Highly integrated autonomous microdosage system $ G. Waibel a , J. Kohnle a , R. Cernosa a , M. Storz a , M. Schmitt c , H. Ernst a,* , H. Sandmaier a , R. Zengerle b , T. Strobelt a a HSG-IMIT, Wilhelm-Schickard-Str. 10, D-78052 Villingen-Schwenningen, Germany b IMTEK, University of Freiburg, Georges-Ko Èhler-Allee 103, D-79110 Freiburg, Germany c IZFM-LMST, University of Stuttgart, Breitscheidstr. 2c, D-70174 Stuttgart, Germany Abstract Forthe®rsttimeafountainpenispresentedincorporatinganelectronicallycontrolled¯uiddosagesystem.Thesystemisequalinsizewith conventionalpens.Itcanberegardedasthe®rstfullyfunctional,highlyintegrated,miniaturizedandself-sustainingmicrodosagesystemofits kind operating under real world conditions. The main components are a closed-loop control system, consisting of a thin-®lm liquid level sensor,amicro-valveandabubble-andparticle-tolerant¯uidicsystem,aswellastheinvolvedpowersupplyandcontrolelectronics.Thepen has been optimized with respect to minimum energy consumption. It contains a programmable ASIC and is powered by two standard watch batteries ensuring operation over a period of 2 years under standard conditions. # 2003 Elsevier Science B.V. All rights reserved. Keywords: Electronic fountain pen; Microdosage system; Bubble-tolerant capillaries; Micro-valve; Closed loop control capacitive level sensor 1. Introduction The operating principle of fountain pens has been known for more than 100 years and has since been utilized without any remarkable changes. Primarily it is based on a capillary transfer of ink from a cartridge to the paper via a nib. Reduced pressure inside the cartridge prevents system leak- age while an integrated system of capillary buffers is responsible for ensuring a constant ink ¯ow. The main disadvantage of this concept is the dependency on ambient temperature and pressure conditions, an implication which in some cases is in fact responsible for system failure. A typicalexampleofsuchafailureispresentedbythereduced cabin pressure experienced inside aircraft cabins at high altitude. This pressure shift causes the gas inside the car- tridge to expand and in consequence results in leakage of the pen. In order to overcome this problem and to achieve an outstanding writing performance at a constant high quality the presented fountain pen was developed in collaboration withtworenownedcompaniesinthepenindustry.Theresult of the development is depicted in Fig. 1 showing the new concept of a fully operational micro-dosing system devel- oped using the full range of available technologies from thin-®lm technology to injection-molding. The presented system consists of a number of elements including ¯uidic components such as a valve, a cartridge venting system and a series of bubble-tolerant capillaries, sensor components such as a ¯uid level sensor, electronic componentssuchasthevalvecontrolsystem,andessentially thepenplatformitselfprovidingthehousingandmechanical support for the above components. The integration of all components inside this setup is an important aspect of the concept as it provides the reducibility of the number of ¯uidic and electrical interconnects to a minimum and in consequence reduces the problems encountered in such joints. In this paper we discuss the novel concept of the micro- valveand,forthe®rsttime,theintegrationaspectsincluding the electronic components as well as the overall perfor- mance of the pen. 2. System concept The presented dosage system guarantees perfect writing conditions by providing a well-de®ned small amount of ink Sensors and Actuators A 103 (2003) 225±230 $ This paper was presented at the 15th IEEE MEMS conference, held in Las Vegas, USA, January 20±24, 2002, and is an expansion of the abstract as printed in the Technical Digest of this meeting. * Corresponding author. Tel.: 49-7721-943-241; fax: 49-7721-943-210. E-mail address: herbert.ernst@hsg-imit.de (H. Ernst). 0924-4247/03/$ ± see front matter # 2003 Elsevier Science B.V. All rights reserved. PII:S0924-4247(02)00349-7