Flexible Metal Electrodes by Femtosecond Laser-Activated Deposition for Human–Machine Interfaces

Abstract

Flexible metal electrodes are essential for flexible electronics, where the main challenge is to obtain mask-free patterned metals directly on substrates such as poly­(dimethylsiloxane) (PDMS) at low cost. This work highlights a feasible strategy named femtosecond laser-activated metal deposition for electroless deposition of metals (Cu, Ni, Ag, and Au) on PDMS, which is suitable for maskless and low-cost fabrication of metal layers on PDMS and even on other materials of different natures including polyethylene terephthalate, paper, Si, and glass. The electrical conductivity of the PDMS/Cu electrode is comparable to that of bulk Cu. Moreover, robust bonding at the PDMS/Cu interface is evidenced by a scotch tape test and bending test of more than 20,000 cycles. Compared with previous studies using a nanosecond laser, the restriction on absorbing sensitizers could be alleviated, and catalysts could originate from precursors without polymer substrates under a femtosecond laser, which may be attributed to nonlinear absorption and ultrashort heating time with the femtosecond laser. Implementing a human–machine interface task is demonstrated by recognizing hand gestures via a multichannel electrode array with high fidelity to control a robot hand.

Autocatalytic Laser Activator for Both UV and NIR Lasers: Preparation of Circuits on Polymer Substrates by Selective Metallization

“…Thus, to solve this issue, electroless nickel plating, electroless silver plating, and electroless gold plating were carried out to deposit the Ni layer, Ag layer, and Au layer on the Cu layer, and Ni–Cu, Ag–Cu, and Au–Cu layers were prepared (Figure ). The Ni, Ag, and Au layers can be further deposited on the Cu layer by the replacement reaction and the autocatalysis effect . Herein, the electroless nickel plating, electroless silver plating, and electroless gold plating times were fixed at 30, 10, and 10 min, respectively.…”

“…The Ni, Ag, and Au layers can be further deposited on the Cu layer by the replacement reaction and the autocatalysis effect. 49 Herein, the electroless nickel plating, electroless silver plating, and electroless gold plating times were fixed at 30, 10, and 10 min, respectively. Note that, during electroless gold plating, the diffusion of Cu to Au is severe, always causing an uneven surface of the Au−Cu layer and resulting in poor surface quality.…”

Laser-Induced Selective Metallization on Polymers for Both NIR and UV Lasers: Preparing 2D and 3D Circuits

“…In the past decade, laser-induced selective metallization (LISM) on polymers has received extensive attention, − which is widely used in communication equipment, − electronic skin, decorative patterns, , and testing equipment, , and has potential applications in energy storage equipment − and triboelectric nanogenerators. − Compared to other metallization methods on polymers, such as photolithography, − inkjet printing, − microcontact printing, and screen printing, LISM owns the advantages of low cost, high time efficiency, and no mask. The main steps of LISM are to make a device by mixing the polymer with laser sensitizers, and then, after laser activation and electroless plating, metal patterns (or circuits) are successfully prepared at the laser-activated surface of the device .…”

“…The first type belongs to the reduction mechanism; the laser activation reduces the laser sensitizer on the substrate’s surface to form metal particles, and these particles become active centers and induce subsequent ECP. These laser sensitizers are usually copper-containing substances, such as Cu 2 (OH)­PO 4 , CuAl 2 O 4 , CuO·Cr 2 O 3 , , copper hydroxyl phosphate (CuAc 2 ), CuC 2 O 4 , copper acetylacetonate [Cu­(acac) 2 ], and ethylenediaminetetraacetate (EDTA-Cu) . The second type of laser sensitizer does not reduce to metal with laser activation, but it owns catalytic activity of its own.…”

Re‐Stickable Yarn Supercapacitors with Vaper Phase Polymerized Multi‐Layered Polypyrrole Electrodes for Smart Garments

“…Wearable electronics have gained rising attention due to their potential applications in human-machine interfaces, [1] personal physiological sensors, [2,3] and wireless communications. [4] In particular, the emerging smart garments with built-in functional devices have become an indispensable subfield for the upcoming wearable era, as the garments are lightweight and flexible, and most importantly they possess inherent wearability.…”