Wearable and implantable BioMEMSs (biomedical microelectromechanical systems) have transformed modern healthcare by enabling continuous, personalized, and minimally invasive monitoring, diagnostics, and therapy. Wearable BioMEMSs have advanced rapidly, encompassing a diverse range of biosensors, bioelectronic systems, drug delivery platforms, and motion tracking technologies. These devices enable non-invasive, real-time monitoring of biochemical, electrophysiological, and biomechanical signals, offering personalized and proactive healthcare solutions. In parallel, implantable BioMEMS have significantly enhanced long-term diagnostics, targeted drug delivery, and neurostimulation. From continuous glucose and intraocular pressure monitoring to programmable drug delivery and bioelectric implants for neuromodulation, these devices are improving precision treatment by continuous monitoring and localized therapy. This review explores the materials and technologies driving advancements in wearable and implantable BioMEMSs, focusing on their impact on chronic disease management, cardiology, respiratory care, and glaucoma treatment. We also highlight their integration with artificial intelligence (AI) and the Internet of Things (IoT), paving the way for smarter, data-driven healthcare solutions. Despite their potential, BioMEMSs face challenges such as regulatory complexities, global standardization, and societal determinants. Looking ahead, we explore emerging directions like multifunctional systems, biodegradable power sources, and next-generation point-of-care diagnostics. Collectively, these advancements position BioMEMS as pivotal enablers of future patient-centric healthcare systems.

Lithography is crucial to semiconductor manufacturing, enabling the production of smaller, more powerful electronic devices. This review explores the evolution, principles, and advancements of key lithography techniques, including extreme ultraviolet (EUV) lithography, electron beam lithography (EBL), X-ray lithography (XRL), ion beam lithography (IBL), and nanoimprint lithography (NIL). Each method is analyzed based on its working principles, resolution, resist materials, and applications. EUV lithography, with sub-10 nm resolution, is vital for extending Moore’s Law, leveraging high-NA optics and chemically amplified resists. EBL and IBL enable high-precision maskless patterning for prototyping but suffer from low throughput. XRL, using synchrotron radiation, achieves deep, high-resolution features, while NIL provides a cost-effective, high-throughput method for replicating nanostructures. Alignment marks play a key role in precise layer-to-layer registration, with innovations enhancing accuracy in advanced systems. The mask fabrication process is also examined, highlighting materials like molybdenum silicide for EUV and defect mitigation strategies such as automated inspection and repair. Despite challenges in resolution, defect control, and material innovation, lithography remains indispensable in semiconductor scaling, supporting applications in integrated circuits, photonics, and MEMS/NEMS devices. Various molecular strategies, mechanisms, and molecular dynamic simulations to overcome the fundamental lithographic limits are also highlighted in detail. This review offers insights into lithography’s present and future, aiding researchers in nanoscale manufacturing advancements.

ABSTRACT This paper presents the development of a non-toxic, low-cost, and portable potassium ion sensor utilizing an Extended Gate Field-Effect Transistor (EGFET) configuration with all-solid-state electrodes fabricated on a printed circuit board (PCB) substrate. An Ag/AgCl-based pseudo-reference electrode (PRE) has been fabricated planar to a ion-selective membrane (ISM) coated on the gold solidcontact electrode (SCE). The PRE has shown <1 mV/day drift potential, exhibiting exceptional stability and reproducibility. While the SCE has demonstrated a high sensitivity of 49 mV/log [ K ⁺ ], covering a wide linear detection range from 10 ^-4 M to 1 M with a rapid response time of less than 10 seconds. The sensor has displayed minimal hysteresis (<15 mV ) and remained stable over a broad pH range ( pH 4 to pH 10). These uni-planar, all-solid-state electrodes along with off-the-shelf FET mitigate the requirement of additional wire bonding by utilizing a common PCB platform for sensing as well as circuitry area. Additionally, the PRE, SCE and the FET in the EGFET-configuration-based sensing system have exhibited a high current sensitivity of 1.43(μ A ) ^1/2 / log [ K ⁺ ]. Our sensor presents a practical and reliable solution for soil nutrient measurement in precision agriculture, offering significant advantages over existing potassium sensors in terms of cost-effectiveness, sensitivity, stability, and environmental safety. The presented approach holds promise for optimizing agricultural productivity and minimizing environmental impact through efficient nutrient monitoring and smart irrigation and fertilization management systems.

