Monitoring of human bodily motion requires wearable sensors that can detect position, velocity and acceleration. They should be cheap, lightweight, mechanically compliant and display reasonable sensitivity at high strains and strain rates. No reported material has simultaneously demonstrated all the above requirements. Here we describe a simple method to infuse liquid-exfoliated graphene into natural rubber to create conducting composites. These materials are excellent strain sensors displaying 10(4)-fold increases in resistance and working at strains exceeding 800%. The sensitivity is reasonably high, with gauge factors of up to 35 observed. More importantly, these sensors can effectively track dynamic strain, working well at vibration frequencies of at least 160 Hz. At 60 Hz, we could monitor strains of at least 6% at strain rates exceeding 6000%/s. We have used these composites as bodily motion sensors, effectively monitoring joint and muscle motion as well and breathing and pulse.

http://pubs.acs.org/doi/pdf/10.1021/nn503454h

Sensitive, High-Strain, High-Rate Bodily Motion Sensors Based on Graphene–Rubber Composites

In recent years, nanocomposites based on various nano-scale carbon fillers, such as carbon nanotubes (CNTs), are increasingly being thought of as a realistic alternative to conventional smart materials, largely due to their superior electrical properties. Great interest has been generated in building highly sensitive strain sensors with these new nanocomposites. This article reviews the recent significant developments in the field of highly sensitive strain sensors made from CNT/polymer nanocomposites. We focus on the following two topics: electrical conductivity and piezoresistivity of CNT/polymer nanocomposites, and the relationship between them by considering the internal conductive network formed by CNTs, tunneling effect, aspect ratio and piezoresistivity of CNTs themselves, etc. Many recent experimental, theoretical and numerical studies in this field are described in detail to uncover the working mechanisms of this new type of strain sensors and to demonstrate some possible key factors for improving the sensor sensitivity.

Piezoresistive Strain Sensors Made from Carbon Nanotubes Based Polymer Nanocomposites

The high specific surface area and the excellent mechanical, electrical, optical and thermal properties of graphene make it an attractive component for high-performance stimuli-responsive or ‘smart’ materials. Complementary to these inherent properties, functionalization or hybridization can substantially improve the performance of these materials. Typical graphene-based smart materials include mechanically exfoliated perfect graphene, chemical vapour deposited high-quality graphene, chemically modified graphene (for example, graphene oxide and reduced graphene oxide) and their macroscopic assemblies or composites. These materials are sensitive to a range of stimuli, including gas molecules or biomolecules, pH value, mechanical strain, electrical field, and thermal or optical excitation. In this Review, we outline different graphene-based smart materials and their potential applications in actuators, chemical or strain sensors, self-healing materials, photothermal therapy and controlled drug delivery. We also introduce the working mechanisms of graphene-based smart materials and discuss the challenges facing the realization of their practical applications. Graphene and its macroscopic assemblies and composites are currently enabling a range of high-performance ‘smart’ materials that are responsive to various stimuli. In this Review, different graphene-based smart materials are described, along with their potential applications in actuators, chemical or strain sensors, self-healing materials, photothermal therapy and controlled drug delivery.

Graphene-based smart materials

Wearable strain sensors for human motion detection are being highlighted in various fields such as medical, entertainment and sports industry. In this paper, we propose a new type of stretchable strain sensor that can detect both tensile and compressive strains and can be fabricated by a very simple process. A silver nanoparticle (Ag NP) thin film patterned on the polydimethylsiloxane (PDMS) stamp by a single-step direct transfer process is used as the strain sensing material. The working principle is the change in the electrical resistance caused by the opening/closure of micro-cracks under mechanical deformation. The fabricated stretchable strain sensor shows highly sensitive and durable sensing performances in various tensile/compressive strains, long-term cyclic loading and relaxation tests. We demonstrate the applications of our stretchable strain sensors such as flexible pressure sensors and wearable human motion detection devices with high sensitivity, response speed and mechanical robustness.

A stretchable strain sensor based on a metal nanoparticle thin film for human motion detection

A stretchable strain sensor based on metal nanoparticle thin film for human motion detector = 동작 감지용 금속 나노입자 박막 기반 신축성 스트레인 센서

Preparation of piezoresistive nano smart hybrid material based on graphene

Electrical impedance properties of different type of carbon nanotubes based bulk electrodes have been investigated to develop chemical and biosensors. The bulk composite electrodes were fabricated with single-wall and multi-wall carbon nanotubes involving ionic conducting host polymer, Nafion, by using traditional solution-casting techniques. Under the various amounts of buffer solution, resistance and capacitance of the electrodes were measured with LCR meter and their characteristics due to ionic conducting host polymer were investigated by means of electrokinetic analysis. The capacitance values showed drastic change while the resistances only changed within few percent ranges. Electrical impedance measurement provided rapid and simple sensing mechanism to develop chemical sensor and biosensors with bulk nano electrodes.

