Name: Spray-Coated Melanin/PEDOT:PSS Films for Sustainable Organic Electrochemical Transistors (Video) | JoVE Journal
Uploaded: 2025-10-28T12:30:00.000+00:00
Duration: 8 min 26 s
Description: Discover spray coating of Melanin/PEDOT:PSS films for high-performance organic electrochemical transistors. This scalable method enables precise control over film thickness and morphology for bioelectronic applications.

ai_agent_IP

ai_agent

maintenance

instantTrialDurationMinutes

isBiopharma

enableNewMyJoveSectionDesign

educationFeatures

seoMetaApi

ai_copilot_institution_blacklist

ai_chat_institution_blacklist

freeAccessWindow

ssoRoleCapture

scheduledMaintenanceBanner

joveLabsFeatures

disable_autoplay_for_bots

extended_trial_duration

5 minutes

This study was financed, in part, by the S&#227;o Paulo Research Foundation (FAPESP), Brazil (process numbers 2013/07296-2, 2020/12356-8, 2022/00410-3, 2022/10998-8, 2025/00301-8); and FINEP (Grant: 01.22.0289.00 (0034-21)). CFOG is thankful for the support of the Brazilian National Council for Scientific and Technological Development (CNPq) under the Instituto Nacional de Ci&#234;ncia e Tecnologia de Nanomateriais para a Vida (NanoVIDA) n&#176; 406079/2022-6.

