WO2013173754A1 - Dispositifs hétérogènes couplés pour détection du ph - Google Patents

Dispositifs hétérogènes couplés pour détection du ph Download PDF

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WO2013173754A1
WO2013173754A1 PCT/US2013/041649 US2013041649W WO2013173754A1 WO 2013173754 A1 WO2013173754 A1 WO 2013173754A1 US 2013041649 W US2013041649 W US 2013041649W WO 2013173754 A1 WO2013173754 A1 WO 2013173754A1
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Prior art keywords
transducer
sensor
channel
equal
nanowire
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PCT/US2013/041649
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English (en)
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Rashid Bashir
Bobby Reddy
Muhammad A ALAM
Pradeep R Nair
Jonghyun GO
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The Board Of Trustees Of The University Of Illinois
Purdue Research Foundation
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Priority to US14/075,557 priority Critical patent/US9835634B2/en
Publication of WO2013173754A1 publication Critical patent/WO2013173754A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/414—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
    • G01N27/4146—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS involving nanosized elements, e.g. nanotubes, nanowires
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/414—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
    • G01N27/4145—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS specially adapted for biomolecules, e.g. gate electrode with immobilised receptors

Definitions

  • the devices and methods disclosed herein are for use in pH measuring and monitoring applications. There is a need in the art for ultrasensitive detection of pH in a rapid and reliable manner.
  • Conventional pH sensors are generally confined by the Nernstian limit of 59 mV/pH, and have a detection limit practically constrained by signal- to-noise interference.
  • Provided herein are devices and methods that vastly improve the pH detection limit by effectively increasing the Nernstian limit by an amplification factor. In this manner, a pH sensitivity that is better than 0.02 pH units is achieved, including as good as 0.002 pH units. Such an improvement represents about an order of magnitude improvement over commercial pH sensors.
  • a sensor and a transducer, so as to obtain an amplification factor that functions to provide an extrinsic pH sensor response that is increased dramatically beyond the Nernst limit, including by factors of 10, 20, 100 or more, or a range of between about 1 0 and 1000.
  • the invention is a method of amplifying a pH signal, such as by providing a sensor comprising a source electrode, a drain electrode, a sensor channel provided between the source and drain electrodes, and a sensing surface over at least a portion of the sensor channel, wherein the sensor channel has a first transconductance.
  • a transducer is provided comprising a source electrode, a drain electrode, and a transducer channel provided between the source and drain electrodes, wherein the transducer channel has a second transconductance, and the second transconductance is greater than the first transconductance.
  • a material is applied to the sensing surface, wherein a change in pH of the material generates a conductance modulation of the sensor channel.
  • a bias of the transducer is adjusted to counterbalance the conductance modulation of the sensor channel, thereby amplifying the pH signal of the material.
  • the amplifying corresponds to selecting an amplification factor that is defined by:
  • ⁇ is the channel mobility
  • W is the channel width
  • L is the channel length
  • V DS is the drain bias
  • Cox is the gate oxide capacitance
  • subscripts 1 and 2 refer to the sensor and the transducer, respectively.
  • an appropriate amplification factor is obtained by adjusting one or more of the parameters that define the amplification factor, including a geometry, mobility scaling, oxide thickness, and/or bias.
  • the amplification factor is greater than or equal to 10, greater than or equal to 20, greater than or equal to 1 00, or selected from a range that is between about 20 and 20,000.
  • the selecting step comprises selecting a width and/or a length of: the transducer, the sensor, or both, so that (W/L) 1 /(W/L) 2 is greater than or equal to 20.
  • any of the sensor channels provided herein is a nanoplate and any of the transducer channels is a nanowire.
  • Such a configuration provides the ability to greatly vary the ratio of Wi/W 2 in the above Eq'n (A) so as to obtain a desired amplification factor.
  • W 1 /W 2 is greater than or equal to 20 and less than or equal to 1 x1 0 6 .
