The authors would like to acknowledge the BPI PIAVE AUTONOTEX grant for the financial support.

1. Patterning Conducting Polymers on Textile
<ol>
	<li>Fix a 10 cm x 10 cm textile sheet on a planar surface for easy handling during the process. For the textile, use a 100% interlock knit polyester fabric with a thickness of 300 &#181;m and a knit direction stretch capability up to 50%.</li>
	<li>To make a mask containing the patterning design, use a 125 &#181;m-thick polyimide film; an example of the pattern is illustrated in Figure 1.
	<ol>
		<li>Use a laser cutter (e.g., Protolaser S, LPKF) to pattern the polyimide mask10; the pattern design of an electrode is illustrated in Figure 1.</li>
		<li>Coat the PDMS formulation (10:1 base to curing agent ratio) on top of the mask (polyimide film) using an automatic tape casting tool (K control print-coater, doctor blade) with a wet film thickness of 200 &#181;m and at a 6 m/min coating speed. Use about 0.5 mL for a mask of 3 cm x 5 cm. Perform this process under the fume hood.</li>
	</ol>
	</li>
	<li>Gently transfer the fabric to the PDMS-coated mask. Leave for 10 min, after which the PDMS should be fully absorbed in the textile structure.</li>
	<li>Cure the sample in an air-oven at 100 &#176;C for 10 min.</li>
	<li>Prepare the conducting polymer:PEDOT:PSS dispersion (80 mL), ethylene glycol (20 mL), 4-dodecylbenzenesulfonic acid (40 &#181;L), and 3-methacryloxypropyltrimethoxysilane (1 mL) in the fume hood.</li>
	<li>Brush-coat the PEDOT:PSS solution on the PDMS-free area of the textile until a homogenous penetration of the solution is obtained. Repeat this step to achieve a uniform pattern color. Apply about 1 mL/cm2.</li>
	<li>Cure the fabric at 110 &#176;C for 1 h to dry the PEDOT:PSS solution. Reduce the temperature to 60 &#176;C for textiles that are sensitive to high-temperature treatment, like nylon.</li>
</ol>
2. Organic Device Fabrication
NOTE: The protocol in Section 1 describes the selective deposition of conducting materials on textiles. The following sections will describe the additional steps needed to fabricate organic devices, like stretch sensors, OECT transistors, cutaneous electrodes, and capacitive sensors.
<ol>
	<li>To fabricate stretch sensors, shown in Figure 3a, pattern the electrode lines on the textile, as described in Section 1, steps 1.1-1.5. 
	NOTE: An example of the pattern design is shown in Figure 3a. The fabrication of such sensors does not require any additional steps.</li>
	<li>To fabricate the transistor design shown in Figure 3b, pattern the transistor arrays on a nylon woven ribbon following the steps described in Section 1. Slightly modify the PDMS annealing and PEDOT:PSS curing steps to avoid the thermal degradation of nylon by curing at 60 &#176;C for a longer time.</li>
	<li>For the fabrication of cutaneous electrodes, shown in Figure 3c, deposit an ionic gel on the patterned PEDOT:PSS textiles.
	<ol>
		<li>Prepare an ionic liquid gel mixture containing the ionic liquid, 1-ethyl-3-methylimidazolium-ethyl sulfate; the cross-linking agent, poly(ethylene glycol)diacrylate; and the photoinitiator, 2-hydroxy-2-methylpropiophenone at a (v/v) ratio of 0.6/0.35/0.05, respectively.</li>
		<li>Coat the PEDOT:PSS electrode with ionic liquid (20 &#181;L/cm2) and add the ionic liquid gel mixture from step 2.3.1 (25 &#181;L/cm2) by drop casting.</li>
		<li>Expose to UV light (365 nm) to initiate a crosslinking reaction for 10-15 min, until the gel solidifies. Perform this step in the fume hood. Use a UV-protective cage during UV exposure.</li>
	</ol>
	</li>
	<li>For capacitive sensor fabrication, use PEDOT:PSS textile electrodes insulated with an insulating material (Figure 3d).
	<ol>
		<li>Insulate the keyboard-like PEDOT:PSS electrodes using the PDMS; the keyboard design can be seen in Figure 2b. Dispense the PDMS formulation on top of the fabric and remove the excess with a squeegee.</li>
		<li>Place the fabric in an oven at 100 &#176;C for 10 min. Perform this step in the fume hood.</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