1. Melanin synthesis and Melanin/PEDOT:PSS blends preparation
<ol>
	<li>Melanin synthesis
	<ol>
		<li>Add 0.3 g of 3,4-dihydroxy-DL-phenylalanine (DL-DOPA) to a glass beaker. Add 60 mL of deionized water to the&#160;beaker to dissolve the DL-DOPA under magnetic stirring.</li>
		<li>Transfer the DL-DOPA solution to the polytetrafluoroethylene (PTFE) liner in a stainless-steel reactor. Add 400 &#181;L of ammonium hydroxide (NH4OH) to start the oxidation process. Close the stainless-steel reactor and increase the pressure to 6 atm with industrial oxygen gas (99.5% purity). Keep under magnetic stirring for 6 h.</li>
		<li>Transfer the synthetic mixture into a dialysis membrane (3,500 MWCO) and dialyze against deionized water to extract and purify the melanin. Replace the dialysis water daily over a period of 7 days. Dry the material in an oven at 90 &#176;C for 12 h to obtain a melanin powder.</li>
	</ol>
	</li>
	<li>Melanin/PEDOT:PSS blends preparation
	<ol>
		<li>Add 3,790 &#181;L of PEDOT:PSS aqueous dispersion (1 wt%, 10 mg/mL) to a 4 mL vial. Add 200 &#181;L (5% v/v) of ethylene glycol and 10 &#181;L (0.25% v/v) of dodecyl benzenesulfonic acid (DBSA) to the vial.</li>
		<li>Add 1, 3, and 5 mg of melanin to three different vials.</li>
		<li>Add 900, 700, and 500 &#181;L of the PEDOT:PSS mother solution prepared in Step 1.2.1 to the vials with 1, 3, and 5 mg of melanin, respectively.</li>
		<li>Add 100, 300, and 500 &#181;L of deionized water to the vials with 900, 700, and 500 &#181;L of the PEDOT:PSS mother solution, respectively, to complete 1 mL in each vial. Transfer 1 mL of PEDOT:PSS mother solution to a clean vial to obtain a pure PEDOT:PSS sample.</li>
		<li>Add 3 mL of deionized water to each vial to obtain 2.5 mg/mL solutions. 
		NOTE: In Step&#8239;1.2.3, 900, 700, and 500&#8239;&#181;L of the PEDOT:PSS mother solution contain approximately 9, 7, and 5&#8239;mg of PEDOT:PSS, respectively. For example, mixing 900&#8239;&#181;L of the PEDOT:PSS mother solution (&#8776;9&#8239;mg PEDOT:PSS) with 1&#8239;mg of melanin results in a 10&#8239;wt% Melanin/PEDOT:PSS ratio; the same applies for the other blend ratios. To ensure all solutions have the same final blend concentration (mass of blend per volume of water), additional water is added in Step&#8239;1.2.4, e.g., 100&#8239;&#181;L of water for the 10&#8239;wt% solution or 500&#8239;&#181;L for the 50&#8239;wt% solution, yielding a final concentration of 10&#8239;mg/mL. This concentration is too viscous for spray coating and could clog the airbrush. Therefore, in Step&#8239;1.2.5, a 4x dilution is performed by adding 3&#8239;mL of water to each 1&#8239;mL solution, resulting in a final working concentration of 2.5&#8239;mg/mL suitable for spray coating.</li>
	</ol>
	</li>
</ol>
2. OECTs assembly and Melanin/PEDOT:PSS spray deposition
<ol>
	<li>Gold electrode deposition
	<ol>
		<li>Wash four 2.5 x 2.5 cm glass slides substrate in a highly concentrated and neutral detergent in an ultrasonic bath for 15 min. Repeat the process in water and isopropanol (IPA) medium.</li>
		<li>Prepare the shadow mask for the source and drain electrode pattern.
		<ol>
			<li>Cut a 0.025&#8239;mm-thick polyimide sheet to dimensions slightly larger than the substrate (here, cut to 3&#8239;&#215;&#8239;3&#8239;cm).</li>
			<li>Use a cutting machine to perform precise cuts on the polyimide sheet.</li>
			<li>Using the machine&#39;s software (Supplemental File 1), design the patterns to be cut from the polyimide sheet. Draw five pairs of electrodes, each 1&#8239;&#215;&#8239;11.5&#8239;mm, separated by 1&#8239;mm within pairs and 3.5&#8239;mm between pairs.</li>
			<li>Place the polyimide sheet in the cutting machine. In the software, click Send (top-right corner). Set the cutting parameters: force&#8239;=&#8239; 20 , speed&#8239;=&#8239; 4 , passes&#8239;=&#8239; 2 , and blade depth&#8239;=&#8239; 3. Then click Send at the bottom of the screen to start cutting.</li>
			<li>Attach the cut polyimide sheet to a perforated metal plate matching the substrate dimensions using polyimide tape (Figure 1A).</li>
		</ol>
		</li>
		<li>Put the substrate below the shadow mask patterned to obtain five pairs of source (S) and drain (D) electrodes in each substrate, separated by 1 mm in length (L) and with 1 mm in width (W) (Figure 1B).</li>
		<li>Deposit 100 nm of gold on the substrates with the shadow masks by the thermal evaporation technique in a vacuum evaporator chamber.
		<ol>
			<li>Place the required amount of gold in the evaporation boat for adequate film thickness and uniform deposition.</li>
			<li>Place the masked samples in the sample holder inside the evaporation chamber.</li>
			<li>Configure the deposition controller to start the gold deposition at a slow rate of 0.2 &#197;/s up to 5nm, allowing controlled nucleation and uniform film formation. After the initial layer, define the deposition rate to 1 &#197;/s until the final thickness of 100 nm is achieved.</li>
			<li>Automatically evacuate the evaporation chamber up to 5 &#215; 10-6&#160;mbar and start the evaporation.</li>
			<li>Wait for the deposition process to finish. Allow the chamber to cool down for 1 h, then remove the substrates from the evaporator.</li>
		</ol>
		</li>
		<li>Cover the gold electrode with an adhesive mask containing openings for the channel deposition.
		<ol>
			<li>Use a cutting machine to perform precise cuts on the adhesive mask.</li>
