3D conductive microstructures containing gold are fabricated by simultaneous photopolymerization and photoreduction via direct laser writing. The photoresist employed consists of water-soluble polymers and a gold precursor. The fabricated microstructures show good conductivity and are successfully employed for 3D connections between gold pads. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of Conductive 3D Gold-Containing Microstructures via Direct Laser Writing

For the past two decades, the researches on stretchable physical sensors have made great technological advances, and have been applied to various applications such as electronic skin for robots, haptic devices, bionics, and wearable/implantable healthcare sensors, etc. The deformable physical sensors have been investigated in two approaches: the electronic sensors with the well-developed fabrication technologies and the iontronic sensors as a new technological alternative. There has been a wide spectrum of researches branching from the two approaches. They have evolved from simple-structured sensors with a single function into high-resolution array sensors with multiple functions. A variety of technological methods and principles have been explored depending on the target applications and the materials in use. The deformable sensors can be differentiated according to the specific methodology and principle; i) type of electrical signal (resistance or impedance, capacitance, induction, voltage or current, frequency), ii) power consumption (use of external power (passive) or self-signaling (active)), iii) data acquisition method (time-division multiple access or event-driven parallel access), and iv) multiple functionality (combination of different sensing units or multimodality). It is not clear at this stage which approach and method are suitable for which applications and materials. This review begins with a comparison of the technological methodologies and summarizes the evolution of deformable physical sensors. Focusing on key conceptual achievements according to the technological methodologies, this review introduces the advances of the electronic sensors in section 2 and the iontronic sensors in section 3. Section 4 discusses the challenges and directions for future researches, along with some possible technological solutions.

Approaches to deformable physical sensors: Electronic versus iontronic

Flexible and wearable sensors have been widely applied in smart monitoring and electronic devices. However, the piezoresistive sensor with high strength and tunable sensing modes remains a challenge. Here, a flexible and magnetically response piezoresistive sensor consisting of silver nanowires (AgNWs) coated flax fiber (FF) as the electronic core (AF) and magnetorheological elastomer (MRE) as the packaging shell (MAF) was developed. Due to good flexibility and magnetic characteristic of MRE shell, MAF sensor is sensitive to the bending stimuli and magnetic field. Furthermore, D-MAF sensor with dual conductive flax fiber which exhibited superb mechanic-electric properties can be constructed. The relative resistance variation ( Δ R / R 0 ) of D-MAF sensor reaches 19.8% under bending angle of 16.2°. Sensors exhibit unique non-tensile behavior, its mechanic-electric–magnetic nature is mainly originated from the piezoresistive performance. The piezoresistive sensor shows excellent mechanical properties thus demonstrating a broad promising in future intelligent devices, like artificial skins and soft robotics.

Non-tensile piezoresistive sensor based on coaxial fiber with magnetoactive shell and conductive flax core

The Sample Environment and Characterization (SEC) group of the European X-ray Free-Electron Laser (EuXFEL) develops sample delivery systems for the various scientific instruments, including systems for the injection of liquid samples that enable serial femtosecond X-ray crystallography (SFX) and single-particle imaging (SPI) experiments, among others. For rapid prototyping of various device types and materials, sub-micrometre precision 3D printers are used to address the specific experimental conditions of SFX and SPI by providing a large number of devices with reliable performance. This work presents the current pool of 3D printed liquid sample delivery devices, based on the two-photon polymerization (2PP) technique. These devices encompass gas dynamic virtual nozzles (GDVNs), mixing-GDVNs, high-viscosity extruders (HVEs) and electrospray conical capillary tips (CCTs) with highly reproducible geometric features that are suitable for time-resolved SFX and SPI experiments at XFEL facilities. Liquid sample injection setups and infrastructure on the Single Particles, Clusters, and Biomolecules and Serial Femtosecond Crystallography (SPB/SFX) instrument are described, this being the instrument which is designated for biological structure determination at the EuXFEL. 

/pdf/3d-printed-devices-and-infrastructure-for-liquid-sample-20a0juwg.pdf

3D printed devices and infrastructure for liquid sample delivery at the European XFEL

Bio‐inspired soft robots provide a promising solution for robots working in human‐centered scenarios and interacting with unstructured environments. However, the functional versatility and multimodal sensing of soft robots still need improvements. On one hand, the configuration of a soft robot is predefined during manufacturing; on the other hand, the multimodal perception of the deformable soft actuator is challenging. In this work, a reconfigurable and proprioceptive soft origami module is presented, where two kinds of basic actuation modes (i.e., extension and bending) are realized, and multimodal perception is enabled using a novel foldable self‐inductance sensor. As a result, the origami module can be reconfigured to assemble multifunctional robots that can measure interaction force, body configuration, and other environmental information. Dedicated experiments are performed to validate the performance of the proposed origami module. An intelligent gripper assembled using three origami modules is designed with the capabilities of grasping mode adjustment, grasping force measurement, and the grasping target's size measurement. An intelligent jellyfish is assembled using five origami modules, and equipped with buoyancy adjustment and underwater grasping capabilities. The proposed proprioceptive modular soft origami provides an effective solution for versatile and intelligent soft robot design.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/aisy.202200081

Modular Origami Soft Robot with the Perception of Interaction Force and Body Configuration

Direct laser lithography (DLL) is a key enabling technology for 3D constructs at the microscale and its potential is rapidly growing toward the development of active microstructures. The rationale of this work is based on the different involved methodology, which is referred as indirect, when passive microstructures become active through postprocessing steps, and direct, when active structures are directly obtained by fabricating microstructures with active materials or by introducing heterogeneous mechanical properties and specific design. An in‐depth analysis of both indirect and direct methods is provided. In particular, the wide range of materials and strategies involved in each method is reported, including advantages and disadvantages, as well as examples of fabricated structures and their applications. Finally, the different techniques are briefly summarized, and critically discussed by highlighting how the new synergies between DLL and active materials are opening completely new scenarios, in particular for sensing (e.g., mechanical) and actuation at the microscale.

A Review on Active 3D Microstructures via Direct Laser Lithography

/pdf/folding-and-bending-planar-coils-for-highly-precise-soft-1ygjbhbrht.pdf

Muhammad Ilyas

Papers

A Review on Active 3D Microstructures via Direct Laser Lithography

Folding and Bending Planar Coils for Highly Precise Soft Angle Sensing