The patterning of conducting materials is one of the first steps in the fabrication of functional electronic devices. This can become challenging, as the fabrication process needs to take into account the chemical and physical properties of such materials, and the process flow needs to consider the material cross-compatibility between the fabrication steps. In the microfabrication of organic electronic devices, these two aspects are even more significant due to the highly reactive nature of organics. Today, however, organic materials are highly attractive to wearable and flexible electronics for their electro-elastic properties14,15. The transfer of such technologies to textiles to obtain fully integrated electronic wearables is limited by their three-dimensional structures. Conventional techniques used in microfabrication are restricted to inkjet or screen printing of conducting inks only on thin substrates and textiles16,17,18. Traditional embroidery technique, where a single fiber is sewn into the textile, still lacks industrial production scalability.
The most critical aspect in the patterning of organic materials is deposition without disturbing the electrical properties. The patterning technique described in Figure 1 relies on the direct deposition of organics, with no need to meet specifications of the deposition technique or the tool. The organic materials are formulated to the best of their performances and can then be directly deposited on the chosen fabric structure. The utility of PDMS is key to pattern materials from solution onto textiles. The application of conducting materials from the low-viscosity solution, rather than using paste-like inks, enables a conformal and deep coating in textile structure. However, it limits the selective deposition and leads to the loss of the patterning resolution. We have overcome this limitation by creating a negative pattern from PDMS to restrain the non-controlled conducting solution penetration into the textile. The strategic choice of the PDMS is based on its visco-elastic properties, which maintain the textile stretchability and flexibility. The PDMS is also hydrophobic and allows the control of the spreading of the PEDOT:PSS water-based solution during the patterning. We observed that the conductive patterns fabricated using this protocol demonstrated good electrical conductivity and stability during mechanical deformations. This method allows the future customization of existing garments with smart components that have electronic capabilities. However, one of the critical and, in some cases, limiting points of the proposed approach is still organic material durability in wearable conditions. Some aspects, such as mechanical stress resistance and behavior after the washing and drying of organic conducting textiles, are still unknown.
The large majority of wearable electronics rely on stretchable devices, where spring-like structures are created to maintain the electrical connection during device deformation. Depending on the textile type, the fibers in knit fabrics are assembled in a horseshoe design, providing mechanical stretchability of the structure. Coating these textiles with conducting materials permits individual fibers to act as strain and motion sensors in smart clothing, as shown in Figure 3a. Moreover, more complex device geometries can easily be patterned, not only on knit, but also on woven fabrics. In Figure 3b, we present an array of OECTs with variable geometries. In conventional photolithography, the simultaneous fabrication of big and small features is almost impossible to achieve without requiring multiple steps. We demonstrate that our patterning technique is able to produce patterns with a resolution that varies from 0.5 mm to about a hundred times greater. Such transistors can be directly used in wearable sweat sensing with an adjustable time response and detection resolution19.
We have demonstrated that PDMS also enables the consecutive deposition of additional functional layers in a selective manner, as shown in Figure 2. Devices can then be integrated in textiles and become fully integrated on wearable systems. The process in Figure 2a shows the fabrication of a cutaneous textile electrode, where the contact between the electrode and the skin is enhanced with an ionic liquid gel. Wearable electrodes in cutaneous electrophysiology suffer from motion artifacts caused by the electrical contact degradation between the wearer and electrodes during recordings. The possibility to integrate ionic gels on textile electrodes opens an efficient communication channel with the human body, which is desired in wearable healthcare devices. An example of such a device can be seen in Figure 3c.
The consecutive deposition of other active materials can result in devices using a stack geometry, such as organic batteries, capacitors, solar cells, transistors, or sensors. Figure 2b shows the deposition route of insulating or dielectric materials. A wearable organic keyboard (Figure 3d) can be fabricated using this process, where the PDMS is used to create a dielectric layer on top of the electrode. Such a device is capable of capacitive variation sensing between the electrode and a finger, which can have potentially interesting applications in wearable computing and human-machine interfacing.

