Lotus-leaf inspired surfaces: hydrophobicity evolution of replicas due to mechanical cleaning and tool wear

Results of the work in the Laser4Fun project has been published as:

Jean-Michel Romano, Antonio Garcia-Giron, Pavel Penchev, Mert Gulcur, Ben R. Whiteside, Stefan Dimov. Lotus-leaf inspired surfaces: hydrophobicity evolution of replicas due to mechanical cleaning and tool wear. 3rd World Congress on Micro and Nano Manufacturing (September 2019), 289-292.

Abstract

Inspired from the dewetting properties of Lotus leaves, the fabrication of dual micro/nano-scale topographies is of interest for many applications. In this research, superhydrophobic surfaces are fabricated by a process chain combining ultrashort pulsed laser texturing of steel inserts and injection moulding to produce polypropylene parts. This manufacturing route is very promising and could be economically viable for mass production of polymeric parts with superhydrophobic properties. However, surface damages, such as wear and abrasion phenomena, can be detrimental to the attractive wetting properties of replicated textured surfaces. Therefore, the final product lifetime is investigated by mechanical cleaning of the textured polypropylene surface with multipurpose cloths following the ASTM D3450 standard. Secondly, the surface damage of replication masters after 350 injection moulding cycles with glass-fiber reinforced polypropylene, to intensify tool wear, was investigated. The degradation of surface textures on replicas had a clear impact on surface topography and thus on their wetting properties.

Springtail-Inspired Triangular Laser-Induced Surface Textures on Metals Using MHz Ultrashort Pulses

Results of the work in the Laser4Fun project has been published as:

Romano, J.M., Helbig, R., Fraggelakis, F., Garcia-Giron, A., Werner, C., Kling, R., Dimov, S., Springtail-Inspired Triangular Laser-Induced Surface Textures on Metals Using MHz Ultrashort Pulses. J. Micro Nano-Manuf  2019, 7(2), 024504. 

Abstract

Considering the attractive surface functionalities of springtails (Collembola), an attempt at mimicking their cuticular topography on metals is proposed. An efficient single-step manufacturing process has been considered, involving laser-induced periodic surface structures (LIPSS) generated by near-infrared femtosecond laser pulses. By investigating the influence of number of pulses and pulse fluence, extraordinarily uniform triangular structures were fabricated on stainless steel and titanium alloy surfaces, resembling the primary comb-like surface structure of springtails. The laser-textured metallic surfaces exhibited hydrophobic properties and light scattering effects that were considered in this research as a potential in-line process monitoring solution. The possibilities to increase the processing throughput by employing high repetition rates in the MHz-range are also investigated.

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Durability and Wear Resistance of Laser-Textured Hardened Stainless Steel Surfaces with Hydrophobic Properties

Results of the work in the Laser4Fun project has been published as:

A. Garcia-Giron, J.M. Romano, A. Batal, B. Dashtbozorg, H. Dong, E. Martinez Solanas, D. Urrutia Angos, M. Walker, P. Penchev, S.S. Dimov (2019) Durability and Wear Resistance of Laser-Textured Hardened Stainless Steel Surfaces with Hydrophobic Properties, Langmuir 35(15) 5353-5363. doi:10.1021/acs.langmuir.9b00398.

Abstract

Hydrophobic surfaces are of high interest to industry. While surface functionalization has attracted significant interest, from both industry and research, the durability of engineered surfaces remains a challenge, as wear and scratches deteriorate their functional response. In this work, a cost-effective combination of surface engineering processes on stainless steel was investigated. Low-temperature plasma surface alloying was applied to increase surface hardness from 172 to 305 HV. Then, near-infrared nanosecond laser patterning was deployed to fabricate channel-like patterns that enabled superhydrophobicity. Abrasion tests were carried out to examine the durability of such engineered surfaces during daily use. In particular, the evolution of surface topographies, chemical composition, and water contact angle with increasing abrasion cycles were studied. Hydrophobicity deteriorated progressively on both hardened and raw stainless steel samples, suggesting that the major contributing factor to hydrophobicity was the surface chemical composition. At the same time, samples with increased surface hardness exhibited a slower deterioration of their topographies when compared with nontreated surfaces. A conclusion is made about the durability of laser-textured hardened stainless steel surfaces produced by applying the proposed combined surface engineering approach.

