Sensors and Actuators A 122 (2005) 159–166 An analytical model of a silicon MEMS vaporizing liquid microthruster and some experimental studies D.K. Maurya ∗ , S. Das, S.K. Lahiri Microelectronics Laboratory, Advanced Technology Centre/E&ECE Department, Indian Institute of Technology, Kharagpur 721302, India Received 14 October 2004; received in revised form 14 April 2005; accepted 15 April 2005 Available online 24 May 2005 Abstract A recent application of the MEMS technology is in the field of microthrusters for micro/nano satellites. A silicon MEMS vaporizing liquid microthruster (VLM) produces continuously variable thrust in the range from N to mN. The theoretical simulation of a VLM involves complex numerical 3D micro-fluidic, thermodynamic and electro-thermal solutions. A fast analytical method is, however, desirable in the initial phase of development of a VLM. In this paper, a simple analytical model of a VLM is presented. The model is based on one-dimensional approximations for fluid-dynamical and heat-flow equations. VLMs are fabricated by bonding two micromachined silicon chips. The device consists of a microcavity, an inlet nozzle, an exit nozzle, a microchannel and an internal p-diffused resistor for heating. The thrust is measured by a sensitive cantilever and a laser based lamp-and-scale arrangement. The experimental results on the variation of thrust with heater power are interpreted with the help of the theoretical model. A novel iterative computation is performed to extract the chamber temperature and other important parameters corresponding to the measured values of thrust for different values of heater power. The model gives some physical insight into the operation of the VLM. © 2005 Elsevier B.V. All rights reserved. Keywords: Microthruster; Micro/nano satellites; Diffused heater; Micromachining; Nozzle 1. Introduction Micro/nano satellites are drawing considerable attention of space technologists in recent years. This new range of satel- lites requires micro-propulsion units [1] with an extremely high precision of control. For miniaturizing propulsion sys- tems, the conventional fabrication technology can hardly be used to scale down the size below several inches. The mi- crofabrication technology of MEMS has been successfully employed to batch-fabricate micro-propulsion systems or mi- crothrusters with the dimension in the range of millimetres to sub millimetres, capable of producing extremely small thrusts from micro-Newtons to milli-Newtons. Of the various types of MEMS microthrusters developed so far, the vaporizing liquid microthruster (VLM) is simple and has been widely investigated [2–4]. VLM can produce ∗ Corresponding author. Tel.: 91 3222281479; fax: 91 3222282013. E-mail address: dkm@ece.iitkgp.ernet.in (D.K. Maurya). continuously variable microthrusts using a non-toxic liquid propellant. The work on VLM reported so far is mostly ex- perimental with little theoretical content [2–4]. The struc- ture of a VLM realised by silicon bulk micromachining is rather complex from the view point of theoretical simula- tion. It involves rigorous numerical simulations using 3D microfluidic, thermodynamic and electrothermal solvers. No detailed simulation results have been published till date. The 3D numerical simulations are computationally cumbersome and not convenient in the initial phase of development. In an attempt to develop silicon VLM independently, the au- thors have developed a simple analytical model of VLM for a rough estimation of the parameters involved and for gaining a physical insight into the operation of the VLM. The model is presented in this paper. The paper also includes a brief description of the fabrication and testing of a VLM. While interpreting the experimental results with the help of the the- oretical model, the physical principles on which the model is based are established. The analytical model is described 0924-4247/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.sna.2005.04.020