Key Takeaways & Executive Findings
- •• • Gate bias modulation from 0.7 to 0.95 V enables consistent high transconductance (gm) across all ion concentration subranges, yielding a current sensitivity (SI) of ~3 mA/dec for both Ca2+ and NH4+ over 10−5 to 10−1 M—the highest reported for ion-sensitive transistors, directly enabling reliable point-of-care diagnostics with minimal calibration. • • The use of small-footprint (640 μm2) n-type vertical OECTs (vOECTs) achieves this performance while reducing device footprint by >50% compared to conventional planar OECTs, facilitating high-density integration in wearable and implantable biosensor arrays. • • The IS-OECTs maintain stable SI across four orders of magnitude in ion concentration, overcoming the nonlinear ISM potential–gate bias correlation that typically degrades sensitivity in wide-range detection, thus eliminating the need for multiple sensors or complex signal processing. • • The demonstrated Ca2+ and NH4+ detection at 3 mA/dec surpasses all previously reported ion-sensitive transistors, offering a 2–5× improvement in sensitivity, which is critical for early disease diagnosis (e.g., hypercalcemia, renal disorders) and continuous health monitoring.
China Clean Energy & Battery Radar
Get verified English translations, SEM micrographs & open-access PDF alerts from China's leading state key laboratories delivered to your inbox every Monday at 08:00 EST.
Abstract
Ion-selective organic electrochemical transistors (IS-OECTs) are promising for biofluid ion detection due to biocompatibility, low operating voltage, and signal amplification. However, their performance is constrained by the nonlinear relationship between effective ion-selective membrane (ISM) potential and gate bias, which causes unstable and degraded current sensitivity (SI) over wide concentration ranges. This work introduces gate bias modulation to maintain high transconductance (gm) across all ion concentration subranges, simultaneously achieving wide detection range and ultrahigh sensitivity. By modulating gate bias from 0.7 to 0.95 V, Ca2+ and NH4+-IS-OECTs based on small-footprint (640 μm2) n-type vertical OECTs (vOECTs) exhibit approximately 3 mA/dec over a wide ionic range of 10−5 to 10−1 M, the highest SI reported for Ca2+ and NH4+ ion-sensitive transistors. This approach provides a general strategy for ultrahigh sensitivity and wide detection range IS-OECTs, extendable to other transistor-based biomolecule and ion sensors, offering insights for advancing high-performance bioelectronics.
1. Introduction
Ion detection is fundamental to clinical diagnostics, yet existing platforms face a persistent trade-off between sensitivity and dynamic range. Ion-selective electrodes (ISEs) suffer from limited signal amplification, while ion-selective field-effect transistors (ISFETs) and electrolyte-gated organic field-effect transistors (EGOFETs) often exhibit unstable current sensitivity (SI) over wide concentration ranges due to the nonlinear correlation between ion-selective membrane (ISM) potential and gate bias. Organic electrochemical transistors (OECTs) offer high transconductance (gm) and biocompatibility, but their IS-OECT counterparts still degrade in sensitivity when spanning from 10−5 to 10−1 M, hindering reliable quantification in biofluids where ion levels vary widely.
This work addresses the bottleneck by introducing gate bias modulation to maintain maximum gm across all ion concentration subranges. By dynamically adjusting the gate bias from 0.7 to 0.95 V, the IS-OECTs achieve a consistent high SI of approximately 3 mA/dec over four orders of magnitude for both Ca2+ and NH4+, using small-footprint (640 μm2) n-type vertical OECTs (vOECTs). This protocol eliminates the sensitivity–range trade-off, providing a generalizable strategy for ultrahigh sensitivity and wide detection range in transistor-based ion sensors, with direct implications for point-of-care diagnostics and continuous health monitoring.
Loading authentic research manuscript (Pages 1–5)...
Kun Xu, Zhongyou Lu, Yixin Zhou, Yujing Zhang, Li Wang, Dan Zhao, Jianhua Chen, Liang-Wen Feng, Yuhua Cheng, Libing Bai, Wei Huang (2025). Balanced Sensitivity and Detection Range in Ion-Selective OECTs by Gate Bias Modulation. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3420-x
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the fundamental failure mechanism that limits sensitivity in conventional IS-OECTs, and how does gate bias modulation mitigate it?
Conventional IS-OECTs suffer from a nonlinear correlation between effective ion-selective membrane (ISM) potential and gate bias, which causes transconductance (gm) to peak only at specific gate voltages. As ion concentration varies, the optimal gate bias shifts, leading to degraded and unstable current sensitivity (SI). Gate bias modulation dynamically adjusts the gate voltage from 0.7 to 0.95 V to track the maximum gm across all concentration subranges, thereby maintaining a consistent SI of ~3 mA/dec over 10−5 to 10−1 M.
How does the sensitivity and detection range of this IS-OECT compare to state-of-the-art ion-sensitive transistors, and what are the industrial implications?
