Submillimeter Sized 2D Electrothermal Optical Fiber Scanner

Magnetically actuatable 3D-printed endoscopic microsystems

In endoscopy, there is a crucial demand for compact system designs to allow for imaging in narrow spaces and reduce the risk of damage during endoscopic procedures. Enhanced functionality of lensed endoscopes can be realized by integrating actuatable imaging systems with flexible fiber bundles. Conventionally fabricated actuatable endoscopes are, however, limited in their miniaturization capability, typically resulting in system diameters greater than 1 mm. In this work, we present highly compact magnetically actuatable 3D-printed and endoscopically integrated microsystems that are fabricated on the end-facet of imaging fiber bundles using two-photon polymerization. Electromagnetic microcoils affixed to the fiber bundles are utilized to stimulate embedded polymer-magnets to achieve axial, lateral, or rotatory displacement of microoptical elements leading to zooming, resolution enhancement, and increased field of view capabilities. All demonstrated systems achieve overall system diameters well below 900 µm, marking a distinct advancement in the miniaturization of actuatable endoscopic devices. This work demonstrates the feasibility of integrating highly functional and compact optical systems within endoscopes, unlocking new potential for their application in diverse fields, for example in minimally invasive ("keyhole") surgery or intravascular imaging.

Correction: Kaur, M.; Menon, C. Submillimeter Sized 2D Electrothermal Optical Fiber Scanner. Sensors 2023, 23, 404

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Actuation for flexible and stretchable microdevices

Flexible and stretchable microdevices incorporate highly deformable structures, facilitating precise functionality at the micro- and millimetre scale. Flexible microdevices have showcased extensive utility in the fields of biomedicine, microfluidics, and soft robotics. Actuation plays a critical role in transforming energy between different forms, ensuring the effective operation of devices. However, when it comes to actuating flexible microdevices at the small millimetre or even microscale, translating actuation mechanisms from conventional rigid large-scale devices is not straightforward. The recent development of actuation mechanisms leverages the benefits of device flexibility, particularly in transforming conventional actuation concepts into more efficient approaches for flexible devices. Despite many reviews on soft robotics, flexible electronics, and flexible microfluidics, a specific and systematic review of the actuation mechanisms for flexible and stretchable microdevices is still lacking. Therefore, the present review aims to address this gap by providing a comprehensive overview of state-of-the-art actuation mechanisms for flexible and stretchable microdevices. We elaborate on the different actuation mechanisms based on fluid pressure, electric, magnetic, mechanical, and chemical sources, thoroughly examining and comparing the structure designs, characteristics, performance, advantages, and drawbacks of these diverse actuation mechanisms. Furthermore, the review explores the pivotal role of materials and fabrication techniques in the development of flexible and stretchable microdevices. Finally, we summarise the applications of these devices in biomedicine and soft robotics and provide perspectives on current and future research.