost fabrication methods. Traditional MEMS/NEMS metallization and off-contact direct-printing methods are not suitable at scale. In contrast, screen printing is a high-throughput, mature printing method. The recent development of conductive nanomaterial inks that are intrinsically stretchable provides an exciting opportunity for scalable fabrication of stretchable electronics. The design of screen-printed inks is constrained by strict rheological requirements during printing, substrate–ink attraction, and nanomaterial properties that determine dispersibility and percolation threshold. Here, this review provides a concise overview of these key constraints and a recent attempt to meet them. We begin with a description of the fluid dynamics governing screen printing, deduce from these properties the optimal ink rheological properties, and then describe how nanomaterials, solvents, binders, and rheological agents are combined to produce high-performing inks. Although this review emphasizes conductive interconnections, these methods are highly applicable to sensing, insulating, photovoltaic, and semiconducting materials. Finally, we conclude with a discussion on the future opportunities and challenges in screen-printing stretchable electronics and their broader applicability.