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For the first time, the necessity to thermally pre-treat ubiquitously used PET substrates for printed electronics, to improve dimensional stability during manufacturing, is clearly defined. The experimental results have proven this phenomenon for both roll-to-roll (R2R) and sheet-to-sheet (S2S) processing of printed electronics. The next generation of electronics manufacturing has pushed the boundaries for low-cost, flexible, printed, and mass produced electronic components and systems. A driving force, and enabling production method, are the R2R printing presses. However, to produce electronics with increasing complexity and high yield in volume production, one must have a highly accurate process. In this article, R2R processing accuracy of printed electronics is evaluated from the point of dimensional accuracy of the flexible polyester substrate (DuPont Teijin Films’ PET Melinex ST504 with and without indium tin oxide, Melinex ST506, and Melinex PCS), precision of printing, and accuracy of layer-to-layer registration with stages that involve tension and elevated temperatures. This study has confirmed that dimensional changes during R2R processing will occur only in the first processing stage and that if a thermal pre-treatment run for the substrate is made—at identical temperature and tension of the processing stage—there is improved stability originating from a new-level strain in the crystalline PET film structure and freezing it in at the tensions and temperatures it is exposed to (i.e. 1400 μm machine direction stretching reduced to 8 μm). Furthermore, it is explained how the dimensional accuracy can be improved and reproducibly maintained in multilayer printing of electronics devices such as organic photovoltaics (OPV). These devices provide a valuable baseline of how the layer-to-layer alignment accuracy plays a crucial role in fully printed electronics devices, which lessons can be applied in all aspects of this field including hybrid systems and system fabrication involving multiple processing methods.

International audience; Printed electronics are expected to meet an increasing demand for improved functionality and autonomy of products in the context of Internet-of-Things. With this trend, the environmental performance of novel technologies is of growing importance. The current study presents the life cycle assessment of two novel devices: an anticounterfeit label based on the electrochromic display and a shock-detection tag based on the piezoelectric sensor, designed for the use in packaging of pharmaceuticals and luxury items to improve the safety and accountability in the supply chain. The devices are manufactured by means of energy-efficient printing techniques on a low-cost flexible and recyclable paper substrate. Comprehensive cradle-to-grave analysis contributes to industrial-scale energy and material life cycle inventories and identifies the main impact hotspots evaluated for a broad range of categories of the ReCiPe midpoint (H) impact assessment method. Results show that major impact burdens are associated with the near-field communication chip and radio-frequency identification antenna, while the impacts of solvents, process energy, electrochromic display/piezoelectric sensor, Li-ion battery, and substrate are comparatively small. In terms of their global warming potential, both the anticounterfeit label and shock-detection tag embody around 0.23 kg of CO2-equiv. Several material-use reduction and material-substitution strategies are quantified and discussed for their potential to reduce high impacts of the antenna.

International audience; The ohmic curing of two silver micro-particle inks was studied. Silver lines of 35 to 75 µm thick were printed on a mixture of polycarbonate and acrylonitrile butadiene styrene (PC+ABS) substrate and on a mineral reinforced Nylon 6 thermoplastic, using a laboratory-made system based on a volumetric dosing dispenser. After 48 h of stabilization in ambient conditions, a current is applied through the printed lines with an imposed intensity value and application time in order to cure the silver inks. Evolutions of the temperature and the resistivity of silver tracks were followed during the process. Printed thermoplastics were characterized at the end of the process in order to check the absence of deformation due to the curing treatment. The study showed that the ohmic curing led to better electrical performances than an oven process with a considerable time saving. Most of the printed line resistivity drop occurred in the first 30 s of the treatment. The ohmic curing induced a local increase of temperature located in the printed line and avoided damaging the substrates, which makes the process compatible with thermal sensitive substrates. Therefore, the ohmic curing is an efficient low-cost process to cure silver micro-particle inks that could be easily implemented at an industrial scale.

Printed piezoresistive strain sensors based on stretchable roll-to-roll screen-printed silver electrodes on polydimethylsiloxane substrates and inkjet-deposited single-wall carbon nanotube micropatterns are demonstrated in this work. With the optimization of surface wetting and inkjet printing parameters, well-defined microscopic line patterns of the nanotubes with a sheet resistance of

As a common type of microelectromechanical systems (MEMS) inertial sensors, comb-structured air-gap acceleration sensors have been applied to various industrial devices and systems. Printed electronics technology has emerged recently as an alternative for fabrication of flexible electronic devices with superior productivity and eco-friendliness to MEMS technology. However, air-gap structures are hard to realize through printing without etching process, and thus comb-structured acceleration sensors have been rarely reported in the printed electronics field in spite of many advantages. This study presents design of a comb-structured air-gap acceleration sensor and materials and processes for highly productive roll-to-roll printed electronic fabrication of the sensor. The sensor is designed to have multiple layers in two parts: fixed fingers are in the lower part while the movable mass and movable fingers in the upper part. Both parts are processed separately on different flexible PET substrates by roll-to-roll gravure printing and drying. Then the upper part is transferred and bonded to the lower one and air-gap structure is formed as a result. This paper also provides electrical characteristics of the proposed comb-structured acceleration sensor by testing capacitance change as a function of acceleration.

Polymer/oxide hybrid thin films, which have excellent electrical and mechanical performance, can be effectively fabricated through the sol-gel process, showing great potential in the future printed electronics. However, gelation of polymer/oxide ink systems can easily occur during a thermal process in which case capillary stress can lead to the crack of printed films due to the long period of stress accumulation. To solve this problem, the effect of different solvent systems on formed PAM/ZrOx hybrid films, which were printed by piezoelectric printing, was studied in this paper, including single solvent systems of glycol and binary solvent systems of glycol and water. The result showed that the microstructure characteristics and mechanical properties of hybrid nanostructures formed in different solvent systems varied significantly, and crack behavior can be regulated by simply adjusting the water volume ratio of the solvent system. The crack formation was significantly inhibited when the water volume ratio reached 25%.

