Flexible Graphene Electrodes Research Articles

Portable glucose sensing analysis based on laser-induced graphene composite electrode.

In this work, a portable electrochemical glucose sensor was studied based on a laser-induced graphene (LIG) composite electrode. A flexible graphene electrode was prepared using LIG technology. Poly(3,4-ethylene dioxythiophene) (PEDOT) and gold nanoparticles (Au NPs) were deposited on the electrode surface by potentiostatic deposition to obtain a composite electrode with good conductivity and stability. Glucose oxidase (GOx) was then immobilized using glutaraldehyde (GA) to create an LIG/PEDOT/Au/GOx micro-sensing interface. The concentration of glucose solution is directly related to the current value by chronoamperometry. Results show that the sensor based on the LIG/PEDOT/Au/GOx flexible electrode can detect glucose solutions within a concentration range of 0.5 × 10-5 to 2.5 × 10-3 mol L-1. The modified LIG electrode provides the resulting glucose sensor with an excellent sensitivity of 341.67 μA mM-1 cm-2 and an ultra-low limit of detection (S/N = 3) of 0.2 × 10-5 mol L-1. The prepared sensor exhibits high sensitivity, stability, and selectivity, making it suitable for analyzing biological fluid samples. The composite electrode is user-friendly, and can be built into a portable biosensor device through smartphone detection. Thus, the developed sensor has the potential to be applied in point-of-care platforms such as environmental monitoring, public health, and food safety.

Transparent shape memory polyimide enables OLED for smart deformation

An innovative process for producing flexible transparent graphene electrodes has been proposed. The electrochemically polished copper-foil was used as the metal substrate to prepare high-quality monolayer graphene. Monolayer graphene was transferred from copper-foil to transparent shape memory polyimide (TSMPI) intactly by novel flow-casting transfer technology, and the smart, ultra-clean and smooth flexible graphene electrode (pG@TSMPI) was fabricated. The light transmittance of pG@TSMPI at 550 nm is 86%, the average sheet resistance is 310 Ω/sq, and the surface roughness (Ra) is 18 nm. Smart white OLED was manufactured using pG@TSMPI as transparent anode, and its luminescence performance was comparable to that of ITO-based device. Depending on the shape memory effect of TSMPI substrate, the smart OLED has the superiorities of variable stiffness and reconfigurable shape, which can transform from 2D structure into complex 3D structure.

Transparent and Flexible Graphene Pressure Sensor with Self-Assembled Topological Crystalline Ionic Gel

This study demonstrates transparent and flexible capacitive pressure sensors using a high-k ionic gel composed of an insulating polymer (poly(vinylidene fluoride-co-trifluoroethylene-co-chlorofluoroethylene), P(VDF-TrFE-CFE)) blended with an ionic liquid (IL; 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide, [EMI][TFSA]). The thermal melt recrystallization of the P(VDF-TrFE-CFE):[EMI][TFSA] blend films develops the characteristic topological semicrystalline surface of the films, making them highly sensitive to pressure. Using optically transparent and mechanically flexible graphene electrodes, a novel pressure sensor is realized with the topological ionic gel. The sensor exhibits a sufficiently large air dielectric gap between graphene and the topological ionic gel, resulting in a large variation in capacitance before and after the application of various pressures owing to the pressure-sensitive reduction of the air gap. The developed graphene pressure sensor exhibits a high sensitivity of 10.14 kPa-1 at 20 kPa, rapid response times of <30 ms, and durable device operation with 4000 repeated ON/OFF cycles. Furthermore, broad-range detections from lightweight objects to human motion are successfully achieved, demonstrating that the developed pressure sensor with a self-assembled crystalline topology is potentially suitable for a variety of cost-effective wearable applications.

