A dual-linear polarized quad-element multi-axis conformal antenna for L-band applications is presented. The lightweight and highly conformal antenna is designed by combining flexible copper-cladded polyimide (CCPM) film and PF-4 foam materials. The antenna comprises four dual-corrugated conformal antennas (DCCA), which offer better profile reduction and higher flexibility compared to the single-corrugated conformal antenna (SCCA). Exciting the four ports with different phases generates horizontal polarization (HP) or vertical polarization (VP). The single antenna and quad-element antennas are fabricated and measured for the flat case as well as conformed to a cylinder with radius of 200 mm,160 mm, and 100 mm. For the flat case, the quad-element antenna has a bandwidth of 8.0% (1.28−1.38GHz) and a boresight gain of 9.4 dBi and 9.2 dBi for VP and HP at 1.32 GHz, respectively.

Researcher/Author: 

Dr Mohammad Ameen and Prof Koen Mouthaan

Published in:  2025 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting (AP-S/CNC-USNC-URSI)

Date Added to IEEE Xplore: 08 December 2025

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DOI: 10.1109/AP-S/CNC-USNC-URSI55537.2025.11266198

A lightweight and stacked conformal filtering antenna is demonstrated using copper-cladded polyimide films (CCPF). The antenna consists of primary, secondary, and parasitic patches as rectangular stubs using multi-corrugated polyimide films to improve bending performance. Good filtering performance is obtained by stub-loading of parasitic elements attached to both ends of the primary radiator. Bandwidth (BW) enhancement is achieved by stacking of corrugated polyimide films combined with nylon spacers, forming a five-layer antenna design. For the flat case, the antenna has a BW ranging from 1.17 GHz to 1.38 GHz (16.5%) and nearly flat gain response with a maximum gain of 8.6 dBi at 1.29 GHz. The antenna is fabricated and measured for the flat case and conformed to cylinders with radii Rc200 mm,160 mm,100 mm,80 mm, and 40 mm.

Researcher/Author: 

Dr Mohammad Ameen and Prof Koen Mouthaan

Published in: 2025 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS)

Added to IEEE Xplore, 06 August 2025

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DOI: 10.1109/FLEPS65444.2025.11105666

A low-cost, modular, bendable dipole antenna array with a wide bandwidth is presented for X-band sensing applications. The antenna elements, realized as printed dipoles on a substrate mounted on a ground plane, use a printed balun to enable broadband, balanced excitation. A parasitic dipole is included to increase the bandwidth of the printed dipole. In total, four arrays of four elements each are printed on Rogers RO4350B-based strips to realize the 4 × 4 array. The ground plane is fabricated using thin flexible copper-clad FR-4 substrate, enabling 1-D flexibility. As an example, the array is conformed to a cylinder with a diameter of 12 cm for beamforming. Minimum variance distortionless response beamforming is used and adapted to the wideband conformal array. Experimental results show that the range of beam steering angles can be significantly extended with the proposed design, while keeping sidelobe levels low.

Researcher/Author: 

Prof Koen Mouthaan, Jiahao Wang, Gong Cheng

Published in: IEEE Sensors Letters ( Volume: 9, Issue: 7 July 2025)

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DOI: 10.1109/LSENS.2025.3575781

This review presents recent advancements in the use of nondestructive methods for plant chemical sensing. It summarizes the different environmental chemicals and plant biomarkers used for assessing plant health. The article also discusses various types of sensing devices and techniques, along with the emerging use of flexible and wearable devices on plants.

Researcher/Author: 

Dr Yi Jing Wong, Dr Yifei Luo, Dr Xian Jun Loh, Prof Xiaodong Chen

Published in: Chemistry Europe (06 June 2025)

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DOI: https://doi.org/10.1002/anse.202500037  

A highly conformable, foldable, and deployable antenna and its 2×2 array configuration are presented. The antenna is made lightweight by combining copper-cladded polyimide film (CCPF), Mylar transparent film, and PF-4 foam strips. A single conformable and foldable antenna (SCFA) at L-band is presented first, which can be completely conformed to a cylinder with radius Rc=40 mm. The SCFA is used to design a 2×2 array, which is completely foldable to 360°. The antenna provides an impedance bandwidth from 1.20−1.32GHz(9.7%), isolation better than 20 dB between the antenna elements, and a gain of 14.1 dBi at 1.26 GHz. The antenna array is measured for the flat case and conformed to cylinders of radius 200 mm,160 mm, and 150 mm.

