Bonding NiTi to glass with femtosecond laser pulses L. Quintino a , L. Liu b,e , R.M. Miranda c,n , R.J.C. Silva d , A. Hu b , Y. Zhou b a IST-UTL Instituto Superior Te´cnico, Universidade Te´cnica de Lisboa, Portugal b Department of Mechanical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L-3G1 c UNIDEMI, Departamento de Engenharia Mecˆ anica e Industrial, Faculdade de Ciˆ encias e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal d CENIMAT/I3N, Faculdade de Ciˆ encias e Tecnologia (FCT), UNL, 2829-516—Monte de Caparica, Portugal e Department of Mechanical Engineering, Tsinghua University, Beijing, 100084, China article info Article history: Received 24 September 2012 Accepted 9 February 2013 Available online 17 February 2013 Keywords: Shape memory alloys NiTi Glass Joining Bonding Femtosecond laser beam interaction abstract Dissimilar joining of shape memory alloy to other materials may find interesting applications in the microelectronics and medical devices, allowing for innovative designs and further miniaturization of parts and devices. Femtosecond laser has been investigated to join NiTi to glass aiming at to assess to which extent NiTi particles will deposit on glass when irradiated by a femtosecond laser beam. This is a non-thermal process and the irradiated areas were observed under SEM with EDS to analyze the morphology of the deposits and changes in the chemical composition. The results show that NiTi can be bonded to glass by femtosecond laser irradiation. Deposited particles show a micrometric granular structure. & 2013 Elsevier B.V. All rights reserved. 1. Introduction The scale-down of parts especially for the medical and electronic industry has driven the need to develop new manufacturing tech- nologies, including joining. Laser beam technology has been largely investigated for welding and joining for micro- and more recently nano-components. When the scale goes down to few micron or even nanometers melting has to be controlled in the range of a few nanometers The ultra fast pulsed lasers and femtosecond lasers are innovative tools in nanoscopic processing [1, 2]. Deposition of struc- tures and spots, with micrometer and nanometer resolution, has a large use in the field of microelectronics and optoelectronics. The medical industry is also a potential beneficiary of such technology. Femtosecond laser irradiation can result in an ultra fast and non-thermal melting of materials with promising results for join- ing dissimilar materials in the micro- or nano-scale ranges [3,4]. Femtosecond laser can also synthesis nanoparticles by ablation. Therefore, it is possible to synthesis and joining nanoparticles at the same time: ablate the material or melt the outer surface depositing this on the substrate surface assisted by the beam jet pressure. Limited work exists on the use of femtosecond laser in materials processing and this concerns laser ablation methods for thin film. Shape memory alloys as NiTi have remarkable properties as biocompatibility, good strength and ductility and research is required to fully exploit their potential in innovative applications [5, 6]. Microdeposition of metal structure on quartz substrate was studied by Tam et al. [7] using different ablation energies. Gold thin films were used as donors. Lines with heights from 20 to 120 nm and widths of 2.5–3.3 mm were obtained. The aim of the present study is to illustrate and detail the effects of femtosecond laser irradiation of NiTi onto a glass substrate identifying the track geometry, the characteristics of the deposited particles both morphological and its chemical composition. 2. Experimental procedure NiTi coupons of 0.4 mm thick were cleaned and etched in a solution of HF:HNO 3 :H 2 0 solution with a dilution of 1:5:10. The coupons were placed on top of glass lamellae and fixed in the laser positioning system. A femtosecond laser from Coherent, Elite Duo USP 1 K was set to impinge on the glass side. Fig. 1 shows the experimental setup comprising: an oscillator at 80 MHz, 800 nm and 10 fs; an amplifier of 1 kHz, 800 nm, 35 fs, a focal lens holder and a 3D sample stage. Focal point position and traverse speed were varied. Other processing parameters were kept constant as listed in Table 1. Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/matlet Materials Letters 0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.02.051 n Corresponding author. Tel.: þ351 212 949 618; fax: þ351 21 2948531. E-mail address: rmiranda@fct.unl.pt (R.M. Miranda). Materials Letters 98 (2013) 142–145