Biodegradable Piezoelectric Materials for Biomedical Applications: A Step Toward Smart Heart Valve Repair
The research of former PhD student Youssif Merhi explores how optimizing the crystallinity of biodegradable Poly-L-Lactic Acid (PLLA) enhances its piezoelectric properties, paving the way for next-generation biomedical sensors, including applications in aortic valve repair.
Piezoelectric materials, which generate electrical signals in response to mechanical stress, play a crucial role in biomedical sensing and wearable electronics. Traditionally, most piezoelectric materials are non-biodegradable and require surgical removal after use. However, the work done by Youssif and his supervisor Shweta Agarwala together with collaborators at Aarhus University have demonstrated that biodegradable PLLA films can be tailored to enhance their piezoelectric properties, making them highly suitable for implantable and resorbable medical devices.
Engineering Biodegradable PLLA for Enhanced Sensitivity
Unlike conventional piezoelectric material fabrication, they have developed a process that ensures scalability while considering environmental impact. Their fabrication of PLLA can be performed at ambient conditions, requires no heat, and no extra treatments, making it highly energy-efficient and eco-friendly.
In a series of studies, they then investigated how mechanical strain, crystallinity, and molecular alignment affect the piezoelectric performance of PLLA. By applying controlled uniaxial drawing and thermal treatments, they successfully increased the crystallinity of PLLA films, leading to a significant enhancement in their piezoelectric output. A key aspect of this research was the use of Terahertz Time-Domain Spectroscopy (THz-TDS) to analyze structural changes in the PLLA films.
Their findings reveal that as PLLA undergoes increased mechanical stretching, its molecular chains become more ordered, leading to a higher piezoelectric response. This correlation between strain-induced crystallinity and electrical output offers new strategies for fine-tuning biodegradable piezoelectric materials for biomedical applications.
How Did They Do It?
To understand how mechanical strain affects the crystallinity and piezoelectric properties of PLLA, the researchers used Terahertz Time-Domain Spectroscopy (THz-TDS), a technique that examines how materials respond to terahertz radiation. This allowed them to see changes in the material at the molecular level.
- Crystallinity Analysis: By analyzing the absorption spectra and refractive index of PLLA films. THz-TDS provided insights into how molecular structures change under mechanical stretching.
- Tracking Structural Changes: The researchers observed a shift in characteristic absorption peaks, indicating a transformation in the PLLA crystalline phases as strain was applied.
- Linking Structure to Performance: These findings confirmed that higher crystallinity correlates with improved piezoelectric response, revealing how processing conditions can be optimized for biomedical sensor applications.
They were able to quantify the nanoscale structural modifications that enhance PLLA’s functional properties, offering a new pathway for designing biodegradable, high-performance piezoelectric materials.
Proof of Concept: PLLA Sensors for Heart Valve Treatment
To demonstrate the real-life potential of their biodegradable piezoelectric material, the researchers tested it in an in vitro setup designed to mimic the function of a heart's aortic valve. They developed a ring-shaped strain sensor made from PLLA, which was placed around a 3D-printed aortic valve model. This sensor provided real-time data on the valve's expansion under varying physiological pressures. The goal was to correlate the sensor's output voltage with the degree of expansion, enabling the researchers to study how aortic annuloplasty influences the behavior of the aortic valve. The sensor successfully detected movements in the valve, proving its potential for real-time monitoring during and after surgery as shown in Figure 2.
Having this real-time feedback could help doctors track how the heart valve is working during and after surgery, leading to better treatment results without the need for permanent implants. The success of this test shows that PLLA could be used as a biodegradable, self-powered sensor, opening new possibilities for heart health monitoring and advanced medical implants.
Interested?
Their upcoming studies will further expand the role of THz spectroscopy in material optimization and explore innovative ways to enhance biodegradable piezoelectric materials!
If you are working on related materials or applications, we invite you to reach out to our Center Manager to discuss potential collaborations or shared research opportunities.
You can find the research behind this article by looking into:
Youssif Merhi, Vincent Goumarre, Yasith Amarasinghe, Pernille Klarskov, Shweta Agarwala
Youssif Merhi, Yasith Amarasinghe, Vincent O. Y. Goumarre, Karem Lozano Montero, Matti Mantysalo, Pernille K. Pedersen, Shweta Agarwala
[3] Harnessing Piezoelectric poly-L-lactic acid (PLLA) for Enhanced Sensing for Aortic Annuloplasty
Youssif Merhi, Karem Lozano Montero, Peter Johansen, Matti Mäntysalo, Shweta Agarwala