  • any of the widths may be described in absolute terms, such as a nanoplate width (Wi) that is greater than or equal to 1 ⁇ and less than or equal to 100 ⁇ , and/or a nanowire width (W 2 ) that is greater than or equal to 1 nm and less than or equal to 1 00 nm.
  • l_i L 2 .
  • the term "nanoplate” has traditionally been used to describe objects with about 100nm dimensions, here we use the term to describe a transistor, including a channel thereof, that is that is about 100nm thick with width (W) that may be greater than nano scale, including widths on the order of about 1 -20 ⁇ wide, to emphasize its pairing with a NW transistor.
  • the term “nanowire” refers to wires that have cross sections on the order of about 1 00 nm, such as diameters that are about 1 0nm to 200nm, or more specifically rectangular or square cross-sections that are (10nm-200nm)x(10nm- 200nm), and any subranges thereof.
  • the lengths of the nanoplate and nanowire can be on the order of many microns, such as greater than 1 ⁇ , greater than 10 ⁇ , or selected from a range of between about 1 ⁇ and 100 ⁇ .
  • the selecting step comprises mobility scaling so that the sensor channel has a higher mobility than a transducer channel mobility. This selecting embodiment may be achieved by providing a first material for the sensor channel and a second material for the transducer channel, wherein the first material has a higher mobility than the second material. Examples of such sensor/transducer (first
  • material/second material pairs include, but are not limited to: AIGaN/Si ; SiNW/Si ;
  • the mobility scaling comprises providing the sensor as part of an n-channel metal-oxide-semiconductor field-effect transistor (nMOS) and the transducer as part of a p-channel metal-oxide-semiconductor field-effect transistor (pMOS).
  • nMOS n-channel metal-oxide-semiconductor field-effect transistor
  • pMOS p-channel metal-oxide-semiconductor field-effect transistor
  • effecting relative changes in sensor and transducer channel mobility provides a means for adjusting the amplification factor of Eq'n (A).
  • the selecting step comprises oxide thickness scaling, such as to obtain a Cox,i that is greater than Cox,2 by at least a factor of 20.
  • the scaling may be achieved by a dual oxide process to provide an oxide layer thickness of the sensor that is greater than an oxide layer thickness of the transducer.
  • the oxide thickness scaling may be by providing a sensor channel material having a higher k-dielectric than a transducer channel material k-dielectric. Examples of k-dielectric materials include those discussed in WO 2012/078340, hereby incorporated by reference.
  • the oxide thickness scaling may comprise both the oxide layer thickness selection and the higher k-dielectric selection.
  • the selecting step comprises bias scaling so that VDS,I is greater than or equal to V DS ,2 by a factor of at least 20.
  • This bias scaling is particularly suited for applications where tuning of the device is desired, such as to change the dynamic range or the pH sensitivity as the other methods generally are fixed upon device manufacture.
  • the bias scaling provides real-time tunability of sensor performance, such as a performance wherein the dynamic range of pH is tuned to cover a pH unit range that is between about 0.01 pH units to about 1 pH unit, or a sensitivity that is tuned to provide about 0.001 pH units sensitivity to about 0.02 pH units sensitivity.
  • any of the methods and devices provided herein may be described by one or more functional parameters, such as having a Nernst response that is greater than or equal to 0.5 V/pH, or that is greater than or equal to 1 0 V/pH, or that is between about 0.5 V/pH and 100 V/pH and any subranges thereof.
  • the functional parameter is a dynamic pH range of up to 0.5 pH.
  • the functional parameter is a pH sensitivity selected from a range that is greater than or equal to 0.001 pH units and less than or equal to 0.01 pH units.
  • the transducer channel is biased to a top gate or to a bottom gate.
  • the sensor channel is biased to a fluid gate that is at least partially immersed in the material, such as a material that is a fluid.
  • the transducer further comprises a transducer surface and the material is provided on the transducer surface in addition to the sensing surface, wherein the second transconductance is substantially independent or is independent of pH, in contrast to the first transconductance.
