Permeable inspection of pharmaceuticals goes in-line

Summary

    Led by Assistant Professor Kou Li, a research group in Chuo University, Japan, has developed a synergetic strategy among non-destructive terahertz (THz)–infrared (IR) photo-monitoring techniques and ultrabroadband sensitive imager sheets toward demonstrating in-line realtime multi-scale quality inspections of pharmaceutical agent pills, with a recent paper publication in Light: Science & Applications.

    While non-destructive in-line monitoring at manufacturing sites is essential for safe distribution cycles of pharmaceuticals, efforts are still insufficient to develop analytical systems for detailed dynamic visualisation of foreign substances and material composition in target pills. Although spectroscopies, expected towards pharma testing, have faced technical challenges in in-line setups for bulky equipment housing, this work demonstrates compact dynamic photo-monitoring systems by selectively extracting informative irradiation-wavelengths from comprehensive optical references of target pills. This work develops a non-destructive in-line dynamic inspection system for pharma agent pills with carbon nanotube (CNT) photo-thermoelectric imagers and the associated ultrabroadband sub-terahertz (THz)–infrared (IR) multi-wavelength monitoring. The CNT imager in the proposed system functions in ultrabroadband regions over existing sensors, facilitating multi-wavelength photo-monitoring against external sub-THz–IR-irradiation. Under recent advances in the investigation of functional optical materials (e.g., gallium arsenide, vanadium oxide, graphene, polymers, transition metal dichalcogenides), CNTs play advantageous leading roles in collectively satisfying informative and efficient photo-absorption and solution-processable configurations for printable device fabrication into freely attachable thin-film imagers in pharmaceutical monitoring sites. The above non-destructive dynamic monitoring system maintains in-line experimental setups by integrating the functional thin-film imager sheets and compact multiple photo-sources. Furthermore, permeable sub-THz–IR-irradiation, which provides different transmittance values specific to non-metallic materials per wavelength or composition, identifies constituent materials for pharmaceutical agents themselves and concealed foreign substances in a non-contact manner. This work finally inspects invisible detailed features of pharmaceutical pills with the non-destructive in-line dynamic photo-monitoring system by incorporating performances of CNT imagers and compact optical setups.

Research background

    While in-line non-destructive monitoring techniques at manufacturing sites are essential for safe distribution cycles of pharmaceutical products, efforts are still insufficient to develop analytical systems for detailed and dynamic visualisation operations of foreign substances and material compositions in target pills. Despite typical spectroscopy measurements widely handle raw materials composing pharmaceutical pills at early stages, inherent complicated and bulky optical setups crucially regulate their operations from in-line situations.

The importance and novelty of this work

To this end, this manuscript made the following significant contributions.

1. Integrating multi-wavelength THz–IR monitoring functions into carbon nanotube (CNT) film photo-thermoelectric (PTE) imagers, which works in ultrabroadband ranges over conventional wide-band sensors at comparable photo-sensitivities with those of existing narrow-band detectors in each region.
2. Developing a portable desktop-scale THz–IR monitoring system, being easily installable into dynamic pill-assembling lines, comprising the light-weight freely attachable ultrabroad CNT film imager sheets and compact multiple photo-sources at a single wavelength region (extracted from reference spectroscopy-based databases as pharmaceutical-specific bands).
3. Demonstrating non-destructive, in-line, and dynamic material composition identification of pharmaceutical agent pills themselves (indistinguishable by human eyesight: Sedative, Antipyretic, and Antiplatelet) and opaquely concealed impurities (hazardous pieces: plastic, glass, and metal) with the presented system.
4. Satisfying fundamental in-line monitoring performances (400 µm spatial resolution at the fastest scanning speed of 3 mm/s for available pills up to a 7-mm-thickness within a 20 % agent concentration) comparable to existing static evaluation methods by the presenting system, while the CNT film imager fully functions over 909 µm–4.33 µm wavelength regions beyond the above narrow- or single-band approaches.

The paper was published online in the international scientific journal, Light: Science & Applications (September 11, 2025).

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