Numerical Investigations on Electric Field Characteristics with Respect to Capacitive Detection of Free-Flying Droplets

Sensors

Andreas Ernst¹  Klaus Mutschler¹  Laurent Tanguy¹  Nils Paust¹  Roland Zengerle¹ 

[1] Laboratory for MEMS Applications, Department of Microsystems Engineering (IMTEK), University of Freiburg, 79110 Freiburg, Germany; E-Mails:

关键词: droplet sensor;    CFD simulation;    capacitive measurement;    multi physics simulation;    non-contact sensor;    online process control;   

DOI  :  10.3390/s120810550

来源: mdpi

【 摘 要 】

In this paper a multi-disciplinary simulation of a capacitive droplet sensor based on an open plate capacitor as transducing element is presented. The numerical simulations are based on the finite volume method (FVM), including calculations of an electric field which changes according to the presence of a liquid droplet. The volume of fluid (VOF) method is applied for the simulation of the ejection process of a liquid droplet out of a dispenser nozzle. The simulations were realised using the computational fluid dynamic (CFD) software CFD ACE+. The investigated capacitive sensing principle enables to determine the volume of a micro droplet passing the sensor capacitor due to the induced change in capacity. It could be found that single droplets in the considered volume range of 5 nL < V_drop < 100 nL lead to a linear change of the capacity up to ΔQ < 30 fC. The sensitivity of the focused capacitor geometry was evaluated to be S_i = 0.3 fC/nL. The simulation results are validated by experiments which exhibit good agreement.

【 授权许可】

CC BY   
© 2012 by the authors; licensee MDPI, Basel, Switzerland.