The field of wearable electronics is a fast-growing market expected to be worth 50 billion euros in 2025, over three times the current market. The main challenge facing current wearable devices is that intrusive solid electronic attachments limit the usage of established devices in wearable systems. Using textiles that are already present in everyday life is a very attractive and straightforward approach to avoid this limitation. Due to its elastic capability, some parts of the clothing that we wear are naturally in tight contact with the skin. Many examples of smart clothes available on the market today are based on thin, plastic displays, keyboards, and light source devices embedded in textiles, linking electronics with humans in a fashionable way1. In sport practice, health monitoring relies on textile electrodes, which offer comfortable alternatives to commonly used adhesive electrodes and metal wristbands. Here, conductive fibers are directly integrated with stretchy fabrics to prevent skin irritation and other discomforts during extended wear. Additionally, textiles offer a number of opportunities to integrate curvature sensors to capture motion2, to integrate shear sensors for the development of functional robotic actuators3, and certainly to integrate biosensors through the detection of an analyte in sweat4.
Modern wearable technology relies on carbon-based semiconductor materials that deliver electronic devices with unique properties. The &#34;soft&#34; nature of organics offers better mechanical properties for interfacing with the human body compared to traditional solid-state electronics. This mechanical compatibility, paired with mechanically flexible substrates, enables the use of non-planar form factors in devices such as textiles. The use of organics is also relevant in life sciences due to their mixed electronic and ionic conductivity5. Besides, organic semiconducting and optoelectronic materials empower a large variety of functional devices with display, transistor, logic, and power capabilities6,7,8,9. The main difficulty in the fabrication of such organic devices is the controlled deposition of functional materials on the non-planar surfaces of textiles. Conventional microfabrication techniques are primarily limited by the incompatibility of the deposition process with the structural dimensionality of textile substrates.
Here, we describe a simple and scalable fabrication protocol that allows for the selective deposition of conducting polymers on structured textiles. The presented process enables the fabrication of wearable and conformal electronic devices. The approach is based on the patterning of the commercially available conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and an elastomeric stencil material polydimethylsiloxane (PDMS) on textile. This combination allows for the efficient confinement of the aqueous PEDOT:PSS solution, as well as for the retention of the soft and stretchable properties of textiles. This simple and reliable fabrication method paves the way for the fabrication of a variety of electronic devices directly on textiles in a cost-efficient and industrially scalable manner.

<table><tbody><tr><td>SYLGARD 184, Silicone elastomer kit (Base and Curing agent)</td><td>Dow Corning</td><td></td><td>PDMS elastomer</td></tr><tr><td colspan="4">&lt;strong&gt;The conducting polymer formulation&lt;/strong&gt;</td></tr><tr><td>CleviosTM PH 1000 PEDOT:PSS</td><td>Heraeus</td><td></td><td>Conductive polymer</td></tr><tr><td>Ethylene glycol</td><td>Sigma-Aldrich</td><td>03750-250ML</td><td>Solvent (EG), CAS: 107-21-1</td></tr><tr><td>3-methacryloxypropyltrimethoxysilane</td><td>Sigma-Aldrich</td><td>M6514</td><td>Cros linker (GOPs), CAS: 2530-85-0</td></tr><tr><td>4-dodecylbenzenesulfonic acid</td><td>Sigma-Aldrich</td><td>44198</td><td>DBSA; CAS: 121-65-3</td></tr><tr><td colspan="4">&lt;strong&gt;The ionic liquid gel&lt;/strong&gt;</td></tr><tr><td>UV lamp DFE 2340</td><td>C.I.F/ ATHELEC</td><td>DP134</td><td>UV-365 nm</td></tr><tr><td>1-Ethyl-3-methylimidazolium ethyl sulfate</td><td>Sigma-Aldrich</td><td>51682-100G-F</td><td>Ionic Liquid (IL), CAS: 342573-75-5</td></tr><tr><td>Poly(ethylene glycol) diacrylate</td><td>Sigma-Aldrich</td><td>455008-100ML</td><td>Mn 700, CAS: 26570-48-9</td></tr><tr><td>2-Hydroxy-2-methylpropiophenon</td><td>Sigma-Aldrich</td><td>405655-50ML</td><td>Phot Initiator (PI), CAS: 7473-98-5</td></tr><tr><td>The textile fabric</td><td>VWR</td><td>Spec-Wipe 7 Wipers</td><td>100% interlock knit polyester fabric</td></tr><tr><td>The polyimide film</td><td>DuPont</td><td>HN100</td><td>Polyimide film with 125 &amp;micro;m thickness</td></tr></tbody></table>

a simple and scalable fabrication method for organic electronic devices on textiles

