Microfluidics integrated n-type organic electrochemical transistor for metabolite sensing

Microfluidics integrated n-type organic

electrochemical transistor for metabolite sensing

Item Type Article

Authors Koklu, Anil;Ohayon, David;Wustoni, Shofarul;Hama, Adel;Chen, Xingxing;McCulloch, Iain;Inal, Sahika

Citation Koklu, A., Ohayon, D., Wustoni, S., Hama, A., Chen, X.,

McCulloch, I., & Inal, S. (2021). Microfluidics integrated n-type organic electrochemical transistor for metabolite sensing.

Sensors and Actuators B: Chemical, 329, 129251. doi:10.1016/

j.snb.2020.129251 Eprint version Post-print

DOI 10.1016/j.snb.2020.129251

Publisher Elsevier BV

Journal Sensors and Actuators B: Chemical

Rights NOTICE: this is the author’s version of a work that was accepted for publication in Sensors and Actuators, B: Chemical. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document.

Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Sensors and Actuators, B: Chemical, [329, , (2020-12-01)] DOI:

10.1016/j.snb.2020.129251 . © 2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://

creativecommons.org/licenses/by-nc-nd/4.0/

Download date 2023-12-08 18:54:27

Link to Item http://hdl.handle.net/10754/666507

S1

Microfluidics integrated n-type organic electrochemical transistor for metabolite sensing

Anil Koklu¹, David Ohayon¹, Shofarul Wustoni¹, Adel Hama¹, Xingxing Chen^2,3, Iain McCulloch ^2,3,4 and Sahika Inal*¹

1Organic Bioelectronics Laboratory,Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia.

2Physical Science and Engineering Division, KAUST, Thuwal, 23955-6900, Saudi Arabia.

3KAUST Solar Center, KAUST, Thuwal, 23955-6900, Saudi Arabia.

4Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London, SW72AZ, UK.

Corresponding Author:

sahika.inal@kaust.edu.sa

S2 1. OECT fabrication

A bilayer resist structure (S1813 photoresist, Microchemicals GmbH; LOR 5B MicroChem Corp.

Westborough, MA) was used to pattern the electrical contacts of the sensor on glass wafers, followed by sputtering deposition of chromium (10 nm)/ gold (100 nm). After the gold lift-off process, the surface of the substrate was encapsulated by Parylene C using vaporization of the dimer (PDS 2010 Labcoater 2, Specialty Coating Systems, Indianapolis, IN). An anti-adhesion layer was spin coated, followed by the deposition of a sacrificial Parylene C layer, which allows for the patterning of the polymer in the desired channel and gate geometry. The metal contacts and the channels were finally exposed using reactive ion etching with O2 (Plasma lab 100 - ICP 380, Oxford Instruments).

Figure S1. Fabrication of the OECT via photolithography and Parylene C peel off. The fabrication process starts from the gold contact lines and gate electrode patterning and ends with the deposition of P-90 solution.

S3

2. Characterization of glucose oxidase immobilized P-90 surface

Figure S2. Fourier-transform infrared (FTIR) spectrum before and after the physical adsorption of glucose oxidase (GOx) on P-90. The dotted lines show the vertical shift.

3. N-type OECT sensor characterization

10^-7 10^-6 10^-5 10^-4 10^-3 0.0

0.4 0.8 1.2 1.6

2.0 w/ microfluidic w/o microfluidic

NR

Glucose Concentration (M)

Figure S3. The normalized relative change of ID obtained with and without microfluidic. The circles and squares represent the data taken from Figure 4 and 5, respectively.

S4

Figure S4. Time-course of variation of a) ID and b) IGupon successive additions of 1 nM of glucose solution into the microfluidic channel. c) Normalized changes in ID and IG over time.

a)

b)

c)

S5

Table S1. The performance of the glucose electrochemical sensors bearing various types of electrodes and prepared via different biofunctionalization methods.

Ref. Method/Device/Medium LoD or SNR Dynamic Range

Biofunctionalization

This work

Chronoamperometry/n-type, microfluidic integrated OECT /PBS

SNR=340 at 1 nM 1 nM-1 mM GOx

[1] Chronoamperometry/ P-90/Au based OECT /PBS

- 10 nM-20 mM

GOx

[2] Chronoamperometry/

PEDOT:PSS/Au based OECT /PBS -- 0.05-3 mM

Ferrocene/Chitosan/GOx

[3] Chronoamperometry/ PEDOT:PSS/

graphene/Pt based OECT /PBS

10 nM 0.01-50 µM Chitosan/GOx

[4]

Chronoamperometry/ PEDOT:PSS/Pt nanoparticles/Multi-walled CNT/Au based OECT /PBS

5 nM 0.005-10 µM Chitosan/GOx

[5]

Chronoamperometry/ PEDOT:PSS- TiO2 nanotubes/Nafion/ Pt nanoparticles/Au based OECT /PBS

