1 Copyright © 2005 by ASME Proceedings of IMECE2005: ASME IMECE '05 November 5-11, Orlando, Florida, USA IMECE2005-81732 MICRO-CANTILEVER BASED METROLOGY TOOL FOR FLOW CHARACTERIZATION OF LIQUID AND GASEOUS MICRO/NANOJETS Jungchul Lee 1 , Kianoush Naeli 2 , Hanif Hunter 1 , John Berg 1 , Tanya Wright 1 , Christophe Courcimault 2 , Nisarga Naik 2 , Mark Allen 2 , Oliver Brand 2 , Ari Glezer 1 , and William King 1 1 Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 2 School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA ABSTRACT This paper reports the development of MEMS metrology tools to characterize liquid and gaseous jets ejected from micro/nanofabricated nozzles. To date few highly local measurements have been made on micro/nanojets, due in part to the lack of characterization tools and techniques to investigate their characteristics. Atomic force microscope cantilevers are well-suited for interrogating these flows due to their high spatial and temporal resolution. In this work, cantilever sensors with either integrated heating elements or piezoresistive elements have been fabricated to measure thrust, velocity, and heat flux characteristics of micro/nanojets. KEYWORDS Atomic Force Microscope, heated cantilever, piezoresistive cantilever, micro/nanojets, anemometry INTRODUCTION Micro- and nanoscale jets have potential applications in drug delivery, micro surgery [1], inkjet printing, microelectronics cooling [2], and precision manufacturing [3]. While O(100 ~ 1000 µm)–scale high-speed gaseous jets have been investigated as potential actuators for flow control applications, little work has been reported on free liquid and gaseous jets having characteristic scales that extend below 10µm. Atomic force microscope (AFM) cantilevers have become perhaps the most widely used transducer for sensing and actuating at the nanometer scale [4]. Micromachined silicon cantilever beams have been applied in liquid fluid flow volume sensing [5, 6] and highly sensitive piezoresistive cantilevers have been introduced for measuring air flow velocity in a small pipe [7]. Due to their high spatial and temporal resolution, micromachined cantilevers can be versatile tools for interrogating micro/nanojets. Liquid jets from microscale nozzle can be examined with optical diagnostic tools but liquid jets from much smaller nozzle or gaseous jets are difficult to visualize or characterize using those tools. The cantilevers used to interrogate the micro/nanojets are of two types: cantilevers with integrated heating elements and piezoresistive cantilevers. The heated cantilevers were originally developed for data storage by Stanford [8] and IBM [9], but have recently been redesigned and fabricated at Georgia Tech to extend their functionality beyond data storage application (Fig.1 (a) and (d)). Both commercially available (Fig. 1 (b) from PSI) and fabricated piezoresistive cantilevers (Fig. 1 (c)) are introduced for deflection sensing since optical lever technique is difficult to be incorporated under the liquid jet environment. The piezoresistive cantilevers can measure deflection which can be correlated into thrust and velocity due to momentum transfer and detect mass of liquid droplets when the liquid sticks to the cantilever surface in a resonant mode. Heater regio 20 µm Heater region 20 µm Heater regio 20 µm Heater region 20 µm µ 20 m µ 20 m Infrared Microscopy (a) (b) (c) (d) Heater regio 20 µm Heater region 20 µm Heater regio 20 µm Heater region 20 µm µ 20 m µ 20 m Infrared Microscopy (a) (b) (c) (d) Figure 1. (a) SEM image of the fabricated heated cantilever (b) commercial Piezolever (c) fabricated piezoresistive cantilever (d) Infrared microscope image of the fabricated heated cantilever with electrical heating.