Today, wearable electronics devices combine a large variety of functional, stretchable, and flexible technologies. However, in many cases, these devices cannot be worn under everyday conditions. Therefore, textiles are commonly considered the best substrate to accommodate electronic devices in wearable use. In this paper, we describe how to selectively pattern organic electroactive materials on textiles from a solution in an easy and scalable manner. This versatile deposition technique enables the fabrication of wearable organic electronic devices on clothes.

Traditional methods for applying colors or patterns to textiles rely on removable masking layers to allow the selective deposition of dyes. In Figure 1, we show the adaptation of such an approach to the patterning of PEDOT:PSS electrodes on textiles. As a masking layer, we used hydrophobic polydimethylsiloxane, which can restrain the non-controllable diffusion of the aqueous PEDOT:PSS solution. Moreover, the softness and stretchability of knitted and woven textiles can be preserved thanks to the elastic and mechanical properties of the PDMS.
In Figure 1, the process starts with the preparation of the patterning master from polyimide film (step 1). The design of the pattern outline is carved onto the film by a laser. Using a tape casting tool, the PDMS is applied on this master (step 2), and the textile is placed on top of it (step 3). The PDMS is then progressively diffused into the textile (step 4). To stop this transfer, a short thermal annealing process is required to cure the PDMS. The viscosity and thickness of the PDMS can be adjusted by using different amounts of the curing agent and coating parameters, respectively, to control the diffusion and to insure the faultless replication of the master design. Finally, the conducting solution is brush-painted on the unprotected textile and baked to dry (step 5). The polyimide master is then delaminated from the textile surface. The results of the fabrication flow are illustrated in Figure 1, on the right. In this case, successful patterning was placed on knitted polyester. The patterning resolution on such a textile is greater than 1 mm. However, lower resolution can also be obtained on tightly knit or woven textiles. Using this deposition technique, the estimated sheet resistance of the conducting textile is close to 230 &#937;/sq.
Examples of functional electronic devices on knit and woven textiles are shown in Figure 3a and b, including successfully fabricated PEDOT:PSS electrodes on knit textiles. The natural horseshoe arrangement of the fibers in knit textiles provides adjustable stretchability to fabrics. This spring-like capability of knit structures can result in highly sensitive strain sensors11. A simple deformation in the textile structure is reflected by a change in the electrical resistivity due to the twisting of conductive fibers in the threads. Additionally, by taking advantage of the hygroscopic capacity of the textiles, the array of electrodes in Figure 3b was patterned on textiles to make planar transistors with rectangular channels and different gate widths, which can be used in wearable sweat sensing. Such a geometrical configuration is used in organic electrochemical transistors (OECT) for sensing which channel and gate are linked by a sample of an analyte12.
The presented patterning technique can be extended to fabricate complex organic electronic devices on textiles. As the PDMS stencil remains in the textile after the patterning process, additional layers can be patterned on PEDOT:PSS-coated conducting textiles. In Figure 2, we present the process in which an ionic liquid gel solution (Figure 2a) and the PDMS formulation (Figure 2b) were applied to functionalize or isolate the surface of a PEDOT:PSS electrode, respectively. Ionic gels are largely used in cutaneous electrodes. The incorporation of an ionic gel in conducting textiles was used to fabricate wearable textile electrodes for electrophysiological monitoring10 and is illustrated in Figure 3c. Capacitive sensors were made by insulating the textile electrode surface with PDMS. A change in the capacitance was detected when the electrode was touched. Such a touch-sensitive device was used to fabricate an organic electronic textile keyboard13, as shown in Figure 3d.
<img alt="Figure 1" src="/files/ftp_upload/55439/55439fig1.jpg" /> 
Figure 1. Process flow illustrating the patterning of conducting polymers onto textiles. Process flow illustrating the patterning of conducting polymers onto textiles. Step 1: mask preparation; step 2: PDMS deposition on the polyimide patterning mask defining the outline of the desired design; step 3: transfer of the masking layer by the placement of the textile on the PDMS-coated mask; step 4: transfer of the PDMS into the bulk of the textile, step 5: deposition of conducting polymer solution onto unprotected textile. The pictures on the right show the results of the key steps of the process flow. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55439/55439fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/55439/55439fig2.jpg" /> 
Figure 2. Two examples of fabrication organic devices. Two examples of fabrication organic devices. a) Ionic liquid gel coating on the PEDOT:PSS textile electrode for cutaneous sensing. b) Insulation layer deposition on the PEDOT:PSS textile electrode for touch sensors. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55439/55439fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" src="/files/ftp_upload/55439/55439fig3.jpg" /> 
Figure 3. Photographs of organic electronic textile devices. a) PEDOT:PSS electrodes for stretch sensing. b) Array of OECT transistors for wearable biosensing. c) Circular PEDOT:PSS electrode coated with an ionic liquid gel for cutaneous electrophysiology. d) Organic touch sensors for a wearable keyboard. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55439/55439fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

