Xudong Ji - Academia.edu (original) (raw)

Papers by Xudong Ji

Nature

Organic electrochemical transistors (OECTs) and OECT-based circuitry offer great potential in bio... more Organic electrochemical transistors (OECTs) and OECT-based circuitry offer great potential in bioelectronics, wearable electronics and artificial neuromorphic electronics because of their exceptionally low driving voltages (<1 V), low power consumption (<1 µW), high transconductances (>10 mS) and biocompatibility1–5. However, the successful realization of critical complementary logic OECTs is currently limited by temporal and/or operational instability, slow redox processes and/or switching, incompatibility with high-density monolithic integration and inferior n-type OECT performance6–8. Here we demonstrate p- and n-type vertical OECTs with balanced and ultra-high performance by blending redox-active semiconducting polymers with a redox-inactive photocurable and/or photopatternable polymer to form an ion-permeable semiconducting channel, implemented in a simple, scalable vertical architecture that has a dense, impermeable top contact. Footprint current densities exceeding 1...

Electrochemical aptamer-based (E-AB) sensors are typically deployed as individual, passive, surfa... more Electrochemical aptamer-based (E-AB) sensors are typically deployed as individual, passive, surface-functionalized electrodes, but they exhibit limited sensitivity especially when the area of the electrode is reduced for miniaturization purposes. We demonstrated that organic electrochemical transistors (OECTs), electrolyte gated tran-istors with volumetric gating, can serve as on-site amplifiers to improve the sensitivity of single electrode-based E-AB sensors. By monolithically integrating an Au working/sensing electrode, on-chip Ag/AgCl reference electrode and Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) counter electrode — also serving as the OECT channel, we can simultaneously perform OECT testing and traditional electroanalytical measurement on E-AB sensors including cyclic voltammetry (CV) and square-wave voltammetry (SWV). This device can directly amplify the current from the E-AB sensor via the in-plane current modulation in the counter electrode/trans...

Proceedings of the nanoGe Spring Meeting 2022, 2022

A series of fully fused n-type mixed conduction lactam polymers p(g 7 NC n N), systematically inc... more A series of fully fused n-type mixed conduction lactam polymers p(g 7 NC n N), systematically increasing the alkyl side chain content, are synthesized via an inexpensive, nontoxic, precious-metal-free aldol polycondensation. Employing these polymers as channel materials in organic electrochemical transistors (OECTs) affords state-of-the-art n-type performance with p(g 7 NC 10 N) recording an OECT electron mobility of 1.20 × 10 −2 cm 2 V −1 s −1 and a μC* figure of merit of 1.83 F cm −1 V −1 s −1. In parallel to high OECT performance, upon solution doping with (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine (N-DMBI), the highest thermoelectric performance is observed for p(g 7 NC 4 N), with a maximum electrical conductivity of 7.67 S cm −1 and a power factor of 10.4 μW m −1 K −2. These results are among the highest reported for n-type polymers. Importantly, while this series of fused polylactam organic mixed ionic−electronic conductors (OMIECs) highlights that synthetic molecular design strategies to bolster OECT performance can be translated to also achieve high organic thermoelectric (OTE) performance, a nuanced synthetic approach must be used to optimize performance. Herein, we outline the performance metrics and provide new insights into the molecular design guidelines for the next generation of high-performance n-type materials for mixed conduction applications, presenting for the first time the results of a single polymer series within both OECT and OTE applications.

Biosensors and Biodetection, 2017

An organic electrochemical transistor (OECT) with a glucose oxidase (GOx) and poly(n-vinyl-2-pyrr... more An organic electrochemical transistor (OECT) with a glucose oxidase (GOx) and poly(n-vinyl-2-pyrrolidone)-capped platinum nanoparticles (Pt NPs) gate electrode was successfully integrated with a microfluidic channel to act as a highly sensitive chip-based glucose sensor. The sensing mechanism relies on the enzymatic reaction between glucose and GOx followed by electrochemical oxidation of hydrogen peroxide (H 2 O 2) produced in the enzymatic reaction. This process largely increases the electrolyte potential that applies on PEDOT:PSS channel and causes more cations penetrate into PEDOT:PSS film to reduce it to semi-conducting state resulting in lower electric current between the source and the drain. The extremely high sensitivity and low detection limit (0.1 μM) of the sensor was achievable due to highly efficient Pt NPs catalysis in oxidation of H 2 O 2. Pt NPs were deposited by a bias-free two-step dip coating method followed by a UV-Ozone post-treatment to enhance catalytic ability. A polydimethylsiloxane (PDMS) microfluidic channel was directly attached to the OECT active layer, providing a short detection time (~1 min) and extremely low analyte consumption (30 μL). Our sensor has great potential for real-time, noninvasive, and portable glucose sensing applications due to its compact size and high sensitivity.

