Name: Fabrication of a Solution-gated Indium-Tin-Oxide-based One-piece Transistor Enabling Sensitive Biosensing (Video) | JoVE Journal
Uploaded: 2025-08-29T14:40:00.000+00:00
Duration: 10 min 45 s
Description: Learn to fabricate a solution-gated indium-tin-oxide-based one-piece transistor for sensitive pH sensing and biosensing applications. This rapid method uses all-by-ITO technology to enhance detection sensitivity.

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5 minutes

This research was supported by MERIT, WINGS Program, and the University of Tokyo.

The reagents and the equipment used in this study are listed in the Table of Materials.
1. Fabrication of one-piece ITO-ISFET (&#160;Figure 1A)
<ol>
	<li>Patterning of OFPR-800
	<ol>
		<li>Wash the glass substrate (12 mm &#215; 24&#160;mm) by sonication in acetone, methanol, and water for 5 min each. Then, dry the substrate with an N2 gas blower and subsequently bake it at 110 &#176;C on a hot plate for longer than 5 min to dry the substrate completely.</li>
		<li>Spin-coat the glass substrate with an OFPR-800 layer at 500 rpm for 5 s and 3000 rpm for 30 s. Check for uniformity of coating.</li>
		<li>Prebake the substrate at 110 &#176;C on a hot plate for 5 min. Then, cool the substrate to room temperature.</li>
		<li>Put the photomask film on the photoresist-coated side of the substrate and fix it with tape (Supplementary Figure 2A).</li>
		<li>Expose the substrate to UV (200 W) for 40 s in a photolithography machine. 
		NOTE: Exposure time depends on the equipment used and is based on the required dose of photoresist.</li>
		<li>Take the substrate out of the photolithography machine and remove the photomask.</li>
		<li>Develop the photoresist in NMD-3 for 1 min and ensure that the photoresist forms a sharp pattern. Then, wash the substrate by dipping it in water.</li>
		<li>Dry the substrate by blowing N2 gas. Then, post-bake the substrate on a hotplate at 110 &#176;C for 5 min.</li>
	</ol>
	</li>
	<li>Deposition of ITO
	<ol>
		<li>Fix the substrate on a substrate holder with tape and introduce it into the vacuum chamber of a sputtering machine.</li>
		<li>Pump down the sputtering chamber below 10-3 Pa.</li>
		<li>Deposit ITO (In2O3 90 wt% and SnO2 10 wt%) to a thickness of ~100 nm by radio frequency sputtering at 4 nm/min under Ar gas (0.2 Pa) without heating.</li>
	</ol>
	</li>
	<li>Patterning of SU-8 (Figure 1B)
	<ol>
		<li>Lift off the photoresist by sonication in acetone, methanol, and water for 5 min each. Ensure that no small fragments of ITO remain on the substrates. If the contamination seems severe, wipe with a clean wiper and then clean the substrate by sonication again.</li>
		<li>Blow the substrate with an N2 gas blower. Then, bake the substrate at 110 &#176;C on a hot plate to completely dry the substrate.</li>
		<li>Spin-coat the glass substrate with an SU-8 3005 layer at 500 rpm for 5 s and 6000 rpm for 30 s. Check for uniformity of coating.</li>
		<li>Prebake the substrate at 95 &#176;C on a hot plate for 5 min and subsequently cool the substrate to room temperature.</li>
		<li>Put the photomask film on the photoresist-coated substrate and fix it with tape (Supplementary Figure 2B).</li>
		<li>Expose the substrate to UV (200 W) for 7 s. Then, take the substrate out of the photolithography machine and remove the photomask.</li>
		<li>Postbake the substrate at 65 &#176;C for 2 min and 95 &#176;C for 5 min.</li>
		<li>Develop the photoresist in the SU-8 developer for 3 min under strong agitation. Then, wash the substrate in 2-propanol for 1 min. Ensure that the photoresist is fully developed.</li>
		<li>Dry the substrate by blowing N2 gas.</li>
	</ol>
	</li>
	<li>Formation of semiconductive ITO channel by etching (Figure 1C)
	<ol>
		<li>Prepare 0.1 M hydrochloric acid (HCl).</li>
		<li>Connect the source and drain electrodes, as shown in Figure 1B, to a semiconductor parameter analyzer.</li>
		<li>Select Classic Test tab and then select I/V-t Sampling.</li>
		<li>Set a sampling interval to 0.5 s.</li>