The development of graphene-based materials with good light-curing ability and excellent electrical conductivity is the key to next-generation electronic devices. Herein, we demonstrate the molecular structure modification of photocurable graphene oxide (PGO) by reacting hydroxyl groups with isocyano groups, which is referred to as grafting of the photosensitive group on pristine GO, resulting in photosensitive PGO flakes that can be photocured during 3D printing using water as a solvent and a developer. Complex-shaped and highly precise 2D and 3D structures of GO as well as thin single-layer or few-layer GO films are obtained by optimizing the concentration and photocuring parameters of the PGO precursor. After thermal reduction of PGO microarchitectures, the reduced cross-linked GO (rCGO) exhibits a minimum square resistance of 213.74 mΩ sq−1, which is similar to that of graphene. Moreover, rCGO demonstrates excellent cell compatibility during cell culture experiments and superior hydrophilicity. The latter property can be exploited to prepare solution-based detection electrodes. The proposed strategy is used to print circuits and 3D bulk conductors, and can facilitate the formation of various electronic devices via photocuring 3D printing or photolithography process.

A stretchable conductor is one of the key components in soft electronics that allows the seamless integration of electronic devices and sensors on elastic substrates. Its unique advantages of mechanical flexibility and stretchability have enabled a variety of wearable bioelectronic devices that can conformably adapt to curved skin surfaces for long-term health monitoring applications. Here, we report a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-based stretchable polymer blend that can be patterned using an inkjet printing process while exhibiting low sheet resistance and accommodating large mechanical deformations. We have systematically studied the effect of various types of polar solvent additives that can help induce phase separation of PEDOT and PSS grains and change the conformation of a PEDOT chain, thereby improving the electrical property of the film by facilitating charge hopping along the percolating PEDOT network. The optimal ink formulation is achieved by adding 5 wt % ethylene glycol into a pristine PEDOT:PSS aqueous solution, which results in a sheet resistance of as low as 58 Ω/□. Elasticity can also be achieved by blending the above solution with the soft polymer poly(ethylene oxide) (PEO). Thin films of PEDOT:PSS/PEO polymer blends patterned by inkjet printing exhibits a low sheet resistance of 84 Ω/□ and can resist up to 50% tensile strain with minimal changes in electrical performance. With its good conductivity and elasticity, we have further demonstrated the use of the polymer blend as stretchable interconnects and stretchable dry electrodes on a thin polydimethylsiloxane (PDMS) substrate for photoplethysmography (PPG) and electrocardiography (ECG) recording applications. This work shows the potential of using a printed stretchable conducting polymer in low-cost wearable sensor patches for smart health applications.

Here, we report a previously unreported low-temperature curable barium strontium titanate (BaXSr1−XTiO3) or BST dielectric nanoparticle ink which shows a high dielectric tunability for printed electronics/additive manufacturing applications. The newly formulated BST ink is optimized to print in aerosol jet printers and can be cured at 150°C, which will allow the fabrication of tunable radio-frequency (RF) and microwave (MW) devices on a wide range of flexible substrates. Characterization of high-frequency dielectric properties showed a high dielectric tunability (~ 15% at 10 GHz with 10 V/µm) and a high dielectric constant (~ 16 at 10 GHz). The linear-reversible tunability, which is very important for tunable devices, was confirmed by the tunability testing at 10 GHz. Characterization of temperature-dependent dielectric properties found < 10% variations of the dielectric constant at 10 GHz from −50°C to 125°C for this BST ink. Detailed information on BST nanoparticle characterization, ink formulation and characterization of dielectric properties is discussed.

In the field of printed electronics, carbon and its allotropes are today among the most studied materials due to their unique physical and chemical properties. In this work, carbon dispersions were used for the preparation of screen-printed carbon electrodes applied as counter electrodes (CEs) for the dye-sensitized solar cells and as working electrodes for electrochemical sensing. Following the simple and quick homogenization process, carbon dispersions were subjected to thermogravimetric analysis to closely examine drying, eventually sintering processes after printing. The influence of the graphite:carbon black ratio was investigated. The structure of composite carbon layers was analyzed by scanning electron microscopy and optical microscopy. The DSSC CEs printed from the dispersion containing 100 wt% of CB exhibited the highest catalytic activity for the effective reduction of oxidized triiodide I3− back to iodide I− within the solar cell. The highest conversion efficiency achieved for the high-temperature processed CE was 3.05% with the fill factor of 0.65. The same composition of the carbon WE was used for the quantitative analysis of neurotransmitter dopamine. Based on the cyclic voltammetry measurements, the sensor showed a limit of detection of 13.3 nM for dopamine.

Printed electronics such as solar cells, RFIDs, and display panels can be made using printed electronic technology by printing viscous liquids having various properties on films or insulating substrates. Among printed electronic production processes, the roll-to-roll process transfers functional ink to an insulation substrate by filling its engravings through repeated contact and rotation of two rolls. Extensive research has been conducted to commercialize this process because it offers several advantages such as low equipment investment and production cost, and high-speed mass production. However, the roll-to-roll process requires further development for commercialization because print quality precision and fine pattern formation are difficult to achieve, and print quality may be affected by processing precision errors and non-uniform printing pressure. Contact printing pressure is the pressure acting on the nip that makes contact with the two rolls, and is a factor that influences roll processing precision. That is, contact printing pressure uniformity must be maintained to enhance print quality. However, previous research on contact printing pressure failed to directly estimate the contact printing pressure due to structural problems, and only indirectly measured it by attaching a load cell at both ends of the impression roll. This study proposes a method of contact printing pressure estimation and control to enhance print quality. The processing precision of a roll can be measured by measuring the rotationally repeatable run-out after dividing the width of the impression roll and plate roll into 25 points. The relationship between the impression roll and the plate roll, with consideration of the contact printing pressure, rotationally repeatable run-out, and force measured by the load cell, is modeled in a manner similar to the relationship between a car body, suspension, and ground in a half-car model, and expressed using state-space equations. This model is then applied to an individual drive type cross-coupled control system for experiments on control of the contact printing pressure; pressure measuring films are used to check for actual improvement in uniformity of contact printing pressure.

Successful precision agriculture decision making requires characterizing soil heterogeneity at high spatiotemporal resolution in real-time in order to optimize input (such as water and nutrient) amounts and location. In order to achieve this goal, a printed soil moisture sensor fabricated from biodegradable materials is demonstrated. These devices are intended to function during the growing season and then harmlessly degrade afterward, enabling high-density deployment, eliminating the need for sensor retrieval, and enabling the use of simple device structures and low-cost materials and fabrication techniques. A capacitive structure is used with a water-soluble zinc electrode printed onto a biodegradable substrate. Rapidly degrading substrate and electrode are encapsulated in a slowly degrading wax blend that protects the device, reduces drift, and controls degradation time. A linear capacitance response is observed for soil samples with a volumetric water content from 0 to 72%. Accelerated degradation testing demonstrates that the sensor responds predictably and stably until the encapsulation is breached, at which point the sensor fails rapidly, providing a clear distinction between the functional and nonfunctional lifetimes of the sensor. These results demonstrate the potential of biodegradable sensors to allow maintenance-free, affordable, and real-time soil moisture measurement at high spatial density for precision irrigation control.

