Developing Battery-Free Biodevices Powered by Body Movements

Using biomechanical energy, which is the energy generated from the movement of the human body, to create electricity is seen as the future of modern medicine. In recent years, driven by rapid advancements in electronic technology, a plethora of portable, wearable and implantable medical devices like pacemaker, neurostimulator, and insulin pumps have emerged for diagnosing, treating, and monitoring various diseases, thereby enhancing people’s living standards. Ensuring a sustainable and body-friendly long-term energy supply for these devices is paramount. While batteries currently address this need, they don’t last very long and need to be replaced often through surgery. To circumvent this hurdle, wireless charging inside the body is emerging as a potential solution.

Recent discoveries have shown that electrical stimulation (ES) can regulate a variety of cellular phenomena, such as cell adhesion, proliferation, differentiation, migration, and programmed cell death, indicating its potential therapeutic effects. For instance, the electric field plays a crucial role in guiding cellular processes that contribute to the orderly healing of wounds.

However, current clinical interventions involving ES often rely on large extracorporeal devices, requiring trained clinicians for operation and thus necessitating patient hospitalization. Hence, implantable electronics hold the promise of stabilizing hearts, alleviating tremors, and facilitating wound healing.

Yet, their current bulky size and intrusive nature, often due to batteries and wires, present serious obstacles. The pressing need, therefore, is for soft, flexible, and miniaturized battery-free devices to overcome these obstacles.

Piezoelectric materials can convert mechanical stress or pressure into electrical energy, and vice versa. They are emerging as promising candidates for various applications. The human body, with its constant movements such as body motions, heartbeats, jaw movements, and blood circulation, serves as an abundant source of mechanical energy. Piezoelectric materials can harness this mechanical energy from such subtle motions and efficiently convert it into electrical energy.

However, most of the piezoelectric materials currently in use are derived from toxic lead-based (Pb) materials, rare-earth elements or heavy metals. These materials are non-biocompatible, brittle, fragile, and require a high temperature processing. Conversely, synthetic polymer-based piezoelectric materials can release toxic components both during their synthesis and decomposition processes. Thus, these materials are neither environmentally friendly nor suitable for use in implantable electronics and biomedical applications, thus limiting their practical utility.

These limitations of existing piezoelectric systems have spurred research efforts aimed at developing naturally flexible, nontoxic, and biocompatible alternatives that can seamlessly integrate with the human body. Piezoelectric properties have long been observed in many natural systems, such as bone, tendon, skin, and hair. These biological tissues exhibit inherent piezoelectric properties. In a recent review article, Santu Bera, Ramanujan Faculty Fellow in the Department of Chemistry at Ashoka University, and his co-author, provide an overview of the latest advancements in synthesizing biological materials such as proteins, peptides, amino acids, spider silk, fish scale, and bacteria. These materials serve as mimetic-based piezoelectric platforms with potential applications in biomedicine.

Currently Dr. Bera’s research group is focused on developing new biomimetic piezoelectric peptides with high efficiency for building self-powered scaffolds and biodevices that can be safely integrated with biological systems. His research emphasizes the design and synthesis of short helical peptides, coiled coil and cross-α amyloid proteins. Helical conformation is particularly promising due to the organized hydrogen bonds within its structure, which result in an inherent dipole moment—a key determinant of piezoelectric properties. This inherent dipole moment makes helical peptides better candidates compared to other protein structures for developing efficient piezoelectric platforms.

Collagen, the most prevalent protein in the human body, is also piezo-active. Its helical structural motif endows it with a variety of important physical properties, such as mechanical strength and flexibility, which are advantageous for nanogenerator applications. However, due to the large size and complexity of collagen, Dr. Bera’s research group aims to design minimalistic, simple peptide sequences that can mimic collagen both in structure and function. By understanding the molecular mechanisms and engineering such systems, they aim to fine-tune the piezoelectric output of these designed biomaterials, to suit specific applications.

In a nutshell, researchers at Ashoka are trying to create new devices using specially designed peptides that can generate their own electricity (nanogenerators). These devices produce electric pulses that can help speed up healing processes, such as wound healing and bone regeneration. Special attention has been given to the biodegradability of these systems, ensuring that they can safely dissolve in the body fluid once their function is complete. The researchers believe that these new nanotechnology will have potential applications in biomedicine, making it possible for all medical devices within the body to operate without the need for batteries.

Edited by Kangna Verma (Intern, Academic Communications, RDO)

Reference Article:
Recent approaches in development of bio-based artificial piezoelectric constructs for biomedical applications. Giant Volume 17, March 2024, 100214, https://doi.org/10.1016/j.giant.2023.100214

Authors: Rohit Kumar, Santu Bera