Octopus-inspired skin adhesive patch with enhanced skin adhesion for wearable energy harvesting applications

다국어 초록 (Multilingual Abstract)

Skin-attachable wearable electronics require strong adhesion and reliable self-powered functionality to ensure stable operation and real-time biosignal monitoring. However, previously reported octopus-inspired adhesive systems have primarily focused on replicating simple protruded geometries inside the suction chamber, without capturing the essential mechanisms of natural suckers—such as muscle-driven active volume modulation, energy dissipation through compliant tissues, adhesion stability under wet conditions, and high conformability to skin topography. As a result, these structures often exhibit reduced adhesion on moist surfaces, strong preload dependence, and interfacial instability during long-term attachment, limiting their practical applicability to wearable devices.
To overcome these limitations, this study proposes a new octopus-inspired adhesive platform based on two complementary design strategies. First, a dome-shaped suction architecture was integrated with a highly stretchable elastomeric substrate whose mechanical properties were tuned, via additive incorporation, to closely match those of human skin. This design enables strong and stable adhesion under both dry and wet conditions, even with minimal preload. Second, a pillar suction mechanism inspired by the contractile behavior of acetabular muscles was engineered, and a soft organogel domain mimicking the compliance of natural soft tissues was incorporated to induce energy dissipation and maintain adhesion stability in moist environments.
The resulting bioinspired platform maintains robust attachment even on highly curved, wrinkled, or hairy skin regions and exhibits long term adhesion reliability under humid conditions. Furthermore, by integrating moisture driven energy harvesting functionality, the proposed system demonstrates significant potential as a self-powered patch platform for wearable devices requiring stable operation, enhanced biosignal monitoring, and expanded therapeutic applicability.

국문 초록 (Abstract)

피부 부착형 웨어러블 전자소자는 안정적인 동작과 실시간 생체신호 모니터링을 위해 강한 점착력과 신뢰성 있는 자가발전 기능이 필수적이다. 그러나 기존의 문어 모사 점착 시스템은 주로 흡반 내부의 단순 돌기의 형상을 재현하는 데에 집중해 왔으며, 실제 문어 흡반의 핵심 메커니즘인 근육 수축 기반의 능동적 부피 조절, 연성 조직을 통한 에너지 소산, 습윤 환경에서의 점착 안정성, 피부 지형에 대한 높은 적응성 등을 충분히 구현하지 못하였다. 이로 인해 기존 구조는 습윤 표면에서 점착력 저하, 피부 물성과 디바이스의 모듈러스 모순, 장시간 부착 시 계면 불안정성 등을 보이며 웨어러블 디바이스로의 실질적 적용에 한계를 가진다. 이러한 한계를 극복하기 위해 본 연구에서는 두 가지 상보적 설계 전략에 기반한 새로운 문어 모사 점착 플랫폼을 제안한다. 첫째, 돔(dome) 형상의 흡반 구조를 고신율 엘라스토머 기판에 통합하였으며, 첨가제 도입을 통해 피부와 유사한 기계적 물성을 구현함으로써 건조 및 습윤 환경 모두에서 최소한의 예압만으로도 강하고 안정적인 점착이 가능하도록 설계하였다. 둘째, 문어의 실제 구조를 모사한 기둥-흡반 메커니즘을 도입하였고, 자연 연성 조직의 컴플라이언스를 모사한 소프트 오가노젤 영역을 결합하여 에너지 소산을 유도하고 습윤 환경에서 점착 안정성을 유지하도록 하였다. 제안된 생체모사 플랫폼은 굴곡이 심한 피부, 주름이 존재하는 피부 등에서도 안정적인 부착 성능을 유지하며, 습도가 높은 환경에서도 장시간 점착 신뢰성을 확보한다. 더 나아가 두 연구 모두 에너지 하베스팅 기능을 통합함으로써, 본 시스템은 안정적인 동작·고정도 생체신호 모니터링·치료적 기능 확대가 요구되는 웨어러블 디바이스용 자가발전형 패치 플랫폼으로서 높은 응용 가능성을 보여준다.

목차 (Table of Contents)

• Chapter 1. Introduction 1
• A. Bioinspired system 1
• B. Bioinspired system of octopus sucker 2
• C. Anatomical and functional characteristics of the octopus sucker 2
• D. Review of octopus inspired skin adhesive patch 3
• E. Motivation of my research 4
• Chapter 2. Stretchable Micro-Wrinkled Carbon Nanotube-Assembled Skin-Adhesive Patches with Suction-Cup Patterns for Human Breath-Derived Moisture Energy Harvesting 6
• 2.1. Introduction 6
• 2.2 Materials and methods 7
• 2.2.1 Fabrication of the suction cup pattern 7
• 2.2.2 Preparation of SP-engraved silicone rubber-polymer film 8
• 2.2.3 Fabrication of SAMEH patch 9
• 2.2.4 Finite element method (FEM) simulation 10
• 2.2.5 Characterization 11
• 2.2.6 Preparation of human philtrum replica 11
• 2.2.7 Measurement of adhesion performance 12
• 2.3 Results and Discussion 13
• 2.3.1 Design and fabrication of the suction cup pattern array patch 14
• 2.3.2. Normal adhesion strength of the suction cup 16
• 2.3.3. Adhesion mechanism of the suction cup 19
• 2.3.4. Normal adhesion strength of the suction cup on porcine skin 23
• 2.3.5. Peel-off strength of the suction cup on curved surface 24
• 2.3.6. Application 26
• 2.4 Conclusions 29
• Chapter 3. An All-Soft Octopus-Inspired Ionic Patch with Reattachable and Energy-Dissipative Adhesion for Wet-Skin-Conformal Triboelectric Nanogenerators 30
• 3.1. Introduction 30
• 3.2 Materials and methods 31
• 3.2.1 Fabrication of a dual-patterned structure for the adhesive layer film 31
• 3.2.2 Fabrication of energy harvesting layer for organogel encapsulation 32
• 3.2.3 Fabrication of OIA-TENG patch 34
• 3.2.4 Finite element method (FEM) simulation 34
• 3.2.5 Characterization 35
• 3.2.6 Fabrication of the tip coating 35
• 3.2.7 Measurement of adhesion performance 37
• 3.3 Results and Discussion 38
• 3.3.1 Design and fabrication of the OIA-TENG patch 38
• 3.3.2. Stress-strain curve of materials 41
• 3.3.3. SEM images of different adhesive architectures 42
• 3.3.4. Adhesion mechanisms of different adhesive architectures 43
• 3.3.5. Normal adhesion strength of different adhesive architectures 45
• 3.3.6. Adhesion modeling 47
• 3.3.7. Images of pillar position 51
• 3.3.8. Adhesion strength of pillar position 54
• 3.3.9. FEM simulations of pillar position 57
• 3.3.10. Effect of organogel integration on adhesion performance 59
• 3.3.11. Tip coating of OIA-TENG patch for measurements on porcine skin 62
• 3.3.12. Adhesion strength of OIA-TENG patch on porcine skin 64
• 3.3.13. Application 65