			<li>Using the machine&#39;s software (see Supplemental File 2), design the patterns to be cut from the adhesive mask. Draw squares to expose the areas where the OECT channels will be deposited by spray coating.</li>
			<li>Place the adhesive mask in the cutting machine. In the software, click Send (top-right corner). Set the cutting parameters: force&#8239;=&#8239; 20 , speed&#8239;=&#8239; 4 , passes&#8239;=&#8239; 2 , and blade depth&#8239;=&#8239; 3. Then click Send at the bottom of the screen to start cutting.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Ag/AgCl gate electrode preparation
	<ol>
		<li>Form a single loop at one end of a silver wire with 5 cm length and 0.5 mm diameter.</li>
		<li>Attach the opposite end of the silver wire to the working electrode of the electrochemical cell. Use a platinum as both the counter and reference electrode, short-circuited together.</li>
		<li>Immerse the single-loop silver wire and the platinum electrode in a 3.0 M potassium chloride solution.</li>
		<li>Apply 1.0 V versus the platinum electrode for 5 min using a potentiostat. Remove the formed Ag/AgCl wire and clean it using deionized water.</li>
	</ol>
	</li>
	<li>Spray coating of Melanin/PEDOT:PSS films 
	NOTE: A modified 3D printer was used as an automated spray-coating system. The original extruder head was replaced with a low-cost painting airbrush. The original extruder head was replaced with a low-cost painting airbrush. We used a pneumatic spray deposition, achieved by connecting compressed air to the airbrush while relying on gravity to feed the solution through the airbrush container (Figure 2). This setup allowed us to automate the spray-coating process by using the printer&#39;s existing motion control system. Through custom programming in G-code (Supplemental File 3), the movement path, speed, spray pattern, and timing were precisely controlled by software, enabling uniform and reproducible film deposition over the substrate.
	<ol>
		<li>System assembly and setup
		<ol>
			<li>Select a robust 3D printer with suitable dimensions as the base platform for the spray-coating system.</li>
			<li>Among the possible spray modes (electrospray, ultrasonic, pneumatic), configure the pneumatic setup and connect a high-precision airbrush equipped with an adjustable reservoir. Integrate optional components such as flowmeter, syringe pump or ultrasonic spray head (Figure 2), depending on the desired spray mode. 
			NOTE: These components were not used in the experiments described in this protocol.</li>
			<li>For mechanical adaptation, modify the printer framework to mount the airbrush. Remove the extruder and place the airbrush on a custom holder.</li>
			<li>Use the X-, Y-, and Z-axis stepper motors to control the airbrush motion and height adjustment. Adapt the extruder to actuate the airbrush trigger, enabling software-controllable spray release. Use required adapters fabricated using the 3D printed pieces, STL files provided as Supplemental File 4 , Supplemental File 5 , Supplemental File 6, and Supplemental File 7.</li>
		</ol>
		</li>
		<li>Spray-coating deposition parameters
		<ol>
			<li>Center the airbrush with respect to the XY plane above the hot plate, maintaining a vertical (Z-axis) distance of 15 cm from the airbrush to the hot plate surface.</li>
			<li>Set up the hot plate temperature to 100 &#176;C. Adjust the compressed air pump pressure to 1 bar.</li>
			<li>Program the G-code to move the airbrush 10 cm along the X-axis at a rate of F8000 (speed parameter). Set the spray opening width to E1.5&#160;(command to move the extruder motor) and define a dwell time of P5000&#160;(time parameter in milliseconds) between the forward and return strokes (defined as one cycle).</li>
			<li>Place the substrate, with the source and drain electrodes already deposited, at the center of the hot plate.</li>
			<li>Add 250 &#181;L of Melanin/PEDOT:PSS solution into the airbrush reservoir. Edit the desired cycle numbers (typically 10 cycles) and run the G-Code.</li>
			<li>Repeat Step 2.3.5 up to a total of 2 mL solution has been deposited (Figure 1C).</li>
			<li>Clean the airbrush reservoir with deionized water after finishing the deposition.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
3. Electrical characterization of OECTs
<ol>
	<li>Place the OECT device on a probe station or test platform, ensuring proper electrical contact with the gate, source, and drain terminals.</li>
	<li>Apply an adhesive mask on top of the device to define and confine the electrolyte area directly above the channel, preventing spreading over the electrodes.</li>
	<li>Prepare an aqueous electrolyte solution of 100 mM sodium chloride (NaCl) using deionized water.</li>
	<li>Drop-cast a small volume of the NaCl solution into the defined area of the adhesive mask, ensuring full coverage of the channel.</li>
	<li>Place an Ag/AgCl wire onto the electrolyte within the confined region, aligning it above the channel to serve as the top gate electrode.</li>
	<li>Connect the source, drain, and gate terminals to the Source Measure Units (SMU).</li>
	<li>Sweep the drain voltage VDS from 0.01 V to -0.5&#160;V at fixed gate voltages VGS ranging from -0.5 V to 0.5 V. Record the drain current IDS at each step.</li>
	<li>Fix the drain voltage VDS at -0.5 V. Sweep the gate voltage VGS from -0.5 V to +0.5&#160;V. Record the drain current IDS.</li>
</ol>