		<li>Apply a voltage of 1 V between the source and drain electrodes and determine the initial current (IDS0).</li>
		<li>Place a drop of the prepared HCl solution (30 &#181;L) onto the exposed ITO channel area. Ensure that the drop fully covers the channel area.</li>
		<li>Monitor the change in conductivity by monitoring the current between the source and drain electrodes. Continue the etching until the current decreases to 10% of&#160;initial&#160;IDS0.</li>
		<li>Immediately rinse the ITO channel with deionized water to stop the etching as soon as the etching current ratio reaches 10% of&#160;initial&#160;IDS0 to control the ITO channel thickness (~10-20 nm). This is regarded as a one-piece transistor with no interfaces among the source, channel, and drain electrodes.</li>
		<li>Gently blow N2 gas to dry the one-piece transistor using an N2 gas blower.</li>
		<li>Store the devices in a vacuum desiccator until measurement.</li>
	</ol>
	</li>
</ol>
2. Electrical measurements of one-piece ITO-ISFET
<ol>
	<li>Set up of the electrical measurement system
	<ol>
		<li>Connect the source and drain electrodes of the one-piece transistor to the semiconductor parameter analyzer via a test fixture.</li>
		<li>Place a silicone O-ring around the ITO channel surface as a well into which a sample is placed.</li>
		<li>Add 30 &#181;L of phosphate buffer (PB, pH 7.41) or other standard pH buffer solutions (pHs 4.01, 6.86, 7.41, and 9.18) carefully into the silicone O-ring to ensure direct contact between the solution and the ITO channel surface. This solution serves as the gate electrolyte.</li>
		<li>Insert an Ag/AgCl reference electrode in a saturated KCl solution, which is connected to the gate electrolyte by a salt bridge.</li>
		<li>Connect the Ag/AgCl reference electrode to the semiconductor parameter analyzer, which works as the gate electrode.</li>
		<li>Turn on the B1500A and start the EasyEXPART software, then open Workspace.</li>
	</ol>
	</li>
	<li>IDS-VGS transfer characteristics
	<ol>
		<li>Select Classic Test tab and then select I/V Sweep.</li>
		<li>Connect the source electrode to the ground.</li>
		<li>Set the parameter to apply a constant drain voltage (VDS) of 1 V. 
		NOTE: The potential of each electrode should be -1 V - 1 V to avoid electrolysis of water.</li>
		<li>Set the sweep range of gate voltages (VGS) to -0.8 V - +0.8 V and the sweep rate to approximately 50 mV/s. 
		NOTE: The sweep rate can be controlled by setting the &#34;number of steps&#34; to 141 and the &#34;delay&#34; to 10 ms, and the &#34;A/D converter&#34; to HR ADC in the PLC mode (Factor: 2).</li>
		<li>Set the number of iterations to 10 cycles, and use the data obtained from the last cycle for analysis. Simultaneously, the leak current between the source and gate electrodes (IGS) is obtained.</li>
		<li>Start measurement. 
		NOTE: All measurement data is automatically saved in the &#34;Results&#34; tab.</li>
	</ol>
	</li>
	<li>IDS-VDS transfer characteristics
	<ol>
		<li>Select CMOS category in&#160;the Application Test tab, then select Id-Vd mode</li>
		<li>Set VGS to change sequentially from 0 V to 0.8 V at 0.1 V intervals.</li>
		<li>Set VDS for each VGS to sweep from 0 V to 1 V at 0.01 V intervals.</li>
		<li>Start measurement.</li>
	</ol>
	</li>
	<li>Follow-up steps
	<ol>
		<li>Remove the O-ring and rinse the channel surface with deionized water. Then, dry the one-piece ITO device by blowing N2 gas.</li>
		<li>Store the device in a vacuum desiccator.</li>
	</ol>
	</li>
</ol>

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</ol>

The authors do not have any conflicts of interest to declare.

According to the above protocol, the one-piece ITO-ISFET can be fabricated as a solution-gated FET sensor (e.g., pH sensor) through a short and simple process (approximately half a day). ITO exhibits semiconducting properties at a depletion layer thickness of approximately 20 nm or less, making it suitable as the channel of a pH-sensitive solution-gated ISFET.
By etching the middle part of a conductive ITO single thin film with an acidic solution to make it ultrathin, a one-piece ITO-ISFET wit...

