Inkjet printed microelectrodes on flexible substrates and its applications

Yoontae Kim

doi:10.17918/rdyz-ct32

Flexible electronics have recently drawn significant attention due to its applicability in a variety of fields such as a display, solar cell, wearable electronics, and biosensor. Different fabrication techniques have been explored to realize flexible electronic devices so far. Photolithography-based microfabrication techniques have been used for various flexible substrates, but the fabrication processes are time-consuming and require a cleanroom facility and hazardous chemicals. Inkjet printing can be a compelling alternative due to its advantages such as quick turnaround (photolithography not necessary), easy processing (cleanroom not necessary), low-cost manufacturing, and low-temperature fabrication. While inkjet printing has been applied to some flexible substrates (polyimides (PI) and Polyethylene terephthalate (PET)), few researchers have studied the direct printing of conductive solutions on polydimethylsiloxane (PDMS) and polyparaxylylene (Parylene) substrates, which are widely used in MEMS, microfluidics, and lab-on-a-chip fields especially for biomedical applications. The main reason is that it is very challenging to inkjet print conductive patterns on the elastomeric and hydrophobic materials. This research is designed to overcome the challenge and develop inkjet printing techniques to create microelectrodes on flexible PDMS and Parylene substrates. This involves fundamental characterization of printing performance as a function of printing parameters. For instance, the printing resolution depends on droplet size, and droplet size is limited by the nozzle diameter, ink viscosity, and temperature. To create fine microelectrodes on PDMS, we investigated the effects of main printing parameters on the quality of printed microelectrodes and identified optimal conditions for printing. Direct inkjet printing of conductive inks on Parylene was very difficult, so we developed a novel fabrication method in which the electrode patterns are printed on PDMS first and then transferred onto Parylene through vapor deposition. This simple way, we were able to create highly flexible thin electrodes and expand application area by combining other conventional techniques. We tested and confirmed a deposition of a thin copper film on the transferred silver pattern using electroplating for improving impedance magnitude of the microelectrodes. Next, we performed a thin gold film deposition on the copper layer using electroless plating for implantable applications (ECoG and spinal prove devices) as a solution of toxicity issue. Furthermore, ArF excimer laser machining is used for creating high-resolution microstructures on the ECoG microelectrodes array application. In summary, the present study demonstrated the performance of inkjet printed microelectrodes on PDMS and Parylene substrates in two specific applications, dielectrophoresis, and electrocorticography (ECoG). The results clearly show that the flexible silver microelectrodes created by the presented method can be used for electrokinetic applications. The ECoG electrodes array were implanted in rat brains for in-vivo studies. Through the experiment, it was confirmed that the flexible microelectrodes were able to detect electrical signals from the neurons. We believe that the rapid and low-cost fabrication method of thin flexible ECoG array presented here will continue to be an essential platform for microfluidics, Lab-on-chip, flexible electronics, medical implants as well as brain-computer interfacing applications.

Inkjet printed microelectrodes on flexible substrates and its applications

Files and links (1)

Abstract

Metrics

Details

Inkjet printed microelectrodes on flexible substrates and its applications

Files and links (1)

Abstract

Metrics

Details

Drexel University Social media