  • This may be achieved by coating or surface treating the nanowire with a chemically inert and/or non-interacting surface material so that the surface does not bind protons.
  • the transducer may be positioned outside of a well in which the material is confined, in contrast to the sensor's sensing surface.
  • the methods and devices provided herein are suitable for use in a range of applications, such as nucleotide sequencing, environmental toxic monitoring, pharmaceutical testing, food testing, cancer monitoring, detection of enzyme activity, or any other application where a change in pH provides information about a process or status.
  • the material comprises a fluid, such as an electrically- conductive fluid or an electrolyte.
  • the fluid is a biological material, or a liquid in which a biological material is suspended.
  • the material or fluid is defined by a sample volume that is applied to the device, such as a fluid well in which the sensing surface forms at least part of a surface.
  • the sample volume that is applied to the device is a low volume sample, such as less than 1 mL, less than 1 ⁇ , or selected from a range that is between about 0.1 and 10 mL, or any sub-ranges thereof.
  • the material comprises a biological cell and intracellular pH, extracellular pH, or both intracellular and extracellular pH is measured.
  • the biological cell is lysed and the internal pH measured, such as by monitoring a change in pH of a fluid in which the cell is lysed.
  • Any of the methods and devices provided herein has a sensing surface that comprises an oxide surface, such as an oxide surface that interacts with a proton.
  • the oxide surface may comprise OH surface groups that react with protons to provide a sensor channel transconductance modulation that is pH dependent.
  • the invention is a device for measuring changes in pH in a fluid, the device comprising : a sensor comprising a fluid gate, a source electrode, a drain electrode, a sensor channel provided between the source and drain electrodes, and a sensing surface over at least a portion of the sensor channel for receiving the fluid, wherein the sensor channel is a nanoplate in electrical contact with the fluid gate; a transducer comprising a top or a bottom gate, a source electrode, a drain electrode, and a transducer channel provided between the source and drain electrodes, wherein the transducer channel is a nanowire in electrical contact with the top or the bottom gate; wherein the sensor channel has a width (Wi) and the nanowire has a width (W 2 ).
  • the ratio of W 2 is greater than or equal to 20, or seleted from a range that is greater than or equal to 20 and less than or equal to 1000.
  • any of the devices have an amplified Nernst response that is greater than or equal to 0.5 V/pH.
  • any of the devices have the transducer channel or nanowire is electrically connected to the top gate, having a pH sensitivity that is greater than or equal to 1 V/pH.
  • the transducer channel or nanowire is electrically connected to the bottom gate, having a pH sensitivity that is greater than or equal to 1 0 V/pH.
  • the nanoplate has a width to length ratio and the nanowire has a width to length ratio (W/L) 2 , wherein (W/L)i /(W/L) 2 is greater than or equal to 20 and less than or equal to 10,000.
  • l_i ⁇ L 2 The methods and devices provided herein are compatible with a wide range of L, wherein L refers to either or both Li and L 2 .
  • l_i and L 2 are independently selected to be greater than or equal to 100 nm and less than or equal to 1 mm.
  • l_i and L 2 are independently selected to be greater than or equal to 1 ⁇ and less than or equal to 100 ⁇ .
  • the nanoplate and the nanowire comprise Si.
  • the nanoplate and the nanowire comprise materials that are different from each other, such as AIGaN/Si ; SiNW/Si ; GaN/Si.
  • the transducer further comprises a transducer surface that contacts the fluid, wherein a transducer channel conductance is not substantially affected by a change in pH of the fluid.
  • the nanowire is physically isolated from the fluid.
  • any of the devices described herein are tunable, such as to achieve a user-selected pH sensitivity, a user-selected pH dynamic range, or both a user-selected pH sensitivity and pH dynamic range, including over any of the ranges described herein.
  • the device has a pH sensitivity that is better than 0.01 pH units.
  • any of the devices provided herein have a sensor and the transducer with a common source and a common drain.
