Characterization of a Robust 3D- and Inkjet-Printed Capacitive Position Sensor for a Spectrometer Application

• Main Authors: Lisa-Marie Faller, Martin Lenzhofer, Christina Hirschl, Martin Kraft, Hubert Zangl
• Format: Article
• Language: English
• Published: MDPI AG 2019-01-01
• Series: Sensors
• Subjects: capacitive sensor; nanometer position measurement; inkjet-printing; 3D-printed metals; additive manufacturing
• Online Access: https://www.mdpi.com/1424-8220/19/3/443

An inkjet- and 3D-printed capacitive sensor system with an all-digital and flexible sensor read-out hardware is reported. It enables spectrometer devices with significantly reduced device outlines and costs. The sensor is developed as multilayer inkjet-printed electrode structure on a 3D-printed copper housing. Very high required position resolutions of <inline-formula> <math display="inline"> <semantics> <mrow> <mi>r</mi> <mi>e</mi> <msub> <mi>s</mi> <mrow> <mi>p</mi> <mi>o</mi> <mi>s</mi> </mrow> </msub> <mo>&lt;</mo> <mn>50</mn> <mspace width="0.17em"></mspace> <mi>nm</mi> </mrow> </semantics> </math> </inline-formula> and a wide measurement range of <inline-formula> <math display="inline"> <semantics> <msub> <mi>r</mi> <mi>m</mi> </msub> </semantics> </math> </inline-formula> = 1000 <inline-formula> <math display="inline"> <semantics> <mi mathvariant="sans-serif">&#956;</mi> </semantics> </math> </inline-formula>m at an offset of <inline-formula> <math display="inline"> <semantics> <msub> <mi>d</mi> <mn>0</mn> </msub> </semantics> </math> </inline-formula> = 1000 <inline-formula> <math display="inline"> <semantics> <mi mathvariant="sans-serif">&#956;</mi> </semantics> </math> </inline-formula>m in the considered spectrometers motivate this work. The read-out hardware provides high sampling rates of up to <inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mi>r</mi> <mi>s</mi> </msub> <mo>&#8776;</mo> <mn>10</mn> <mspace width="0.17em"></mspace> <mi>ns</mi> </mrow> </semantics> </math> </inline-formula> and enables the generation of trigger signals, i.e., the mirror control signal, without a time lag. The read-out circuitry is designed as a carrier frequency system, which enables flexible choices of bandwidth and measurement signal frequency. It thus allows for separation in frequency from coupling parasitics, i.e., other frequencies present in the device under test, and makes the read-out quasi-noise-immune.