New technique maps out electrical conductivity at a microscopic level

Currently deemed highly challenging or even impossible, the ability to quantify dielectric properties at a microscopic level would enable many advancements in materials and biomedicine. Unlocking this ability would enable researchers to optimize conductivity distribution within a flexible circuit, better understand bone quality and density, and improve our simulations of tissue conductivity.

Chen et al. developed a technique called quantitative thermoacoustic microscopy, or qTAM, that resolves conductivity at a microscopic level, which can recover electrical conductivity images of both non-biological materials and biological tissue.

“We demonstrate the utilities of qTAM in imaging the electric conductivity maps of flexible circuits, rabbit bone, and mouse brain tissue,” author Huabei Jiang said.

The team’s technique involved a thermoacoustic microscopy system, which converts microwaves to ultrasound energy to image a specimen, and a custom-built algorithm that converted those data signals into electrical conductivity measurements. Using data collected by the system, the team formed electrical conductivity mappings by implementing their algorithm using a numerical method called finite-element analysis.

“We implemented an algorithm for image reconstruction of electrical conductivity using a finite-element-based iterative inversion strategy,” Jiang said.

The team plans to evaluate the method for non-destructive detection of materials and disease detection in animal models and in humans. The authors also note that more work can be done to improve the speed and performance of their technique.

“A major limitation of our qTAM technique is its computational cost involving a large number of matrix operations,” Jiang said. “Therefore, it is necessary to optimize the algorithm in the future, such as by using graphics processing unit (GPU) based computation.”

Source: “Quantitative microwave-induced thermoacoustic microscopy,” by Yi Chen, Zihui Chi, Shuang Du, Qiuchao Fang, and Huabei Jiang, Applied Physics Letters (2024). The article can be accessed at https://doi.org/10.1063/5.0182399 .