Photonic curing has shown great promise in maintaining the integrity of flexible thin polymer substrates without structural degradation due to shrinkage, charring or decomposition during the sintering of printed functional ink films in milliseconds at high temperatures. In this paper, single-step photonic curing of screen-printed nickel (Ni) electrodes is reported for sensor, interconnector and printed electronics applications. Solid bleached sulphate paperboard (SBS) and polyethylene terephthalate polymer (PET) substrates are employed to investigate the electrical performance, ink transfer and ink spreading that directly affect the fabrication of homogeneous ink films. Ni flake ink is selected, particularly since its effects on sintering and rheology have not yet been examined. The viscosity of Ni flake ink yields shear-thinning behavior that is distinct from that of screen printing. The porous SBS substrate is allowed approximately 20% less ink usage. With one-step photonic curing, the electrodes on SBS and PET exhibited electrical performances of a minimum of 4 Ω/sq and 16 Ω/sq, respectively, at a pulse length of 1.6 ms, which is comparable to conventional thermal heating at 130 °C for 5 min. The results emphasize the suitability of Ni flake ink to fabricate electronic devices on flexible substrates by photonic curing.

This paper examines various ways of combining paper and glass as a laminate and the effects on transparency. Laminate in this context means a layer of paper sandwiched in between layers of glass held together with an adhesive. Different kinds of papers and adhesives were used to study the potentials of glass-paper-laminates as related to transparency and translucency. These laminates may find applications in building construction, safety glass, printed electronics and more. Utilizing a variety of adhesives and papers, qualitative evidence found that epoxy achieves the best with regards to transparency and adheres most effectively.

Sessile droplets of colloidal dispersions tend to exhibit the coffee-ring phenomenon in the drying process. The suspended particles are transported especially at the final stage of the drying process, which is called the rush hour. Conventional inkjet printers require the ink liquid to have a sufficiently low viscosity for inkjet discharge, but such liquids tend to be subject to the coffee-ring effect. The coffee-ring effect is an issue for conventional printing applications and drawing wires in printed electronics. We show by microscopy movie data analysis based on single particle tracking that the addition of a small amount of cellulose nanofibers (CNFs) to the colloidal dispersion works in such a way that the initial low concentration satisfies the low viscosity requirement, and the three-dimensional structural order of the CNFs formed during the final stage of droplet drying owing to the high concentration hinders the transport of particles to the periphery, suppressing the coffee-ring effect. This is a spatio-temporally controlled process that makes use of the inherent process of ordinary ink printing situations by the simple protocol. This is also an approach to seamlessly link the ink and substrate since CNFs are regarded as a promising substrate material for flexible devices in printed electronics because of their fine texture that keeps conductive nanoparticles on the surface.

The new ink feed unit (IFU) developed and installed based on the serial model of Anycubic I3 Mega 3D printer. The developed unit can be easily integrated into the control system of the printer by connecting the control line of the standard step motor responsible for supplying the plastic wire. The minimum volume 0.3 mm3 ink drops were reached using the syringe with an inner diameter of 10 mm and the volume can be reduced to 0.01 mm3 by using the syringe with 2 mm diameter. The tracks of various widths were printed using needles of different diameters and the 0.5% aqueous colloidal solution of carbon nanotubes (CNTs) in 1 wt% of polyvinyl alcohol (PVA) ink was used. The electrical resistivity values of the printed tracks were obtained on a 5 mm section by the standard four-probe method, and they were within 0.040–0.008 Oh m−1.

Reusable electronics have received widespread attention and are urgently needed. Here, nanocellulose-based liquid metal (NC-LM) printed circuit has been fabricated by the evaporation-induced transfer printing technology. In this way, the liquid metal pattern is embedded into the nanocellulose membrane, which is beneficial for the stability of the circuit during use. Besides, the NC-LM circuit is ultrathin with just tens of microns. In particular, the finished product is environmentally friendly because it can be completely dissolved by water, and both the liquid metal ink and the nanocellulose membrane can be easily recollected and reused, thereby reducing waste and pollution to the environment. Several examples of flexible circuits have been designed to evaluate their performance. The mechanism of evaporation-induced transfer printing technology involves the deposition, aggregation, and coverage tightly of the nanosized cellulose fibrils as the water evaporated. This study provides an economical and environmentally friendly way for the fabrication of renewable flexible electronics.

Low operating voltages, rapid response, and high-throughput fabrication compatibility are key advantages for the development of electrolyte-gated field effect transistors (EGFETs) for biological sensing. Among the key components in EGFET biosensors, electrolyte materials are relatively less investigated, especially alternatives to water-based liquid electrolytes such as ionic liquids, ion gels, polyelectrolytes, and solid polymer electrolytes. These electrolytes enable portable devices and environmental stability superior to their water-based liquid alternatives. In this review, we offer an up-to-date evaluation of the state of EGFET research and gauge the strengths and limitations of high-performance electrolytes for use in EGFET biosensor applications as well as the potential for computer-aided design of such sensing platforms. The recent progress of EGFET biosensors for some popular analytes are reviewed and the performance of these alternative electrolytes in transistor biosensing is assessed. The challenges and opportunities for electrolytes in EGFETs are discussed for future research directions in this field.

Hybrid structural electronics (HSE) consists of printed electronics, conventional rigid electronics, and load-bearing supporting parts of a device (plastic, glass etc.). Extra-large area and flexible lighting elements with embedded light-emitting diodes (LEDs) are an example of such applications. LEDs can be used, for example, as light sources, to create smart surfaces for the architectural or automotive industry. Once the LEDs are embedded into the structure, they cannot be replaced. To make sustainable HSE products with long lifetime, the new type of designs is needed. The elements of HSE undergo conditions with elevated thermal stresses while in operation. That is known to have an impact on their performance and lifetime, thus making a proper heat management of the LED crucial. Due to the novel additive manufacturing methods, structures, and unconventional material combinations, many thermal management related aspects are not known. In this study, a two-step hybrid method, including thermal modeling and measurements, is used to estimate the thermal behavior of a surface-mounted LED on polymer substrate used in HSE. The model is created and simulated in COMSOL Multiphysics. The validity and accuracy of the model’s thermal behavior are verified through measurements with thermal transient measurements. Based on the experimental verification, the proposed simulation model only has small (less than 2%) temperature variations when compared with measurements. Hence, the developed model can be used as a basis for designing structural LED elements and predicting their performance characteristics in different user cases.