<ol><li>Rivnay, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Organic+electrochemical+transistors%5BTitle%5D)+AND+%22Nat+Rev+Mater%22%5BJournal%5D)">Organic electrochemical transistors.</a> Nat Rev Mater. 3, 17086(2018).</li>
<li>Friedlein, J. T., McLeod, R. R., Rivnay, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Device+physics+of+organic+electrochemical+transistors%5BTitle%5D)+AND+%22Org+Electron%22%5BJournal%5D)">Device physics of organic electrochemical transistors.</a> Org Electron. 63, 398-414 (2018).</li>
<li>Saleh, A., Koklu, A., Uguz, I., Pappa, A. -M., Inal, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Bioelectronic+interfaces+of+organic+electrochemical+transistors%5BTitle%5D)+AND+%22Nat+Rev+Bioeng%22%5BJournal%5D)">Bioelectronic interfaces of organic electrochemical transistors.</a> Nat Rev Bioeng. 2 (6), 408-423 (2024).</li>
<li>Sun, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Review+on+application+of+PEDOTs+and+PEDOT%3APSS+in+energy+conversion+and+storage+devices%5BTitle%5D)+AND+%22J+Mater+Sci+Mater+Electron%22%5BJournal%5D)">Review on application of PEDOTs and PEDOT:PSS in energy conversion and storage devices.</a> J Mater Sci Mater Electron. 26 (6), 4438-4462 (2015).</li>
<li>Song, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((High-conductivity%2C+flexible+and+transparent+PEDOT%3APSS+electrodes+for+high-performance+supercapacitors%5BTitle%5D)+AND+%22Polymers+%28Basel%29%22%5BJournal%5D)">High-conductivity, flexible and transparent PEDOT:PSS electrodes for high-performance supercapacitors.</a> Polymers (Basel). 12 (2), 450(2020).</li>
<li>Nozella, N. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Melanin%2FPEDOT%3APSS+organic+synaptic+transistors%3A+a+step+towards+sustainable+neuromorphic+applications%5BTitle%5D)+AND+%22Neuromorph+Comput+Eng%22%5BJournal%5D)">Melanin/PEDOT:PSS organic synaptic transistors: a step towards sustainable neuromorphic applications.</a> Neuromorph Comput Eng. 5 (1), 014014(2025).</li>
<li>Nozella, N. L., Lima, J. V. M., de Oliveira, R. F., Graeff, C. F. deO. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Melanin%2FPEDOT%3APSS+blend+as+organic+mixed+ionic+electronic+conductor+%28OMIEC%29+for+sustainable+electronics%5BTitle%5D)+AND+%22Mater+Adv%22%5BJournal%5D)">Melanin/PEDOT:PSS blend as organic mixed ionic electronic conductor (OMIEC) for sustainable electronics.</a> Mater Adv. 4 (11), 4732-4743 (2023).</li>
<li>Nishinaka, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((High-transconductance+organic+electrochemical+transistor+fabricated+on+ultrathin+films+using+spray+coating%5BTitle%5D)+AND+%22Small+Struct%22%5BJournal%5D)">High-transconductance organic electrochemical transistor fabricated on ultrathin films using spray coating.</a> Small Struct. 2 (1), 2000089(2021).</li>
<li>Paulin, J. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+greener+prescription%3A+the+power+of+natural+organic+materials+in+healthcare%5BTitle%5D)+AND+%22RSC+Sustain%22%5BJournal%5D)">A greener prescription: the power of natural organic materials in healthcare.</a> RSC Sustain. 2 (8), 2190-2198 (2024).</li>
<li>Bronze-Uhle, E. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Melanin+synthesis+under+oxygen+pressure%5BTitle%5D)+AND+%22Polym+Int%22%5BJournal%5D)">Melanin synthesis under oxygen pressure.</a> Polym Int. 65 (12), 1339-1346 (2016).</li>
<li>Paulin, J. V., Graeff, C. F. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((From+nature+to+organic+%28bio%29electronics%3A+a+review+on+melanin-inspired+materials%5BTitle%5D)+AND+%22J+Mater+Chem+C%22%5BJournal%5D)">From nature to organic (bio)electronics: a review on melanin-inspired materials.</a> J Mater Chem C. 9 (44), 14514-14531 (2021).</li>
<li>Migliaccio, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Impact+of+eumelanin-PEDOT+blending%3A+increased+PEDOT+crystalline+order+and+packing-conductivity+relationship+in+ternary+PEDOT%3APSS%3Aeumelanin+thin+films%5BTitle%5D)+AND+%22Adv+Electron+Mater%22%5BJournal%5D)">Impact of eumelanin-PEDOT blending: increased PEDOT crystalline order and packing-conductivity relationship in ternary PEDOT:PSS:eumelanin thin films.</a> Adv Electron Mater. 5 (7), 1900126(2019).</li>
<li>Nozella, N. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Probing+n-type+conduction+in+eumelanin+using+organic+electrochemical+transistors%5BTitle%5D)+AND+%22ACS+Appl+Electron+Mater%22%5BJournal%5D)">Probing n-type conduction in eumelanin using organic electrochemical transistors.</a> ACS Appl Electron Mater. 7 (6), 3176-3181 (2025).</li>
<li>Van De Burgt, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+non-volatile+organic+electrochemical+device+as+a+low-voltage+artificial+synapse+for+neuromorphic+computing%5BTitle%5D)+AND+%22Nat+Mater%22%5BJournal%5D)">A non-volatile organic electrochemical device as a low-voltage artificial synapse for neuromorphic computing.</a> Nat Mater. 16 (4), 414-418 (2017).</li>
</ol>

