Biocompatible and biodegradable materials based nanogenerators for self-powered healthcare sensors

Abstract

Self-powered sensors have recently emerged as a revolutionary advancement for modern medical healthcare. Unlike conventional devices that depend on external batteries or wired connections, these sensors derive energy from the human body or the surrounding environment, utilizing mechanisms such as piezoelectric, triboelectric, and thermoelectric effects. This innovation effectively overcomes key challenges related to battery limitations, maintenance demands, and environmental concerns associated with traditional power sources. These sensors enable continuous, real-time tracking of vital signs, wound recovery, respiratory function, body movements, and biochemical markers without external energy input. By integrating into wearable, implantable, or skin- adhesive formats, self-powered sensors improve patient mobility and reduce the inconvenience of frequent battery changes or recharging. Additionally, by providing consistent, real-time health data, these sensors facilitate early diagnosis, immediate medical attention, and improved results during therapy. The shift toward sustainable healthcare solutions is further facilitated by the adoption of eco-friendly materials and energy- harvesting abilities. Furthermore, self-powered healthcare systems offer a cost-effective, scalable option that can increase access to advanced healthcare monitoring, particularly in remote areas. The rapidly advancing field of energy harvesting technologies, particularly piezoelectric and triboelectric nanogenerators (TENGs), is playing an increasingly important role in enabling self-powered systems. These technologies convert mechanical energy from environmental vibrations into electrical energy, providing self-powered battery-free power sources for a wide range of applications, including sensors, wearable electronics, environmental monitoring, and healthcare devices. This collection of chapters highlights the various innovative approaches and applications of piezoelectric and triboelectric nanogenerators, with a focus on their biocompatibility, sustainability, and potential for real-world integration in self-powered systems. This thesis covers various chapters about different types of biomaterials, their synthesis methods, biocompatibility, biodegradability, fabrication of energy harvesting devices such as PENGs and TENGs, and their applications in self-powered sensors and smart healthcare. In recent years, the demand for wearable sensors capable of evaluating physical activities has increased significantly, driven by the growing interest in health monitoring technologies. Among various energy harvesting techniques, PENGs have emerged as one of the most promising solutions due to their ability to convert mechanical energy from physical movements into electrical energy using piezoelectric material. In Chapter III, we examine the development of a biocompatible PENG that utilizes a composite material of calcium titanate (CaTiO₃) and polyvinylidene fluoride (PVDF), which has shown superior piezoelectric properties. The PENG exhibits impressive output characteristics, generating an output voltage of 20 V, a current of 250 nA, and a power density of 0.19 μW/cm² under mechanical deformation. This device is capable of harvesting energy from physical activities, such as skipping, and is particularly suited for applications where power needs to be derived from the motion of the body. This chapter also explores how the energy generated can be stored in commercial capacitors, enabling the potential use of this system for powering health monitoring systems without the need for conventional batteries. The ability to track and evaluate exercise using a self- powered sensor opens new avenues for personalized health and fitness monitoring, ultimately contributing to more sustainable healthcare solutions. The exploration of sustainable materials in energy harvesting devices is becoming increasingly important, particularly for applications that require biocompatibility and eco-friendliness. Chapter IV focuses on the development of a TENG made from chitosan, a biopolymer derived from chitin found in crustacean shells. Chitosan is not only a sustainable material but also biocompatible, making it an ideal