Graphene-Based Flexible Electrode for Electrocardiogram Signal Monitoring

With the rapidly aging society and increased concern for personal cardiovascular health, novel, flexible electrodes suitable for electrocardiogram (ECG) signal monitoring are in demand. Based on the excellent electrical and mechanical properties of graphene and the rapid development of graphene device fabrication technologies, graphene-based ECG electrodes have recently attracted much attention, and many flexible graphene electrodes with excellent performance have been developed. To understand the current research progress of graphene-based ECG electrodes and help researchers clarify current development conditions and directions, we systematically review the recent advances in graphene-based flexible ECG electrodes. Graphene electrodes are classified as bionic, fabric-based, biodegradable, laser-induced/scribed, modified-graphene, sponge-like, invasive, etc., based on their design concept, structural characteristics, preparation methods, and material properties. Moreover, some categories are further divided into dry or wet electrodes. Then, their performance, including electrode–skin impedance, signal-to-noise ratio, skin compatibility, and stability, is analyzed. Finally, we discuss possible development directions of graphene ECG electrodes and share our views.

Probing Light-Stimulated Activities in the Retina via Transparent Graphene Electrodes.

Graphene has triggered tremendous research due to its superior properties. In particular, the intrinsic high light transmission illustrates the unique advantage in neural biosensing. Here, we combine perforated flexible graphene electrodes with microfluidic platforms to explore real-time extracellular electrical activities of retinal ganglion cells (RGCs). Under light stimulation, the transparent graphene electrodes have demonstrated the capability of recording the electrical activities of stimulated RGCs in direct contact. Different types of RGCs have shown three distinct light induced patterns, ON, OFF, and ON-OFF, which are primarily operated by cone photoreceptors. Moreover, the observed spiking waveforms can be divided into two groups: the biphasic waveform usually occurs at contacts with soma, while the triphasic waveform is likely related to the axon. Under high K+ stimulation, the graphene electrodes exhibit higher electrical sensitivity than gold counterparts with an average 2.5-fold enhancement in spiking amplitude. Furthermore, a strong response has been observed with the firing rate first increasing and then ceasing, which could be due to the potassium-induced neural depolarization. These results show that graphene electrodes can be a promising candidate in the electrophysiology studies of retina and offer a route to engineering future two-dimensional materials-based biosensors.

Flexible graphene electrodes from potentiodynamic reduction in neutral medium for enhanced specific capacitance and cyclic stability

High performance, flexible graphene electrode on PET (In2O3/Au/Ag on PET) substrate prepared through potentiodynamic reduction of graphene oxide in neutral medium shows enhanced specific capacitance and cyclic stability in supercapacitor application. The specific capacitance achieved for flexible graphene electrode is 787.37 Fg−1 with a cyclic stability of more than 1000 cycles. The supercapacitance performance of graphene oxide and reduced graphene oxide on PET is compared with that on FTO substrate. The attained specific capacitance and cyclic stability for reduced graphene oxide on FTO is respectively 479.65 Fg-1and 500. The factors that contribute to the enhanced performance of PET based flexible graphene electrode are (i) better interfacial adhesion between graphene and substrate (ii) the application of a widened potential window and (iii) the more porous nature of the graphene electrode.

Laser-enabled flexible electrochemical sensor on finger for fast food security detection

Today’s rampant abuse of antibiotics and lean meat powder disturbs environment and threatens public human health. Therefore, fast in-site detection of antibiotics or lean meat powder residue could avoid potential risks. In this work, flexible graphene electrodes (FGE) were easily and facilely patterned and prepared by CO2 laser at room environment, which was coupled with a portable electrochemical analyzer for electronic signal transmission. Laser-enabled flexible electrochemical sensor on finger can be used for rapid real-time in-site electrochemical identification of chloramphenicol (CAP), clenbuterol (CLB) and ractopamine (RAC) in meat. The electrochemical response of CAP, CLB and RAC is investigated with the limit of detection of 2.70, 1.29 and 7.81 μM and the linear range of 10–200, 5–80 and 25–250 μM in phosphate buffer saline (PBS) pH 7.0, correspondingly. The minimum detection concentrations of CAP, CLB and RAC were 20, 10 and 30 μM, respectively, in actual samples of pork. And the minimum detection concentrations of CAP, CLB and RAC were 10, 5 and 25 μM in milk, respectively. Such an integrated sensing platform enriches application of sensors on finger in food security and provides information that prevents drug containments from entering food chain.