The innate capability of direct heat–electricity conversion endows thermoelectric (TE) materials with great application potential in the fields of low-grade heat harvesting, solid-state cooling, and sensing. Recently, the rapid development of information technology such as the Internet of Things and the popularization of wearable electronic devices have stimulated a period of prosperity for the research on flexible thermoelectric (FTE) devices. At the same time, the research on printed electronics (PEs) is expected to provide scalable and cost-effective manufacturing approaches for FTE devices. This review focuses on the recent progress in printed flexible thermoelectric (PFTE) devices and their applications. At first, the fundamental theories behind TEs and the related performance optimization strategies for FTE devices, as well as the history and applications of PEs, are introduced. Then, the state-of-the-art materials adopted in FTE devices, including materials for TE legs, solvents, dispersants, surfactants, and adhesives for printable inks/pastes, substrates, and electrodes, and the related printing methods are summarized. Subsequently, the applications and device performance of PFTE devices in thermoelectric generators (TEGs), thermoelectric coolers (TECs) and thermoelectric sensors (TESs) over the last decade are reviewed. At last, the challenges existing currently in the PFTE field are discussed and some perspectives on the future investigations toward high-performance, low-cost PFTE devices are proposed.

Printed sensors are among the most successful groups of devices within the domain of printed electronics, both in terms of their application versatility and the emerging market share. However, reports on fully printed gas sensors are rare in the literature, even though it can be an important development toward fully printed multisensor platforms for diagnostics, process control, and environmental safety-related applications. In this regard, here, we present the traditional tin oxide-based completely inkjet-printed co-continuous and mesoporous thin films with an extremely large surface-to-volume ratio and then investigate their NO2 sensing properties at low temperatures. A method known as evaporation-induced self-assembly (EISA) has been mimicked in this study using pluronic F127 (PEO106-PPO70-PEO106) as the soft templating agent and xylene as the micelle expander to obtain highly reproducible and spatially homogeneous co-continuous mesoporous crystalline SnO2 with an average pore diameter of the order of 15-20 nm. The fully printed SnO2 gas sensors thus produced show high linearity for NO2 detection, along with extremely high average response of 11,507 at 5 ppm NO2. On the other hand, the sensors show an ultralow detection limit of the order of 20 ppb with an easy to amplify response of 31. While the excellent electronic transport properties along such co-continuous, mesoporous structures are ensured by their well-connected (co-continuous) ligaments and pores (thereby ensuring high surface area and high mobility transport at the same time) and may actually be responsible for the outstanding sensor performance that has been observed, the use of an industrial printing technique ascertains the possibility of high-throughput manufacturing of such sensor units toward inexpensive and wide-range applications.

This work investigated the photophysical pathways for light absorption, charge generation, and charge separation in donor–acceptor nanoparticle blends of poly(3-hexylthiophene) and indene-C60-bisadduct. Optical modeling combined with steady-state and time-resolved optoelectronic characterization revealed that the nanoparticle blends experience a photocurrent limited to 60% of a bulk solution mixture. This discrepancy resulted from imperfect free charge generation inside the nanoparticles. High-resolution transmission electron microscopy and chemically resolved X-ray mapping showed that enhanced miscibility of materials did improve the donor–acceptor blending at the center of the nanoparticles; however, a residual shell of almost pure donor still restricted energy generation from these nanoparticles.

Evaporative self-assembly of semiconducting polymers is a low-cost route to fabricating micrometer and nanoscale features for use in organic and flexible electronic devices. However, in most cases, rate is limited by the kinetics of solvent evaporation, and it is challenging to achieve uniformity over length- and time-scales that are compelling for manufacturing scale-up. In this study, we report high-throughput, continuous printing of poly(3-hexylthiophene) (P3HT) by a modified doctor blading technique with oscillatory meniscus motion-meniscus-oscillated self-assembly (MOSA), which forms P3HT features ∼100 times faster than previously reported techniques. The meniscus is pinned to a roller, and the oscillatory meniscus motion of the roller generates repetitive cycles of contact-line formation and subsequent slip. The printed P3HT lines demonstrate reproducible and tailorable structures: nanometer scale thickness, micrometer scale width, submillimeter pattern intervals, and millimeter-to-centimeter scale coverage with highly defined boundaries. The line width as well as interval of P3HT patterns can be independently controlled by varying the polymer concentration levels and the rotation rate of the roller. Furthermore, grazing incidence wide-angle X-ray scattering (GIWAXS) reveals that this dynamic meniscus control technique dramatically enhances the crystallinity of P3HT. The MOSA process can potentially be applied to other geometries, and to a wide range of solution-based precursors, and therefore will develop for practical applications in printed electronics.

The conductivity of screen printing films at microwave frequency is one of the most important properties of conductive ink when applied in printed electronics. However, the existing methods of conductivity characterization at microwave frequency focus on homogeneous metal films or semiconductors, which are not suitable for conductive composite materials with poor thickness uniformity, like screen printing films. In this research, by applying a classic stripline ring resonator, a rigorous electromagnetic model was set up, and the conductivity of the screen printing film was able to be deduced by comparison between the measurement and simulation results. As a result, the equivalent conductivity of the film is 2 × 106 S/m at 1–3 GHz, which is a little higher than its average direct current conductivity of 1.82 × 106 S/m. This method has been proved to be feasible in measuring the conductivity of screen printing films at microwave frequency. Furthermore, it has great potential in the characterization of other printed conductive composite materials on rough surfaces, like textiles.