candidate for healthcare applications. The TENG in this chapter is designed to operate in a single-electrode mode and demonstrates an output voltage of 20 V, a current of 200 nA, and a charge density of 12 nC. The key application discussed is the use of the TENG in oral health monitoring, where it powers a bite sensor to measure biting force, offering real- time feedback on oral health conditions. This chapter underscores the potential of utilizing biowaste-derived materials to create sustainable energy harvesting solutions for medical applications. The use of chitosan-based TENGs also introduces the possibility of creating disposable, low-cost, and environmentally friendly sensors for long-term health monitoring without relying on traditional power sources. The ability to detect and monitor environmental conditions, such as humidity, is critical in various applications, including agriculture, healthcare, and smart home systems. In Chapter V, the development of a polydopamine-based TENG for humidity sensing is discussed. Polydopamine (PDA), known for its strong adhesion properties and biocompatibility, is utilized as the triboelectric material in this device. The TENG demonstrated an impressive output of 90 V, with a current of 2.4 μA, and it exhibited high sensitivity over a wide range of relative humidity (RH), from 25% to 92%. The sensitivity of the device is found to be 1.55 V/10 RH%, making it a highly responsive sensor for environmental monitoring. In addition to its high performance, the PDA-based TENG is biocompatible, which makes it suitable for integration into wearable electronics or other bio-integrated systems. This chapter highlights the growing interest in developing energy-harvesting sensors that can operate autonomously, without the need for batteries, and at the same time, contribute to environmental sustainability. The potential applications of this TENG include real-time monitoring of indoor air quality, personal health devices, and even integration into smart home systems for more efficient environmental control. Chapter VI focuses on the application of TENGs for biosensing, specifically for detecting pathogenic bacteria through carbohydrate–protein interactions. A biodegradable, self-powered biosensor is developed by combining a TENG with a sensor capable of detecting Escherichia coli (E. coli) bacteria. The sensor uses D-mannose- functionalized 3D printed polylactic acid (PLA) with a silver electrode to bind specifically to the lectin protein found on the surface of E. coli. The PLA-TENG generates an output of 70 V, a current of 800 nA, and a charge of 22 nC. This biosensor offers a rapid, cost-effective, and sustainable solution for pathogen detection, including real-time detection in samples like tap water and unpasteurized milk. The chapter discusses the importance of integrating energy harvesting technologies with biosensing to create autonomous, self-powered devices capable of performing real-time environmental monitoring. The use of biodegradable materials further enhances the environmental benefits of this technology, contributing to the development of sustainable, eco-friendly biosensors that can be employed in fields like healthcare, food safety, and environmental monitoring. Wound healing is a complex biological process that restores tissue integrity. However, slow or non-healing wounds pose risks such as infections, clot formation, hemorrhages, and chronic pain. Therefore, promoting rapid tissue regeneration, remodeling, and wound monitoring is crucial. Chapter VII discusses a self-powered wound healing patch integrated with a TENG for accelerated wound healing. The patch was fabricated using pectin and curcumin, which are bio-derived, biocompatible, and known for their strong antibacterial, anti- inflammatory, and pH-responsive properties. The TENG device generated a consistent electrical output of 50 V, 160 nA, and 2.7 μW at a load resistance of 500 MΩ. This electrical stimulation was shown to significantly accelerate cell migration in vitro, a crucial step in wound healing. Moreover, the wound healing patch exhibited a pH-sensitive release behavior, ensuring that curcumin was released preferentially under infected or inflamed conditions. In vivo animal studies confirmed the efficacy of the patch, showing nearly 90% of wound closure