Non-contact process control sensors for nanoliter dispensing systems ; Kontaktfreie Sensoren zur Prozesskontrolle von Nanoliter Dosiersystemen

Author:

Ernst, Andreas [claim]

Description:

This thesis deals with the design, the development and the characterisation of non - contact process control sensors to monitor the droplet ejection process of drop-on-demand dispensing systems in the nanoliter range. The design of the sensors is focussed on a small mounting size to enable a smart integration to the dispensing device. The non - contact working method implements a contamination free and non - invasive measurement technique which does not affect the dispensing process. In contrast to the commonly applied process observation systems, which are mostly unable to provide online process information, the developed sensors serve with analogue signals which enable to realise a real-time process control. As the entire sensors are fabricated in printed circuit board technology, very cost effective competitors to the stateof- the-art systems can be placed on market. The implementation of the process control sensors is realised by an optical approach, based on the effects of geometrical optics induced by a droplet passing a measurement light beam and a capacitive measurement method, exploiting the interaction of a dispensed droplet with the electric field of an open capacitor. The volumes of the droplets which are measured by the sensors are in the range V = { 5 to 100 nl }. This volume range arises from the applied dispensing system, based on the PipeJetTM technology, and defines the minimum size of the individual measurement transducers. The application of the optical measurement method is based on the change of the intensity of a measurement light beam while a liquid droplet passes through it. The light beam is present in the flight path of the dispensed droplet and changes it’s intensity due to absorption, refraction and reflection effects. This enables to extract droplet dependent analogue signals which are used to analyse several parameters like droplet velocity, droplet shape, malfunctions in the dispensing process or to identify the reproducibility of successively ejected droplets by the correlation ...

Year of Publication:

2013

Document Type:

doctoral_thesis ; [Doctoral and postdoctoral thesis]

Language:

eng

Subjects:

Berührungsloser Sensor ; Fluidischer Sensor ; Prozessüberwachung ; Dispensieren ; Fluidik ; Mikrotropfen ; Online-Ressource

DDC:

004 Data processing & computer science

Rights:

free