  • the sensor and transducer are electrically connected to physically distinct sources and physically distinct drains.
  • FIG. 1 Schematic diagram of a standard ISFET pH sensor.
  • the surface groups (OH) react with protons (H + ) in electrolyte, and the reaction products (OH 2 + and O " ) create a net surface charge
  • (b) Changes in the pH of the electrolyte are reflected in the change of surface charge and eventually changes in channel current (l D ) from source (S) to drain (D).
  • the change in fluidgate bias (AV G ) required to restore l D to the original value defines the pH sensitivity of the ISFET.
  • NP is always biased by the fluid gate, but the NW can be biased via the top or bottom gate, illustrated as schematics in (d).
  • FIG. 1 [033] Figure 2.
  • the dashed lines indicate the corresponding theoretical estimates dictated by Eq (4).
  • the solid shaded region represents the classical sensitivity regi me below the Nernst li mit (59 mV/pH).
  • FIG. 3 The simulated pH sensitivity of GN scheme with various types of sensing devices (T-i in Figure 1 c) in the literature: AIGaN 13 (squares), GaN 14 (>), and Si NW 15 (0)-based ISFETs.
  • a Si n-MOSFET serves as T 2 .
  • the rest (black) symbols indicate the experi mental data from several DG FET sensors in the literature. 6"8
  • the solid black line represents the theoretical limit of the DGFET sensors.
  • FIG. 4 (a) The measured sensitivity (top of plot dots) of an isolated nanoplate ⁇ ) sensor and instrument noise (open circles) as a function of nanoplate gate bias (V G ,i ), as defined in Fig. 1 d. (b) Corresponding plot for the nanoplate- nanowire (T T 2 ) sensor scheme proposed in this paper. The measured sensitivity in (b) represents the top of plot dots in Fig. 2e. The theoretical lower li mit of 1 /f noise are also shown (solid curve).
  • Figure 8 Schematic of a device for amplifying a pH signal and measuring pH.
  • FIG. 9 Schematic of a nanowire-nanoplate pH sensor configuration. A constant DC bias is applied to the gate of T2, the plate device. The gate of T1 , the wire, is swept while the total current I is measured as a function of the pH over T2.
  • Figure 10 A- Transfer characteristics for the nanoplate (for 5 different pH values) and for the nanowire. B- Zoomed in region around the rectangle in part A.
  • Figure 11 The transfer characteristics of the combined nanowire-nanoplate device as a function of pH.
  • the line associated with AV t shows an example of how the shift in threshold voltage for the device is calculated.
  • Example 1 Coupled Heterogeneous Nanowire-Nanoplate Planar Transistor Sensors for Giant Nernst Response
  • ⁇ / ⁇ 59 mV/pH x a
  • 59 mV/pH the Nernst response
  • a an amplification factor that depends on the geometrical and electrical properties of the sensor and transducer nodes.
  • ISFETs such as the label-free detection of biomolecules in human genome sequencing 5 , however, requires the ability to detect just a few hundred protons ( ⁇ 0.02) in rapid flux (milliseconds response). For those applications, ability to amplify the Nernst signal can simplify design and increase throughput.
  • a recent trend for such amplification is based on double-gate silicon-on-insulator FET (DGFET) and a "super" Nernst response of ⁇ 1 V/pH has been demonstrated 6"9 .
  • DGFET double-gate silicon-on-insulator FET
  • SOI silicon-on-insulator
  • FIG. 1 c an alternative is presented based on a highly integrated Si nanoplate (NP)-nanowire (NW) transistor pair that is compatible with planar Si processing technology, see Fig. 1 c.
  • the nanoplate acts as the pH sensor node biased through the fluid gate, while the transducer node, defined by the NW, is biased either through the top-gate (top-gated NW) or the bottom gate
  • ISFET fluid gate
  • S source
  • D drain
  • Any shift in pH of the electrolyte changes the surface charge at the electrolyte-oxide interface through the site-binding process.