Flexible Graphene substrates for electrochemical analysis and construction of functional nanostructures

Graphene as a highly conductive, adsorptive, and structurally flexible material has been widely employed to develop advanced electronic devices and sensors. In this study, by simply drop-casting the desired amount of industrial grade, graphene nano-platelets onto conventional double-sided conductive tape, we developed a convenient, versatile, and scalable graphene substrate (namely, flexible graphene substrate in a snap) with much-improved in-plane conductivity for electrochemical analysis and template-assisted deposition of functional nanostructures. Particularly cyclic voltammetric measurements with reversible redox couples showed ideal responses on such “flexible graphene electrodes” with superior reproducibility and stability. The quantitation of medically relevant, trial analysts (i.e., ascorbic acid and dopamine) showed excellent linearity in established calibration curves (R2 > 0.995) and satisfactory detection sensitivity. More remarkably, by affixing nano-porous templates (polycarbonate or AAO membranes) onto these flexible graphene substrates, we can fabricate various metallic nanostructures via a conventional bench-top electrode position process, which exhibit excellent electro-analytical (Au nano-clusters as ideal ultra-microelectrode arrays) and catalytic activities (Pt nanowires towards modulated H2O2 reduction). Beyond the application of quantitative electrochemical analysis and bench-top creation of functional nanostructures, we envision that such “flexible graphene substrate in a snap” as a versatile, scalable platform material can be adapted to many other designs of graphene-based sensors and analytical devices.

Enhancing the capacitance and tailoring the discharge times of flexible graphene supercapacitors with cobalt ferrite nanoparticles

This work reports the use of cobalt ferrite nanoparticles (NPs) for the fabrication of flexible supercapacitors (SCs). According to the microscopy analysis, the cobalt ferrite NPs have quasi-spherical shapes and their average sizes were 10.2 ± 1 nm, 12.3 ± 1 nm and 8.8 ± 1 nm when they are synthesized with cobalt concentrations of 0, 25 and 33 mol%, respectively. Moreover, the X-ray diffraction patterns indicated that all the cobalt ferrite NPs presented a cubic phase. Flexible supercapacitors were made with two flexible graphene electrodes (FGEs) and one of them (anode) was coated with different cobalt ferrite NPs (the FGE electrode had 5 wt percent (wt%) of NPs) synthesized with several cobalt concentrations. The electrochemical characterization of these flexible SCs revealed that not only the capacitance was enhanced from 77.8–337.1 F g−1 (at 1 A g−1) when the cobalt concentration increases from 0 to 33 mol% but also the discharge times from 1650 to 4957 s. Moreover, other SCs devices were fabricated using different wt% of the cobalt ferrite synthesized with a cobalt concentration of 33 mol%. As a result, the capacitance increases from 337.1–835.7 F g-1 (at 1 A g−1) and the discharge times from 4957 to 21969s when the content of cobalt ferrite increases from 5 to 10 wt%. The enhancement of capacitance and discharge times was associated to the increase of the surface area and electrical conductivity of the anodes, which was caused by the presence of cobalt ferrite NPs on them.

High energy density of flexible graphene supercapacitors with discharge times controlled by silica microparticles

This work reports the electrochemical performance of flexible symmetric supercapacitors which employs two flexible graphene electrodes (FGEs) and silica microparticles (SiO2-MPs) in the electrolyte solution. The discharging time of the supercapacitors increased up to six times after increasing the SiO2-MPs content from 10 to 30 wt%. The introduction of SiO2-MPs played two main roles: i) to enhance the specific surface area of the electrodes (up to 145 % with respect to the electrodes without SiO2- MPs), which in turn, raises the capacity for the ion storage in the devices; and, ii) to generate the SiO, SiOH, SiOC chemical bonds and defects sites, which in turn, enhanced the charge storage by redox (faradaic) reactions. The supercapacitors presented a high energy density value of 748 Wh/kg and specific capacitance of 1663.3 F/g due to the charge storage by the redox reactions and to the high specific surface area available in the FGEs. The long discharge times, high energy densities and flexibility of the supercapacitors, suggest that they could be useful for applications of portable devices which need long operating times.

