Laser Direct Structured 3D Circuits on Silicone

Abstract

Silicone rubber is a biocompatible elastomeric polymer, with great potential for mechanical and biologic sensing applications, if electrical circuits can be reliably integrated. Laser direct structuring is a bottom-up circuit fabrication process, whereby copper is chemically grown on laser exposed regions of a modified substrate, promoting adhesion by laser roughening the circuit tracks. In this Research Article, we successfully demonstrate this process using superflexible biocompatible silicone (30 hardness on Shore 00) with copper chromite additive, cast into both 2D planar and 3D contour substrates. A horseshoe pattern circuit, meander and Hilbert fractal inductors, and a 3D hemispherical helix trace are fabricated and tested. The range of laser power and copper chromite concentration are explored. Mechanical testing is performed to determine breakage strain and elastic modulus. Material stiffness and trace peel strength are shown to increase with copper chromite concentration. Peel strength is measured to be very high, from approximately 1 to 5 kN/m, depending on dopant loading. With high adhesion and conductivity, the simple laser-writing process presented here enables highquality circuit integration into elastomeric silicone.

Direct Laser Writing: From Materials Synthesis and Conversion to Electronic Device Processing

“…The second mechanism is based on the catalytic activity of the sensitizer towards the electroless plating process. [ 196 ] According to the literature, copper aluminum oxide, [ 197 ] ethylenediaminetetraacetate, [ 198 ] copper hydroxyl phosphate, [ 199 ] multiwalled CNTs, [ 200 ] copper oxalate, [ 89 ] copper−chromium oxide, [ 201 ] molybdenum trioxide, [ 196 ] and antimony‐doped tin oxide (ATO) [ 202 ] can be used as sensitizers. In alternative to the incorporation of sensitizers within the substrate matrix, laser activation can also be performed with the substrate immersed in a sensitizer solution.…”

“…Particularly, Ren et al performed LISM of silver NPs on a PI substrate, where the catalytic layer presents a porous structure enhancing the stability of the electroless plating. [75] The advantage LISM is the straightforward capability to write activated patterns in a myriad of substrates, including glass, [203] PI, [75,204] polyurethane (PU), [198] polyamide (PA), [205] polypropylene (PP), [200] polybutylene terephthalate (PBT), [206] polyvinyl butyral (PVB), [207] polystyrenes, [89,194,196,208,209] polydimethyl siloxane (PDMS), [83,195,196,210] Ecoflex, [201] cement, [211] ceramics, [212,213] and 3D printed resins. [214] It is worth mentioning that although most works report the use of 1064 nm wavelength lasers, other laser systems are also compatible with the LISM process, in-cluding CO 2 , [207] UV, [208] and femtosecond lasers.…”

Low-power laser manufacturing of copper tracks on 3D printed geometry using liquid polyimide coating

“…Laser-based processes usually rely on the use of high-power lasers for depositing metals such as copper on polymeric materials and working in the ablation regime. Some examples include laser direct structuring (LDS) [8][9][10][11] , femtosecond laser reductive sintering and laser-induced forward transfer (LIFT) [12][13][14] . A distinct advantage of using lasers for photopatterning is the ability to modify substrates without applying any mechanical contact 15 .…”

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

“…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.…”

“…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 .…”