Two-photon polymerization (TPP) is capable of fabricating 3D structures with dimensions from sub-µm to a few hundred µm. As a direct laser writing (DLW) process, fabrication time of 3D TPP structures ...scale with the third order, limiting its use in large volume fabrication. Here, we report on a scalable fabrication method that cuts fabrication time to a fraction. A parallelized 9 multi-beamlets DLW process, created by a fixed diffraction optical element (DOE) and subsequent stitching are used to fabricate large periodic high aspect ratio 3D microstructured arrays with sub-micron features spanning several hundred of µm
. The wall structure in the array is designed with a minimum of traced lines and is created by a low numerical aperture (NA) microscope objective, leading to self-supporting lines omitting the need for line-hatching. The fabricated periodic arrays are applied in a cell - 3D microstructure interaction study using living HeLa cells. First indications of increased cell proliferation in the presence of 3D microstructures compared to planar surfaces are obtained. Furthermore, the cells adopt an elongated morphology when attached to the 3D microstructured surfaces. Both results constitute promising findings rendering the 3D microstructures a suited tool for cell interaction experiments, e.g. for cell migration, separation or even tissue engineering studies.
The creation of hole, cavity or channel structures in low-temperature cofired ceramics (LTCCs), using different sacrificial volume materials (SVMs) was tested. The main functionality of the SVMs ...should be: easy application into the holes; protection of holes during lamination; uninhibited lamination between layers; and, during firing should burn out before the pores of the LTCCs close, to leave the empty holes clear of any residue. Five different materials were tested—hydroxyethyl cellulose (HEC) 2 wt%, HEC 5 wt%, agar-agar, gelatin, and commercial carbon paste—and compared to a reference sample where no SVMs were used. In all cases, lamination parameters were minimised in order to preserve the tested hole structures. Matrixes with holes ranging from 158 to 268 µm, with pitches of 573 µm in a green state, were tested. The agar-agar caused ceramic deformation as a result of thermal burst during firing and the lamination between the layers was compromised. The carbon paste was difficult to handle, requiring extra equipment for hole filling and incomplete filling of the larger holes. Traces of carbon paste were left as a landing pad on top of the holes, inhibiting lamination at these areas. The gelatin and the 2 wt% and 5 wt% hydroxyethylcellulose (HEC 2 wt% and HEC 5 wt%) filled all holes completely, and also worked as adhesive-assisted lamination (AAL) materials with excellent lamination between layers. Excellent lamination was also observed in the no-SVM case. Thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) analyses established that, for all SVMs tested, the remaining residue is negligible after firing. As a result, the HEC 2 wt% material was considered ideal for use as an SVM.
In this paper we present an infrared laser pointer, consisting of a vertical-cavity surface-emitting laser (VCSEL) and a diffractive optical element (DOE), encapsulated into a scleral contact lens ...(SCL). The VCSEL is powered remotely by inductive coupling from a primary antenna embedded into an eyewear frame. The DOE is used either to collimate the laser beam or to project a pattern image at a chosen distance in front of the eye. We detail the different SCL constitutive blocks, how they are manufactured and assembled. We particularly emphasize the various technological challenges related to their encapsulation in the reduced volume of the SCL, while keeping the pupil free. Finally, we describe how the laser pointer operates, what are its performances (e.g. collimation, image formation) and how it can be used efficiently in various application fields such as visual assistance and augmented reality.
The shrinkage of Low Temperature Co-fired Ceramics (LTCC) during firing is one of the most difficult features to control in LTCC fabrication, as many factors may impact on the result. The shrinkage ...given by the tape manufacturer is not perfectly transposable to a production environment where preparation, use and equipment is not in exact accordance. Thus, predictable shrinkage models are of main importance in order to fabricate LTCC devices according to specifications. The objective of this work is to develop such models for the Ferro L8 tape using the powerful Design of Experiments (DOE) technique. Four factors are varied; the stack thickness, the device surface, the applied pressure and the temperature during lamination. Other factors such as operator, lamination time or firing profile are kept to a fixed value during these experiments. The result variables are lamination quality and x, y and z-direction shrinkage. Lamination quality is found to be mainly impacted by the interaction between the stack thickness and the surface area of the stack, while for the z-direction shrinkage this interaction together with lamination temperature are significant factors and finally for the lateral shrinkage the main effects stack thickness, surface area and temperature are significant. Numerical models for shrinkage in z- and lateral directions are established. This work enforces the understanding of the shrinkage of LTCC and permits for the Ferro L8 users correctly compensate the layout for shrinkage.
This paper presents work on micro heat pipe (MHP) fabrication in Low Temperature Cofired Ceramics (LTCC) modules for cooling purpose. The MHPs are fabricated in a 10 layer structure using ESL41020 ...tape. Different fabrication settings have been tested to minimize swelling and groove deformation. The best result is obtained by using fugitive tape, extended firing profile, and hot lamination at 50°C for 5 minutes with 70 bar pressure.
Since 2009, Lab-STICC has established an LTCC prototyping laboratory where we, to this day, have worked on microwave devices, devices based on gaped waveguide technology for millimeter-wave/fluidic ...applications (60 GHz), grooved laminated waveguides (30 to 170 GHz), grid array antennas (145 GHz), spintronic devices as well as more basic subjects as design kit and design rule check development, passive component design, and most recently LTCC cooling implementation. This paper presents an overview of the aforementioned devices from simulation, fabrication and measurement phases as well as our fabrication possibilities and limitations.
This paper reports on the results of the design and manufacturing of straight sections, tees, bends and loads in a Grooved Laminated Waveguide (GLWG) topology. These devices, intended for the U-, V-, ...W- and G-band, are fabricated in Low Temperature Co-fired Ceramics (LTCC) technology using the low relative permittivity tape, ESL41110, from ElectroScience Laboratory. Measurements ranging from 40 to 170 GHz prove the concept of grooved laminated waveguides.
Expanding cell studies and tissue engineering from a 2D platform to a 3D mimic of their natural environment demands fabrication methods capable of creating scaffolds covering large volumes with ...feature sizes down to a few μm 1. Two-photon polymerization (TPP) is a direct writing method capable of fabricating free-form 3D structures with sub-wavelength features and is therefore well-suited for template fabrication for cell motility and tissue engineering 2.
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