Enhancing the voltage and discharge times of graphene supercapacitors depositing a CNT/V2O5 layer on their electrodes

This work reports the electrochemical properties of graphene supercapacitors that employ flexible graphene electrodes (FGEs) coated by V2O5 (VOx) or carbon nanotubes (CNTs)/VOx layers. According to scanning electron microscopy images, the morphology of VOx consists in micro-ribbons with lengths of 20–45 μm and widths from 5 to 12 μm. The CNTs form interconnected long fibers, which were functionalized with carboxylic groups for producing defects. We demonstrated that the gel electrolyte used for the supercapacitors produces V4+-oxygen vacancies (VO) defects. Both, the CNTs and V4+-VO defects act as redox centers, which delay the current discharge in the supercapacitors. The presence of the carboxylic groups, defects in CNTs, defects in VOx, and oxidation states (V4+ and V5+), were confirmed by the UV–Vis, XPS, and FTIR techniques. The electrochemical characterization of the supercapacitors indicated that the devices made with FGEs coated by VOx or CNTs/VOx layers produced constant voltages of 0.14 V and 0.38 V during 535 and 593 min, respectively. The increase of voltage is explained by the increase of surface area and by the extra redox centers (defects) introduced by the CNTs. The results indicated that the CNTs/VOx layer increases the voltage and discharge times of the graphene supercapacitors, which can be of interest for the development of graphene systems with high charge storage capabilities.

Universal laser-assisted growth of transition metal nanoparticles on a flexible graphene electrode for a nonenzymatic glucose sensor

A universal laser-assisted method was used for the construction of transition metal nanoparticles on graphene as a glucose sensor.

Laser induced flexible graphene electrodes for electrochemical sensing of hydrazine

In this work, electrochemical sensing of hydrazine is reported using laser induced flexible graphene as the sensing electrode. The electrodes were fabricated by simple lasing and patterning of polyimide films at ambient conditions. Cyclic voltammetry technique was used for electrochemical sensing of hydrazine. These sensors exhibited linear response to change in concentration of hydrazine. The sensor had a sensitivity of up to 115% at 0.5 mM hydrazine, limit of detection of 70 µM, and was reliable after 500 bending cycles. Overall, the hydrazine sensor exhibited good reproducibility, sensitivity, selectivity, lifetime, and is promising for developing low cost flexible hydrazine sensor.

Vertically Aligned Graphene-Carbon Fiber Hybrid Electrodes with Superlong Cycling Stability for Flexible Supercapacitors.

Graphene electrode-based supercapacitors are in high demand due to their superior electrochemical characteristics. A major bottleneck of using the supercapacitors for commercial applications lies in their inferior electrode cycle life. Herein, a simple and facile method to fabricate highly efficient supercapacitor electrodes using pristine graphene sheets vertically stacked and electrically connected to the carbon fibers which can result in vertically aligned graphene-carbon fiber nanostructure is developed. The vertically aligned graphene-carbon fiber electrode prepared by electrophoretic deposition possesses a mesoporous 3D architecture which enabled faster and efficient electrolyte-ion diffusion with a gravimetric capacitance of 333.3 F g-1 and an areal capacitance of 166 mF cm-2 . The electrodes displayed superlong electrochemical cycling stability of more than 100 000 cycles with 100% capacitance retention hence promising for long-lasting supercapacitors. Apart from the electrochemical double layer charge storage, the oxygen-containing surface moieties and α-Ni(OH)2 present on the graphene sheets enhance the charge storage by faradaic reactions. This enables the assembled device to provide an excellent gravimetric energy density of 76 W h kg-1 with a 100% capacitance retention even after 1000 bending cycles. This study opens the door for developing high-performing flexible graphene electrodes for wearable energy storage applications.

