University of Michigan team builds 40-plus microring sensor array for photoacoustic imaging

Researchers at the University of Michigan developed a polymer microring resonator array that uses light and sound to image biological tissue with higher resolution and functional detail. The system could help detect cancer earlier by measuring blood flow, oxygenation and vessel density in tissue samples.

Why it matters: - The new sensor array pushes photoacoustic tomography closer to clinical use by improving how doctors can detect tissue changes linked to cancer. - The platform can measure oxygen levels, blood flow and blood vessel density, which are key signals in early tumor development. - The work also shows a scalable path for manufacturing dense optical ultrasound sensor arrays at lower cost.

What happened: - A University of Michigan team led by Professors Xueding Wang, Guan Xu and L. Jay Guo developed a polymer-based microring resonator array with more than 40 elements. - The researchers used the array to demonstrate photoacoustic tomography with optical arrays. - The paper appeared online March 30, 2026, and was published June 7, 2026, in Volume 9, Issue 6 of Opto-Electronic Advances.

The details: - Photoacoustic tomography uses short laser pulses to generate ultrasound waves from light absorption in tissue. - The method combines optical contrast with ultrasound imaging and can probe deeper than purely optical techniques. - Conventional piezoelectric ultrasound transducers can limit bandwidth, miniaturization and integration density. - Optical ultrasound sensors such as microring resonators offer high sensitivity, wide bandwidth and compatibility with photonic integration. - The microring array was fabricated with nanoimprint lithography. - Nanoimprint lithography can produce nanometer-scale features over large areas. - The team precisely controlled each microring radius at the nanometer scale. - That control produced multiple distinguishable resonances within a narrow spectral window. - The design maintained high optical quality factors needed for sensitive ultrasound detection. - Integrated into a PAT system, the array delivered acoustic detection bandwidth above 170 MHz. - The system achieved spatial resolution on the order of tens of micrometers. - In ex vivo mouse prostate tissue, the images matched known biological structures, including blood vessel regions. - Spectral analysis of the photoacoustic signals separated normal from cancerous prostate tissue. - The paper lists the title as "Imprinted high-Q polymer micro-ring resonator array for high-resolution photoacoustic tomography." - The DOI is 10.29026/oea.2026.250215. - The study received support from the National Cancer Institute and the National Institute of Diabetes and Digestive and Kidney Diseases.

Between the lines: - The main technical hurdle in photoacoustic imaging has been scaling optical ultrasound sensors without losing performance. - This work suggests polymer microring arrays can provide both dense integration and the sensitivity needed for biomedical imaging. - The same nanoimprint approach could also matter for optical communications and integrated photonic circuits. - The result is as much about manufacturability as imaging performance, which is critical for eventual clinical adoption.

What's next: - The University of Michigan team will likely need to test the platform in more complex biological settings before clinical translation. - Further development could focus on in vivo imaging, larger arrays and system integration for medical devices. - Broader adoption will depend on whether the fabrication approach can be scaled reliably for mass production.

The bottom line: - The study shows a practical route to sharper, more functional tissue imaging using a scalable polymer sensor array.