Flexographic printing, which involves high-speed contact of an inked stamp against a substrate, is of increasing interest for scalable manufacturing of electronics in new formats. However, the adaptation of flexography to thinner, finer features which are generally required for printed electronics requires improved understanding of stamp-substrate contact mechanics. Here, we present a desktop plate-to-roll (P2R) printing apparatus which enables the study of flexographic printing in a semi-continuous format that mimics industrial printing. In particular, we tailor the specifications of the machine to use nanoporous stamps which have been shown to enable flexographic printing of ultrathin ink features with micron-scale linewidth. Printing with nanoporous stamps requires precise control of stamp-substrate contact force (2–250 mN) and elimination of shear force at the interface among others; these are accomplished using a flexure-supported substrate, and by coordinated rotary-linear motion of the system. We detail the design and evaluation of the P2R machine and demonstrate printing of high-resolution features (

Printed electronics (PE) enables disruptive applications in wearables, smart sensors, and healthcare since it provides mechanical flexibility, low cost, and on-demand fabrication. The progress in PE raises trust issues in the supply chain and vulnerability to reverse engineering (RE) attacks. Recently, RE attacks on PE circuits have been successfully performed, pointing out the need for countermeasures against RE, such as camouflaging. In this article, we propose a printed camouflaged logic cell that can be inserted into PE circuits to thwart RE. The proposed cell is based on three components achieved by changing the fabrication process that exploits the additive manufacturing feature of PE. These components are optically look-alike, while their electrical behaviors are different, functioning as a transistor, short, and open. The properties of the proposed cell and standard PE cells are compared in terms of voltage swing, delay, power consumption, and area. Moreover, the proposed camouflaged cell is fabricated and characterized to prove its functionality. Furthermore, numerous camouflaged components are fabricated, and their (in)distinguishability is assessed to validate their optical similarities based on the recent RE attacks on PE. The results show that the proposed cell is a promising candidate to be utilized in camouflaging PE circuits with negligible overhead.

In printed electronics, coating is a key process used not only in the fabrication of solar cell and organic light-emitting diodes but also in display devices. For this purpose, coating devices are designed with several unique characteristics. In particular, slot die coaters and inkjet coaters are advantageous in terms of high-quality morphology and a small dispensing area, respectively. This study proposes a slot die with a narrow-width coating as a fusion device derived from a slot die coater and an inkjet printer. This device is termed a micro-slot die and comprises a micro pump and a narrow-width slot. The device was designed and assembled with appropriate consideration of both dynamic and fluid motions. Consequently, the fabricated device achieves a high-quality coating suitable for application in the display industry. The proposed device is expected to be used in laboratory-scale research applications that require a minimal coating of ink.

Eco-friendly and cost-effective materials and processes to manufacture functional substrates are crucial to further advance the area of printed electronics. One potential key component in the printed electronics platform is an electrically functionalized paper, produced by simply mixing common cellulosic pulp fibers with high-performance electroactive materials. Herein, an electronic paper including nanographite has been prepared using a standardized and scalable papermaking technique. No retention aid was needed to achieve a conducting nanographite loading as high as 50 wt %. The spontaneous retention that provides the integrity and stability of the nanographite paper, likely originates partially from an observed water-stable adhesion of nanographite flakes onto the fiber surfaces. The resulting paper exhibits excellent electrical characteristics, such as an in-plane conductivity of 107 S/cm and an areal capacitance of 9.2 mF/cm(2), and was explored as the back-electrode in printed electrochromic displays. Funding Agencies|Digital Cellulose Centre, a competence center set up by the Swedish Innovation Agency VINNOVA; consortium of Swedish forest industries; Wallenberg Wood Science Center (Knut and Alice Wallenberg Foundation); VINNOVA "EPIC" projectVinnova [2017-05413]; Karl-Erik Onnesjo Foundation

It is common in the field of printed electronics that polydimethylsiloxane (PDMS) be used as a dielectric layer for capacitive sensors because of its high elasticity and restoration force. However, capacitive sensors with the PDMS dielectric layer have a lower sensitivity than those with an air-gap structure that has been fabricated by the conventional micro-electromechanical system (MEMS) process. This paper presents a productive method for fabricating air-gap structures for touch sensors by roll-to-roll slot-die coating. The air-gap is formed by coating and removing a sacrificial layer. Cantilever-structured capacitive touch sensors with an air-gap are fabricated as follows: First, the bottom electrode, the dielectric layer, and the poly(vinyl alcohol) (PVA) sacrificial layer are roll-to-roll slot-die-coated on a flexible substrate. In addition, the spacer layer is spin-coated. On the sacrificial and spacer layers, the top electrode and structural layer are formed by spin-coating. Then, the air-gap and cantilever structure are made by removing the sacrificial layer in water. The cantilever-structured sensor samples are examined in terms of sensitivity, hysteresis, and repeatability. In particular, the electrical performance of the samples is compared to those with the PDMS dielectric layer. Experimental results show that the cantilever-structured sensor samples have significantly higher sensitivity compared to those with the PDMS dielectric layer.

Aerosol jet printing (AJP) is a promising method for micro-scaled digital additive manufacturing for printed electronics. It usually requires a high sintering temperature (280 °C) and a long sintering time (e.g., 12 h on a glass substrate) to guarantee a high conductivity of the printed structures, which has limited AJP to only a few types of substrates. Moreover, the printed metallic structure peels off from the substrate easily. In this paper, a procedure of AJP printing on cellulose fiber paper is proposed, which includes the use of cellulose fiber paper as the substrate, and a new sintering method, i.e., hot-air sintering with an optimized sequence. With the proposed approach, the sintering temperature is significantly lowered (80 °C), and the sintering time is considerably shortened (40 min). The printed structure has a measured sheet resistance of 1.13 × 10−2 Ω/m2 which is equivalent to a conductivity of greater than 106 S/m and close to that of the bulk silver (6.30 × 107 S/m), and it has good adhesion to the substrate. The determinant factors underlying the diffusion and curing processes of AJP, i.e., the properties of the substrate (cellulose fiber paper), the printing parameters, the sintering parameters, and the sequence were systematically investigated. The investigation is carried out through evaluation of the morphologies of the printed structures based on scanning electron microscope (SEM) images and through the study of the correlation between the morphology and the conductivity of the structures. Moreover, the proposed paper-based AJP electronics offer tremendous flexibility. They can be folded, bent, and pasted to any surface. This proposed cellulose-fiber-paper-based AJP opens a window for low-cost, eco-friendly, flexible, and high-resolution printed electronics. It will be an essential alternative fabrication approach for flexible electronic circuits, antennas, and electromagnetic-functioning surfaces, such as reconfigurable meta-surfaces.

The Printed Electronics (PE) is expected to revolutionise the way electronics will be manufactured in the future. Building on the achievements of the traditional printing industry, and the recent advances in flexible electronics and digital technologies, PE may even substitute the conventional silicon-based electronics if the performance of printed devices and circuits can be at par with silicon-based devices. In this regard, the inorganic semiconducting materials-based approaches have opened new avenues as printed nano (e.g. nanowires (NWs), nanoribbons (NRs) etc.), micro (e.g. microwires (MWs)) and chip (e.g. ultra-thin chips (UTCs)) scale structures from these materials have been shown to have performances at par with silicon-based electronics. This paper reviews the developments related to inorganic semiconducting materials based high-performance large area PE, particularly using the two routes i.e. Contact Printing (CP) and Transfer Printing (TP). The detailed survey of these technologies for large area PE onto various unconventional substrates (e.g. plastic, paper etc.) is presented along with some examples of electronic devices and circuit developed with printed NWs, NRs and UTCs. Finally, we discuss the opportunities offered by PE, and the technical challenges and viable solutions for the integration of inorganic functional materials into large areas, 3D layouts for high throughput, and industrial-scale manufacturing using printing technologies.