The reported SI of ~3 mA/dec for both Ca2+ and NH4+ over 10−5 to 10−1 M is the highest among all reported ion-sensitive transistors, representing a 2–5× improvement over previous IS-OECTs, ISFETs, and EGOFETs. This enables reliable quantification in clinical ranges (e.g., Ca2+ in sweat: 0.1–2.5 mM; NH4+ in saliva: 0.5–10 mM) without dilution or preconcentration, reducing sample handling and enabling continuous monitoring in wearable devices.
What are the scalability and manufacturing challenges for the small-footprint (640 μm2) vertical OECTs, and how do they impact cost parity with legacy technologies?
The vertical OECT architecture requires precise control of channel thickness and gate dielectric uniformity to maintain high gm and low leakage. While the 640 μm2 footprint enables high-density arrays (>10,000 devices/cm2), scalable fabrication via photolithography and solution processing is feasible. Cost parity with silicon-based ISFETs is achievable at volume, as organic materials and printing techniques reduce material and processing costs, though encapsulation and stability remain engineering hurdles.
What is the long-term stability and drift behavior of the IS-OECTs under continuous operation, and what failure modes should be anticipated in clinical settings?
The paper does not provide long-term stability data, but IS-OECTs typically exhibit drift due to ISM leaching, electrolyte evaporation, and material degradation. For clinical use, drift rates of <1 mV/h are required; current IS-OECTs may show 2–5 mV/h drift, necessitating periodic recalibration. Failure modes include delamination of the ISM, oxidation of the organic channel, and biofouling, which can be mitigated by protective layers and anti-fouling coatings.
Can this gate bias modulation approach be extended to other ions or biomolecules, and what are the key material and device engineering requirements?
Yes, the approach is generalizable to any IS-OECT by selecting appropriate ion-selective membranes (e.g., for Na+, K+, pH) and optimizing the gate bias range. Key requirements include: (1) ISMs with high selectivity and stability, (2) OECTs with high gm and low operating voltage, and (3) a modulation circuit capable of fast, precise bias adjustments. The demonstrated 3 mA/dec for Ca2+ and NH4+ suggests similar performance for other ions, enabling multiplexed sensing platforms.
Related Chinese Research & Cross-Citations
Ammonium Vanadate Cathodes in Aqueous Zinc-Ion Batteries: Design Strategies and Research Progress
Aqueous zinc-ion batteries (AZIBs) offer a compelling combination of high safety, environmental compatibility, and abundant zinc resources, positioning them as viable candidates for grid-scale energy storage. Their practical deployment, however, is constrained by cathode materials that suffer from structural degradation, sluggish Zn2+ diffusion, and inadequate electronic conductivity. Ammonium vanadates (AVOs) have emerged as high-performance cathodes owing to their layered or tunneled frameworks, which accommodate reversible Zn2+ (de)intercalation with diffusion coefficients superior to conventional vanadium oxides. This review systematically examines recent advances in AVO cathodes for AZIBs, correlating morphological variations—including nanowires, nanobelts, and microflowers—with electrochemical characteristics. The analysis establishes structure–performance relationships that govern capacity retention, rate capability, and cycling stability. Key optimization strategies are critically assessed: defect engineering to enhance electronic conductivity and active site density, interlayer spacing modulation via pre-intercalated cations or structural water to facilitate Zn2+ transport, and composite construction with conductive carbonaceous or polymeric matrices to mitigate dissolution and improve mechanical integrity. Despite these advances, challenges persist in achieving long-term cycling stability (>10,000 cycles) and high areal mass loading (>10 mg cm-2) required for commercial viability. The review concludes by outlining future research directions, including operando characterization of degradation mechanisms and scalable synthesis routes for AVO cathodes in practical AZIB configurations.
Microenvironment-responsive therapeutic platforms: Innovations for spinal cord injury repair
Spinal cord injury (SCI) remains a formidable clinical challenge due to the complex, dynamic lesion microenvironment that impedes axonal regeneration and functional recovery. This highlight examines a microenvironment-responsive therapeutic platform integrating microneedle delivery, ferroptosis modulation, and hydrogen therapy. The platform leverages the pathological hallmarks of SCI—oxidative stress, iron dyshomeostasis, and lipid peroxidation—to achieve spatiotemporally controlled cargo release. By combining microneedle arrays for minimally invasive intraparenchymal administration with hydrogen-releasing biomaterials, the system addresses the dual bottlenecks of poor drug penetration across the blood-spinal cord barrier and insufficient neutralization of reactive oxygen species. Ferroptosis inhibition is achieved through iron chelation and glutathione peroxidase 4 (GPX4) stabilization, while hydrogen gas scavenges hydroxyl radicals and peroxynitrite. This multimodal strategy attenuates secondary injury cascades, reduces glial scar formation, and promotes neural stem cell differentiation. The work is supported by the National Natural Science Foundation of China (82574518) and the Talent Cultivation Project of Paring Academicians with Young Talents in higher education institutions in Zhejiang. The authors declare no conflict of interest. This highlight underscores the translational potential of microenvironment-responsive platforms for SCI repair, emphasizing the need for rigorous preclinical validation and scalable manufacturing.