A solution-gated ion-sensitive field-effect transistor (ISFET) was proposed for detecting ions in biological environments1. In this device, an electrolyte solution induces the interfacial potential between the solution and the gate insulator instead of a metal gate in a metal-oxide-semiconductor (MOS) transistor, even though it is essential to use a reference electrode in the solution. A gate insulator is mostly composed of oxide or nitride membranes such as Ta2O5, Al2O3, SiO2, and Si3N4; therefore, hydroxyl groups at the oxide or nitride surface in a solution reach the equilibrium state with hydrogen ions through protonation (−OH + H+<img alt="Chemical equilibrium equations, reversible reaction symbols (⇌), diagram for educational use." src="/files/ftp_upload/68755/68755eq1.jpg" style="margin: auto;" data-altupdatedat="1762509930000" data-alt="Equation 1">−OH2+) and deprotonation (−OH <img alt="Chemical equilibrium equations, reversible reaction symbols (⇌), diagram for educational use." src="/files/ftp_upload/68755/68755eq1.jpg" style="margin: auto;" data-altupdatedat="1762509930000" data-alt="Equation 1">−O- + H+) because the change in pH is detected from the change in the surface charge on the basis of the principle of the field effect2,3 (Supplementary Figure 1). This is why the original ISFET sensor is still utilized as a pH sensor. Such ISFET sensors mostly have a silicon substrate, but various semiconducting materials have recently been applied to pH-sensitive ISFET sensors, which require the gate insulator or channel surface in contact with the electrolyte solution to be covered by functional groups such as hydroxy groups, carboxy groups, and amino groups4,5,6,7,8,9.
Such a solution-gated ISFET, whose gate insulator or channel surface is modified with biologically or chemically active receptors, has been applied to portable biosensors, which can be built into some electronic devices10,11,12. This biologically coupled gate (channel) FET, often called bio-FET, must realize quantitative and selective biosensing by detecting charges of biomolecules or ions included in body fluids. In addition, various low-dimensional materials have recently been utilized to enhance the sensitivity of bio-FETs, such as MoS2, WSe213,14, graphene15,16, and Si nanowires17,18. However, the complexity associated with the structure and fabrication processes has hindered the widespread usage of low-dimensional bio-FETs since they usually require disparate materials for the channel, source/drain electrodes, and gate-insulating film.
Our previous work revealed that a one-piece sheet of indium tin oxide (ITO) can work as a two-dimensional (2D)-like bio-FET on the basis of the fact that ITO, which is a conductive oxide, becomes semiconductive when its thickness is as small as ~20 nm19,20,21,22. By etching the middle part of a conductive ITO single thin film with an acidic solution to make it ultrathin, which enables the fabrication of the one-piece ITO with a semiconductive channel, the source and drain electrodes and channel without any interfaces can be fully integrated21,22. Then, the ITO channel surface is soaked in sample solutions with a reference electrode, thus functionalizing as a solution-gated ITO-ISFET. The solution-gated one-piece ITO-ISFET shows a steeper subthreshold slope (SS), which is mainly attributed to the direct contact of the ITO channel surface with a sample solution, compared to a conventional solution-gated silicon-based ISFET (Supplementary Figure 1B). This means that a relatively large electric double-layer capacitance at the ITO channel/solution interface acts as a dominant factor that determines SS19,20,21,22. Moreover, the solution-gated one-piece ITO-ISFET shows pH responsivity in accordance with a chemical thermodynamic relationship (i.e., Nernst equation)4,19,21. The ITO channel surface, which is in contact with an aqueous solution, conveniently has hydroxy groups that maintain an equilibrium state with hydrogen ions with positive charges, depending on pH, in the same manner as other oxide or nitride membranes2,3. Furthermore, by functionalizing the solution-gated one-piece ITO-ISFET, it was possible to detect biomolecules such as viruses and DNA molecules20,22.
This article describes a simple and rapid way to fabricate a solution-gated one-piece ITO-ISFET for biosensing. In particular, photolithography and etching processes for the fabrication are simply used, and then an electrolyte solution is added to the ITO channel surface with a reference electrode; that is, a sample solution serves as a solution gate electrode. Therefore, the solution-gated one-piece ITO-ISFET works as a pH sensor obtained by the fabrication process that takes only half a day.