  • ISFET detects pH shifts in the electrolyte by monitoring changes in Si channel current due to charge modulation of surface group at electrolyte-oxide interface 10 .
  • the pH sensitivity is obtained by measuring shift of fluid gate voltage (AV G ) at a given amount of pH changes in constant current operation.
  • any change in buffer pH manifests as an effective change in surface potential (or an effective change in applied bias for constant current operation) as
  • the maximum pH sensitivity known as the Nernst limit
  • AV G I ⁇ 59mV I pH in room temperature.
  • the sensitivity is always less than the intrinsic Nernst limit (associated with electrolyte/oxide interface) due to the high electrolyte screening, protonation affinity of sensor surface, and most importantly, finite semiconductor capacitance of an ISFET 10 .
  • GN "Giant” Nernst (GN) scheme.
  • the NP FET acts a sensor transistor Ti and is exposed to the buffer solution for pH sensing, while the NW FET T 2 acts as a transducer and is isolated from the buffer, or is not reactive to the buffer. Since the transistors are compatible with planar top-down technology and are processed simultaneously, the process is simple and no additional masks are necessary.
  • ⁇ 2 is the channel mobility
  • Cox ,2 is the gate oxide capacitance
  • W and L is the channel width and length
  • V D s,2 is the drain bias
  • AV G 2 is the gate bias modulation. Since Ti and T 2 are in accumulation regime, the band bending at the channel surface is very small. Hence the current modulation of ⁇ due to any pH-induced modulation of top-oxide/buffer interface potential is given by ⁇ » ⁇ ⁇ 1 ⁇ 1 ( W / L )i vDS , AV G 1 ⁇ NOTE
  • Equation (4) suggests that GN scheme achieves significant amplification over DGFET sensors [i.e., GN » a SN ) by (i) Scaling of device dimension, so that W/L of Ti far exceeds that of T 2 (and hence the use of NP and NW transistor couple), (ii) Mobility scaling so that Ti has higher mobility than T 2 . This can be achieved by using
  • Oxide thickness scaling - this option is similar to the DGFETs. For maximum amplification, C 0X L » C OX 2 . This is achieved through oxide thickness scaling in a dual oxide process or by using higher-k dielectrics for Ti compared to T 2 or a combination thereof. And finally, (iv) Bias scaling so that V DS of T 2 is smaller than that of Ti .
  • This option of bias scaling provides a post-process, point-of-care option to tune the sensor performance. Since the geometry of DGFET precludes the use of device, bias, and mobility scaling, the response is typically limited to ⁇ 1 V/pH.
  • FIG. 2 demonstrates the experimental validation of Giant Nernst (GN) scheme, with the maximum GN response of >10V/pH.
  • NW Giant Nernst
  • FIG. 2 demonstrates the experimental validation of Giant Nernst (GN) scheme, with the maximum GN response of >10V/pH.
  • Fig. 2a shows the isolated transfer characteristics (/ D , 2 vs. V G , 2 ) of the nanowire (T 2 ) measured in dry air with bottom gate operation.
  • the NW gate bias V G , 2 needs to be shifted versus pH changes ( ⁇ ) at the constant current level of / ⁇ vs. V G 2 in Fig. 2c.
  • V G ,i we measure the shift of curves (AV G 2 ) for a constant current level. This measured sensitivity (AV G 2 / ⁇ ) of the first configuration is shown in Fig. 2e as dots at the top of the plot.
  • AIGaN serving as Ti
  • Eq. (4) therefore defines the fundamental upper limit of pH sensing for NW-NP based sensors. In practice, this upper limit may not be achieved due to fundamental and practical issues, as discussed in the next section.
  • any of the Ti/T 2 pairs provided in FIG. 3, or the literature associated herein, are utilized in any of the methods and devices provided herein to further increase the amplification factor.
  • the 1/f noise is the dominant source of noise at frequencies relevant for pH sensors 17 and its power-spectrum is given by s v ⁇ (sv G ) 2 ⁇ i/ A (A is a device area), or (sv e ) 2 ⁇ ⁇ ⁇ ⁇ ( ⁇ is a prefactor).