Electrical impedance properties of carbon nanotube composite electrodes for chemical and biosensor.

Electrical impedance properties of bulk carbon nanotube (CNT) composite electrodes have been studied to develop
chemical and biosensors. The CNTs embedded in composite electrodes were fabricated by means of traditional film
casting and electrospun nanoweb. The morphology of the bulk CNT electrode was investigated by scanning electron
microscopy (SEM) and transmission electron microscopy (TEM). Under the various amounts of buffer solution,
electrical impedance of the composite electrodes was measured by means of LCR meter. It is generally known that
electrical impedance measurement provides rapid and simple sensing mechanism. In this study, we found out that CNT
bulk composite electrodes showed good sensing properties for chemical and bio sensors.

Electrical impedance properties of bulk carbon nanotube composites for chemical sensors and biosensors

나노기술은 원자와 분자수준의 물질을 제어하고 조작하는 기술로, 제2의 산업혁명을 이끌어 나갈 핵심기술 로 인식되고 있다. 그러나 나노수준의 구조체가 인체와 환경에 잠재적인 역효과를 줄 수 있다는 우려가 제기되면서 이 에 관한 정부차원의 대응이 요구되고 있다. 본 연구는 이러한 나노기술의 환경.보건.안전성 영향에 관한 미국, 일본, EU 등의 주요 나노기술개발국가와 OECD, ISO 등의 국제기구 등의 대응현황을 살펴보고, 주요 주제분야별 연구개발 동 향을 진단하였다. 또한, 계량정보분석기법을 사용하여 연구개발동향의 정량적 분석을 시도하였다. 연도별 논문발행 추 이 및 주요 연구자, 연구기관, 국가별 연구개발현황을 분석하였으며, 인용빈도수, 네트워크 분석 등을 통하여 나노기술 의 환경.보건.안전성 영향에 관한 세계적인 연구개발 추이를 진단하였다. 나노기술의 책임감 있는 개발을 위해서는 시기별, 분야별 연구로드맵의 작성과 국가적 차원의 전략개발이 요구되고 있다.

/pdf/r-d-trend-on-the-environmental-health-and-safety-impacts-of-2hmyr19303.pdf

R&D Trend on the Environmental, Health and Safety Impacts of Nanotechnology

나노기술은 과학기술적인 가치와 경제적 파급효과로 인하여 제2의 산업혁명을 불러일으키는 핵심 기술 로 간주되며 국가 자원배분의 효율성을 제시하고 있다. 그러나 기술개발로 인한 사회적 영향문제가 부각 되면서, 연구개발의 연속적인 지지를 위한 새로운 정당성의 확보가 요구되고 있다. 따라서 서구 국가에서는 나노기술의 연구개발에 따른 예측치 못한 사회적 영향문제에 대한 대응책을 모색하고 있으며, 나노기술에 대한 대중의 이해 와 태도를 조사하는 작업은 우선적인 연구 분야로 주목을 받고 있다. 본 고에서는 이러한 나노기술 인식도 및 태 도 조사에 대한 한국, 미국, 일본, EU, 영국, 스위스 등의 주요 조사결과를 살펴보고, 연구문헌 분석을 통한 주요 연구자 및 기관, 국가 활동에 대한 정량 분석을 시도하여, 나노기술에 대한 대중 인식도 및 태도 연구 현황을 입 체적으로 고찰하였다. 나노기술에 대한 대중의 지식을 측정하는 단순한 대중 서베이에서 이제는 과학기술적 측면 뿐만 아니라 연구개발 체계 및 정보 확산 구조에 대한 포괄적 시스템에 대한 대중의 태도를 조사하는 “구성주의 적 대중의 과학이해(PUS)” 접근법이 조명을 받고 있다.

https://www.cheric.org/PDF/PIC/PC11/PC11-5-0062.pdf

Dae-Sup So

Papers

Preparation of piezoresistive nano smart hybrid material based on graphene

Electrical impedance properties of carbon nanotube composite electrodes for chemical and biosensor.

Electrical impedance properties of bulk carbon nanotube composites for chemical sensors and biosensors

R&D Trend on the Environmental, Health and Safety Impacts of Nanotechnology

Public Understanding and Attitude toward Nanotechnology