Researcher/Author: 

Dr. Mohammad Ameen and Prof Koen Mouthaan

Published in: 2025 19th European Conference on Antennas and Propagation (EuCAP)

Added to IEEE Xplore, 21 May 2025

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DOI:  10.23919/EuCAP63536.2025.11000048

Machine learning accelerates material discovery which includes selection of candidate small molecules and polymers for high-efficiency organic photovoltaic (OPV) materials. However, conventional machine learning models suffer from data scarcity for conjugated oligomers, crucial for OPV material production. To address this challenge, transfer learning within a graph neural network was introduced to reduce the data requirement while accurately predicting the electronic properties of the conjugated oligomers. By leveraging on transfer learning using original conjugated oligomer data and pre-trained models from the renowned PubChemQC dataset, the limitations posed by insufficient data were mitigated. The models in this study achieved a low mean absolute error, ranging from 0.46 to 0.74 eV, for the HOMO, LUMO, and HOMO–LUMO gap. An original candidate dataset of 3710 conjugated oligomers was constructed for materials discovery, and a high-throughput screening pipeline was developed by integrating the models with density functional theory. This pipeline effectively identified 46 promising conjugated oligomer candidates, showcasing its effectiveness in accelerating the discovery of advanced materials for organic photovoltaics. These results demonstrated the potential of the approach used in this study to overcome data scarcity while accelerating the discovery of new innovative materials in organic electronics.

Researcher/Author: 

NTU – Dr Siyan Deng, Jing Xiang Ng, Assoc Prof Shuzhou Li 

Published in:

Molecular Systems Design & Engineering (7th May 2025)

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DOI:  10.23919/EuCAP63536.2025.11000048E

This letter reports a resistive-type wearable strain sensor fabricated using an electrically conductive hybrid network of single-walled carbon nanotubes (CNTs) and silver nanowires (AgNWs). AgNWs degrade over time due to silver corrosion in ambient conditions, leading to electrode failure.

To mitigate this issue, CNTs were incorporated as a protective shield, effectively interlinking the AgNWs. This not only improved the stability and durability of the AgNWs but also resulted in a robust and highly conductive CNTs/AgNWs hybrid network. The hierarchical CNTs/AgNWs-based strain sensor exhibited better performance, achieving a large elongation of up to 100% with high sensitivity, demonstrated by a gauge factor (GF) of 79. It also featured a fast response time of 42 ms and outstanding mechanical stability, maintaining performance over 5000 stretch-release cycles.

The sensor’s performance was assessed under normal environmental conditions for a period of 180 days (approximately 6 months), showing minimal degradation in GF. This provides valuable insights into long-term changes, aiding the development of more robust, durable, and reliable nanocomposite-based strain sensors for practical applications. The sensor was used to monitor various human motions, including finger, throat, and elbow movements.

Researcher/Author: 

Dr. Jagan Singh Meena, Dr Lucia Lum Yu Xiang and Prof Lim Yeow Kheng

Published in: IEEE Sensors Letters ( Volume: 9, Issue: 5, May 2025)

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DOI:  https://doi.org/10.1109/LSENS.2025.3560735

Sensorimotor functions, the seamless integration of sensing, decision-making, and actuation, are fundamental for robots to interact with their environments. Inspired by biological systems, the incorporation of soft materials and devices into robotics holds significant promise for enhancing these functions. However, current robotics systems often lack the autonomy and intelligence observed in nature due to limited sensorimotor integration, particularly in flexible sensing and actuation. As the field progresses toward soft, flexible, and stretchable materials, developing such materials and devices becomes increasingly critical for advanced robotics. Despite rapid advancements individually in soft materials and flexible devices, their combined applications to enable sensorimotor capabilities in robots are emerging. This review addresses this emerging field by providing a comprehensive overview of soft materials and devices that enable sensorimotor functions in robots. We delve into the latest development in soft sensing technologies, actuation mechanism, structural designs, and fabrication techniques. Additionally, we explore strategies for sensorimotor control, the integration of artificial intelligence (AI), and practical application across various domains such as healthcare, augmented and virtual reality, and exploration. By drawing parallels with biological systems, this review aims to guide future research and development in soft robots, ultimately enhancing the autonomy and adaptability of robots in unstructured environments.