  • sv ⁇ (sv G ) 2 ⁇ i/ A A is a device area
  • sv e 2 ⁇ ⁇ ⁇ ⁇
  • ⁇ is a prefactor
  • Example 2 Fabrication Methods of Nanowire and Nanoplate Devices. The devices are fabricated using top down fabrication, starting with bonded SOI wafers.
  • Wafers were doped with boron at 1 0 KeV at a dose of 10 14 cm '2 and a tilt of 7 ° .
  • the gate dielectric was formed.
  • the wafers are dry oxidized for 1 minute at 1000 ° C to form a gate oxide of around 50 A, which was measured via ellipsometry on monitor wafers also present during the oxidation run. This also serves as a dopant activation step.
  • HfO 2 devices after a brief BOE dip and dopant activation in nitrogen for 3 minutes at 1000 ° C, the wafers were placed into an atomic layer deposition (ALD) machine for 150 cycles of HfO2 for a target thickness of 150 A.
  • ALD atomic layer deposition
  • the main sensing chip with the nanoplate device (2 ⁇ wide) had a 150 A thick HfO 2 dielectric, while the device exhibiting the GN response (a 50 nm wide nanowire device) contained a 50 A thick SiO 2 dielectric. Both chips were fitted with open PDMS wells for containing the fluid. The values for the pH for each solution were measured separately with a commercial pH meter. The fluidic environments over the two separate chips were biased with two leak-free Ag/AgCI reference electrodes purchased from Warner Instruments. A 1 X phosphate buffer saline (PBS) solution at pH 7.4 was used for the nanowire device for the entire experiment to enable normal transfer characteristics.
  • PBS X phosphate buffer saline
  • Robinson buffers (0.04 M of phosphoric, boric, and acetic acid) with titrated HCI and NaOH, which have good buffering capacity over wide pH ranges, were manually pipetted and rinsed in the PDMS well over the nanoplate device, followed by a 5 minute settling time to allow the surface charge to equilibrate. Transfer characteristics were measured using a Keithley 4200 semiconductor characterization system. The source and drain nodes of the devices were shorted together to create the full GN response sensor, and current was measured at the shorted source nodes of the devices.
  • ⁇ ⁇ >1 ⁇ , V DS 1 Q 0 (Jl + V G 1 / ⁇ 0 - + (V G , + AV G 1 ) /V 0 ). (S3)
  • Equation (S4) can be simplified such that AV G 2 ⁇ a GN (Q O if V G 1 » AV G 1 ,V 0 .
  • This analytical expression implies the
  • the GN scheme still offers significant amplification over DGFET sensors as a GN »1 .
  • Equation (S5) represents the electrostatics of the buffer (/3 ⁇ 4-ion concentration), while eq. (S6) describes the semiconductor (n, - intrinsic carrier concentration and ⁇ / ⁇ is the p-type doping density).
  • Eq. (S7) describes top oxide/buffer interface whose RHS denotes the pH dependent charge due to the protonation/de-protonation of surface OH groups. This charge is modeled as function of buffer H + concentration through the well-known site binding model Oand will not be discussed in detail here.
  • FIG. 5 shows the bias-dependent amplification for GN scheme (symbols indicate numerical simulation results while solid lines indicate analytical results).
  • T 2 is in linear regime while the bias applied to Ti is varied.
  • GN scheme achieves ⁇ 10V/pH in accumulation regime, which is many orders of magnitude better than the current DGFET sensors (0.1 ⁇ 1 V/pH). While in depletion mode of Ti the sensitivity is slightly reduced but still much higher than that of DGFET. In general, therefore one should operate the sensing device in accumulation regime to achieve maximum sensitivity.
  • /V t is the volume trap density in the gate oxide layer
  • A is the tunneling parameter
  • C eff is the capacitance per area
  • a is the coulomb scattering coefficient
  • Fig. 7 shows how the DC current and its noise changes in a nanoplate (Ti , left)- nanowire (T 2 , right) pair.