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Subwavelength Direct Laser Nanopatterning Via Microparticle Arrays For Functionalizing Metallic Surfaces

Results of the work in the Laser4Fun project has been published as:

Jean-Michel Romano, Rajib Ahmed, Antonio Garcia-Giron, Pavel Penchev, Haider Butt, Olivier Delléa, Melissa Sikosana, Ralf Helbig, Carsten Werner, Stefan Dimov (2019) Subwavelength Direct Laser Nanopatterning Via Microparticle Arrays For Functionalizing Metallic Surfaces, Journal of Micro- and Nano-Manufacturing 7(1) 010901. doi:10.1115/1.4042964.

Abstract

Functionalized metallic nanofeatures can be selectively fabricated via ultrashort laser processing; however, the cost-effective large-area texturing, intrinsically constrained by the diffraction limit of light, remains a challenging issue. A high-intensity near-field phenomenon that takes place when irradiating microsized spheres, referred to as photonic nanojet (PN), was investigated in the transitional state between geometrical optics and dipole regime to fabricate functionalized metallic subwavelength features. Finite element simulations were performed to predict the PN focal length and beam spot size, and nanofeature formation. A systematic approach was employed to functionalize metallic surface by varying the pulse energy, focal offset, and number of pulses to fabricate controlled array of nanoholes and to study the generation of triangular and rhombic laser-induced periodic surface structures (LIPSS). Finally, large-area texturing was investigated to minimize the dry laser cleaning (DLC) effect and improve homogeneity of PN-assisted texturing. Tailored dimensions and densities of achievable surface patterns could provide hexagonal light scattering and selective optical reflectance for a specific light wavelength. Surfaces exhibited controlled wetting properties with either hydrophilicity or hydrophobicity. No correlation was found between wetting and microbacterial colonization properties of textured metallic surfaces after 4h incubation of Escherichia coli. However, an unexpected bacterial repellency was observed.

Link(s)

Mechanical durability of hydrophobic surfaces fabricated by injection moulding of laser-induced textures

Results of the work in the Laser4Fun project has been published as:

J.-M. Romano, M. Gulcur, A. Garcia-Giron, E. Martinez-Solanas, B.R. Whiteside and S.S. Dimov. Mechanical durability of hydrophobic surfaces fabricated by injection moulding of laser-induced textures. Applied Surface Science 476 (2019) 850-860

Abstract

The paper reports an investigation on the mechanical durability of textured thermoplastic surfaces together with their respective wetting properties. A range of laser-induced topographies with different aspect ratios from micro to nanoscale were fabricated on tool steel inserts using an ultrashort pulsed near infrared laser. Then, through micro-injection moulding the topographies were replicated onto polypropylene surfaces and their durability was studied systematically. In particular, the evolution of topographies on textured thermoplastic surfaces together with their wetting properties were investigated after undergoing a controlled mechanical abrasion, i.e. reciprocating dry and wet cleaning cycles. The obtained empirical data was used both to study the effects of cleaning cycles and also to identify cleaning procedures with a minimal impact on textured thermoplastic surfaces and their respective wetting properties. In addition, the use of 3D areal parameters that are standardised and could be obtained readily with any state-of-the-art surface characterisation system are discussed for monitoring the surfaces’ functional response.

Link(s)

Jean-Michel Romano awarded for his paper at WCMNM2018

JMR_WCMNM2018_awardOn the 20th September 2018, the World Congress on Micro and Nano Manufacturing took place in Portoroz, Slovenia. Jean-Michel Romano, an Early Stage Researcher (ESR) in the Laser4Fun project, was awarded of the Honorable Mention Paper Award for his contribution entitled “Towards large area submicron surface texturing by femtosecond laser irradiation of microparticle arrays”.

The award was presented by the scientific committee chair: Dr. Irene Fassi, National Research Council (CNR), Italy; Dr. Samuel Bigot, Cardiff University, UK; and Prof. Dr. Joško Valentinčič, University of Ljubljana, Slovenia.

WCMNM2018 LogoWCMNM 2018 was jointly organised by the Multi Material Micro Manufacturing association (4M), the International Institution for Micro Manufacturing (I2M2) and the International Forum on Micro Manufacturing (IFMM).