100 nM 0.1 µM-5 mM GOx

[6] Chronoamperometry/ PEDOT:PSS-/

Polyaniline/ Nafion/ Graphene/Pt based OECT /PBS

30 nM 0.001-3 µM GOx

[7] Chronoamperometry/ CNT/In2O3

nanoribbon/Au based FET/PBS, Tear, Sweat, Saliva

10 nM (PBS) 10 nM-1 mM GOx/Chitosan

[8]

Chronoamperometry/ PVP-capped/Pt nanoparticles/Au based OECT /PBS, Saliva

100 nM (PBS) 0.1-100 µM GOx/Chitosan

[9] Chronoamperometry/ Pt based electrochemical sensor/PBS

200 µM 0.2-15 mM GA/BSA/APTES/GOx

[10]

Cyclic voltammetry / inkjet-printed CNTs/Graphene oxide/Au nanoparticles/PBS

50 µM 0.05-6 mM GOx

[11] Chronoamperometry/ SWCNT on ITO electrodes/PBS

SNR=3 at 200 µM 0.2-10 mM GDH/MG/SWCNT

[12]

Impedance based detection/ Au/zinc oxide electrodes within porous polyamide/human sweat

5.6 µM

5.6 µM -5.5 mM

DSP(linker)/GOx antibody/GOx Abbreviations: LoD (Limit of Detection), SNR (Signal to Noise Ratio), Au (gold), Pt (platinum), GOx (Glucose Oxidase), TiO2

(Titanium Dioxide), In2O3 (Indium (III) oxide), FET (Field Effect Transistor), GA (Glutaraldehyde), BSA (Bovine Serum Albumin), APTES (3-aminopropltriethoxysilane), GDH (glucose dehydrogenase), MG (Methylene Green), DSP (Dithiobis [succinimidyl propionate]) CNT (carbon nanotube), SWCNT (single walled carbon nanotubes, ITO (indium tin oxide)

S6 4. Theory and numerical simulations

A full understanding of the process requires an extensive model that couples the physics of the electrostatics and ionic transport in the fluidic domain, as well as specific chemical reaction in the polymer. For the current study, we have only simulated the fluidic part where the electric field and transport equations are solved to predict the system behavior. The governing equations for the electrode/electrolyte system are posed by Gauss’ law and the charge conservation equation without convection current assuming quasi electrostatic field (negligible magnetic field effect),

𝜌_𝑞 = 𝛁 ∙ (𝜀𝑬) (1a)

𝜕𝜌_𝑞

𝜕𝑡 + 𝛁 ∙ (𝜎𝑬) = 0 (1b)

𝛁 × 𝑬 = 0 (1c)

where 𝜌_𝑞 is the space charge density, 𝜀 is the permittivity of the fluid, 𝑬 is the electric field, 𝜎 is the electrical conductivity of the medium.

The computational domain is 2D and contains a dilute, completely dissociated electrolyte between gate and source-drain. The simulation domain is illustrated in Figure S-4. The concentrations of ions inside the electrolyte (Na⁺ and Cl^-) are described by the Nernst-Planck equation:

𝜕𝑐_𝑖

𝜕𝑡 + 𝛁 ∙ (−𝐷_𝑖𝛁𝑐_𝑖 −𝑧_𝑖𝐷_𝑖𝐹𝑐_𝑖

𝑅𝑇 𝛁𝜓) = 0 (5)

where 𝐷_𝑖 is the diffusion coefficient of species 𝑖 and 𝜓 is the electric potential. The electric field in the media is governed by Poisson equation:

𝛁 ∙ (𝜀𝑬) = 𝐹 ∑ 𝑧_𝑖𝑐_𝑖

𝑖

(6) where, 𝑬 is the electric field (𝑬 = −𝛁𝜓).

The simulation parameters and the boundary conditions are as follows. The operating temperature is 300 K and diffusivities of Na⁺ and Cl^- ions are fixed at 1.33 × 10^-9 m²/s and 2.30 × 10^-9 m²/s, respectively. The relative permittivity of medium is considered 78. All the boundaries are fixed as

S7

insulating boundary condition, except gate and organic channel which are excited at a constant voltage (Figure S2).

The bottom boundary is considered ideally polarizable without Faradic processes, so the ionic fluxes vanish at these boundary (𝒏 ∙ 𝑱_𝑖 = 0), while all the other boundaries are subjected to bulk ionic concentrations, except the left axisymmetric region. The initial cation and anion concentrations are set to the bulk concentrations and the initial potential is set to zero. The domain height is large enough so that the current is not changing with further increase in the domain size.

COMSOL Multiphysics software is used to solve the coupled Poisson-Nernst-Plank equations.

Figure S5. Numerical simulation domain along with the boundary conditions for electrical and transport of ionic species physics.

S8

Figure S6. Electric field distribution and cation concentration distribution for (a), (c) 30 µm and (b), (d) 1000 µm height domains. The zoomed in parts show the vicinity of the channel and the gate electrode.

a) b)

c) d)

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.0

0.1 0.2 0.3 0.4 0.5 0.6

Cations Concentration (M)

V_G (V)

1000 mm Channel Height 30 mm Channel Height

Figure S7. The average cation concentration on P-90 surface at varying gate voltages for 30 and 1000 µm microfluidic channel heights.

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