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A Simple and Scalable Fabrication Method for Organic Electronic Devices on Textiles

In this paper, we present a protocol to selectively deposit organic materials on textiles, which allows for the direct integration of organic electronic devices with wearables. The fabricated devices can be fully integrated in textiles, respecting their mechanical appearance and enabling sensing capabilities.

Today, wearable electronics devices combine a large variety of functional, stretchable, and flexible technologies. However, in many cases, these devices ...

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Nanyang Technological University

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Bioengineering

10.4K Views.  Ecole Nationale Supérieure des Mines de Saint-Étienne, CMP-EMSE, MOC. In this paper, we present a protocol to selectively deposit organic materials on textiles, which allows for the direct integration of organic electronic devices with wearables. The fabricated devices can be fully integrated in textiles, respecting their mechanical appearance and enabling sensing capabilities.

Video: A Simple and Scalable Fabrication Method for Organic Electronic Devices on Textiles

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Engineering

Fabrication of Fully Solution Processed Inorganic Nanocrystal Photovoltaic Devices

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal inks. For the photoactive absorber layer, colloidal CdTe and CdSe nanocrystals (3-5 nm) are synthesized using an inert hot injection technique and cleaned with precipitations to remove excess starting reagents. Similarly, gold nanocrystals (3-5 nm) are synthesized under ambient conditions and dissolved in organic solvents. In addition, precursor solutions for transparent conductive indium tin oxide (ITO) films are prepared from solutions of indium and tin salts paired with a reactive oxidizer. Layer-by-layer, these solutions are deposited onto a glass substrate following annealing (200-400 &#176;C) to build the nanocrystal solar cell (glass/ITO/CdSe/CdTe/Au). Pre-annealing ligand exchange is required for CdSe and CdTe nanocrystals where films are dipped in NH4Cl:methanol to replace long-chain native ligands with small inorganic Cl- anions. NH4Cl(s) was found to act as a catalyst for the sintering reaction (as a non-toxic alternative to the conventional CdCl2(s) treatment) leading to grain growth (136&#177;39 nm) during heating. The thickness and roughness of the prepared films are characterized with SEM and optical profilometry. FTIR is used to determine the degree of ligand exchange prior to sintering, and XRD is used to verify the crystallinity and phase of each material. UV/Vis spectra show high visible light transmission through the ITO layer and a red shift in the absorbance of the cadmium chalcogenide nanocrystals after thermal annealing. Current-voltage curves of completed devices are measured under simulated one sun illumination. Small differences in deposition techniques and reagents employed during ligand exchange have been shown to have a profound influence on the device properties. Here, we examine the effects of chemical (sintering and ligand exchange agents) and physical treatments (solution concentration, spray-pressure, annealing time and annealing temperature) on photovoltaic device performance.

This protocol describes the synthesis and solution deposition of inorganic nanocrystals layer by layer to produce thin film electronics on non-conductive surfaces. Solvent-stabilized inks can produce complete photovoltaic devices on glass substrates via spin and spray coating following post-deposition ligand exchange and sintering.

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal ...