<table><tbody><tr><td>1M HCl</td><td>FUJIFILM Wako Pure Chemicals Corp.</td><td>083-01095</td><td></td></tr><tr><td>2-propanol</td><td>FUJIFILM Wako Pure Chemicals Corp.</td><td>166-04831</td><td></td></tr><tr><td>Acetone</td><td>FUJIFILM Wako Pure Chemicals Corp.</td><td>019-00353</td><td></td></tr><tr><td>Ag wire</td><td>The Nilaco Corp.</td><td>AG-401385</td><td></td></tr><tr><td>Agar</td><td>FUJIFILM Wako Pure Chemicals Corp.</td><td>010-15815</td><td></td></tr><tr><td>Buffer Solution Standard (Phosphate pH Standard Equimolal Solution) pH6.86 (25 degrees C)</td><td>FUJIFILM Wako Pure Chemicals Corp.</td><td>025-03195</td><td></td></tr><tr><td>Buffer Solution Standard (Phthalate pH Standard Solution) pH4.01 (25 degrees C)</td><td>FUJIFILM Wako Pure Chemicals Corp.</td><td>028-03185</td><td></td></tr><tr><td>Buffer Solution Standard (Tetraborate pH Standard Solution) pH9.18 (25 degrees C)</td><td>FUJIFILM Wako Pure Chemicals Corp.</td><td>028-03205</td><td></td></tr><tr><td>Carbon tape</td><td>Nisshin-EM</td><td>7321</td><td></td></tr><tr><td>Electrochemical Analyzer</td><td>BAS Instrument</td><td>618 E</td><td></td></tr><tr><td>Film mask</td><td>UnnoGiken Co., Ltd.</td><td></td><td>custom-made</td></tr><tr><td>Hot plate</td><td>As One Corp.</td><td>ND-1</td><td></td></tr><tr><td>Methanol</td><td>FUJIFILM Wako Pure Chemicals Corp.</td><td>137-01823</td><td></td></tr><tr><td>Micro Cover Glass</td><td>Matsunami Glass Ind., Ltd</td><td>12&amp;times;24 No.5</td><td>for glass substrate</td></tr><tr><td>Micropipette</td><td>Eppendorf SE</td><td>3123000055</td><td></td></tr><tr><td>NMD-3</td><td>Tokyo Ohka Kogyo Co., Ltd.</td><td>NMD-3</td><td></td></tr><tr><td>OFPR-800</td><td>Tokyo Ohka Kogyo Co., Ltd.</td><td>OFPR-800</td><td></td></tr><tr><td>Phosphate pH standard solution</td><td>FUJIFILM Wako Pure Chemicals Corp.</td><td>166-17445</td><td></td></tr><tr><td>Photolithography Machine</td><td>Neutronix Quintel</td><td>PhL Q-2001CT</td><td></td></tr><tr><td>Pottasium Chrolide</td><td>FUJIFILM Wako Pure Chemicals Corp.</td><td>163-03545</td><td></td></tr><tr><td>Semiconductor Device Parameter Analyzer</td><td>Keysight</td><td>B1500A</td><td>softwere verion: rev 5 and 6</td></tr><tr><td>Semiconductor Device Parameter Analyzer Source measurement units</td><td>Keysight</td><td>B1517A</td><td>for source, drain and gate&amp;nbsp;&amp;nbsp;</td></tr><tr><td>Semiconductor Device Parameter Analyzer Test Fixture</td><td>Keysight</td><td>B1500A Opt A5F</td><td></td></tr><tr><td>Siliconce O-ring</td><td>MasuokaTokyo Co., Ltd.</td><td>P-5</td><td></td></tr><tr><td>Spin coater</td><td>MIKASA Co., Ltd</td><td>MS-A100</td><td></td></tr><tr><td>Sputtering machine</td><td>ULVAC Inc.</td><td></td><td>custom-made</td></tr><tr><td>SU-8 3005</td><td>Nippon Kayaku Co., Ltd.</td><td>SU8-3005</td><td></td></tr><tr><td>SU-8 developer</td><td>Nippon Kayaku Co., Ltd.</td><td>SU-8 Developer</td><td></td></tr><tr><td>Ultrasonic bath</td><td>SND Co., Ltd.</td><td>US-102</td><td></td></tr><tr><td>White-light Interferometer</td><td>KEYENCE Corp.</td><td>VK-X3000</td><td></td></tr></tbody></table>

fabrication of a solution-gated indium-tin-oxide-based one-piece transistor enabling sensitive biosensing