Antonio García Girón and Jean-Michel Romano attended WCMNM 2018

JMR_at_WCMNM2018A delegation of the University of Birmingham participated in the 2nd World Congress on Micro and Nano Manufacturing (WCMNM 2018) that took place on September 18-20, 2018 in Portoroz, Slovenia. WCMNM 2018 is a joint conference of the 13th International Conference on MicroManufacturing (ICOMM), the Multi Material Micro Manufacture (4M), and the International Forum on Micro Manufacturing (IFMM). It was the opportunity for ESRs Antonio García Girón and Jean-Michel Romano to disseminate results of the Laser4Fun project to a large community of micromanufacturing experts, coming from Northamerica, Europe and Japan.

FoWCMNM2018 Logor more information:
http://www.4m-association.org/conference/2018

Combined Surface Hardening and Laser Patterning for Producing Wear Resistant Hydrophobic Surfaces

Results of the work in the Laser4Fun project has been published as:

Antonio Garcia-Giron, Jean-Michel Romano, Y. Liang, Behnam Dashtbozorg, Hanshan Dong, Pavel Penchev, Stefan Dimov. Combined Surface Hardening and Laser Patterning for Producing Wear Resistant Hydrophobic Surfaces. 2nd World Congress on Micro and Nano Manufacturing (September 2018); doi: 10.3850/978-981-11-2728-1_16

Abstract

This work reports a laser patterning method for producing surfaces with dual scale topographies on ferritic stainless steel plates that are hardened by low temperature plasma surface alloying. Nitrogen and carbon based gasses were used in the alloying process to obtain surface layers with an increased hardness from 172 HV to 1001 HV and 305 HV, respectively. Then, a nanosecond infrared laser was used to pattern the plasma treated surfaces and thus to obtain super-hydrophobicity, by creating cell- or channel-like surface structures. The combined surface hardening and laser patterning approach allowed super-hydrophobic surfaces to be produced on both nitrided and carburised stainless steel plates with effective contact angles higher than 150°. The hardened layers on nitrided samples had cracks and was delaminated after the laser patterning while on plasma carburised samples remained intact.  The results showed that by applying the proposed combined approach it is possible to retain the higher hardness of the carburised stainless steel plates and at the same time to functionalise them to obtain super-hydrophobic properties.

Towards Large Area Submicron Surface Texturing by Femtosecond Laser Irradiation of Microparticle Arrays

Results of the work in the Laser4Fun project has been published as:

Jean-Michel Romano, Rajib Ahmed, Antonio Garcia-Giron, Pavel Penchev, Olivier Dellea, Stefan Dimov. Towards Large Area Submicron Surface Texturing by Femtosecond Laser Irradiation of Microparticle Arrays. 2nd World Congress on Micro and Nano Manufacturing (September 2018); doi: 10.3850/978-981-11-2728-1_10

Abstract

The direct laser submicron texturing of X6Cr17 stainless steel plates is reported. A hexagonal close-packed monolayer of 1um transparent silica microspheres deposited onto the metallic surface was irradiated with near-infrared femtosecond laser source to generate an array of Photonic Jets (PJ). The PJ intensity profiles were calculated by simulation. PJ full width at half maximum was estimated to be ~500nm on the surface. The influence of pulse energy and focal offset on material removal and microspheres’ ejection was studied. Different 1um-periodic submicron topographies were fabricated by a single-shot irradiation, i.e. ranging from 30nm-height bumps to 200nm-to-1um diameter holes. Consecutive multi pulse processing generated triangular laser-induced surfaces structures (LIPSS). In addition, the dry laser cleaning effect and large area texturing employing PJ were investigated.

Triangular self-organized surface textures produced by femtosecond laser irradiation on stainless steel and titanium alloy

Results of the work in the Laser4Fun project has been published as:

Jean-Michel Romano, Antonio Garcia-Giron, Pavel Penchev, Stefan Dimov. Triangular self-organized surface textures produced by femtosecond laser irradiation on stainless steel and titanium alloy. 2nd World Congress on Micro and Nano Manufacturing (September 2018); doi: 10.3850/978-981-11-2728-1_09

Abstract

The large area uniformity of laser-induced periodic surface structures (LIPSS) on ferritic stainless steel and titanium alloy is studied. A single-step process was designed to generate low spatial frequency LIPSS (LSFL) over relatively large areas. For the first time, a new LIPSS morphology is fabricated using near-infrared ultrashort pulsed laser. Extraordinarily uniform self-organized triangular structures in hexagonal arrangements were fabricated in the subwavelength range. The generation of such LSFL was found to be highly repeatable, not material dependent but very sensitive to the used laser processing settings. Therefore, the sensitivity of triangular-LSFL formation to pulse fluence and scanning speed were investigated.