image: Top: Zn and Co/Ni electrodeposition for anode and cathode, respectively, to fabricate CN-ZAMB (Inset of the figure illustrates the reversible Zn ⇌ ZnO conversion at the anode and the bifunctional ORR/OER processes at the cathode, facilitated by the presence of electrolyte ions such as NH4⁺, Zn2⁺, and Cl− and H2O molecules). Bottom: (L) Digital photographs of the Au IDE chip having total area 2.25 cm × 0.75 cm) and active area (1.15 cm × 0.6 cm), CN-ZAMB and Pt-ZAMB. (R) Three Pt-ZAMBs in series effectively powered an indoor–outdoor thermometer with a hygrometer clock.
Credit: S. R. Pattanayak, et al., “ Microscale Near-Neutral Zinc–Air Battery on Interdigitated Electrode Chips for High Current Operation.” Small Methods 9, no. 12 (2025): e01562.
Sensors small enough to disappear into the body, microrobots that move without wires, and smart systems hidden inside everyday materials - all require a battery to function. As electronics shrink towards the micrometre scale, conventional batteries become bulky, impractical, or impossible to integrate in these tiny devices. To address this gap, Subhra Pattanayak, PhD student from T. N. Narayanan’s lab at the Tata Institute of Fundamental Research, Hyderabad (India), in collaboration with researchers from University College London (UK) has developed a planar micrometre-scale zinc–air battery, in which the cathode and anode are patterned in a single plane, thus developing a sleeker battery, that can be fabricated directly onto a microchip. Built with interdigitated electrodes having width of 200 micrometres and operating in a safe, near-neutral gel electrolyte, the device delivers real electrochemical performance and cyclability at a scale previously out of reach.
Zinc–air chemistry is well suited for microscale devices because it uses oxygen from the surrounding air, reducing the need for stored reactants. However, until now, there have been very few demonstrations of true micrometre-scale zinc–air batteries based on interdigitated electrodes that operate in a safe, near-neutral electrolyte (NH4Cl, ZnCl2 based). Most existing designs are either primary batteries or rely on stacked architectures (which take up more space) and strongly alkaline electrolytes, making them unsuitable for biomedical applications and on-chip integration.
The researchers developed a planar micro zinc–air battery that integrates bifunctional cathode catalysts, a near-neutral gel electrolyte, and micrometre-scale interdigitated electrodes. Leveraging electrodeposition and microplotter assisted microfabrication for precise material coverage, the device delivers high energy and power at elevated currents, even powering an LED and a digital thermometer. This demonstrates that chip-scale systems can now host their own onboard power source, enabling fully autonomous micro-devices.
The breakthrough is the result of a two-institution partnership:
TIFR Hyderabad (India): catalyst chemistry, materials development, electrochemistry.
University College London (UK): micro-fabrication, micro-plotting, device engineering.
As with any first step, challenges remain. Over long cycling, the anode and cathode gradually lose material, leading to capacity decay. Current research efforts are aimed at anchoring catalysts more robustly, developing efficient bifunctional cathode material and suppressing zinc dendrites to get more areal energy and areal power for a longer time period. Success here would enable commercial deployment of micro-batteries in wearables, IoT nodes, implantable sensors, and soft microrobotics—potentially reshaping how, where, and at what scale electronics can operate.
Journal
Small Methods
Method of Research
Experimental study
Article Title
Microscale Near-Neutral Zinc–Air Battery on Interdigitated Electrode Chips for High Current Operation
Article Publication Date
10-Nov-2025
COI Statement
The authors declare no conflict of interest.