Packaged integrated opto-fluidic solution for harmful fluid analysis

Abstract

Advances in nuclear fuel reprocessing have led to a surging need for novel chemical analysis tools. In this paper, we present a packaged lab-on-chip approach with co-integration of optical and micro-fluidic functions on a glass substrate as a solution. A chip was built and packaged to obtain light/fluid interaction in order for the entire device to make spectral measurements using the photo spectroscopy absorption principle. The interaction between the analyte solution and light takes place at the boundary between a waveguide and a fluid micro-channel thanks to the evanescent part of the waveguide's guided mode that propagates into the fluid. The waveguide was obtained via ion exchange on a glass wafer. The input and the output of the waveguides were pigtailed with standard single mode optical fibers. The micro-scale fluid channel was elaborated with a lithography procedure and hydrofluoric acid wet etching resulting in a 150±8 µm deep channel. The channel was designed with fluidic accesses, in order for the chip to be compatible with commercial fluidic interfaces/chip mounts. This allows for analyte fluid in external capillaries to be pumped into the device through micro-pipes, hence resulting in a fully packaged chip. In order to produce this co-integrated structure, two substrates were bonded. A study of direct glass wafer-to-wafer molecular bonding was carried-out to improve detector sturdiness and durability and put forward a bonding protocol with a bonding surface energy of γ>2.0 J.m -2 . Detector viability was shown by obtaining optical mode measurements and detecting traces of 1.2 M neodymium (Nd) solute in 12±1 µL of 0.01 M and pH 2 nitric acid (HNO3) solvent by obtaining an absorption peak specific to neodymium at 795 nm.

Heterogeneous integration of KY(WO4)2-on-glass: a bonding study

“…A disadvantage of the latter methods is the curing/annealing temperature, which is around 250°C for an optimal strong bond. The curing/annealing can be performed at lower temperatures (∼150°C), leading to longer process times (>10 hours) and often to weaker bonds [25]. The specifications of the mentioned adhesives are shown in Table 1.…”

“…This change entailed an increase of the annealing time to 72 hours in order to provide enough energy to create the covalent bonds. A previous study [25] showed that, with such a process, a surface energy, γ, greater than 1 J/m 2 is achieved, which allows the bond to withstand standard mechanical processes such as dicing and polishing. After the molecular bonding, both surfaces are crack free, as shown in Fig.…”

Optofluidic sensor engineering towards plutonium concentration measurements

“…The substrate is then plunged into a molten salt bath in order to proceed to the ion exchange. On the other hand, the fluidic wafer is obtained with a wet HF etching process, described in detail in previous work 7 . The microfluidic channel allows interaction of 2 cm, with a channel depth of 150 μm.…”