Sensors and Actuators B 160 (2011) 804–821 Contents lists available at SciVerse ScienceDirect Sensors and Actuators B: Chemical j o ur nal homep a ge: www.elsevier.com/locate/snb Gas sensors based on gravimetric detection—A review S. Fanget a , S. Hentz a,1 , P. Puget a , J. Arcamone a , M. Matheron a , E. Colinet a,1 , P. Andreucci a , L. Duraffourg a,∗ , Ed. Myers b , M.L. Roukes b a CEA-LETI, MINATEC-Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France b Departments of Physics, Applied Physics, and Bioengineering and Kavli Nanoscience Institute, California Institute of Technology, MC 114-36 Pasadena, California 91125, USA a r t i c l e i n f o Article history: Received 1 February 2011 Received in revised form 20 June 2011 Accepted 24 August 2011 Available online 2 September 2011 PACS: 62.23-c, 63.25-g Keywords: Micro-electromechanical system Nano-electromechanical system Gas sensor Gravimetric detection a b s t r a c t These last 10 years, smaller, less expensive, and higher performance sensors are required for gas sensing applications. To date no true detection principle has been recognized as the best candidate for such appli- cation. Microsytems or Micro/Nano ElectroMechanical Systems (M/NEMS) used as gravimetric detectors are among the probable candidates. The technology can indeed be manufactured en masse and can pro- vide multi-gas analysing platform. In this paper, we present a comprehensive overview of micro/nano sensors based on the gravimetric effect to detect an absorbed gas on top of their surfaces. The paper pro- vides a comparison between different electromechanical devices (Bulk Acoustic Wave, Surface Acoustic Wave, Capacitive Micro-machined Ultrasonic Transducer, Micro/Nano cantilevers) with an introduction to gas adsorption mechanisms, material selection, detection principles and design guidance useful to researchers or engineers. © 2011 Elsevier B.V. All rights reserved. 1. Introduction These last 10 years, gas sensors based on numerous techniques have been developed for a large variety of gases (for instance CO 2 , NO x , organophosphate compounds for nerve agent attacks or pes- ticide poisoning in the food chain, insecticides, and many other volatile organic compounds). In particular, carbon dioxide (CO 2 ), present in Earth’s atmo- sphere at concentrations close to 390 ppm [1] is one of the major gases to be detected. It participates in the greenhouse effect in Earth’s atmosphere and is suspected to be the main source of global warming. CO 2 is also among gases to be checked for indoor air qual- ity monitoring. It can be present in certain industrial environments and must be detected to prevent workers from possible poisoning. More recently, needs have been expressed for the detection of Volatile Organic Compounds (VOCs). According to the European Community Directive (Solvent Emissions Directive – 1999), VOCs are defined as organic compounds having at 20 ◦ C a vapor pres- sure of 10 Pa or more. In addition, an organic compound is defined as any compound containing at least the element carbon and one or more of hydrogen, halogens, oxygen, sulphur, phosphorus, sili- con, or nitrogen. Carbon oxides, inorganic carbonates, bicarbonates, ∗ Corresponding author. E-mail address: laurent.duraffourg@cea.fr (L. Duraffourg). 1 Present address: Condensed Matter Physics 114-36, California Institute of Technology, Pasadena, CA 91125, USA. methane, ethane, CO, CO 2 , organometallic compounds and organic acids are excluded from this definition. VOCs are emitted from a number of manufactured solids or liquids and some of them have short- and long-term adverse health effects: eye, nose, and throat irritation, headaches, loss of coordination, nausea, damage to liver, kidney, and central nervous system. Some VOCs can cause cancer in animals and some of them are suspected or known to cause cancer in humans. Their concentration is higher indoors than outdoors: up to 10 times higher in well isolated buildings. This is due to a large number of potential VOCs sources indoors like: paints, paint strip- pers, cleaning supplies, building materials and furnishings, office equipment such as copiers and printers, graphics and craft mate- rials including glues and adhesives. As can be seen there are a lot different VOCs with very ill assorted molar mass and chemical com- position. Three well known of them are presented in Table 1. Nerve agents, which are a class of organophosphates, are also actively studied for obvious national security reasons [2]. These gases are hazards in their liquid and vapor states and can cause death within minutes after exposure. They basically stop the acetyl- cholinesterase fabrication process in tissue and cause an excess of acetylcholine, a neurotransmitter. Nerve agents are classified in two types: G-agents that are the oldest species developed in Germany in the Second World War and V-agents that were devel- oped later. Tabun (GA), Sarin (GB), Soman (GD), and Cyclosarin (GF) gases are among the well known G-agents. Practically, the Dimethyl methylphosphonate (DMMP) molecule is usually used as a simu- lant for the sarin gas to evaluate the sensitivity of gas detector to nerve agent. 0925-4005/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2011.08.066