Researcher/Author: 

NTU – Prof Xiaodong Chen, Dr Jiangtao Su, Dr Ke He, Dr Yanzhen Li, Dr Jiaqi Tu

Published in: 

Chemical Reviews (March 31, 2025)

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DOI: https://doi.org/10.1021/acs.chemrev.4c00906

Copper-clad polyimide film (CCPF) is combined with Beyolex transparent film to realize a lightweight flexible, stretchable, and foldable antenna. The antenna is designed for 1.20 GHz using a corrugated patch and the ground plane using CCPFs. The corrugations on both sides of the antenna facilitate complete bending in both concave and convex directions. The antenna is fabricated and tested for various bending and stretching scenarios. The antenna has an impedance bandwidth (IBW) of 2.0% and gain of 7.8 dBi at 1.20 GHz under normal conditions. The antenna is tested by conforming it to cylinders with radius Rc = 200, 160, 100, 80, 40, and 20 mm. The antenna gain values are slightly reduced from 7.8 dBi to 6.2 dBi while reducing Rc from 200 mm to 40 mm. The antenna resonant frequency shifts from 1.20 GHz to 1.21 GHz when applying a strain of 6.3% to 18.8%.

Researcher/Author: 

Dr. Mohammad Ameen and Prof Koen Mouthaan

Published in: 2025 IEEE International Workshop on Antenna Technology (IWAT)

Added to IEEE Xplore, 24 March 2025

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DOI:  10.1109/iWAT64079.2025.10931234

A simple, lightweight, multi-axis bendable and foldable antenna based on flexible copper-clad polyimide (FCCPM) patches is presented. First, a single antenna is designed comprising a semi-elliptical shaped conformal patch operating at 1.25 GHz. The single antenna is used to design a four-element antenna by rotating each additional element sequentially. Dual polarization (DP) is achieved by exciting the conformal antenna pairs with equal magnitude and 180° phase difference. The DP antenna provides a 10 dB return loss bandwidth of 20%, isolation better than 20 dB, and gain of 7.6 dBi at 1.25 GHz. Antennas are analyzed for the flat case and conformed to cylinders in horizontal, vertical, and diagonal directions with radius of 200, 160, 150, 100, and 80 mm.

Researcher/Author: 

Dr. Mohammad Ameen, Dr Peng Khiang Tan and Prof Koen Mouthaan

Published in: 2025 IEEE International Workshop on Antenna Technology (IWAT)

Added to IEEE Xplore, 24 March 2025

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DOI:  10.1109/iWAT64079.2025.10931191

The development of autonomous bioelectronic devices capable of dynamically adapting to changing biological environments represents a significant advancement in healthcare and wearable technologies. Such systems draw inspiration from the precision, adaptability, and self-regulation of biological processes, requiring materials with intrinsic versatility and seamless bio-integration to ensure biocompatibility and functionality over time. Silk fibroin (SF) derived from Bombyx mori cocoons, has emerged as an ideal biomaterial with a unique combination of biocompatibility, mechanical flexibility, and tunable biodegradability. Adding autonomous features into SF, including self-healing, shape-morphing, and controllable degradation, enables dynamic interactions with living tissues while minimizing immune responses and mechanical mismatches. Additionally, structural tunability and environmental sustainability of SF further reinforce its potential as a platform for adaptive implants, epidermal electronics, and intelligent textiles. This review explores recent progress in understanding the structure–property relationships of SF, its modification strategies, and its great potential for integration into advanced autonomous bioelectronic systems while addressing challenges related to scalability, reproducibility, and multifunctionality. Future opportunities, such as AI-assisted material design, scalable fabrication techniques, and the incorporation of wireless and personalized technologies, are also discussed, positioning SF as a key material in bridging the gap between biological systems and artificial technologies.

Researcher/Author: 

NTU – Prof Xiaodong Chen,

Yanling Wang

Tsinghua University – Xue Feng

Published in:

Advanced Materials (23 March 2025)

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DOI:  https://doi.org/10.1002/adma.202500073

Compact and low profile shared aperture dual-band antennas are presented for space applications. The shared aperture antennas consist of a regular stacked patch for the high band and two channel shaped patch antennas with differential feed for the low band. The mutual coupling between antennas working at two bands is suppressed by using antennas with dual-resonance for out-of-band radiation suppression.

A prototype operating at low band (1.04–1.11 GHz) and high band (1.19–1.35 GHz) is fabricated and measured. The measured results generally agree with the simulated results, making it a candidate for shared aperture dual band applications.