within 9 days, which was markedly faster compared to conventional treatments. This study is one of the first to report a biomaterial-based, functionalized, self-powered wound healing patch capable of simultaneously delivering electrical stimulation and therapeutic agents in a biocompatible and sustainable system. The self- powered behavioral monitoring of the animal mode was also demonstrated using wearable TENG for pain management assessment. This study presents a self-powered, low-cost, easy-to-fabricate patch for accelerated wound healing and monitoring. This collection of chapters presents a comprehensive overview of the potential and applications of PENGs and TENGs in self-powered sensor technologies. From exercise monitoring, oral health assessments, environmental sensing, pathogen detection, to accelerated wound healing, the diverse applications of these energy-harvesting devices highlight their versatility and importance in a wide range of industries, including healthcare, environmental monitoring, and smart systems. These chapters emphasize the growing need for biocompatible and sustainable materials in energy harvesting technologies, as well as the importance of fabricating devices that are self-powered and do not require external power sources or batteries. The advancements made in this thesis showcase the transformative potential of self-powered sensor systems, paving the way for more sustainable, efficient, and eco-friendly solutions in various applications. As research continues to progress, it is expected that the integration of energy harvesting devices with sensors will play a critical role in the development of next-generation healthcare devices. Keywords: Biomaterials, Nanogenerators, Self-powered sensors, Wound healing, Biocompatible|자가 구동 센서는 최근 현대 의료 분야에서 혁신적인 발전으로 떠오르고 있습니다. 기존 장치들이 외부 배터리나 유선 연결에 의존하는 반면, 자가 구동 센서는 압전, 마찰전기, 열전기 효과와 같은 메커니즘을 이용해 인체 또는 주변 환경으로부터 에너지를 수집합니다. 이러한 혁신은 기존 전원에서 발생하는 배터리 한계, 유지보수 부담, 환경 문제를 효과적으로 해결합니다. 자가 구동 센서는 외부 전원 없이도 생체 신호, 상처 회복, 호흡 기능, 신체 움직임, 생화학적 지표 등을 연속적이고 실시간으로 추적할 수 있게 해줍니다. 이 센서들은 착용형, 이식형, 피부 접착형 형태로 통합되어 환자의 이동성을 높이고 배터리 교체 또는 충전의 번거로움을 줄입니다. 또한 지속적이고 실시간으로 제공되는 건강 데이터는 조기 진단, 신속한 의료 대응, 치료 효과 향상에 기여합니다. 지속 가능한 헬스케어 솔루션을 향한 전환은 친환경 소재와 에너지 수확 능력의 채택을 통해 더욱 가속화되고 있습니다. 자가 구동 헬스케어 시스템은 비용 효율적이며 확장 가능한 옵션으로, 특히 의료 접근성이 낮은 지역에서 첨단 모니터링 기술에 대한 접근을 확대할 수 있습니다. 에너지 수확 기술, 특히 압전 및 마찰전기 나노발전기(PENG 및 TENG)의 급속한 발전은 자가 구동 시스템 구현에 있어 점점 더 중요한 역할을 하고 있습니다. 이러한 기술은 환경의 진동 등에서 발생하는 기계적 에너지를 전기로 변환하여 배터리가 필요 없는 자가 구동 전력원을 제공합니다. 이는 센서, 착용형 전자기기, 환경 모니터링 및 의료기기 등 다양한 분야에 적용됩니다. 본 논문은 압전 및 마찰전기 나노발전기의 생체적합성, 지속 가능성, 자가 구동 시스템으로의 통합 가능성을 중점적으로 다루며 다양한 혁신적 접근과 응용 사례들을 소개합니다. 이 논문은 다양한 바이오소재, 이들의 합성 방법, 생체적합성 및 생분해성, 에너지 수확 장치(PENG 및 TENG)의 제작, 그리고 자가 구동 센서 및 스마트 헬스케어 응용에 대해 다루는 여러 장으로 구성되어 있습니다. 최근 신체 활동을 평가할 수 있는 착용형 센서의 수요가 건강 모니터링 기술에 대한 관심 증가로 크게 늘어나고 있습니다. 다양한 에너지 수확 기술 중 PENG는 신체 움직임으로부터 기계적 에너지를 전기 에너지로 변환하는 능력으로 인해 가장 유망한 솔루션 중 하나로 주목받고 있습니다. 3장에서는 우수한 압전 특성을 갖는 칼슘타이타네이트(CaTiO₃)와 PVDF 복합소재를 활용한 생체적합 PENG의 개발에 대해 다룹니다. 이 장치는 기계적 변형 하에서 20V, 250nA, 0.19μW/cm²의 출력 특성을 보여주며, 줄넘기와 같은 활동을 통해 에너지를 수확할 수 있습니다. 본 장에서는 수확된 에너지를 커패시터에 저장하고 이를 통해 기존 배터리 없이 헬스 모니터링 시스템에 전력을 공급하는 가능성도 제시합니다. 4장에서는 생체적합하고 지속 가능한 소재인 키토산을 사용하여 개발된 TENG에 대해 설명합니다. 본 장치의 출력 전압은 20V, 전류는 200nA, 전하 밀도는 12nC이며, 구강 건강 모니터링에 응용되어 씹는 힘을 측정하는 바이트 센서로 작동합니다. 키토산 기반의 TENG는 폐기 가능하고 저비용이며 친환경적인 센서 개발에 유망합니다. 5장에서는 습도 감지를 위한 PDA 기반 TENG를 다룹니다. PDA는 강한 접착력과 생체적합성으로 알려져 있으며, 이 장치는 90V, 2.4μA의 출력과 함께 25~92%의 상대 습도 범위에서 1.55V/10%RH의 민감도를 보여줍니다. 이는 환경 모니터링, 착용형 전자기기, 스마트 홈 시스템에 유용한 자가 구동 센서입니다. 6장에서는 자가 구동 바이오센서를 이용해 병원성 박테리아(E. coli)를 검출하는 응용을 소개합니다. D-만노스를 기능화한 3D 프린팅 PLA와 은 전극을 활용하여 E. coli의 렉틴 단백질과 선택적으로 결합합니다. PLA-TENG는 70V, 800nA, 22nC의 출력을 나타내며, 수돗물이나 비살균 우유에서의 병원균 검출에 효과적입니다. 이 장은 지속 가능하고 자가 구동이 가능한 바이오센서 개발의 중요성을 강조합니다. 7장에서는 전기 자극 및 약물 방출 기능을 결합한 자가 구동 상처 치유 패치에 대해 설명합니다. 이 패치는 펙틴과 커큐민을 이용해 제작되었으며, 전기 자극(50V, 160nA, 2.7μW)은 세포 이동을 촉진해 상처 치유를 가속화합니다. 감염 시 pH 변화에 따라 커큐민이 방출되며, 동물 실험에서 9일 이내에 약 90%의 상처 폐쇄 효과가 확인되었습니다. 이 장치는 저비용, 자가 구동, 생분해성 치유 패치의 실현 가능성을 제시합니다. 이 논문은 PENG 및 TENG의 응용 가능성을 포괄적으로 다루며, 운동 모니터링, 구강 건강 평가, 환경 감지, 병원균 검출, 상처 치유에 이르기까지 다양한 자가 구동 기술의 활용을 보여줍니다. 생체적합성 및 지속 가능성을 갖춘 소재의 중요성과 외부 전원 없이 작동하는 장치 개발의 필요성을 강조하며, 자가 구동 센서 시스템의 혁신적 잠재력을 제시합니다. 앞으로 자가 구동 센서와 에너지 수확 기술의 통합은 차세대 의료기기의 핵심 기술로 자리잡을 것입니다.

주요어: 바이오소재, 나노발전기, 자가 구동 센서, 상처 치유, 생체적합성