Sensing of Barrier Tissue Disruption with an Organic Electrochemical Transistor

The gastrointestinal tract is an example of barrier tissue that provides a physical barrier against entry of pathogens and toxins, while allowing the passage of necessary ions and molecules. A breach in this barrier can be caused by a reduction in the extracellular calcium concentration. This reduction in calcium concentration causes a conformational change in proteins involved in the sealing of the barrier, leading to an increase of the paracellular flux. To mimic this effect the calcium chelator ethylene glycol-bis(beta-aminoethyl ether)-N,N,N&#39;,N&#39;-tetra acetic acid (EGTA) was used on a monolayer of cells known to be representative of the gastrointestinal tract. Different methods to detect the disruption of the barrier tissue already exist, such as immunofluorescence and&#160;permeability assays. However, these methods are time-consuming and costly and not suited to dynamic or high-throughput measurements. Electronic methods for measuring barrier tissue integrity also exist for measurement of the transepithelial resistance (TER), however these are often costly and complex. The development of rapid, cheap, and sensitive methods is urgently needed as the integrity of barrier tissue is a key parameter in drug discovery and pathogen/toxin diagnostics. The organic electrochemical transistor (OECT) integrated with barrier tissue forming cells has been shown as a new device capable of dynamically monitoring barrier tissue integrity. The device is able to measure minute variations in ionic flux with unprecedented temporal resolution and sensitivity, in real time, as an indicator of barrier tissue integrity. This new method is based on a simple device that can be compatible with high throughput screening applications and fabricated at low cost.

The Organic Electrochemical Transistor is integrated with live cells and used to monitor ion flux across the gastrointestinal epithelial barrier. In this study, an increase in ion flux, related to disruption of tight junctions, induced by the presence of the calcium chelator EGTA (ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetra acetic acid), is measured.

The gastrointestinal tract is an example of barrier tissue that provides a physical barrier against entry of pathogens and toxins, while allowing the ...

Scalable Solution-processed Fabrication Strategy for High-performance, Flexible, Transparent Electrodes with Embedded Metal Mesh

Here, the authors report the embedded metal-mesh transparent electrode (EMTE), a new transparent electrode (TE) with a metal mesh completely embedded in a polymer film. This paper also presents a low-cost, vacuum-free fabrication method for this novel TE; the approach combines lithography, electroplating, and imprint transfer (LEIT) processing. The embedded nature of the EMTEs offers many advantages, such as high surface smoothness, which is essential for organic electronic device production; superior mechanical stability during bending; favorable resistance to chemicals and moisture; and strong adhesion with plastic film. LEIT fabrication features an electroplating process for vacuum-free metal deposition and is favorable for industrial mass production. Furthermore, LEIT allows for the fabrication of metal mesh with a high aspect ratio (i.e., thickness to linewidth), significantly enhancing its electrical conductance without adversely losing optical transmittance. We demonstrate several prototypes of flexible EMTEs, with sheet resistances lower than 1 &#937;/sq and transmittances greater than 90%, resulting in very high figures of merit (FoM) &#8211; up to 1.5 x 104 &#8211; which are amongst the best values in the published literature.

This protocol describes a solution-based fabrication strategy for high-performance, flexible, transparent electrodes with fully-embedded, thick metal mesh. Flexible transparent electrodes fabricated by this process demonstrate among the highest reported performances, including ultra-low sheet resistance, high optical transmittance, mechanical stability under bending, strong substrate adhesion, surface smoothness, and environmental stability.

Here, the authors report the embedded metal-mesh transparent electrode (EMTE), a new transparent electrode (TE) with a metal mesh completely embedded in a ...

Reactive Vapor Deposition of Conjugated Polymer Films on Arbitrary Substrates

We demonstrate a method of conformally coating conjugated polymers on arbitrary substrates using a custom-designed, low-pressure reaction chamber. Conductive polymers, poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-propylenedioxythiophene) (PProDOT), and a semiconducting polymer, poly(thieno[3,2-b]thiophene) (PTT), were deposited on unconventional highly-disordered and textured substrates with high surface areas, such as paper, towels and fabrics. This reported deposition chamber is an improvement of previous vapor reactors because our system can accommodate both volatile and nonvolatile monomers, such as 3,4-propylenedioxythiophene and thieno[3,2-b]thiophene. Utilization of both solid and liquid oxidants are also demonstrated. One limitation of this method is that it lacks sophisticated in situ thickness monitors. Polymer coatings made by the commonly used solution-based coating methods, such as spin-coating and surface grafting, are often not uniform or susceptible to mechanical degradation. This reported vapor phase deposition method overcomes those drawbacks and is a strong alternative to common solution-based coating methods. Notably, polymer films coated by the reported method are uniform and conformal on rough surfaces, even at a micrometer scale. This feature allows for future application of vapor deposited polymers in electronics devices on flexible and highly textured substrates.

