CSIR-National Physical Laboratory (CSIR-NPL), New Delhi, developed biocompatible invisible luminescent election ink, which is invisible in daylight and emits a red luminescent colour under 365 nm ultraviolet LED-based device. This ink is a strategically designed colloidal suspension composed of luminescent pigment in a protein linker medium for Finger Marker to Deterrent Double Voting. This outcome is a result of the continuous and rigorous effort of the last three years.

This ink was used for the first time in the CSIR Cooperative Society Election held at CSIR Headquarters, Anusandhan Bhawan, New Delhi, on 12 December 2023 for approximately 320 voters.

Voters of CSIR society members highly appreciated the feedback on this ink, and all were highly excited about this ink.

Furthermore, this ink was rigorously tested for chemical stability on fingers by various bleaching agents (Water, Oil, soap solution detergent, bleach, ethanol, isopropanol, acetone and chloroform, etc.) before its first use in the CSIR Cooperative Society Election and was also demonstrated to voters for its stability test during the election. The UV radiation safety test using a dosimeter was also performed to ensure the safety exposure of the device to humans. The UV-A LED source device with controlled power was used to excite and show the luminescent ink’s red colour. When the power of the UV-A LED source is in a safe range, the dosimeter shows a green colour, and when the power exceeds, it shows red colour. The live demonstration of the UV-A LED source power limit was also done with the voters while voting.