Enhancing the capacitance/discharge times of flexible graphene supercapacitors with ionic liquid/Li electrolytes

This work reports a novel method for the fabrication of supercapacitors (SCs) which employs flexible graphene electrodes (FGEs), an aqueous Li electrolyte, and a separator (semipermeable membrane) between electrodes. In some devices, the Li electrolyte was improved with the addition of BMIMBF4-an Ionic liquid (IL), which enhanced the gravimetric capacitance of the devices, reaching a maximum value of 1558 F/g. Moreover, the presence of the IL enhanced from 272 to 800 min the discharge time, which suggests that the SCs release their energy as slow as batteries. In addition, the thickness of the separator was increased from 200 to 400 µm, which allows stabilizing the discharge time for at least 120 min. Thus, the proposed combination of FGEs and electrolytes will open the opportunity to develop SCs with discharge cycles comparable to Li-based batteries.

(Invited) Emerging Nanomaterial Inks for Additive Manufacturing of Wearable Sensors

The versatility of direct write techniques such as aerosol jet printing (AJP) and ink jet printing (IJP) has recently intersected with two-dimensional (2D) materials research to enable novel wearable sensors. Graphene and 2D transition metal nitrides, carbides and carbonitrides (MXenes) are of particular interest for wearable sensor applications due to their biocompatibility and multifunctional nature. However, these 2D materials must be contacted by biocompatible metals, e.g. platinum, in order to enable functional devices such as wearable and/or implantable electrochemical sensors and neural interfaces.[1 - 3] In this study, we report the printing of 2D materials, graphene, titanium carbide Mxenes (Ti3C2), and platinum nanoparticles via AJP and IJP. Ink characterization was performed with atomic force microscopy, scanning and transmission electron microscopy (SEM and TEM), DLS and Raman spectroscopy. Graphene sheets were obtained via solvent assisted exfoliation and then dispersed in 85:15 cyclohexanone/terpineol to formulate graphene inks at a concentration of 3.5 mg/ml.[4,5] Graphene sheets exhibited an average thickness of 16 nm +/- 15 nm and crystal domains with lateral dimensions ranging from ~50 nm to 200 nm. Platinum ink (20 wt.%) was formulated with the dispersion of platinum nanopowders and 70:30 water/ethylene glycol mix. Dispersed platinum nanoparticles exhibited an average particle size of 7.8 nm +/- 2.3 nm. Finally, an AJP compatible multi-layered MXene ink was obtained by in situ HF etching of the pre-cursor Ti3AlC2 MAX phase.[6] The obtained colloidal suspension containing 2D MXene flakes was sonicated with deionized water for 3 hours at 55 W. The resultant ink had a concentration of 1 mg/mL and an average flake size of 100 nm +/- 10 nm, as confirmed by dynamic light scattering (DLS) measurements. Platinum, graphene and Ti3C2 inks have demonstrated good compatibility with an Optomec Aerosol Jet 200 and a Dimatix 2850 materials inkjet printer, while platinum and graphene have shown additional compatibility with IJP. For good electrical conductivity graphene was sintered at 390 C for one hour and platinum was sintered at 450 C for 130 hours, while MXenes showed good conductivity without sintering. Optical microscopy, SEM, stylus profilometry, and two/four-point resistance measurements were used to examine the quality of the printed MXene and platinum structures. Initial printing with MXenes resulted in feature heights ranging from ~ 620 nm to 4.80 µm, depending on the number of print passes denoted as N. Our most uniform prints were N = 15 and N = 20 having a height of 2.50 µm +/- 0.10 µm and 3.50 µm +/- 0.10 µm, respectively. Electrical resistance varied between R = 568 kΩ and R = 60 kΩ for N = 5 and N = 25 respectively. Platinum exhibited good electrical conductivity as R = 70 Ω for N = 10, having a height of 3 µm and a feature width of ~50 µm. Furthermore, the electrochemical properties of fully inkjet printed graphene electrodes on a flexible polyimide substrate for pH and electrolyte sensing were investigated. Printed electrodes consisted of a printed 1x1 cm graphene square with a total of 17 layers with printed silver contact pads and a SU-8 as a passivation layer. Electrochemical activity of inkjet printed graphene electrodes was demonstrated with both cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements in a room temperature 10 mM ferricyanide aqueous solution (1 M KCl supporting electrolyte). Ag/AgCl and platinum electrodes were used as the reference and counter electrode, respectively. Additionally, pH sensing capabilities were investigated by measuring the potentiometric response of polyaniline coated graphene electrodes over three different pH values (4, 7 and 10). The response of printed and flexible graphene electrodes was comparable to that of a conventional glass electrode. In conclusion, AJP compatible Ti3C2 MXene inks along with AJP and IJP compatible platinum and graphene inks have been developed. Printing of these biocompatible materials is intended to support the fabrication of nanomaterial based flexible hybrid electronics such as biosensors for electrochemical sensing of a broad spectrum of biomarkers, and also neural interface systems. Furthermore, our results provide new fundamental insights on role of structure-property-performance correlations in printed graphene electrodes for electrochemical sensing. The combination of our works highlight the significant potential of novel material inks for additively manufactured wearable sensors. [1] Kenry et al., Microsystems Nanoeng., Sep. 2016. [2] Sinha et al., Trends Analyt Chem, 2018. [3] A. Sridhar et al., Mater. Matters, 2009. [4] J. N. Coleman et al., Acc. Chem. Res., 2013. [5] F. Torrisi et al., ACS Nano, 2012. [6] M. Alhabeb et al., Chemistry of Materials, 2017.

