Transfer Printing Research Articles

3D Wetting Gradient Janus Sports Bras for Efficient Sweat Removal: A Strategy to Improve Women's Sports Comfort and Health.

Developing Janus fabrics with excellent one-way sweat transport capacity is an attractive way for providing comfort sensation and protecting the health during exercise. In this work, a 3D wetting gradient Janus fabric (3DWGJF) is first proposed to address the issue of excessive sweat accumulation in women's breasts, followed by integration with a sponge pad to form a 3D wetting gradient Janus sports bra (3DWGJSB). The 3D wetting gradient enables the prepared fabric to control the horizontal migration of sweat in one-way mode (x/y directions) and then unidirectionally penetrate downward (z direction), finally keeping the water content on the inner side of 3DWGJF (skin side) at ≈0%. In addition, the prepared 3DWGJF has good water vapor transmittance rate (WVTR: 0.0409gcm-2h-1) and an excellent water evaporation rate (0.4704gh-1). Due to the high adhesion of transfer prints to the fabrics and their excellent mechanical properties, the 3DWGJF is remarkably durable and capable of withstanding over 500 laundering cycles and 400 abrasion cycles. This work may inspire the design and fabrication of next-generation moisture management fabrics with an effective sweat-removal function for women's health.

Dual‐Interface Competitive Fracture Model for Curvature‐Based Transfer Printing Method

AbstractTransfer printing is a key technology in the fabrication of flexible electronics. Transfer printing method based on curvature provides a simple and effective way to transfer films onto weakly adhesive or even adhesiveless surfaces, overcoming the shortage of traditional transfer printing methods that it is difficult to print functional materials from strong interface to weak interface and can only be applicable to surfaces with certain interfacial strength. So far, the theoretical principle of the curvature‐based transfer printing method has not yet been developed. In this article, a dual‐interface competitive fracture model is established to analyze the mechanism of printing and picking up processes and quantitatively provide the critical transfer printing radius in terms of material and geometric properties of the transfer printing system. This model is verified to be both correct and widely applicable by rich experimental results, providing a new and reliable theory for the fabrication of inorganic flexible electronics.

Non‐Contact Transfer Printing Enabled by an Ultrasonic Droplet Stamp

AbstractTransfer printing is an important material heterogeneous technique with unique capability for developing existing and envisioned electronic or optoelectronic systems. Here, a simple design of ultrasonic droplet stamp is reported featuring a water droplet on an acoustic resonator attached to a glass sheet, for developing an efficient non‐contact transfer printing. The water droplet offers the benefits of a gentle and conformal contact, yielding an enough adhesion for a reliable pickup in the absence of ultrasound, and ejects a sub‐droplet rapidly due to the Raleigh instability with the ultrasound for an easy non‐contact printing. Experimental studies are carried out to investigate the transient response of ultrasonic droplet stamp under the action of ultrasound and showed that the proposed stamp exhibited extraordinary capabilities of damage‐free pickup and receiver‐independent printing. Demonstrations of the ultrasonic droplet stamp in transfer printing of thin inks with different materials and shapes onto various flat, curved and rough surfaces illustrate its great potential for heterogeneous integration and deterministic assembly.

Damage-free dry transfer method using stress engineering for high-performance flexible two- and three-dimensional electronics.

Advanced transfer printing technologies have enabled the fabrication of high-performance flexible and stretchable devices, revolutionizing many research fields including soft electronics, optoelectronics, bioelectronics and energy devices. Despite previous innovations, challenges remain, such as safety concerns due to toxic chemicals, the expensive equipment, film damage during the transfer process and difficulty in high-temperature processing. Thus a new transfer printing process is needed for the commercialization of high-performance soft electronic devices. Here we propose a damage-free dry transfer printing strategy based on stress control of the deposited thin films. First, stress-controlled metal bilayer films are deposited using direct current magnetron sputtering. Subsequently, mechanical bending is applied to facilitate the release of the metal bilayer by increasing the overall stress. Experimental and simulation studies elucidate the stress evolution mechanisms during the processes. By using this method, we successfully transfer metal thin films and high-temperature-treated oxide thin films onto flexible or stretchable substrates, enabling the fabrication of two-dimensional flexible electronic devices and three-dimensional multifunctional devices.