The authors have no conflicts of interest to declare.

The results presented here show how blending melanin directly into the PEDOT:PSS solution affects both the structural and electrical properties of the resulting spray-coated films for OECT applications. The variation in film thickness with melanin content follows a non-monotonic trend: the thickness decreases at 10% melanin, while further increasing melanin concentration leads to thicker films. This behavior can be explained by the combined effects of structural reorganization within PEDOT:PSS12 a...

Organic electrochemical transistors (OECTs) have emerged as promising devices for bioelectronics, neuromorphic systems, and sustainable electronics due to their unique ability to couple ionic and electronic transport1. The performance of these devices critically depends on the properties of the semiconducting channel, which must combine high transconductance with biocompatibility and low-voltage operation2,3. Among the materials studied for this purpose, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) stands out for its excellent conductivity and processability4,5. Recently, bio-inspired materials such as melanin have gained attention for their potential to enhance memory characteristics and offer sustainable alternatives for organic bioelectronics6,7.
Conventional deposition techniques for organic films, like spin-coating, suffer from limited scalability and high material waste, making them less suitable for large-area and industrial applications. In contrast, spray-coating is an additive wet-coating, low-cost, and scalable deposition technique that enables uniform film formation over diverse substrates and geometries. It also allows for precise control of film thickness and morphology, parameters that are crucial for optimizing OECT performance8. Specifically, in a pneumatic spray-coating technique, compressed air atomizes a liquid coating solution into fine droplets, which are directed onto a substrate through a low-cost airbrush. This method provides precise geometrical control over the deposition area via nozzle positioning and masking. However, the use of spray coating to deposit functional blends like Melanin/PEDOT:PSS remains relatively unexplored.
In this work, we investigate the use of spray-coated films of melanin blended with PEDOT:PSS as the active layer in OECTs. By integrating a sustainable, water-soluble melanin9,10,11 into the channel material and employing a scalable fabrication method, we aim to address both environmental and technological challenges in organic bioelectronics. Our results demonstrate that this approach not only preserves the desired electronic properties of PEDOT:PSS but also supports the development of eco-friendly, high-performance OECTs suitable for neuromorphic and bioelectronic applications.