Researcher/Author: 

Dr Gong Chen, Dr Fujiang Lin and Prof Koen Mouthaan

Published in: 2024 IEEE 12th Asia-Pacific Conference on Antennas and Propagation (APCAP)

Added to IEEE Xplore, 20 Feb 2025

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DOI:  10.1109/APCAP62011.2024.10881502

A flexible dual linear polarized H-shaped aperture coupled S-band array is presented. The array uses flexible polyimide printed circuit board (FPC) technology and polyethylene foam (PF-4). The antenna comprises an aperture FPC layer, two separate FPC layers for the feed networks of the orthogonal polarizations, and an FPC patch. These layers are separated by PF-4 foam to enable conformability.

The antenna is tested on a flat surface and conformed to cylindrical surfaces with radius of 200 mm,150 mm, and 100 mm. The measured antenna provides conformability, dual linear polarization, high impedance bandwidth (20-25%), and port isolation larger than 30dB.

Researcher/Author: 

Dr. Xiang Li, Dr Gong Chen and Prof Koen Mouthaan

Published in: 2024 IEEE 12th Asia-Pacific Conference on Antennas and Propagation (APCAP)

Added to IEEE Xplore, 20 Feb 2025

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DOI:  10.1109/APCAP62011.2024.10881384

A multilayer and lightweight conformal antenna (MLWCA) is demonstrated using a U-slotted patch and stacked polyimide films. The antenna consists of a rectangular patch with a U-shaped slot placed above the stacked Kapton polyimide (KPM) and transparent polyester plastic film (TPPF), which provides enhanced bandwidth (BW) and bending performance. The antenna has a bandwidth from 1.18 GHz to 1.36GHz(14.1%) with a maximum gain of 8.0 dBi at 1.27 GHz.

The antenna is designed and analyzed for the flat case and conformed along the x – and y-axis to cylinders with a radius of 200,160,100, and 80 mm.

Researcher/Author: 

Dr.Mohammad Ameen and Prof Koen Mouthaan

Published in: 2024 IEEE 12th Asia-Pacific Conference on Antennas and Propagation (APCAP)

Added to IEEE Xplore, 20 Feb 2025

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DOI:  10.1109/APCAP62011.2024.10881976

For system-technology co-design (STCO) of BEOL compatible beyond-Silicon heterogeneously integrated (Oxide & 2D material) materials, we investigated the monolithic 3D integration of vertically stacked 1T1R and 2T0C1R DRAM-RRAM hybrid memory array with IGZO FETs and MoS2 analog RRAMs for low voltage switching. Our wafer-scale process (<400∘C) demonstrates good device performance. The ITO-enhanced IGZO selecting transistors (Ion=196.5μA/μm,Ioff =1pA/μmatVd=1V) integrated with solution deposited MoS2 switching layer (3.6 nm), enable 1T1R memory cells with programming current <100μA and voltage <1V, compatible with CMOS logic core voltages.

Furthermore, to address RRAMs endurance limitations, we propose an ultra-compact vertically stacked 2T0C1R gain cell DRAM-RRAM hybrid using dual-gated IGZO FET. We also propose an all-IGZO buffer capable of 3D BEOL data pipelining for concurrent multi-stacked array operations. Such 3D analog compute-in-memory architecture significantly reduces ADC energy overheads, achieving 121 TOPS/W efficiency and 4.73 TOPS throughput.

Researcher/Author: 

Dr. Baoshan Tang, Dr. Zihang Fang, Dr. Ruyue Wan, Dr. Sonu Hooda, Dr. Jin Feng Leong, Dr. Quanzhen Wan, Dr ChunKuei Chen, Dr Evgeny Zamburg, Dr JoongSik Kim and Prof Aaron Thean

Published in: 2024 IEEE International Electron Devices Meeting (IEDM)

Added to IEEE Xplore, 18 Feb 2025

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DOI: 10.1109/IEDM50854.2024.10873575

An L-band 4×4 dual-polarization array with full digital receiving beamforming using two synchronized radio frequency system-on-chip (RFSoC) is presented. The array has 32 dipoles, 16 for each polarization, connected to the 2×16 channels of the two RFSoCs. The constituting element for the array are two dipoles placed orthogonal to each other.

Details of the dipoles, the antenna array, the synchronized RFSoCs, and the calibration are provided. The digital beamformer is first compared with an analog beamformer for measured boresight patterns. Subsequently, digital beamsteering is demonstrated in elevation. The array provides the building block for larger arrays with application in synthetic aperture radar (SAR).

Researcher/Author: 

Dr. Peizhou Yang, Dr Gong Chen and Prof Koen Mouthaan

Published in:  2024 IEEE Asia-Pacific Microwave Conference (APMC)

Added to IEEE Xplore, 13 Feb 2025

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DOI:  10.1109/APMC60911.2024.10867535