Angewandte Chemie, 2021

Supporting information for this article is given via a link at the end of the document.

Proceedings of the nanoGe Fall Meeting 2021, 2021

Journal of Materials Chemistry C, 2020

N-type semiconducting polymers have been recently utilized in thermoelectric devices, however the... more N-type semiconducting polymers have been recently utilized in thermoelectric devices, however they have typically exhibited low electrical conductivities and poor device stability, in contrast to p-type semiconductors, which have been much higher performing.

Nano Select, 2021

With fast recovery time and effective in situ tumor tissue killing ability, thermal ablation has ... more With fast recovery time and effective in situ tumor tissue killing ability, thermal ablation has become a popular treatment for tumors compared with chemotherapy and radiation. The thermal dose measurement of current technology is usually accompanied by monitoring a large area impedance across two ablation catheters and the localized impedance measurement is difficult to achieve. In this work, thermal-resistive sensor and impedance sensor are fabricated on the curved surface of a capillary tube with 1 mm outer diameter. The device is applied for real-time in situ tissue impedance monitoring during thermal ablation. The calibrated thermal-resistive sensors have an average temperature coefficient of resistance (TCR) of 0.00161 ± 5.9% • C-1 with an accuracy of ±0.7 • C. By adding electro-polymerized PEDOT:PSS (poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate)) on the 300 µm diameter gold electrodes, the interface impedance reduces two orders from 408 to 3.7 kΩ at 100 Hz. The Randles equivalent circuit model fittings show a two-order improvement in the electrode capacitance from 7.29 to 753 nF. In the ex vivo porcine liver laser ablation test, the temperature of the porcine liver tissue can reach 70 • C and the impedance would drop by 50% in less than 5 minutes. The integration of laser ablation fiber with the impedance and temperature sensors can further expand the laser ablation technique to smaller scale and for precise therapeutics.

ACS Applied Materials & Interfaces, 2018

Crystals of organic semiconductors are excellent candidates for flexible and array-based electron... more Crystals of organic semiconductors are excellent candidates for flexible and array-based electronics. Large-scale synthesis of organic crystals in a controllable way while maintaining homogeneous single-crystal property has been a great challenge. The existence of grain boundaries and small crystal domains, however, restrict the device performance and limit the access to commercially viable organic electronics in the industry. Herein, we report the inch-scale synthesis of highly oriented 2,7-dioctyl[1]benzothieno[3,2b][1]benzothiophene (C 8-BTBT) organic single crystal by nucleation seed-controlled shearing method. The organic field-effect transistors developed from such single crystal have excellent carrier mobility as high as 14.9 cm 2 V −1 s −1 and uniformity (standard deviation is 1.3 cm 2 V −1 s −1) of 225 devices. We also found that the rotation of the principal axis in the crystal is governed by the orientations of seeds and the possible mechanism behind this phenomenon is proposed based on the density functional theory calculations. We anticipate that this proposed approach will have great potential to be developed as a platform for the growth of organic crystals with high crystallinity on a large scale.

Advanced Science, 2018

Various physical signal sensors such as pulse, [5] temperature, [6] skin pressure, [7] blood pres... more Various physical signal sensors such as pulse, [5] temperature, [6] skin pressure, [7] blood pressure, [8] or electrical signal sensors like ECG, [9] EEG, [10] EMG [11] have been successfully demonstrated. These devices can provide real-time information of human body or particular organs. Besides these physical and electrical signals, surgical tools integrated with OFET-based sensors to measure the chemical and biological signals are also critical for monitoring the health conditions of patients during surgery. For example, C-reactive protein (CRP), a biomarker of inflammation widely distributed in our blood stream, can be used to indicate the levels of inflammation in our body. A normal CRP value in human blood is usually below than 10 µg mL −1 , while in inflammation case, the CRP level can go up to 40 µg mL −1. Under the bacterial inflammation, the CRP concentration in our blood can be as high as 100 µg mL −1. [12] As a result, if a surgical tool like catheter can be integrated with a CRP sensor to monitor the real-time inflammation level during cardiac surgery, especially cardiopulmonary bypass (CPB), it would be more than useful for doctors to promptly treat systemic inflammation, which is a primary cause of various postoperative complications leading to vital organ dysfunction and Organic field-effect transistors (OFETs)-based sensors have a great potential to be integrated with the next generation smart surgical tools for monitoring different real-time signals during surgery. However, allowing ultraflexible OFETs to have compatibility with standard medical sterilization procedures remains challenging. A novel capsule-like OFET structure is demonstrated by utilizing the fluoropolymer CYTOP to serve both encapsulation and peeling-off enhancement purposes. By adapting a thermally stable organic semiconductor, 2,10-diphenylbis[1]benzothieno[2,3-d;2′,3′-d′]naphtho[2,3b;6,7-b′]dithiophene (DPh-BBTNDT), these devices show excellent stability in their electrical performance after sterilizing under boiling water and 100 °C-saturated steam for 30 min. The ultrathin thickness (630 nm) enables the device to have superb mechanical flexibility with smallest bending radius down to 1.5 µm, which is essential for application on the highly tortuous medical catheter inside the human body. By immobilizing anti-human C-reactive protein (CRP) (an inflammation biomarker) monoclonal antibody on an extended gate of the OFET, a sensitivity for detecting CRP antigen down to 1 µg mL −1 can be achieved. An ecofriendly water floatation method realized by employing the wettability difference between CYTOP and polyacrylonitrile (PAN) can be used to transfer the device on a ventricular catheter, which successfully distinguishes an inflammatory patient from a healthy one. Organic Transistors The development of organic field-effect transistors (OFETs)based sensors has attracted increasing attention recently for their biomedical and conformal applications on organ