CuInSe2 nanocrystals offer promise for optoelectronics including thin-film photovoltaics and printed electronics. Additive manufacturing methods such as photonic curing controllably sinter particle...

X-ray tomographic reconstruction reveals that the distribution of Ag after inkjet printing and sintering a nanoparticle conducting ink on a woven polyester textile substrate is strongly controlled by the fiber surface properties and fabric architecture. Capillarity confines the transport of the ink predominantly within the warp or weft yarns of the fabric and there is little transport of ink between the yarns. Changing the fiber surface energy through the Scotchgard treatment leads to an increase in the contact angle, reducing ink transport along the fibers and an increase in conductance. A similar effect is seen when printed drop spacing is reduced, increasing the local Ag concentration. Electrical conductivity is strongly influenced by the fiber density in each yarn direction and, in this case, the different densities lead to different electrical conductance values. Through the use of image segmentation, it is possible to identify a low level of electrical interconnection between the warp and weft yarns. Conductance within a yarn is shown to depend on Ag concentration via a percolation mechanism and this is confirmed by a simple model relating the volume of the largest interconnected Ag object present to the measured conductance. These results illustrate the complexity of the interaction between conductive inks and fibrous substrates and that concepts, such as sheet resistance, used to characterize printed conductors on solid substrates are not applicable to textile substrates.

The study of photonic sintering has gained interest based on the advantages of fast processing at room temperature. However, printed electronics made from photonic sintering with an intensive pulsed light (IPL) energy source exhibit more mechanical instability than those made from conventional thermal sintering processes. To solve the mechanical instability problems, we fabricated Ag flake hybrid pastes with a variety of concentrations of Ag flake (0, 25, 50, 75, and 100 wt.%). All of the screen-printed hybrid Ag circuits were fabricated on polyimide substrates and were sintered at 3.5 MW. Surface porosity was analyzed using the Brunauer-Emmett-Teller method. An IPC (Packaging Electronic Circuits) sliding test was performed to analyze the flexibility of the screen-printed Ag flake hybrid circuits. The adhesion strength of the hybrid circuits was evaluated with a roll-type 90° peel test. The hybrid Ag printed circuit showed improvements in both the flexibility and adhesion strength with the addition of Ag flake.

E-jet is a novel microfabrication technology of producing high-resolution patterns for various application areas like printed electronics, biotechnology, etc. Judicious selection of the operating scenario can improve the quality of the fabrication performance of E-jet. The objective of this study is to experimentally evaluate different operating scenarios of the E-jet microfabrication process while considering the deposited droplet diameter and droplet ejection frequency as performance characteristics simultaneously. Experimentations were carried out on the developed E-jet setup according to the design of experiment technique considering nozzle stand-off height, applied voltage, and ink flow rate as process control parameters. The effect of each control parameter on the process response is investigated. The relative weight values of each performance characteristic or response variable are determined by principal component analysis, which makes the weight evaluation procedure more rigorous and eliminates the dependence on the practitioner’s judgment. A hybrid grey relational grade analysis and technique for order preference by similarity to ideal solution methodology is employed to evaluate the optimal operating scenario of E-jet. Both methodologies indicated a similar desirable operating condition for E-jet. Moreover, the variance study called analysis of variance is employed to discover the pattern in which the control parameters affect the fabrication process. The variance study suggests that the ink flow rate is the most dominant parameter in the experimental domain.

Different conductive bonding strategies for the hybrid integration of flexible, inkjet-printed electronics are investigated. The focus of the present work lies on providing a practical guide comprising standard techniques that are inexpensive, easily implementable and frequently used. A sample set consisting of identical conductive test structures on different paper and plastic substrates was prepared using silver (Ag) nanoparticle ink. The sintered specimens were electrically contacted using soldering, adhesive bonding and crimping. Electrical and mechanical characterization before and after exposing the samples to harsh environmental conditions was performed to evaluate the reliability of the bonding methods. Resistance measurements were done before and after connecting the specimens. Afterwards, 85 &deg, C/85% damp-heat tests and tensile tests were applied. Adhesive bonding appears to be the most suitable and versatile method, as it shows adequate stability on all specimen substrates, especially after exposure to a 85 &deg, C/85% damp-heat test. During exposure to mechanical tensile testing, adhesive bonding proved to be the most stable, and forces up to 12 N could be exerted until breakage of the connection. As a drawback, adhesive bonding showed the highest increase in electrical resistance among the different bonding strategies.

Graphene (G) has been combined with carboxymethyl cellulose (C) for the development of environmentally friendly inks for printed electronics applications. Water based ink formulations have been developed for screen printing with graphene content up to 90 wt.%. The printed patters show a good distribution of the graphene within the cellulose matrix, allowing a good screen-printed pattern definition with line thickness of 200 μm. The electrical percolation threshold is found around 0.18 of volume fraction, corresponding to 1.9 wt.% of graphene in the ink composition. A maximum electrical conductivity of ρ= 1.8×10-2 Ω.m has been obtained for the G90:C10 ink composition, allowing the printing of suitable conductive patters for printed electronics. Further, the multifunctionality of the developed inks is demonstrated by the interesting thermoresistive and piezoresistive properties of the screen-printed G30:C70 and G65:C35 materials, respectively. The maximum thermoresistive sensitivity of S=-0.27 and piezoresistive Gauge-Factor of 1, This work has been supported by national funds through FCT – Fundação para a Ciência e Tecnologia within the Strategic Project UID/FIS/04650/2020, projects PTDC/FISMAC/28157/2017 and PTDC/BTM-MAT/28237/2017, and grant SFRH/BPD/110914/2015 (PC). We also tank the FEDER and ANI project with reference POCI-01-0247-FEDER-033566. Financial support from the Basque Government Industry and Education Department under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs, respectively, is also acknowledged. Graphenest is also acknowledge for supplying the high-quality graphene used in this work.