<table><tbody><tr><td>3,4-Dihydroxy-DL-phenylalanine&amp;nbsp;</td><td>Sigma Aldrich</td><td>63-84-3</td><td>melanin synthesis reagent</td></tr><tr><td>3D printer</td><td>Creality</td><td>Ender 5+</td><td>The 3D printer was modified by replacing the extruder head with a mount for the airbrush, enabling automated activation and precise movement through G-code control.</td></tr><tr><td>Adhesive mask</td><td>Pimaco</td><td>0085</td><td>Adhesive mask to cover the gold electrodes and spary coated film delimitation</td></tr><tr><td>air compressor</td><td>Onetools</td><td></td><td>Direct-drive air compressor equipped with presure regulator and air filter.</td></tr><tr><td>Airbrush</td><td>Steula</td><td>BC 62</td><td>The airbrush was equipped with a 1/8&quot; mini filter with drain to ensure stable airflow and prevent moisture contaminatino during deposition.</td></tr><tr><td>Ammonium hydroxide&amp;nbsp;</td><td>Sigma Aldrich</td><td>1336-21-6</td><td>oxidant reagent for melanin synthesis</td></tr><tr><td>Deposition Controller</td><td>Inficon</td><td>SQC-310</td><td>Deposition controller to gold deposition</td></tr><tr><td>Dialysis membrane 3500 MWCO</td><td>Servapor</td><td>44563.02</td><td>dialysis membrane for melanin purification</td></tr><tr><td>Dodecyl benzenesulfonic acid&amp;nbsp;</td><td>Merck</td><td>12635-25G-F</td><td>reagent to prepare the PEDOTPSS mother solution&amp;nbsp;</td></tr><tr><td>Ethylene glycol</td><td>Sigma Aldrich</td><td>107-21-1</td><td>reagent to prepare the PEDOTPSS mother solution&amp;nbsp;</td></tr><tr><td>Gate source</td><td>Agilent&amp;nbsp;</td><td>33210A</td><td>Source wave form generator to gate voltage bias</td></tr><tr><td>Glass slides</td><td>Olen</td><td>K5-7101</td><td>glass slides used as substrates</td></tr><tr><td>Hotplate</td><td>Marconi</td><td>MA 085</td><td>A hotplate mainstained the substrate at a controlled temperature throughout the deposition process.</td></tr><tr><td>Isopropanol</td><td>Sigma Aldrich</td><td>67-63-0</td><td>solvent to clean the substrate</td></tr><tr><td>PEDOT:PSS</td><td>Heraeus, Clevios PH1000</td><td>PD-084-01&amp;nbsp;</td><td>PEDOTPSS PH1000 to prepare thin film solution&amp;nbsp;</td></tr><tr><td>Polyimide sheet 0.025 mm</td><td>Kapton</td><td></td><td>Polyimide sheet used as shadow mask</td></tr><tr><td>Potassium chloride&amp;nbsp;</td><td>Sigma Aldrich</td><td>7447-211-8</td><td>reagent to prepare the KCl electrolyte&amp;nbsp;</td></tr><tr><td>Repetier-Host (Software V2.3.2)</td><td></td><td></td><td>Repetier-Host, a slicer software commonly used in 3D printing, was repurposed to control the spray deposition path and to modify the G-code.</td></tr><tr><td>Sodium chloride</td><td>Sigma Aldrich</td><td>7647-14-5</td><td>reagent to prepare the NaCl electrolyte&amp;nbsp;</td></tr><tr><td>Source and Drain measurements</td><td>Keitlhey</td><td>2450</td><td>Equipment for drain voltage and current measurements</td></tr></tbody></table>

spray-coated melanin/pedot:pss films for sustainable organic electrochemical transistors

Spray-Coated Melanin/PEDOT:PSS Films for Sustainable Organic Electrochemical Transistors

A simple and scalable protocol for the fabrication of Melanin/PEDOT:PSS organic electrochemical transistors (OECTs) via spray coating is presented. The method includes melanin synthesis, blending with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) PEDOT:PSS at different mass ratios (0, 10, 30, and 50&#8239;wt%, named Pure PEDOT:PSS, 10Mel, 30Mel, and 50Mel, respectively), and deposition onto gold-patterned substrates using a 3D printer-adapted spray-coating system. Electrical characterization is performed using a top-gate Ag/AgCl electrode in 100&#8239;mM NaCl aqueous electrolyte, with output and transfer curves recorded. Addition of 10&#8239;wt% melanin increases the&#160;normalized transconductance by approximately 2x compared to pristine PEDOT:PSS, while maintaining a high ON/OFF current ratio (&#62;100). Threshold voltage shifts toward more negative potential, reflecting dedoping effects and the influence of melanin on device operation. Film morphology and thickness were systematically evaluated, providing insights into reproducibility across different compositions. This protocol enables the production of sustainable, high-performance OECTs for bioelectronic applications such as sensors, memory devices, and neuromorphic-inspired systems.

UV-Vis and FTIR characterization of the melanin/PEDOT:PSS blends confirmed successful incorporation of melanin into the conductive polymer matrix (Figure 3A,B). UV-Vis spectra show characteristic melanin absorption bands, while FTIR analysis reveals interactions between the functional groups of melanin and PEDOT:PSS. The disappearance of characteristic PEDOT:PSS absorption bands indicate chemical interactions between the two components, suggesting that melanin incorporation ...