  • the initial noise of Ti and T 2 is proportional to their widths: and W 2 , respectively.
  • W ] /W 2 1 00 and j(SV G 1 ) 2 is 1 mV, then the noise ratio is 10 thus T 2 noise is 10mV, which is the dominant one in the GN scheme (T1-T2).
  • the noise of GN sensor (T1 -T2), denoted as ⁇ ⁇ 1 TM , is fundamentally equal to that of a single nanoplate pH sensor since any signal buried under the noise of NP ( ⁇ ) in GN scheme (T T 2 ) would not be also detectable in T 2 .
  • NP-NW GN
  • GN scheme has its advantage over NP- alone sensor in terms of pH resolution in Cases (2) and (3) in which the pH resolution of GN scheme is much smaller than that of a single NP sensor. Since Cases (2) and (3) are the dominant situation especially for the point-of-care devices whose measurement instrument is not sophisticated enough ( V ⁇ ⁇ 1 -1 ⁇ in general), the GN scheme always enhance the minimum pH resolution by the factor of a GN for the sensors with relatively low-precision instruments.
  • the device has a sensor 20 and a transducer 200.
  • the sensor 20 comprises a fluid gate 30 and corresponding fluid gate bias 40 (V G ,i ) .
  • the fluid gate 30 is at least partially immersed in a material or fluid 50 in which pH is measured.
  • a sensor channel 60 is positioned between a source electrode 70 and a drain electrode 80 along with a sensing surface 65 that physically contacts and supports the fluid 50.
  • the sensor channel may further comprise a layer 62 that interacts with the fluid to generate a detectable electrical property, such as transconductance that is modulated based on the pH of the fluid.
  • the layer 62 may be an oxide layer, as illustrated in FIG. 1 (a).
  • the sensor channel 60 is a nanoplate (labeled NP in FIG. 1 (d)).
  • the transducer 200 comprises a top or bottom gate 210 (see FIG. 1 (d) top panel for bottom gate embodiment and bottom panel for top gate embodiment) and corresponding gate bias 240 (V G ,2) .
  • source and drain electrodes are illustrated as corresponding to the source 70 and drain 80 electrodes of the sensor.
  • source and drain electrodes used with the transducer 200 are separate and distinct from those used with the sensor 20.
  • a transducer channel 260 is positioned between the source and drain electrodes.
  • the illustrated embodiment depicts fluid droplet 50 that is not in contact with the transducer 200.
  • the sensor and transducer channels from a fluid well for receiving a fluid 50, in which case the transducer is configured such that the transconductance of the transducer is
  • the transducer channel may be nanowire (NW).
  • the sensor and transducer channel widths are Vl- and W 2 , respectively.
  • l_i and l_ 2 defines the sensor and transducer channel lengths. The illustrated embodi ment shows those lengths as equal and corresponding to the distance between the source and drain. Optionally, the lengths are not equal.
  • any of the lengths may be less than the separation distance between the source and drain, such as by patterning of sensor, transducer, source or drain shape, including by one or more channel ends that are separated from source and drain, but electrically connected thereto by an electrical interconnection.
  • a channel current 300 (l D ) including a source-drain current for each of the sensor (I D,I) and transducer (l D ,2) is monitored along with drain bias 400 (V D D), including the drain bias of the sensor (V D, i) and the transducer (V D ,2) , thereby measuring pH, including detecting changes in pH, by the amplification factor arising from the unique sensor and transducer configurations.
  • Example 3 Ultrasensitive pH Detection by Nanowire-Nanoplate Combination Sensor:
  • the two transistors have separate fluid wells and separate reference electrodes, which can be used to control the separate fluid potentials separately.
  • T1 is considered to be the sensing element, and is exposed to solutions of varying pH with a fixed gate bias
  • VFG2- T2 is the "transducer" element, and is exposed to only a reference solution throughout the experiments. Transfer characteristics of T2 are used as the output characteristic (by sweeping V F GI), while the pH of the solutions over T2 is the input characteristic.
