Development of a Polydimethylsiloxane‐Based Flexible Digital Bolus Dosimeter: From Unit‐Cell Characterization to Linear Array for Skin‐Dose Distribution Verification

In this study, we developed a flexible digital bolus dosimeter based on a polycrystalline HgI ₂ photoconductor embedded in a tissue‐equivalent polydimethylsiloxane (PDMS) matrix, incorporating a 70 μm protective layer for skin‐dose evaluation. The dosimeter exhibited excellent linearity ( R ² = 0.9996) within 2–400 MU and superior repeatability (standard deviation of 1.59%). Although the signal gradually decreased by approximately 8.3% (range from 5.6% to −2.7%) as the dose rate increased from 100 to 600 MU/min due to charge trapping and polarization, a stable response was maintained using a dose‐rate‐dependent correction factor or integrating advanced signal processing techniques. Mechanical stability tests up to 1000 bending cycles suggested the need for baseline correction on curved surfaces due to increased drift‐charge and photo‐charge. Subsequently, a 24‐pixel linear array dosimeter was fabricated on a flexible printed circuit board (fPCB) to evaluate continuous spatial dose distribution. When applied to a curved RSD chest phantom, the array reproduced consistent spatial dose distribution trends compared to radiochromic film at various gantry angles, with absolute dose differences of 3.51–7.05 cGy (7%–12%). These results demonstrate that the proposed platform is practical and suitable for evaluating skin‐dose distributions in complex geometries during radiotherapy.