Moisture self-regulating ionic skins with ultra-long ambient stability for self-healing energy and sensing systems

Dehydration has been a key limiting factor for the operation of conductive hydrogels in practical application. Here, we report self-healable ionic skins that can self-regulate their internal moisture level by capturing extenral moistures via hygroscopic ion-coordinated polymer backbones through antipolyelectrolyte effect. Results show the ionic skin can maintain its mechanical and electrical functions over 16 months in the ambient environment with high stretchability (fracture stretch ∼2216 %) and conductivity (23.5 mS/cm). The moisture self-regulating capability is further demonstrated by repeated exposures to harsh environments such as 200°C heating, freezing, and vacuum drying with recovered conductivity and stretchability. Their reversible ionic and hydrogen bonds also enable self-healing feature as a sample with the fully cut-through damage can restore its conductivity after 24 h at 40 % relative humidity. Utilizing the ionic skin as a building block, self-healing flexible piezoelecret sensors have been constructed to monitor physiological signals. Together with a facile transfer-printing process, a self-powered sensing system with a self-healable supercapacitor and humidity sensor has been successfully demonstrated. These results illustrate broad-ranging possibilities for the ionic skins in applications such as energy storage, wearable sensors, and human-machine interfaces.

Three-dimensional triboelectric nanogenerator manufacturing using water transfer printing

Triboelectric nanogenerators (TENGs) have been widely studied due to their efficient energy harvesting capabilities and fast electrical response signals. In this study, a processing method based on water transfer printing (WTP) is developed for preparing TENG devices with three-dimensional (3D) structures. With this method, electrodes and ink layers can be integrated onto a variety of 3D objects to form a one-piece structure, which offers advantages including application to 3D surfaces, abrasion resistance, handling ease, adaptability, and decorativeness. The process istaken to prepare a 5 × 5 cm2 single-electrode TENG (IF-TENG), with FEP serving as the negative triboelectric layer and ink serving as the positive triboelectric layer. The TENG’s open-circuit voltage and short-circuit current are 184 V and 1.53 μA, respectively. Additionally, a door handle TENG (DH-TENG) device has been built for practical application demonstrations. The DH-TENG device is used in wireless alarm systems that prevent children from accidentally ingesting medication. It is also used in self-powered guidance systems that illuminate LED arrow lights to help the elderly or children at night. Seamless integration of 3D surface TENG devices using WTP is expected to have applications in smart home systems, smart transportation and security, wearable electronics, and energy harvesting.

Prototyping of microelectrode devices applied by transfer printing

In this study, ion implantation was adopted to treat the surface of the mold to improve detachability in the nanoimprinting. A nanoimprinting was performed successfully for the fabrication of a micro-electrode pattern with the smallest dimension of 100 nm by using the treated mold with proper conditions. It is found that both the wettability and roughness of the mold surface affect the detachability and it is important to decrease the wettability and keep the surface roughness lower. An optimal dose volume exists for the detachability.

Wafer-Scale GaN-Si(100) Monolithic Heterogeneous Integration Inverters With Improved Output Voltage Swing and Fast Switching Capability by Transfer Printing and Self-Aligned Etching Technology

Wafer-Scale GaN-Si(100) Monolithic Heterogeneous Integration Inverters With Improved Output Voltage Swing and Fast Switching Capability by Transfer Printing and Self-Aligned Etching Technology

The Effectiveness of Thermal Transfer Printing (Sublimation) on Metal Surfaces to Enrich the Appearance of Jewelry

The Effectiveness of Thermal Transfer Printing (Sublimation) on Metal Surfaces to Enrich the Appearance of Jewelry

84‐1: Invited Paper: Flexible Transparent Micro‐LED Array for Applications in Display and Visible Light Communication

In this work, based on transfer printing technology, planar integration of RGB InGaN‐based micro‐LEDs on flexible transparent material was realized. By measuring the optoelectronic parameters, we demonstrated the feasibility of this integrated device in full‐color display applications. In addition, based on the on‐off keying modulation and wavelength division multiplexing, visible light communication in parallel channels can be achieved. Relevant studies have demonstrated the broad prospects of InGaN‐based micro‐LED devices in multifunctional flexible integrated optoelectronics applications.

High-performance near-infrared OLEDs maximized at 925 nm and 1022 nm through interfacial energy transfer

Using a transfer printing technique, we imprint a layer of a designated near-infrared fluorescent dye BTP-eC9 onto a thin layer of Pt(II) complex, both of which are capable of self-assembly. Before integration, the Pt(II) complex layer gives intense deep-red phosphorescence maximized at ~740 nm, while the BTP-eC9 layer shows fluorescence at > 900 nm. Organic light emitting diodes fabricated under the imprinted bilayer architecture harvest most of Pt(II) complex phosphorescence, which undergoes triplet-to-singlet energy transfer to the BTP-eC9 dye, resulting in high-intensity hyperfluorescence at > 900 nm. As a result, devices achieve 925 nm emission with external quantum efficiencies of 2.24% (1.94 ± 0.18%) and maximum radiance of 39.97 W sr−1 m−2. Comprehensive morphology, spectroscopy and device analyses support the mechanism of interfacial energy transfer, which also is proved successful for BTPV-eC9 dye (1022 nm), making bright and far-reaching the prospective of hyperfluorescent OLEDs in the near-infrared region.