Advanced materials (Deerfield Beach, Fla.), 2018

Organic optical memory devices keep attracting intensive interests for diverse optoelectronic app... more Organic optical memory devices keep attracting intensive interests for diverse optoelectronic applications including optical sensors and memories. Here, flexible nonvolatile optical memory devices are developed based on the bis[1]benzothieno[2,3-d;2',3'-d']naphtho[2,3-b;6,7-b']dithiophene (BBTNDT) organic field-effect transistors with charge trapping centers induced by the inhomogeneity (nanosprouts) of the organic thin film. The devices exhibit average mobility as high as 7.7 cm V s , photoresponsivity of 433 A W , and long retention time for more than 6 h with a current ratio larger than 10 . Compared with the standard floating gate memory transistors, the BBTNDT devices can reduce the fabrication complexity, cost, and time. Based on the reasonable performance of the single device on a rigid substrate, the optical memory transistor is further scaled up to a 16 × 16 active matrix array on a flexible substrate with operating voltage less than 3 V, and it is used to m...

Advanced Materials Technologies, 2016

Organic electrochemical transistor (OECT)based enzymatic biosensor exhibits great potential in de... more Organic electrochemical transistor (OECT)based enzymatic biosensor exhibits great potential in detection metabolite concentration in body fluid and other biomedical applications. Modified OECT-based biosensors with poly(N-vinyl-2-pyrrolidone)-capped platinum nanoparticles and microfluidic channel show not only high sensitivity on single analyte glucose or lactate but also compatible with multianalyte sensing. The current device has excellent potential on real-time noninvasive healthcare diagnostic.

Nature Communications

Electrochemical aptamer-based sensors are typically deployed as individual, passive, surface-func... more Electrochemical aptamer-based sensors are typically deployed as individual, passive, surface-functionalized electrodes, but they exhibit limited sensitivity especially when the area of the electrode is reduced for miniaturization purposes. We demonstrate that organic electrochemical transistors (electrolyte gated transistors with volumetric gating) can serve as on-site amplifiers to improve the sensitivity of electrochemical aptamer-based sensors. By monolithically integrating an Au working/sensing electrode, on-chip Ag/AgCl reference electrode, and Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) counter electrode — also serving as the channel of an organic electrochemical transistor— we can simultaneously perform testing of organic electrochemical transistors and traditional electroanalytical measurement on electrochemical aptamer-based sensors including cyclic voltammetry and square-wave voltammetry. This device can directly amplify the current from the electrochemical apt...

Nature Communications, 2021

Associative learning, a critical learning principle to improve an individual’s adaptability, has ... more Associative learning, a critical learning principle to improve an individual’s adaptability, has been emulated by few organic electrochemical devices. However, complicated bias schemes, high write voltages, as well as process irreversibility hinder the further development of associative learning circuits. Here, by adopting a poly(3,4-ethylenedioxythiophene):tosylate/Polytetrahydrofuran composite as the active channel, we present a non-volatile organic electrochemical transistor that shows a write bias less than 0.8 V and retention time longer than 200 min without decoupling the write and read operations. By incorporating a pressure sensor and a photoresistor, a neuromorphic circuit is demonstrated with the ability to associate two physical inputs (light and pressure) instead of normally demonstrated electrical inputs in other associative learning circuits. To unravel the non-volatility of this material, ultraviolet-visible-near-infrared spectroscopy, X-ray photoelectron spectroscopy...