A basic protocol for fabricating high-transconductance Melanin/PEDOT:PSS organic electrochemical transistors (OECTs) using spray coating is described. The method allows precise control over film deposition, thickness, and morphology, providing reproducible devices for sustainable and scalable bioelectronic applications.

A simple and scalable protocol for the fabrication of Melanin/PEDOT:PSS organic electrochemical transistors (OECTs) via spray coating is presented. The ...

In this research, we developed sustainable organic electronic devices through a scalable deposition approach using low-cost setup and solution processable materials. The center devices involved with solution processing of bio-compatible agreeing materials like melanin and the integration into functional electronic device. To begin, add 0.3 grams of three four dihydroxy DL phenylalanine to a glass beaker.Add 60 milliliters of deionized water to the beaker to dissolve the three four dihydroxy DL phenylalanine under magnetic stirring. Add 400 microliters of ammonium hydroxide to start the oxidation process. Transfer the prepared solution to a polytetrafluoroethylene liner inside a stainless steel reactor.Then, close the reactor and increase the pressure to six atmospheres with industrial oxygen gas. Keep the mixture under magnetic stirring for six hours. Transfer the synthetic mixture into a dialysis membrane.Dialyze against deionized water to extract and purify the melanin, replacing the water daily for seven days or until it becomes colorless. Dry the purified material in an oven at 90 degrees Celsius for 12 hours to obtain melanin powder. Then place the substrate below a shadow mask pattern to obtain five pairs of source and drain electrodes on each substrate separated by one millimeter in length and in width.Afterwards, place the shadow mask with the substrates in the evaporation support. Now place the required amount of gold in the evaporation boat to ensure adequate film thickness and uniform deposition. Place the masked samples into the sample holder inside the evaporation chamber.Next, configure the deposition controller to begin gold deposition at a slow rate of 0.2 angstroms per second until a thickness of five nanometers is reached for controlled nucleation and uniform film formation. Then set the deposition rate to one angstrom per second until the final thickness of 100 nanometers is achieved. Automatically evacuate the evaporation chamber until a vacuum of five times 10 to the power of negative six millibars reached and start the evaporation process.Wait for the deposition process to complete. Once the evaporation chamber has cooled for one hour, refill the chamber until one atmosphere and remove the substrates. Then, cover the gold electrodes with an adhesive mask that has openings for the channel deposition.Select a robust three dimensional printer with suitable dimensions to use as the base platform for the spray coating system. Then modify the three dimensional printer framework to mount the airbrush for mechanical adaptation. Remove the extruder and place the airbrush on a custom holder.Use the x, y and z axis stepper motors to control the motion and height of the airbrush. Adapt the extruder to actuate the airbrush trigger, enabling software controlled spray release. Then center the airbrush in the XY plane directly above the hot plate, maintaining a vertical distance of 15 centimeters from the airbrush to the hot plate surface.Now set the hot plate temperature to 100 degrees Celsius and adjust the compressed air pump to a pressure of one bar. Program the G code to move the airbrush 10 centimeters along the x axis at a speed parameter of F 8, 000. Set the spray opening width using the E 1.5 command and define a dwell time of P 5, 000 between forward and return strokes.Then place the masked substrate with the source and drain electrodes already deposited at the center of the hot plate. Add 250 microliters of the melanin and P.PSS solution into the airbrush reservoir. Edit the desired number of spray cycles in the G code, typically setting it to 10 cycles and run the program.Clean the airbrush reservoir with deionized water after completing the deposition. To measure the output curves of OECTs, sweep the drain voltage from zero volts to minus 0.6 volts. Record the drain current at each step.To measure the transference curve, fix the drain voltage at minus 0.5 volts. Sweep the gate voltage from minus 0.5 volts to plus 0.6 volts and record the drain current. UV visible spectra confirmed successful incorporation of melanin into P.PSS films by the appearance of characteristic melanin absorption bands.FTIR analysis showed interactions between melanin and P.PSS demonstrated by the disappearance of characteristic P.PSS absorption bands. Profilometry revealed that pristine P.PSS films had the highest thickness of 961 nanometers, which decreased to 342 nanometers upon addition of 10%melanin, then increased to 493 nanometers at 30%and 562 nanometers at 50%melanin. Atomic force microscopy showed that the surface roughness of pristine P.PSS films was 4.4 nanometers, decreased to 3.3 nanometers with 10%melanin and increased to 7.8 nanometers and 15.6 nanometers with 30%and 50%melanin respectively.Output curves showed that pristine P.PSS devices produced high drain currents, which decreased upon addition of 10%melanin. Transfer characteristics for 10%melanin devices displayed a pronounced hysteresis loop and an on and off current ratio of approximately 150. Trans conductance measurements revealed that the maximum GM value shifted to more negative gait voltages as melanin concentration increased.The normalized maximum trans conductance was highest for the 10%melanin blend, which had the lowest film thickness. We demonstrate that automated spray deposition enables controlled thickness increase leading to a higher volumetric capacitance and improved OECT performance compared to conventional deposition techniques. Melanin speed up P.PSS enhanced transduction transit in organic electronic comply, while controlling deposition and AB tuning of response timing, memory effects.Now we aim to understand the effect of spray coating on OECT parameters and their implementation in neuromorphic and electronic devices.