Polyacrylic acid (PAA) applied as surface modifier of zero-valent copper nanoparticles (CuNPs) for electronic printing inks has great potential to replace presently used polymers, because of its favorable technical, environmental and biodegradability characteristics. Continuous synthesis (400°C, 30 MPa) of nanoparticles in supercritical water with short reaction times (1.1 s) was used to form PAA-surface-modified zero-valent (34–46 nm) CuNPs. CuNP particle sizes decreased with an increase in PAA molecular mass (5000, 250,000) and were stable as dispersions in methanol and 1-propanol, respectively. The resistivity of conductive films prepared with CuNPs decreased with an increase in heating temperature. The minimum resistivity of the PAA-modified CuNPs was 1.4 × 10−5 Ω cm at 320°C (PAA25000) and 4.2 × 10−4 Ω cm at 350°C (PAA5000), demonstrating the feasibility of PAA as a dispersant and surface modifier for CuNPs. Polyacrylic acid is thus effective as a surface modifier for zero-valent metal nanoparticles and expands the possible applications in sustainable printed electronics.

Laser-induced graphitization (LIG) is a method of converting a carbon-rich precursor into a highly conductive graphite-like carbon by laser scribing. This method has shown great promise as a versatile and low-cost patterning technique. Here we show for the first time how an ink based on cellulose and lignin can be patterned using screen printing followed by laser graphitization. Screen printing is one of the most commonly used manufacturing techniques of printed electronics, making this approach compatible with existing processing of various devices. The use of forest-based materials opens the possibility of producing green and sustainable electronics. Pre-patterning of the ink enables carbon patterns without residual precursor between the patterns. We investigated the effect of the ink composition, laser parameters, and additives on the conductivity and structure of the resulting carbon and could achieve low sheet resistance of 3.8 Ω sq−1 and a high degree of graphitization. We demonstrated that the process is compatible with printed electronics and finally manufactured a humidity sensor which uses lignin as the sensing layer and graphitized lignin as the electrodes.

Recent advances in nanomaterials and nano-microfabrication have enabled the development of flexible wearable electronics. However, existing manufacturing methods still rely on a multi-step, error-prone complex process that requires a costly cleanroom facility. Here, we report a new class of additive nanomanufacturing of functional materials that enables a wireless, multilayered, seamlessly interconnected, and flexible hybrid electronic system. All-printed electronics, incorporating machine learning, offers multi-class and versatile human-machine interfaces. One of the key technological advancements is the use of a functionalized conductive graphene with enhanced biocompatibility, anti-oxidation, and solderability, which allows a wireless flexible circuit. The high-aspect ratio graphene offers gel-free, high-fidelity recording of muscle activities. The performance of the printed electronics is demonstrated by using real-time control of external systems via electromyograms. Anatomical study with deep learning-embedded electrophysiology mapping allows for an optimal selection of three channels to capture all finger motions with an accuracy of about 99% for seven classes., Though wearable electronics remain an attractive technology for bioelectronics, fabrication methods that precisely print biocompatible materials for electronics are needed. Here, the authors report an additive manufacturing process that yields all-printed nanomaterial-based wireless electronics.

In printed electronics systems, the roll-to-roll process is a next-generation process technology that may be applied to the production of various electronic products such as flexible electronic devices, solar cells, and display panels. The process allows for production at low unit cost and high speed. As a factor for improving the print quality, there are ink viscosity, printing speed, printing pressure, and alignment precision. Among these factors, alignment precision, a critical factor in the performance of an electronic circuit, is the accurate alignment of layers in a multi-layered structure. In our previous study, we suggested a measurement method for improving the alignment precision by using an optical pre-measuring device and an alignment pattern that is printed by roll-to-roll printing process. In the measuring system, when a web is transported in the web feed direction, the optical pre-measuring device measures the quantity of light reflected by the alignment pattern. A lateral position can be aligned accurately based on the measured signal. However, because the position is measured in advance in the web feed direction, it is not applicable to a real-time printing system, and when the lateral position is measured using the optical pre-measuring device, a lateral position error, that is generated by disturbances induced by tension acting on the web and the vibration of the motor, can be estimated. A motor driven linear translation stage for lateral direction is used to minimize the lateral position errors in roll-to-roll systems. In this paper, we propose a preview control system to reflect the measured lateral position error to the printing result at the appropriate time for improving the alignment precision in roll-to-roll printing. As a control method, using roll-to-roll model, the system of disturbance, lateral angle and lateral position can be expressed as a state-space equation. Based on this equation, a preview controller to find the optimal value of state and control error is designed in a similar method to the conventional preview control method used for the active suspension system of a vehicle. Then, the alignment results are verified using another optical measuring device of a web transport system.

Metal nanoparticles have become attractive as original materials for nano-inks and nano-pastes, which are used in printed electronics. Synthesizing various metal nanoparticles has been researched. We investigated the possibility of reducing metal oxide in a metal by using high-voltage pulses in this paper. This method should save electrical consumption power compared with conventional methods that use high-temperature and high-pressure plasma such as arc discharge. Reduced Al nanoparticles were obtained by applying high-voltage pulses to solutions. By analyzing elements and the composition of reduced Al nanoparticles by STEM and EDX, a large amount of reduced Al nanoparticles with diameters of a few 100 nm and thin oxide film of around 1 nm on metal surfaces were produced in experiments for reducing Al oxide. It was found from hydrogen generation using reduced Al nanoparticles by applying high-voltage pulses to solutions to evaluate reduction rate that a high reduction efficiency of 97% was obtained at maximum. We concluded that using high-voltage pulses for reduction can be suitably applied to printed electronics because the oxide film on reduced Al nanoparticles is thin. Also, because this method is similar to laser ablation in liquids using pulse lasers, the similarities were discussed in this paper.

Advances in printed electronics (PE) enables new applications, particularly in ultra-low-cost domains. However, achieving high-throughput printing processes and manufacturing yield is one of the major challenges in the large-scale integration of PE technology. In this article, we present a programmable printed circuit based on an efficient printed lookup table (pLUT) to address these challenges by combining the advantages of the high-throughput advanced printing and maskless point-of-use final configuration printing. We propose a novel pLUT design which is more efficient in PE realization compared to existing LUT designs. The proposed pLUT design is simulated, fabricated, and programmed as different logic functions with inkjet printed conductive ink to prove that it can realize digital circuit functionality with the use of programmability features. The measurements show that the fabricated LUT design is operable at 1 V.