  • VFG2- T2 is the "transducer" element, and is exposed to only a reference solution throughout the experiments.
  • Transfer characteristics of T2 are used as the output characteristic (by sweeping V F GI), while the pH of the solutions over T2 is the input characteristic.
  • As the pH is changed over T1 large changes in the total current I will be induced due to the surface potential changes over T1 .
  • very large shifts in the I- VFG2 are required, as illustrated in FIG. 11. These large shifts are amplified by a factor of approximately W2/
  • FIG. 10 Individual transfer characteristics of the nanowire device and the nanoplate device at five different pH values are shown in FIG. 10.
  • the nanowire current is seen to be significantly lower ( ⁇ 20X) than the current through the plate.
  • a blown up view of the nanoplate as a function of changing pH is shown in FIG. 10B. Values around
  • This sensitivity factor is approximately equal to:

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  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

La présente invention concerne des procédés et des dispositifs pour mesurer le pH et pour amplifier un signal de pH pour obtenir la détection ultrasensible de changements de pH. Cela est obtenu en produisant un capteur et un transducteur, la transconductance du capteur étant sensible aux changements de pH et la transconductance du transducteur n'étant pas affectée par un changement de pH. Au lieu de cela, le transducteur compense les changements de transconductance du capteur dus à un changement de pH. La configuration unique du capteur et du transducteur l'un par rapport à l'autre permet des augmentations substantielles d'un facteur d'amplification de pH, de manière à produire des dispositifs de détection de pH ayant une réponse de Nernst amplifiée et, par conséquent, une sensibilité au pH nettement augmentée.
PCT/US2013/041649 2012-05-17 2013-05-17 Dispositifs hétérogènes couplés pour détection du ph WO2013173754A1 (fr)

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US9488614B2 (en) 2012-10-16 2016-11-08 Abbott Laboratories Localized desalting systems and methods
US10527579B2 (en) 2014-03-28 2020-01-07 The Board Of Trustees Of The University Of Illinois Label free analyte detection by electronic desalting and field effect transistors
WO2020060664A1 (fr) * 2018-09-17 2020-03-26 Rutgers, The State University Of New Jersey Transducteur acoustique à haute fidélité électro-osmotique
CN111295581A (zh) * 2017-11-09 2020-06-16 国际商业机器公司 用于分析物检测的pH控制
WO2021130525A1 (fr) * 2019-12-24 2021-07-01 Università Degli Studi Di Bari Aldo Moro Système de dosage biologique à base de transistor comprenant une plaque de réception d'accouplement et une plaque d'électrode de grille

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9488614B2 (en) 2012-10-16 2016-11-08 Abbott Laboratories Localized desalting systems and methods
US9821321B2 (en) 2012-10-16 2017-11-21 Abbott Laboratories Localized desalting systems and methods
US10052639B2 (en) 2012-10-16 2018-08-21 Abbott Laboratories Localized desalting systems and methods
US10527579B2 (en) 2014-03-28 2020-01-07 The Board Of Trustees Of The University Of Illinois Label free analyte detection by electronic desalting and field effect transistors
CN111295581A (zh) * 2017-11-09 2020-06-16 国际商业机器公司 用于分析物检测的pH控制
WO2020060664A1 (fr) * 2018-09-17 2020-03-26 Rutgers, The State University Of New Jersey Transducteur acoustique à haute fidélité électro-osmotique
US20220032340A1 (en) * 2018-09-17 2022-02-03 Rutgers, The State University Of New Jersey Electroosmotic High Fidelity Acoustic Transducer
WO2021130525A1 (fr) * 2019-12-24 2021-07-01 Università Degli Studi Di Bari Aldo Moro Système de dosage biologique à base de transistor comprenant une plaque de réception d'accouplement et une plaque d'électrode de grille

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