Graphene-Anchored Cuprous Oxide Nanoparticles from Waste Electric Cables for Electrochemical Sensing

We demonstrate development of electrochemical nanosensors for planetary health applications using nanocuprous oxide synthesized from recycled materials. Laser-scribed graphene electrodes were enhanced with copper liberated from waste cables, and cuprous oxide nanospheres were synthesized via precipitation at low temperature using lactose as a reducing agent and four different surfactants as capping agents. These laser-scribed electrodes are a low-cost, lithography-free approach to direct synthesis of flexible carbon circuits. Sensors were fabricated by anchoring nanoparticles to flexible graphene electrodes, and then material properties and sensor performance were compared for each surfactant. Surfactant molecular weight and terminal group played an important role in nanoparticle size, band gap, ferromagnetic response, and electron transport. As proof of principle, we show development of catecholamine and mercury sensors for planetary health applications using the best material. Dopamine sensors were line...

The Structure of Silver Modified Flexible Graphene Electrodes for Actuators in Biomimetic Systems

We present a novel model for semiquantitative estimation of optimal concentrations of silver modifier necessary to increase the conductivity of graphene electrodes in actuators with electroactive polymers and to ensure long-term performance of the system. The model predicts approximately equal masses of silver and graphene in the electrodes after the reduction for the characteristic size of graphene flakes ∼10 nm. Also, the concentration is shown to depend strongly on the size of the flakes.