Printed electronics (PE) is a fast-growing field with promising applications in wearables, smart sensors, and smart cards, since it provides mechanical flexibility, and low-cost, on-demand, and customizable fabrication. To secure the operation of these applications, true random number generators (TRNGs) are required to generate unpredictable bits for cryptographic functions and padding. However, since the additive fabrication process of the PE circuits results in high intrinsic variations due to the random dispersion of the printed inks on the substrate, constructing a printed TRNG is challenging. In this article, we exploit the additive customizable fabrication feature of inkjet printing to design a TRNG based on electrolyte-gated field-effect transistors (EGFETs). We also propose a printed resistor tuning flow for the TRNG circuit to mitigate the overall process variation of the TRNG so that the generated bits are mostly based on the random noise in the circuit, providing a true random behavior. The simulation results show that the overall process variation of the TRNGs is mitigated by 110 times, and the generated bitstream of the tuned TRNGs passes the National Institute of Standards and Technology – Statistical Test Suite. For the proof of concept, the proposed TRNG circuit was fabricated and tuned. The characterization results of the tuned TRNGs prove that the TRNGs generate random bitstreams at the supply voltage of down to 0.5 V. Hence, the proposed TRNG design is suitable to secure low-power applications in this domain.

There is great interest in carbon-based printed electronics as a promising technology to achieve lighter, thinner and flexible electronic devices at low-costs. Despite the surge of enthusiasm in this area, research advances in printed electronics are not yet able to realize diverse carbon structures yet. This is due to the limitations in conventional solution-based printing methods (e.g., inkjet printing, roll-to-roll, screen printing). Processes such as polymer phase-inversion offer one possibility but a much faster and efficient method should be devised for reliable production. Here, we demonstrate laser printing combined with intense pulsed-light (IPL) annealing as a novel and efficient technique which can form inter-connected carbon spheres electrode on flexible polymer substrate. Our observations show that the printed patterns from a laser printer consist of a solid-state polymer matrix with inorganic nanoparticles randomly embedded inside. Through ultrafast (5 ms) IPL treatment, core/shell type nanosphere arrays of carbon-coated SiO2 were successfully fabricated, which could be used as a functional platform for highly selective NO2 gas sensing.

For the commercialization of a resistive switching memory device, many researchers are designing different memory structures for a crossbar array. In the present work, we propose a flexible Schottky diode-based resistive memory device based on a zinc oxide (ZnO) and methylene blue (MB) heterojunction. The operating voltage of the proposed memory device is ±3 V, and high-resistance state (HRS) and low-resistance state (LRS) are 20.408 GΩ and 126.795 MΩ, respectively, and the Roff/Ron ratio is ∼ 160.97 at a voltage read of −0.30 V. It shows high retention and endurance performance for more than 500 cycles and 30 days, respectively, with bending capability up to 10 mm. The proposed device can be used in flexible and printed electronics for memory and storage purposes.

Eddy current heating with synchronized thermography (ST) is utilized for the contactless characterization of flexible hybrid electronics. A proposed approach is used for analyzing the uniformity of large area electronics being the basis for the quality assurance of hybrid electronics manufacturing. Flexible polymer substrate with printed conductors, bonded conventionally manufactured light-emitting diode (LED) chips and current regulators were used as test samples. Obtained results show that ST with eddy current heating is an effective and roll-to-roll compatible measurement tool for in-situ quality monitoring of hybrid electronics manufacturing.

In-mold electronics (IME) is a novel manufacturing technology which combines printed electronics and film insert molding to produce electronics-integrated plastic components. Basically, the IME process includes printing, thermoforming, and injection molding. During the thermoforming process, the printed circuit undergoes deformation which results in a variation of the electrical resistance of the circuit, and, therefore, the thermoforming process is one of the important processes which determine the performance of the IME product. In this regard, this study aims to investigate the details of the resistance variation based on the deformation of the printed circuit during the thermoforming process. The deformation of the printed circuit is characterized experimentally and numerically, while a regression model is constructed to describe the relationship between deformation and electrical resistance of the circuit. Then, the electrical resistance distribution of the circuit after the thermoforming process is predicted based on the numerical results and the regression model, which is compared with experimental data. The effect of geometrical parameter is also investigated both experimentally and numerically.

Electrochromic devices (ECDs) with reversible transmittance change represent a promising alternative to smart windows. However, the low−cost facile fabrication of ECDs, particularly flexible devices, remains challenging. In this study, novel NiO is synthesized by a solid state method, and the as−prepared NiO is introduced as an electrochromic anodic layer and fabricated onto a transparent conductive electrode (indium tin oxide, ITO or flexible silver nanowires, AgNW) by a sol–gel spin coating and low temperature annealing (80 °C-150 °C). The solvent, thickness of NiO, and annealing temperature are evaluated to obtain higher ECD performance. NiO/ITO ECDs exhibit very high transmittance variation (ΔT = ~84%) at 700 nm with applied potentials of −3.0 and 0 V. The stability and transmittance variation of NiO/ITO are significantly improved in the presence of a WO3 cathodic electrode at lower applied voltages of 1.5 to 0 V. The low processing temperature of 80 °C demonstrates the potential of the flexible ECDs. The flexible NiO–WO3 device achieves a transmittance variation of ~38% at 700 nm with applied potential of 2.0 and 0 V, and retains the ECD performance. The application of low−cost solution−processed NiO and NiO/WO3−based ECDs in flexible transparent conductive electrodes provides a new pathway for the fabrication of optical devices and printed electronics.

Hypothesis Most functional inkjet inks are sterically stabilized nanoparticle dispersions that require a post-printing-process to remove stabilizing materials and gain functionality. This post-process limits material selection and increases fabrication time and complexity for printed devices. By optimizing the electrostatic stability of a carbon nanomaterial dispersed in water or ethylene glycol via pH adjustment, a stable and printable ink should be attainable without a steric stabilizing material and hence the post-process may be avoided. Experiments The electrostatic stability of multilayer graphene nanoshells (MGNS)—an inexpensive and net carbon-negative nanomaterial—dispersed in water and ethylene glycol was studied by measuring zeta potential as a function of pH and modeling energetic potentials between particles. Requirements for electrical percolation of printed MGNS were analyzed and corroborated with electrical measurements. Findings Electrostatic stability improved with increased zeta potential caused by an increased pH. Ionic strength also increased with pH, causing strong destabilization. By increasing zeta potential while minimizing ionic strength, the maximum solid-loading of MGNS in DI water and ethylene glycol was increased up to 20%. For the MGNS solid-loading achieved here, electrical percolation occurs with 20–30 consecutively printed layers producing a resistivity of 30 Ω-cm. The inexpensive, environmentally-friendly MGNS are a promising material for printed, flexible electronics.