spray-coated-melaninpedotpss-films-for-sustainable-organic

Research

JoVE Journal

Engineering

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.

Sensing of Barrier Tissue Disruption with an Organic Electrochemical Transistor

A method of fabricating, in ambient conditions, organic photovoltaic tandem devices in a parallel configuration is presented. These devices feature an air-processed, semi-transparent, carbon nanotube common cathode.

Ambient Method for the Production of an Ionically Gated Carbon Nanotube Common Cathode in Tandem Organic Solar Cells

A method for fully printable, fullerene-free, highly air-stable, bulk-heterojunction solar cells based on Ti alkoxides as the electron acceptor and the electron-donating polymer fabrication is described here. Moreover, a method for controlling the morphology of the photoactive layer through the molecular bulkiness of the Ti-alkoxide units is reported.

Morphology Control for Fully Printable Organic&#8211;Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer

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.

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

A protocol is presented for fabricating high-performance, pure blue ZnCdS/ZnS-based quantum dots light-emitting diodes by employing an autoxidized aluminum cathode.

Enhanced Electron Injection and Exciton Confinement for Pure Blue Quantum-Dot Light-Emitting Diodes by Introducing Partially Oxidized Aluminum Cathode

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

Development of Efficient OLEDs from Solution Deposition

We describe aqueous and organic solvent systems for the electropolymerization of poly(3,4-ethylenedioxythiophene) to create thin layers on the surface of gold microelectrodes, which are used for sensing low molecular weight analytes.

Electrochemical Preparation of Poly(3,4-Ethylenedioxythiophene) Layers on Gold Microelectrodes for Uric Acid-Sensing Applications

This work describes the development of flexible interdigitated electrodes for implementation in 3D brain tumor models, namely, in vitro culture, in ovo model, and in vivo murine model. The proposed method can be used to evaluate the effects of pulsed electric fields on tumors at different levels of complexity.

Flexible Organic Electronic Devices for Pulsed Electric Field Therapy of Glioblastoma

This paper describes a simple technique for coating electrospun PAN nanofibers with electroactive polymers using vapor deposition. The effects of the oxidant FeCl₃ on the deposition of poly(3,4-ethylenedioxythiophene) coatings on PAN were investigated to understand and optimize polymer growth, fiber diameter, and overall mechanical strength of the nanofiber mats.

Vapor Phase Deposition of Electroactive Poly(3,4-ethylenedioxythiophene) onto Electrospun Commodity Polymer Nanofibers

Here, we present a protocol for using organic electrochemical transistors (OECTs) to translate extracellular electron transfer (EET) activity in Shewanella oneidensis into electrical signals. The hybrid OECT system provides enhanced robustness, sensitivity, and potential for rapid, high-throughput testing, making it an effective tool for EET measurements.

Translating Extracellular Electron Transfer Activities with Organic Electrochemical Transistors

Discover spray coating of Melanin/PEDOT:PSS films for high-performance organic electrochemical transistors. This scalable method enables precise control over film thickness and morphology for bioelectronic applications.

Spray-Coated Melanin/PEDOT:PSS Films for Sustainable Organic Electrochemical Transistors

Explore More Videos