This paper presents a protocol for reactive vapor deposition of poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), and poly(thieno[3,2-b]thiophene) films on glass slides and rough substrates, such as textiles and paper.

We demonstrate a method of conformally coating conjugated polymers on arbitrary substrates using a custom-designed, low-pressure reaction chamber. ...

Chemistry

Fabrication of Flexible Image Sensor Based on Lateral NIPIN Phototransistors

Flexible photodetectors have been intensely studied for the use of curved image sensors, which are a crucial component in bio-inspired imaging systems, but several challenging points remain, such as a low absorption efficiency due to a thin active layer and low flexibility. We present an advanced method to fabricate a flexible phototransistor array with an improved electrical performance. The outstanding electrical performance is driven by a low dark current owing to deep impurity doping. Stretchable and flexible metal interconnectors simultaneously offer electrical and mechanical stabilities in a highly deformed state. The protocol explicitly describes the fabrication process of the phototransistor using a thin silicon membrane. By measuring I-V characteristics of the completed device in deformed states, we demonstrate that this approach improves the mechanical and electrical stabilities of the phototransistor array. We expect that this approach to a flexible phototransistor can be widely used for the applications of not only next-generation imaging systems/optoelectronics but also wearable devices such as tactile/pressure/temperature sensors and health monitors.

We present a detailed method to fabricate a deformable lateral NIPIN phototransistor array for curved image sensors. The phototransistor array with an open mesh form, which is composed of thin silicon islands and stretchable metal interconnectors, provides flexibility and stretchability. The parameter analyzer characterizes the electrical property of the fabricated phototransistor.

Flexible photodetectors have been intensely studied for the use of curved image sensors, which are a crucial component in bio-inspired imaging systems, ...

Fabrication and Characterization of a Conformal Skin-like Electronic System for Quantitative, Cutaneous Wound Management

Recent advances in the development of electronic technologies and biomedical devices offer opportunities for non-invasive, quantitative assessment of cutaneous wound healing on the skin. Existing methods, however, still rely on visual inspections through various microscopic tools and devices that normally include high-cost, sophisticated systems and require well trained personnel for operation and data analysis. Here, we describe methods and protocols to fabricate a conformal, skin-like electronics system that enables conformal lamination to the skin surface near the wound tissues, which provides recording of high fidelity electrical signals such as skin temperature and thermal conductivity. The methods of device fabrication provide details of step-by-step preparation of the microelectronic system that is completely enclosed with elastomeric silicone materials to offer electrical isolation. The experimental study presents multifunctional, biocompatible, waterproof, reusable, and flexible/stretchable characteristics of the device for clinical applications. Protocols of clinical testing provide an overview and sequential process of cleaning, testing setup, system operation, and data acquisition with the skin-like electronics, gently mounted on hypersensitive, cutaneous wound and contralateral tissues on patients.

This article presents methods to fabricate and characterize a conformal, skin-like electronic system and protocols for the use in clinical applications, particularly on cutaneous wound management.

Recent advances in the development of electronic technologies and biomedical devices offer opportunities for non-invasive, quantitative assessment of ...

Hybrid Printing for the Fabrication of Smart Sensors

A method to combine additively manufactured substrates or foils and multilayer inkjet printing for the fabrication of sensor devices is presented. First, three substrates (acrylate, ceramics, and copper) are prepared. To determine the resulting material properties of these substrates, profilometer, contact angle, scanning electron microscope (SEM), and focused ion beam (FIB) measurements are done. The achievable printing resolution and suitable drop volume for each substrate are, then, found through the drop size tests. Then, layers of insulating and conductive ink are inkjet printed alternately to fabricate the target sensor structures. After each printing step, the respective layers are individually treated by photonic curing. The parameters used for the curing of each layer are adapted depending on the printed ink, as well as on the surface properties of the respective substrate. To confirm the resulting conductivity and to determine the quality of the printed surface, four-point probe and profilometer measurements are done. Finally, a measurement set-up and results achieved by such an all-printed sensor system are shown to demonstrate the achievable quality.