Fabrication of a Solution-gated Indium-Tin-Oxide-based One-piece Transistor Enabling Sensitive Biosensing

A simple and rapid method to fabricate a solution-gated one-piece indium-tin-oxide (ITO)-based ion-sensitive field-effect transistor (ISFET) (ITO-ISFET) for biosensing is presented in this report. Although ITO is a conductive oxide, it exhibits semiconducting properties at a depletion layer thickness of approximately 20 nm or less, making it suitable as the channel of a pH-sensitive solution-gated ISFET. Specifically, by etching the middle part of a conductive ITO single thin film with an acidic solution to make it ultrathin, a one-piece ITO-ISFET with a semiconductive channel can be fabricated. The source, drain electrodes, and channel are fully integrated without any interfaces. The ITO channel surface is then soaked in sample solutions with a reference electrode, enabling it to function as a solution-gated ISFET. Thus, the one-piece ITO-ISFET can be fabricated simply and rapidly using only sputtering followed by etching through a photolithography technique, with the sample solution conveniently serving as the gate.

Figure 2A shows the change in current (IDS0) measured during etching. IDS0 remained almost constant around 800 s after the start of etching. With further etching, IDS0 began to decrease rapidly. This indicates that the thickness of the ITO film decreased, which was approaching the thickness of the depletion layer in the ITO film19; thereby, electrons as carriers began to be affected in the channel by the surf...

This protocol describes the fabrication of a one-piece indium-tin-oxide (ITO)-based ion-sensitive field-effect transistor (ISFET), which can be constructed as a solution-gated FET sensor (e.g., pH sensor) using a short and simple process (approximately half a day). This one-piece ITO-ISFET can also be applied to biosensing.

A simple and rapid method to fabricate a solution-gated one-piece indium-tin-oxide (ITO)-based ion-sensitive field-effect transistor (ISFET) (ITO-ISFET) ...