High sensitivity, high selectivity, reproducibility and quick response are of prime importance for ion detection in various applications. In this respect, electrochemical detection is the best technique as compared to the traditional flame photometry, ion chromatography and surface plasmon resonance [1]. In an ion sensitive field effect transistor (ISFET), directly exposing the gate oxide of field effect transistor (FET) to an ionic solution causes ion penetration into the oxide layer. This is reflected in I-V characteristics that show voltage-dependent hysteresis due to ion penetration [2]. Extended gate field effect transistor (EGFET) shows great potential over the usual methods of ISFETs or ion sensitive electrode (ISE). EGFET effectively improves the reliability by separating the sensor and the transducer, associating the two by interconnect. It also provides a wide range of detection with possibility for device miniaturization and is extremely easy to fabricate [3]. In this work, we present a novel combination of solid-state ISE and FET integrated on same platform. Thus, creating an EGFET. We have built an electrochemical sensing unit comprised of all solid-state electrodes, an Ag/AgCl reference electrode and ionophore coated gold electrode. Unlike any of the earlier reports, all the electrodes are integrated with a FET in a single plane of printed circuit board (PCB), hence mitigating the issues of separate wire bonding or external connection between the sensing element and the transducer by using PCB traces [2]. In this work, we demonstrate for the first time, the use of ISE in EGFET configuration without degrading the linearity and sensitivity due to the external voltage bias. Potentiometric measurement on our potassium ion (K⁺) ISE shows near Nernstian limit sensitivity (49 mV/decade), low concentration for the limit of detection (10⁻⁶ M), and linearity over a large range of detection (10⁻⁴ M to 1 M). We demonstrate a simple approach to develop an array of miniaturized two terminal planar solid state electrode device consisting of an ion selective membrane (ISM) on gold as the working electrode (WE) and solid state silver/silver chloride (Ag/AgCl) as the reference electrode (RE), both clamped to the metal contacts of the FET. 18-crown-6 (ionophore) has been utilized in ion selective membrane on WE to achieve high selectivity towards K⁺ ions [4]. Highly stable and low cost Ag/AgCl electrode with the drift potential of less than 2mV is used as pseudo RE [5]. The principle mechanism behind our sensing approach is transduction of ionic stimulus into electrical signal. Concentration dependent change in the ISM potential at WE/electrolyte interface prompts a corresponding adjustment in overall gate potential, thus modifying the charge transport in FET. Sensitivity and linearity of potassium ion (K⁺) ISE is determined by potentiometric measurements at several concentrations ranging from 1M to 10⁻⁶ M. The electrodes are reusable after each measurement by simply rinsing it in deionized water. Our study shows that voltage biasing does not affect the electromotive force (V_cell). This makes the device suitable and robust for EGFET configuration to enhance the sensitivity for the ion detection applications. Two-fold increase in the sensitivity (100mV/decade, much higher than reported values ion selective electrodes [3,6]) is observed in EGFET configuration. The innovative approach used in our solid-state K⁺ EGFET has great potential to propel the future in micro-devices with commercialized product for the applications of clinical investigation, environmental and agricultural field. Our methodology represents a handy procedure by using facile fabrication technique for the accomplishment of multipurpose, versatile, and cost-effective ion sensing devices. Reference Dorothee Grieshaber, et al. “Electrochemical Biosensors - Sensor Principles and Architectures”, Sensors, Mar 2008. Q. Li, et al. "Stable Thin-Film Reference Electrode on Plastic Substrate for All-Solid-State Ion-Sensitive Field-Effect Transistor Sensing System," IEEE Electron Device Letters, Oct 2017. Salzitsa Anastasova, et al. “Multi-parametric rigid and flexible, low-cost, disposable sensing platforms for biomedical applications”, Biosensors and Bioelectronics, Apr 2018. Sunita Kumbhat, et al. “A potassium-selective electrochemical sensor based on crown-ether functionalized self assembled monolayer”, Journal of Electroanalytical Chemistry, Jan 2018. Despina Moschou, et al. “Surface and Electrical Characterization of Ag/AgCl Pseudo-Reference Electrodes Manufactured with Commercially Available PCB Technologies”, Sensors, July 2015. He Q, et al. “Enabling Inkjet Printed Graphene for Ion Selective Electrodes with Postprint Thermal Annealing”, ACS Applied Materials & Interfaces, Feb 2017. Figure 1

This work presents a comprehensive study on the sensitivity optimization of electrical impedance flow cytometry devices for identifying analytes suspended in a flowing liquid. The optimization is achieved by investigating the influence of various parameters, including applied frequency, electrode geometry dimensions, bacterial properties, and buffer characteristics. The study utilizes COMSOL Multiphysics simulation to analyze the impedance variation based on differential Maxwell’s equations solved using finite element methods. The frequency optimization reveals that the sensitivity peak is around 12.6 kHz when considering imaginary impedance due to medium conductivity. Geometry optimization involves electrode dimensions with a length of 30 µm and a gap of 15 μm, as well as a channel width and height of 20 μm. Furthermore, the paper explores the effect of buffer conductivity, showing that it plays a significant role in defining total impedance with or without cells/particles. Higher buffer conductivity leads to dominant changes in real impedance, while lower conductivity affects imaginary impedance more prominently. The study also investigates the impact of variations in bacterial parameters, such as cell membrane permittivity and cytoplasm conductivity. These parameters influence total impedance, with cell radius showing a notable effect on sensitivity. By optimizing these parameters, the sensitivity and performance of impedance-based flow cytometry devices can be enhanced, making them more effective for bacterial analysis and characterization in various applications.

We report a two-terminal gas sensor based on gold nanoparticle (AuNP)-decorated silicon nanowire (SiNW) thin films for selective detection of hydrogen sulfide ($\text{H}_{2}\text{S}$), a toxic gas of environmental concern. Field Emission Scanning Electron Microscopy (FESEM) and optical profilometry confirm clustered nanowire films with $\sim$10 nm AuNPs serving as catalytic adsorption sites. Electrical characterization reveals nonlinear Poole–Frenkel transport in intrinsic SiNW thin films, with slow annealing producing uniform networks and nearly an order of magnitude higher current than rapid annealing. Gas sensing measurements show concentration-dependent responses from 1–10 ppm $\text{H}_{2}\text{S}$, with slow-annealed AuNP–SiNW devices achieving a maximum sensor response of $\sim$171% at 10 ppm. Selectivity tests demonstrate strong discrimination against $\text{SO}_{2}$, $\text{NO}_{2}$, NO, $\text{CO}_{2}$, and $\text{NH}_{3}$, owing to the high sulfur–gold affinity. These results highlight AuNP–SiNW thin films as a compact, low-power platform for real-time $\text{H}_{2}\text{S}$ monitoring in environmental and climate safety applications.