A micro-patterning technique regarded as micro transfer printing is studied for gold electrode patterning on cellulose electro-active paper (EAPap), aiming at biodegradable and flexible MEMS fabrication. EAPap is known as a smart material due to the interesting actuation phenomenon of cellulose paper. Accordingly, EAPap can be used for sensor and actuator devices. Since EAPap is made with cellulose, a biodegradable and flexible MEMS device can be made with this material. However, since cellulose-based EAPap is hydrophilic and flexible, conventional lithography and etching techniques cannot be used for micro-patterning. This paper reports a new micro-patterning technique using the micro transfer printing (MTP) method on flexible EAPap material. The MTP technique consists of a master fabrication, a polydimethylsiloxane (PDMS) stamp construction, and a micro pattern transfer. Details of the technique and key issues are addressed. To demonstrate the feasibility of the MTP technique, a gold electrode pattern for a surface acoustic wave (SAW) MEMS device and a gold micro-strip pattern for a microwave dipole rectenna are made on cellulose paper substrates.

The causes of Au-electrode damage to an electroactive paper (EAPap) actuator coated with Au and polypyrrole (PPy) were investigated with various electric field frequencies and strengths. The resonance frequency of 3.5 Hz was obtained for 3 and 4 V. Electric field frequencies below (2 Hz) the resonance frequency yielded a faster bending displacement reduction than those of the higher resonance frequency. High electric field strength (4 V) shows a faster reduction of bending displacement than lower field strength (3 V). The degree of Au-electrode damage after a certain period of actuation is shown in field emission scanning electron microscope (FESEM) images. The electric field strength and frequency and bending displacement reduction were found to be closely related to the degree of Au-electrode damage.

Micro-contact printing (μ-CP) and liftoff techniques were employed to fabricate Au micro-patterns onto electro-active paper (EAPap) for biodegradable and flexible microelectromechanical system (MEMS) application. Conventional lithography and etching techniques cannot be utilized to fabricate micropatterns on EAPap having interesting actuating properties due to its hydrophilic and flexible characteristics. The cause of nanodefects on the Au pattern after the μ-CP process was investigated to enhance the pattern quality. Three different solvents were utilized to investigate the consequence of the solvent polarity during the 3-mercaptopropyltrimethoxysilane (MPTMS) self-assembled monolayer (SAM) fabrication and after the μ-CP process. The defects, such as microcracks and nanograins, were closely related to the solvent polarity. The higher polar solvent turned out smaller defects than the lower polar solvent due to the reduction of the solvent swell onto the PDMS stamp during SAM layer formation. The liftoff technique exhibited a new way of fabricating various metal patterns on EAPap without any nanodefects.

Cellulose has been discovered as a smart material, which is termed as electro-active paper (EAPap). EAPap actuator revealed large displacement upon low actuation voltage and low electrical power consumption. However, the performance of the actuator was reduced as the actuation time increased. To investigate the performance degradation of the actuator, field emission scanning electron microscope (FESEM) images were taken on the surfaces of gold electrode of the actuator, and energy dispersive spectroscopy (EDS) was performed on them. Nanoparticles and nanoholes were observed on the surfaces of gold electrode after actuation, which might be strongly associated with the degradation of the actuator performance. The compositions of nanoparticles were gold and sodium. The degradation rate of the actuator performance and the number of nanoparticles at a low actuation frequency (2 Hz) were larger than those of a higher frequency (5 Hz). As the actuation voltage increased, the actuator performance degraded rapidly.

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