This paper presents a review of electrothermal micro-actuators and applications. Electrothermal micro-actuators have been a significant research interest over the last two decades, and many different designs and applications have been investigated. The electrothermal actuation method offers several advantages when compared with the other types of actuation approaches based on electrostatic and piezoelectric principles. The electrothermal method offers flexibility in the choice of materials, low-cost fabrication, and large displacement capabilities. The three main configurations of electrothermal actuators are discussed: hot-and-cold-arm, chevron, and bimorph types as well as a few other unconventional actuation approaches. Within each type, trends are outlined from the basic concept and design modifications to applications which have been investigated in order to enhance the performance or to overcome the limitations of the previous designs. It provides a grasp of the actuation methodology, design, and fabrication, and the related performance and applications in cell manipulation, micro assembly, and mechanical testing of nanomaterials, Radio Frequency (RF) switches, and optical Micro-Electro-Mechanical Systems (MEMS).

The development of graphene and graphene hybrid inks is reviewed, with particular focus on their formulation, properties and applications. Please note this image is selected from Y. Gao, W. Shi, W. Wang, Y. Leng and Y. Zhao, Ind. Eng. Chem. Res., 2014, 53, 16777.

The development of metal particle-free inks is reviewed, with particular attention on their formulation, patterning and post-processing techniques.

Recent advances in flexible printed RFID antennas are reviewed, with an emphasis on material categories and properties, fabricating technologies, structure design and applications.

Micromachined stacked patch antenna devices with high efficiency and wideband characteristics are reported. Polymer based fabrication and assembly processes have been developed in order to produce the stacked suspended antenna devices. Millimeter thick micromachined SU8 based polymer rings are used to create air gaps between the patches and the microwave substrate for optimized high efficiency operation. Thin film liquid crystal polymer (LCP) and polyimide substrates are used to support the radiating and parasitic patch elements. The polymer rings also form cavities to protect the patches and substrate from moisture and dust. The antenna structures are fabricated in layers and then assembled to obtain 3D devices. The antenna devices have been designed using an electromagnetic simulation package. The aperture coupled devices are impedance matched for wideband operation. RF measurements show wideband operation of the devices and the results are in good agreement with that of simulation. Typical gain and bandwidths are 7.8 dBi and 39% for a microstrip fed antenna device while they are 7.6 dBi and 44% for a CPW fed device. The predicted efficiency from the results of simulation is above 97% for the antenna devices.