Here we present a protocol for the fabrication of inkjet-printed multilayer sensor structures on additively manufactured substrates and foil.

A method to combine additively manufactured substrates or foils and multilayer inkjet printing for the fabrication of sensor devices is presented. First, ...

Development of Efficient OLEDs from Solution Deposition

The use of highly efficient organic emitters based on the thermally activated delayed fluorescence (TADF) concept is interesting due to their 100% internal quantum efficiency. Presented here is a solution deposition method for the fabrication of efficient organic light-emitting diodes (OLEDs) based on a TADF emitter in a simple device structure. This fast, low-cost, and efficient process can be used for all OLED emissive layers that follow the host-guest concept. The fundamental steps are described along with necessary information for further reproduction. The goal to establish a general protocol that can be easily adapted for principal organic emitters currently under study and development.

Presented here is a protocol for the fabrication of efficient, simple, solution-deposited organic light-emitting diodes with low roll-off.

The use of highly efficient organic emitters based on the thermally activated delayed fluorescence (TADF) concept is interesting due to their 100% ...

Fabrication of Fine Electrodes on the Tip of Hypodermic Needle Using Photoresist Spray Coating and Flexible Photomask for Biomedical Applications

We have introduced a fabrication method for electrical impedance spectroscopy (EIS)-on-a-needle (EoN: EIS-on-a-needle) to locate target tissues in the body by measuring and analyzing differences in the electrical impedance between dissimilar biotissues. This paper describes the fabrication method of fine interdigitated electrodes (IDEs) at the tip of a hypodermic needle using a photoresist spray coating and flexible film photomask in the photolithography process. A polyethylene terephthalate (PET) heat shrink tube (HST) with a wall thickness of 25 &#181;m is employed as the insulation and passivation layer. The PET HST shows a higher mechanical durability compared with poly(p-xylylene) polymers, which have been widely used as a dielectric coating material. Furthermore, the HST shows good chemical resistance to most acids and bases, which is advantageous for limiting chemical damage to the EoN. The use of the EoN is especially preferred for the characterization of chemicals/biomaterials or fabrication using acidic/basic chemicals. The fabricated gap and width of the IDEs are as small as 20 &#181;m, and the overall width and length of the IDEs are 400 &#181;m and 860 &#181;m, respectively. The fabrication margin from the tip (distance between the tip of hypodermic needle and starting point of the IDEs) of the hypodermic needle is as small as 680 &#181;m, which indicates that unnecessarily excessive invasion into biotissues can be avoided during the electrical impedance measurement. The EoN has a high potential for clinical use, such as for thyroid biopsies and anesthesia drug delivery in a spinal space. Further, even in surgery that involves the partial resection of tumors, the EoN can be employed to preserve as much normal tissue as possible by detecting the surgical margin (normal tissue that is removed with the surgical excision of a tumor) between the normal and lesion tissues.

The fabrication method for fine interdigitated electrodes (gap and width: 20 &#181;m) at the tip of a hypodermic needle (diameter: 720 &#181;m) is demonstrated using a spray coating and flexible film photomask in the photolithography process.

We have introduced a fabrication method for electrical impedance spectroscopy (EIS)-on-a-needle (EoN: EIS-on-a-needle) to locate target tissues in the ...

A Simple and Scalable Fabrication Method for Organic Electronic Devices on Textiles

Summary

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Chapters in this video

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Fabrication of Fully Solution Processed Inorganic Nanocrystal Photovoltaic Devices

Sensing of Barrier Tissue Disruption with an Organic Electrochemical Transistor

Scalable Solution-processed Fabrication Strategy for High-performance, Flexible, Transparent Electrodes with Embedded Metal Mesh

Reactive Vapor Deposition of Conjugated Polymer Films on Arbitrary Substrates

Fabrication of Flexible Image Sensor Based on Lateral NIPIN Phototransistors

Fabrication and Characterization of a Conformal Skin-like Electronic System for Quantitative, Cutaneous Wound Management

Hybrid Printing for the Fabrication of Smart Sensors

Development of Efficient OLEDs from Solution Deposition

Fabrication of Fine Electrodes on the Tip of Hypodermic Needle Using Photoresist Spray Coating and Flexible Photomask for Biomedical Applications