Inkjet Printing of Graphene for Wearable and Flexible Electrochemical Sensors

Printed and flexible electronics is a rapidly advancing technology with the potential to develop into a multi-billion-dollar wearable electronics industry.[1] One of the main challenges limiting high volume manufacturing of wearable electronics is the lack of high performance and multifunctional inks compatible with existing direct write technologies such as inkjet printing (IJP). Graphene, a promising nano-material, is hypothesized to be great electrode material for flexible and wearable electrochemical sensors due to its flexible nature and high electrochemical activity at defect sites.[2] Furthermore, due to its high specific surface area, high carrier mobility, and compatibility with large scale manufacturing techniques, graphene has shown extraordinary properties and created tremendous breakthroughs in electronic related applications, particularly when it comes to trace gas and vapor sensing.[3] To date, inkjet printing of graphene has been well established.[4] However, fully printed electrochemical sensors that offer high sensitivity and are operational under realistic environmental conditions utilizing graphene electrodes has not yet been accomplished. The complexity lies in decoupling the sensing mechanisms of printed graphene structures from environmental factors such as temperature, relative humidity, and radiation.[2] This is also complicated by the interaction of the printed graphene with the underlying substrate. Surface roughness, surface energies, adhesiveness, and chemical reactivity, can greatly affect the quality and properties of the printed structure.[5] In this study, we investigated electrochemical properties of fully inkjet printed graphene electrodes on flexible substrate for pH and electrolyte sensing wearable devices. Graphene is obtained via solvent assisted exfoliation[6] and characterized via AFM, SEM, TEM, and Raman spectroscopy (Fig. 1a-f). We find the graphene flakes to range from an average thickness of 16nm +/- 15nm and crystal domains with lateral dimensions ranging from ~50 nm to 200 nm. To synthesize our graphene ink, we dispersed the flakes via sonication in a mixture of 85% cyclohexanone and 15% terpineol, which has been shown to be compatible with IJP.[7] This resulted in an ink concentration of 3.5mg/ml as confirmed by UV-Vis-IR absorption spectroscopy. The graphene dispersion was printed into (17 printed layers) of 1cm x 1cm squares with printed silver contact pads and printed SU-8 as a passivation later. These test structures were printed on polyimide substrates using a Dimatix 2850 materials inkjet printer. The tool platen temperature, nozzle diameter, and cartridge temperature were optimized to ensure the dimensions and material deposition were adequate to obtain uniform structures. The graphene printed structures were then annealed at about 390°C for one hour to remove solvents and binders in order to increase electrical conductivity (Fig. 2a, b). To investigate the electrochemical activity of inkjet printed graphene electrodes, both cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements were carried out in a 10 mM ferricyanide aqueous solution (1 M KCl as the supporting electrolyte) at room temperature. A Ag/AgCl electrode and a platinum electrode were used as the reference and counter electrode, respectively. Inkjet printing of the electrodes assisted in developing a homogenous graphene layer on the surface, which is a key requirement to obtain an electrode with a good electrochemical reversibility.[8] To evaluate the performance of the electrode we measured the ratio of the anodic and cathodic peaks (Ipa/Ipc) and the peak-to-peak separation potential (ΔEp). In the CV curve see in (Fig. 2c), clear maxima in the cathodic and anodic currents can be observed, as well the peak separation, suggesting IJP can enable a uniform printed graphene electrode. We then performed pH sensing experiments by coating the printed graphene electrodes with an inkjet printed polyaniline thin film. Potentiometric response of the electrodes was studied over three different pH values (4, 7 and 10). The pH response of our printed and flexible graphene electrodes was comparable to that of a conventional glass electrode. In conclusion, our results provide new fundamental insights on role of structure-property-performance correlations in printed graphene electrodes for electrochemical sensing. We find that the key parameters important for sensing performance including uniformity of the printed electrodes, response time, stability and reproducibility, can be optimized via inkjet printing of graphene. Such findings have significant implications for miniaturization, reliability, and large-scale manufacturing of flexible and wearable electronics systems for electrochemical based human performance monitoring. [1] Kenry et al., Microsystems Nanoeng., Sep. 2016. [2] S. Cinti et al., Biosens. Bioelectron., 2016. [3] F. Schedin et al., Nat. Photonics, 2016. [4] J.Heinzl et al., Adv. Electron Phys., 1985 [5] A. Sridhar et al., Mater. Matters, 2009. [6] J. N. Coleman et al.,Acc. Chem. Res., 2013. [7] F. Torrisi et al., ACS Nano, 2012. [8] B. Li, G et al., Biosens. Bioelectron., 2015. Figure 1

Структура гибких графеновых электродов, модифицированных серебром, для разработки актюаторов биомиметических систем

Структура гибких графеновых электродов, модифицированных серебром, для разработки актюаторов биомиметических систем