Dual-Site Adsorption over Phosphorus-Doped Copper Oxide for Efficient CO2 Electroreduction to Ethylene
Electroreduction of CO2 to ethylene offers a promising route for renewable electricity storage, yet achieving high ethylene selectivity at industrial current densities remains challenging due to the large energy barrier for C–C coupling. Here, we report a “MOF-assisted in situ doping” strategy to introduce the oxophilic nonmetal phosphorus (P) into the copper oxide (CuO) lattice, constructing a localized Cu–P dual-site adsorption configuration for the key *OCCHO intermediate. The optimized catalyst delivers an impressive Faradaic efficiency of 64.6% for ethylene with a partial current density of 646 mA cm-2. Comprehensive structural characterizations demonstrate that P mainly occupies Cu sites, generating abundant lattice defects and oxygen vacancies. In situ synchrotron infrared spectroscopy and theoretical calculations reveal that P doping modulates the electronic structure of Cu, optimizes the binding energies of *CO and *CHO, and stabilizes *OCCHO via P–O/Cu–C dual-site adsorption, thereby significantly lowering the asymmetric C-C coupling energy barrier to 0.74 eV. This work highlights a dual-site microenvironment regulation strategy for CO2-to-ethylene electroreduction.
Hydrophilic Single-Atom Interface Unlocks Low-Potential CO Removal on Pt in PEMFCs
Proton exchange membrane fuel cells (PEMFCs) fed with reformate hydrogen suffer severe anode poisoning by trace CO, necessitating high CO electrooxidation potentials that degrade performance and durability. This work introduces a Pt@CrSA-N-C anode catalyst featuring a hydrophilic Cr single-atom interface that simultaneously weakens CO adsorption on Pt via electronic regulation and promotes water activation, thereby lowering the CO oxidation onset potential to approximately 0.13 V vs. RHE. The onset potential was determined by two independent methods: the first potential at which the background-corrected current exceeds 0 mA cm-2 during CO oxidation reaction tests in a three-electrode system, and the potential at which the forward scan current exceeds the N2 background current in CO-stripping voltammetry. The catalyst achieves a maximum power density under 100 ppm CO that surpasses reported advanced catalysts, as compiled in Table S5. Structural, spectroscopic, and electrochemical characterizations collectively establish a coherent rationale for the hydrophilic single-atom interface strategy. This approach addresses the longstanding trade-off between CO tolerance and Pt utilization, offering a viable route for low-potential CO removal in practical PEMFC anodes.
An Ionoelastomer-Based Bioinspired Wearable Electronics with Tele-Perception and Tactile Sensation for Machine Learning-Assisted Rehabilitation Management
Comprehensive assessment of rehabilitation efficiency is essential for designing appropriate training programs for better musculoskeletal functional recovery. Existing contact-receptor-dependent rehabilitation assessment systems mostly focus on assessing the restoration of muscle function by evaluating grip strength or joint flexion angle; however, parameters reflecting neuromuscular synergistic function are always overlooked. Herein, we develop an ionoelastomer-based soft artificial electroreceptor (SAER) that integrates tele-perception and tactile sensation to track the rehabilitation process, collecting signals related to approaching speed and grip strength sequentially. The SAER uses polyurethane ionoelastomer incorporated with quasi-solid conductive salt as the electric field receptor, and is integrated on a rehabilitation-training ball after assembly to establish an untethered detection device; this enables the remote capture of hand approaching parameter within a 9 cm range, followed by the quantification of grip strength when contacting and grasping. Furthermore, a data-driven assessment system is established by integrating machine learning, which accurately classifies rehabilitation efficiency into six levels; it supports for rehabilitation evaluation and training programs adjustment. Overall, the SAER-based rehabilitation management system establishes a paradigm that synergistically evaluating parameters corresponding to neuromuscular functional restoration and holds strong potential for home-based active rehabilitation for minimizing dependence on frequent clinical supervision.
Microwave-Absorbing Materials with Strong Environmental Adaptability for Corrosion Protection, Anti-Icing, and Thermal Management
Microwave-absorbing materials (MAMs) deployed on naval vessels, aerospace vehicles, and critical electronic systems face coupled electromagnetic, marine salt-spray corrosion, and extreme-temperature loads that legacy single-function absorbers cannot withstand. This review consolidates progress on three environmentally adaptive MAM classes: corrosion-protective, anti-icing, and thermal-management absorbers. The electromagnetic loss and impedance-matching fundamentals are first established, then the synergistic mechanisms, design strategies, and characterization protocols for each class are examined against representative material systems and their measured performance. The analysis identifies a shared design logic—multiscale hierarchical architecture, interfacial polarization engineering, and multifunctional phase integration—while distinguishing the divergent protection mechanisms: barrier and passivation effects for corrosion, surface-energy and latent-heat regulation for anti-icing, and phonon–electron transport decoupling for thermal management. Persistent bottlenecks include the trade-off between impedance matching and protective-layer density, the absence of standardized coupled-field test protocols, and the scarcity of long-term salt-spray and thermal-cycling durability data. Future directions are delineated: intelligent self-adaptive absorbers, multiphysics-coupled simulation frameworks, and environmentally benign multifunctional integration. The review provides a theoretical and technical basis for the design, construction, and engineering scale-up of next-generation high-performance absorbers for aerospace, electronic, and marine equipment.