Photonic resonator absorption microscopy for dynamic point of care biosensing

This dissertation introduces Photonic Resonator Absorption Microscopy (PRAM), a label-free, digital-resolution biosensing platform designed for highly sensitive and accessible point-of-care diagnostics. By coupling photonic crystal (PC) surfaces with gold nanoparticle (AuNP) tags, PRAM enables attomolar detection of biomolecules without enzymatic amplification or complex workflows. To advance PRAM for real-world applications, several innovations are presented. A portable, automated PRAM system (ap-PRAM) integrates motorized autofocus, large field-of-view (FOV) tiling, and a differential dynamic detection algorithm to enable real-time, single-particle kinetic analysis of binding and unbinding events. These capabilities are demonstrated in both sandwich immunoassays for viral antibodies (HIV, HCV) and a target recycling amplification assay for miRNA, achieving detection limits as low as 1 aM. In parallel, a miniaturized PRAM system (PRAM Mini) is developed, featuring compact optics, smartphone integration, and digital image processing for decentralized or resource-limited settings. To further enhance signal spatial uniformity and polarization independence, a two-dimensional PC substrate is designed and fabricated, improving signal consistency across the sensor surface. Together, these developments establish PRAM as a versatile and scalable platform with broad potential for clinical diagnostics, liquid biopsy, and dynamic biosensing in both laboratory and point-of-care environments.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Electrical & Computer Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Liu, Weinan

Contributors dc:contributor

• Cunningham, Brian T.
• Do, Minh N.
• Gruev, Viktor
• Zhao, Yang

• Digital-resolution Biosensing
• Photonic Crystal
• Point-of-care
• Microscopy
• Metasurface
• Computational Imaging
• Biomedical Detection

Statement dc:rights

• Copyright 2025 Weinan Liu

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/130098

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F130098