The scope of this research is to demonstrate a simple and rapid method for fabricating a solution-gated one-piece transistor for pH sensing and highly sensitive biosensing. To increase the detection sensitivity of solution-gated FET biosensors, the technologies of miniaturization and lower dimensioning of material have been made used. We have found that a solution-gated FET can be easily fabricated by simply etching a portion of conductive ITO thin film to a thickness that exhibits semiconductivity, providing an all-by-ITO technology.Using this method, a solution-gated FET can be fabricated more easily than with other protocols, and the fabricated device shows a steep subthreshold slope, which is related to sensitivity. The proposed method provides an all-by-ITO technology, leading pH sensing and highly sensitive biosensing, because the source, drain electrodes, and the channel are fully integrated without any interfaces. To begin, wash the glass substrate by sonicating it in acetone, methanol, and water for five minutes each.Using a nitrogen gas blower, dry the substrate thoroughly and bake it on a hot plate at 110 degrees Celsius for more than five minutes to ensure it is completely dry. Spin-coat the dried glass substrate with an OFPR-800 layer at 500 RPM for five seconds, followed by 3, 000 RPM for 30 seconds. Pre-bake the coated substrate on a hot plate at 110 degrees Celsius for five minutes.Allow the substrate to cool down to room temperature before proceeding. Position the photomask film on the photoresist-coated side of the substrate and use tape to fix it securely in place. Then expose the substrate to ultraviolet light using a photolithography machine for 40 seconds.Now, take the substrate out of the photolithography machine and carefully remove the photomask from the surface. To develop the photoresist, immerse the substrate in NMD-3 developer for one minute and verify that a sharp pattern is formed. Then dip the substrate in water to wash away the developer.After drying the washed substrate by blowing nitrogen gas, bake it on a hot plate at 110 degrees Celsius for five minutes. To begin deposition, fix the substrate onto a substrate holder using tape and introduce it into the vacuum chamber of a sputtering machine. Pump down the sputtering chamber pressure to below 10 to the power of 3 pascals.Then deposit a 100 nanometer thick layer of indium tin oxide via radiofrequency sputtering at four nanometers per minute under argon without substrate heating. To lift off the photoresist, sonicate the substrate in acetone, methanol, and then water for five minutes. Then blow the substrate dry using a nitrogen gas blower, and bake it on a hot plate at 110 degrees Celsius until fully dry.To spin-coat the clean substrate with SU-8 3005, spin at 500 RPM for five seconds, followed by 6, 000 RPM for 30 seconds. Pre-bake the SU-8-coated substrate on a hot plate set to 95 degrees Celsius for five minutes. Then place the photomask film on the photoresist-coated substrate and secure it with tape to prevent any movement during exposure.Expose the SU-8-coated substrate to ultraviolet light for seven seconds using a photolithography machine. Then remove the substrate from the machine and carefully detach the photomask. Post-bake the exposed substrate first at 65 degrees Celsius for two minutes, then at 95 degrees Celsius, and continue baking for five minutes.Immerse the substrate in SU-8 developer for three minutes under strong agitation to develop the photoresist. Rinse the substrate in 2-propanol for one minute, and dry the developed substrate using a nitrogen gas blower. To begin forming the semiconductive indium tin oxide channel, prepare 0.1 molar hydrochloric acid solution.Then connect the source and drain electrodes to a semiconductor parameter analyzer. Turn on the B1500A device, and start the EasyEXPERT software. Then open the workspace interface to begin setup.On the analyzer interface, select the Classic Test Tab, then choose the IVT Sampling option. Set the sampling Interval to 0.5 seconds. Apply a voltage of one volt between the source and drain electrodes, and record the initial current.Using a micropipette, place a 30 microliter drop of the prepared hydrochloric acid solution directly onto the exposed indium tin oxide channel area. Monitor the current between the source and drain electrodes continuously, and observe the conductivity change during etching. Continue the process until the current drops to 10%of the initial value.Then immediately rinse the etched indium tin oxide channel with deionized water to stop the etching once the current reaches 10%of the initial current. Dry the one-piece transistor by gently blowing nitrogen gas over the rinsed substrate using a nitrogen gas blower. Using a test fixture, connect the source and drain electrodes of the one-piece transistor to the semiconductor parameter analyzer.Place a silicone O-ring around the surface of the indium tin oxide channel to form a liquid well. Add 30 microliters of phosphate buffer or another standard pH buffer solution into the silicone O-ring well while making full contact with the indium tin oxide channel surface. Then insert a silver or silver chloride reference electrode into a saturated potassium chloride solution, which is connected to the gate electrolyte by salt bridge.Connect the silver or silver chloride reference electrode to the semiconductor parameter analyzer, so that it functions as the gate electrode. On the semiconductor parameter analyzer, select the Classic Test tab, then choose the I/V Sweep mode. Connect the source electrode to ground to establish a reference potential.Set the applied drain voltage to a constant value of one volt. Set the sweep range of gate voltages from minus 0.8 volts to plus 0.8 volts and adjust delay, integration time, and measurement interval. Then set the number of iterations to 10 cycles and use the data from the final cycle for analysis.Simultaneously, ensure that the leak current between the source and gate electrodes is recorded and start the measurement. On the semiconductor parameter analyzer, select the CMOS category in the Application Test tab, then choose the Id-Vd mode. Set the gate voltage to increase sequentially from zero volts to 0.8 volts in 0.1 volt intervals.For each gate voltage value, set the drain voltage to sweep from zero volts to one volt in 0.01 volt intervals and start the measurement. Now, remove the silicone O-ring from around the channel surface. Then rinse the channel area thoroughly with deionized water.Dry the one-piece indium tin oxide device using a nitrogen gas blower. The indium tin oxide ion-sensitive field effect transistor demonstrated a steep subthreshold slope of approximately 81 millivolts per decade, indicating near ideal switching behavior at 25 degrees Celsius. The gate leakage current remained four orders of magnitude lower than the drain current, even when the channel was directly exposed to the electrolyte solution.The drain current increased with the drain voltage and showed saturation behavior at each gate voltage, confirming good field effect transistor characteristics. The on/off current ratio exceeded 10, 000 for channel thicknesses below 20 nanometers, but dropped drastically at greater thicknesses. The one-piece indium tin oxide ion-sensitive field effect transistor responded linearly to pH changes, exhibiting a voltage shift of approximately 51 millivolts per pH unit.The pH sensitivity increased slightly after five days of wet storage, approaching the ideal Nernstian limit, and was retained even after 16 days.

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Learn to fabricate a solution-gated indium-tin-oxide-based one-piece transistor for sensitive pH sensing and biosensing applications. This rapid method uses all-by-ITO technology to enhance detection sensitivity.

Fabrication of a Solution-gated Indium-Tin-Oxide-based One-piece Transistor Enabling Sensitive Biosensing

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