Tunable and Reversible Adhesive of Liquid Metal Ferrofluid Pillars for Magnetically Actuated Noncontact Transfer Printing.

Transfer printing techniques based on tunable and reversible adhesives enable the heterogeneous integration of materials in desired layouts and are essential for developing both existing and envisioned electronic systems. Here, a novel tunable and reversible adhesive of liquid metal ferrofluid pillars for developing an efficient magnetically actuated noncontact transfer printing is reported. The liquid metal ferrofluid pillars offer the appealing advantages of gentle contact force by minimizing the preload effect and exceptional shape adaptability by maximizing the interfacial contact area due to their inherent fluidity, thus enabling a reliable damage-free pickup. Moreover, the liquid metal ferrofluid pillars harness the rapid stiffness increase and shape change with the magnetic field, generating an instantaneous ejection force to achieve a receiver-independent noncontact printing. Demonstrations of the adhesive of liquid metal ferrofluid pillars in transfer printing of diverse objects with different shapes, materials and dimensions onto various substrates illustrate its great potential in deterministic assembly.

Contribution of Plant Transfer Printing to Sustainable Fashion

Nowadays, there is a growing awareness of environmental protection, new findings in the field of sustainable chemistry, the use of biodegradable materials, and the increased use of eco-friendly textile products. For this reason, natural dyes are being used more and more frequently, giving rise to a new way of decorating textiles, namely, plant transfer printing, popularly known as “eco-printing”, in which the shape and/or pigment of a plant is transferred to the textile. In addition, the great interest of the young generation in the application and research into the use of natural dyes can create incentives for cultural and social sustainability through the preservation of national heritage. Plant transfer printing is a method that combines scientific technology and artistic design with corresponding benefits for the eco system. The very fact that the patterns are unique and unpredictable brings out the notion of artistic freedom. In the work, plant transfer printing was carried out on undyed cotton material and on material dyed with pomegranate peels, walnut leaves, coffee, and aleppo pine bark. The influence of the pH value and the capillarity of the fabric, as well as the treatment of the leaves with iron(II) sulphate heptahydrate solution, on the aesthetics of the print and the colour fastness during washing was investigated. Based on the optimised parameters and a sustainable fabric design, the clothing collection “Hamadryad”, inspired by Greek mythology, was realised.

Cutting nanodisks in graphene down to 20 nm in diameter

A direct focused He+ beam direct machining is presented to fabricate solid-state nano-disk at the surface of a graphene multilayer micro-flake deposited on an Au/Ti/sapphire surface. At irradiation doses larger than 5.0 × 1017 ions cm−2 and with a beam size well below 1 nm, graphene disks down to 20 nm in diameter have been machined with for nano-disk down to 50 nm in diameter, a central hole for preparing the positioning of a rotation axle. The local heat generated by this irradiation is inducing a partial graphene amorphization and deformation, leading to a complete graphene nano-disk vaporization at doses larger than 5 × 1018 ions cm−2. A dry transfer printing technique followed by a graphene surface cleaning was used to transfer the nano-disks from its initial surface to a fresh and clean surface. Tapping mode atomic force micrograph have been recorded to follow the vaporization as a function of the He+ dose to confirm the graphene solid-state nano-disk fabrication limit to about 20 nm with this process.

Multiscale Transfer Printing via Shape Memory Polymer with High Adhesion and Modulus Switchability.

Flexible electronics have gained significant attention as an innovative solution to meet the growing need for information collection from the human body and the environment. However, a critical challenge lies in the need for a transfer printing technique that can fabricate rigid and brittle devices on flexible organic substrates. Here, we develop a multiscale transfer printing technique using an ultraviolet-curable shape memory polymer (SMP) that serves as both the stamp and the receiver substrate. The SMP demonstrates exceptional mechanical performance with toughness at room temperature and remarkable flexibility near its glass transition temperature. The SMP material exhibits an impressive shape recovery ratio and remarkable adhesion switchability. We demonstrate robust transfer printing of diverse objects with different materials and morphologies and in situ transfer of multiscale metallic structures. In addition, the in situ fabricated transparent hyperthermia patches with embedded metal grids are demonstrated, offering potential application in the field of sensors, wearable devices, and electronic skin.

Highly stretchable and customizable microneedle electrode arrays for intramuscular electromyography.

Stretchable three-dimensional (3D) penetrating microelectrode arrays have potential utility in various fields, including neuroscience, tissue engineering, and wearable bioelectronics. These 3D microelectrode arrays can penetrate and conform to dynamically deforming tissues, thereby facilitating targeted sensing and stimulation of interior regions in a minimally invasive manner. However, fabricating custom stretchable 3D microelectrode arrays presents material integration and patterning challenges. In this study, we present the design, fabrication, and applications of stretchable microneedle electrode arrays (SMNEAs) for sensing local intramuscular electromyography signals ex vivo. We use a unique hybrid fabrication scheme based on laser micromachining, microfabrication, and transfer printing to enable scalable fabrication of individually addressable SMNEA with high device stretchability (60 to 90%). The electrode geometries and recording regions, impedance, array layout, and length distribution are highly customizable. We demonstrate the use of SMNEAs as bioelectronic interfaces in recording intramuscular electromyography from various muscle groups in the buccal mass of Aplysia.

