Direct metal micropatterning on needle-type structures towards bioimpedance and chemical sensing applications

Abstract

Direct metal patterning methods, such as screen printing, inkjet printing and gravure/flexography printing, are widely used to form electrodes or interconnections for printed electronic devices due to their inexpensive, simple and rapid fabrication as compared to vacuum-based conventional metallization processes. Here, we present direct metal patterning by modified screen printing on the curved surface of needle-type rod structures (i.e. rods with radius of ρ < 1 mm). We achieved various microscale patterns such as straight lines, zigzag lines, wavy lines and alphabetic words with a minimum width of 70 µm on the surface of the rod. Also, four pairs of line patterns were printed on the single rod for electrical interconnection. Printed patterns on the surface of the rod were used as electrodes for the control of a light emission diode (LED) as well as the real-time electrochemical impedance spectroscopy of electrolyte solutions and solid objects by the rod insertion. Furthermore, needles with multiple pairs of microelectrodes were used to measure the electrical impedance of biological samples such as fat and muscle tissues of porcine meat. In addition, a needle-type probe sensor with gas sensing capability was demonstrated by using a needle with printed Ag electrodes and Pd thin films.