Flexible Infrared Optoelectronics for Large-Area Wearable Sensing

Introduction

Optical wearable sensing leverages the interaction of light with biological tissues to non-invasively monitor physiological parameters such as heart rate and blood oxygenation. This approach, widely adopted in consumer devices through techniques like photoplethysmography (PPG), has become essential for continuous and real-time wellness and health tracking.

Beyond consumer-grade sensing, the same optical principles are now applied to more advanced and medically relevant applications that require area-based measurements, such as functional near-infrared spectroscopy (fNIRS) for brain imaging, muscle oxygenation mapping for performance optimization, breast tissue screening, and tissue viability monitoring in wounds or transplants.

In these applications, longer infrared wavelengths, particularly those within the first and second near-infrared (NIR) biological windows (650–1350 nm), are critical due to their deeper tissue penetration and reduced scattering. This enables more accurate and volumetric sensing of tissue oxygenation, hemoglobin concentration, and water content.

However, current hardware for such systems remains largely based on discrete LEDs and photodiodes, which presents challenges for high-resolution, scalable, and cost-effective area sensing. Systems like fNIRS often require bulky, complex setups with limited spatial resolution, making miniaturization and wearability difficult. An additional bottleneck is accessing the second NIR window (1000–1350 nm), which offers high tissue transparency and is sensitive to key biomolecules such as water, lipids, and collagen. Yet, traditional optoelectronics struggle in this range due to limited availability of efficient and affordable emitters and detectors, hindering the development of wearable systems that can exploit these richer spectral features.

Topic

This PhD aims to develop next-generation flexible and wearable optoelectronic systems for non-invasive health and wellness monitoring. The goal is to leverage the large-area processing capabilities of thin-film semiconductors to surpass the current state-of-the-art in spatial resolution, enable low-cost solutions, and extend the operating spectral range beyond 1 μm.

The project will proceed in two phases:

1. Design and fabrication of efficient infrared emitter arrays based on thin-film semiconductors such as quantum dots or perovskites, targeting wavelengths in the second NIR window.
2. Integration of emitter arrays with imec’s thin-film infrared photodetectors on flexible substrates to create large-area wearable demonstrators.

The candidate

You are a highly motivated recent graduate holding a master’s degree in nano-engineering, physics, material science, chemistry, electrical engineering, or related. You have an interest in the processing of thin-film semiconductors, optical modelling of such materials, and electrical and optical characterization. You will be expected to work safely in a lab environment and acquire necessary processing and characterization skills. It is expected that you will present results regularly.  You are a team player and have good communication skills as you will work in a multidisciplinary and multicultural team spanning several imec departments. Given the international character of imec, an excellent knowledge of English is a must.