Hybrid Transfer Printing of Liquid Metals and Allied Inks for Rapid Fabrication of Multifunctional Soft Electronics.

The newly emerging liquid metal flexible electronics are gaining increasing applications over the world due to their outstanding adaptability and printability. Here, we proposed a generalized purpose thermo-activated hybrid transfer printing method for the rapid fabrication of multifunctional soft electronics, which can significantly reduce the difficulty facing existing technologies. This printing involves two delivery and deposition processes of liquid metals and the allied inks (toners) based on their adhesion selection mechanisms. Through developing office supplies, the laser printer could directly print toner masks on soft substrates, such as polydimethylsiloxane film. The heating plate was applied to remove the toner sacrificial mask after rolling liquid metal inks, resulting in retaining the liquid metal circuits on the target substrate. For illustration, diverse materials and inks are adapted to the strategy of constructing flexible electronics. Particularly, colorful circuits, flexible heaters, transparent circuitry, and soft programmable light-emitting diode array displays with multilayer circuits have been fabricated and tested. This general and easily accessible method allows for the rapid acquisition of user-designed soft electronics and is expected to promote the widespread use of flexible electronics in e-skin, sensing, displays, etc.

Recent Developments in Quantum Dot Patterning Technology for Quantum Dot Display

Colloidal quantum dot (QDs) have emerged as a crucial building block for LEDs due to their size-tunable emission wavelength, narrow spectral line width, and high quantum efficiency. Tremendous efforts have been dedicated to improving the performance of quantum dot light-emitting diodes (QLEDs) in the past decade, primarily focusing on optimization of device architectures and synthetic procedures for high quality QDs. However, despite these efforts, the commercialization of QLEDs has yet to be realized due to the absence of suitable large-scale patterning technologies for high-resolution devices., This review will focus on the development trends associated with transfer printing, photolithography, and inkjet printing, and aims to provide a brief overview of the fabricated QLED devices. The advancement of various quantum dot patterning methods will lead to the development of not only QLED devices but also solar cells, quantum communication, and quantum computers.

MEMS flexible conformal hydrophone based on heterogeneous integration technology

PurposeHuman-induced marine environmental noise, such as commercial shipping and seismic exploration, is concentrated in the low-frequency range. Meanwhile, low-frequency sound signals can achieve long-distance propagation in water. To meet the requirements of long-distance underwater detection and communication, this paper aims to propose an micro-electro-mechanical system (MEMS) flexible conformal hydrophone for low-frequency underwater acoustic signals. The substrate of the proposed hydrophone is polyimide, with silicon as the piezoresistive unit.Design/methodology/approachThis paper proposes a MEMS heterojunction integration process for preparing flexible conformal hydrophones. In addition, sensors prepared based on this process are non-contact flexible sensors that can detect weak signals or small deformations.FindingsThe experimental results indicate that making devices with this process cannot only achieve heterogeneous integration of silicon film, metal wire and polyimide, but also allow for customized positions of the silicon film as needed. The success rate of silicon film transfer printing is over 95%. When a stress of 1 Pa is applied on the x-axis or y-axis, the maximum stress on Si as a pie-zoresistive material is above, and the average stress on the Si film is around.Originality/valueThe flexible conformal vector hydrophone prepared by heterogeneous integration technology provides ideas for underwater acoustic communication and signal acquisition of biomimetic flexible robotic fish.

Contact stiffness of the multi-indenter contact interface

Mechanical contact plays a pivotal role in both industrial and daily life applications. Contact stiffness of a multi-indenter contact interface fundamentally determines force–deformation relations. However, the understanding of the overall contact stiffness from the historical perspective is limited owing to inherent difficulties in precisely characterizing the interaction in multi-indenter contacts. In this study, the mechanical strong interaction among indenters is pinpointed. A theoretical model for accurately determining the contact stiffness of multi-indenter contact interface is developed. The physical mechanism of the contact stiffness of multi-indenter contact interface is revealed. The theoretical model is solidly validated by experiment and simulation. More importantly, the present theoretical model can predict the contact stiffness of contact interfaces with complex and irregular configurations, which may be filled up with indenters of hierarchical structures. The critical load is determined to guarantee the finished product rate during transfer printing. This is experimentally evidenced by the transfer printing of silicon wafers with complexly customized patterns. The present study provides a profound guidance for various engineering applications such as fabrication and integration of micro- and nano-electronic chips as well as electronic devices.