At present, many areas of industry have strong tendencies towards miniaturization of products. Mechanical components of these products as a rule are manufactured using conventional large-scale equipment or micromechanical equipment based on microelectronic technology (MEMS). The first method has some drawbacks because conventional large-scale equipment consumes much energy, space and material. The second method seems to be more advanced but has some limitations, for example, two-dimensional (2D) or 2.5-dimensional shapes of components and materials compatible with silicon technology. In this paper, we consider an alternative technology of micromechanical device production. This technology is based on micromachine tools (MMT) and microassembly devices, which can be produced as sequential generations of microequipment. The first generation can be produced by conventional large-scale equipment. The machine tools of this generation can have overall sizes of 100–200 mm. Using microequipment of this generation, second generation microequipment having smaller overall sizes can be produced. This process can be repeated to produce generations of micromachine tools having overall sizes of some millimetres. In this paper we describe the efforts and some results of first generation microequipment prototyping. A micromachining centre having an overall size of 130 × 160 × 85 mm3 was produced and characterized. This centre has allowed us to manufacture micromechanical details having sizes from 50 µm to 5 mm. These details have complex three-dimensional shapes (for example, screw, gear, graduated shaft, conic details, etc), and are made from different materials, such as brass, steel, different plastics etc. We have started to investigate and to make prototypes of the assembly microdevices controlled by a computer vision system. In this paper we also describe an example of the applications (microfilters) for the proposed technology.

Purpose – The purpose of this study is to suggest the joint use of computer-aided design (CAD) and additive manufacturing (AM) technology for the fabrication of custom-made moulds, designed for the manufacture of polymethyl methacrylate (PMMA) implants for cranio-maxillofacial reconstruction to reduce their fabrication time. Even though tailor-made skull prostheses with a high technological level and state-of-the-art materials are available in the market, they are not always accessible to the general population in developing countries. Design/methodology/approach – Computed tomography data were handled to create a three-dimensional (3D) model of the injury of the patient, by reconstructing Digital Imaging and Communications in Medicine (DICOM) images into an Standard Tessellation Language (STL) file that was further used to design the corresponding implant using CAD software. Accordingly, a two-piece core and cavity moulds that replicated the implant geometry was also CAD designed. The 3D-CAD data were sent to an AM machine (fused deposition modelling) and the moulds were fabricated using polycarbonate as thermoplastic material. A reacting mixture to produce PMMA was poured directly into the fabricated moulds, and left to polymerise until cure. Finally, a clear bubble-free case of study PMMA implant was obtained. Findings – The fabrication of CAD-designed moulds with AM, replacing the production of the injury model, resulted in the reduction of the lead-time in the manufacturing of PMMA around 45 per cent. Additionally, the implant showed better fit than the one produced by conventional process. The use of AM moulds for the fabrication of PMMA implants has demonstrated the reduction in lead-time, which potentially can reduce the waiting time for patients. Social implications – Currently, the demand of cranio-maxillofacial implants at only the Hospital General de México “Dr Eduardo Liceaga” (HGM) is 4,000 implants per year, and the average waiting time for each patient is between 5 and 10 weeks, including third-party services’ delays and the time needed to obtain the economical resources by the patient. Public hospitals in Mexico lack manufacturing facilities, so patients have to make use of laboratories abroad and most of the population have no access to them. The implementation of this suggested procedure in public hospitals may improve the accuracy of the implant, increase the number of patients attended per year (up to 83 per cent) and the reduction in waiting time can also reduce mortality and infection rates. Originality/value – The authors of this paper suggest the joint use of CAD and AM technologies to significantly reduce the production time of PMMA implants by producing moulds rather than the injury model, maintaining the general terms and known steps of the process already established for PMMA implants.

Extracellular recordings of electrical activity in freely moving rats are fundamental to understand brain function in health and disease. Such recordings require a small-size, lightweight device that includes movable electrodes (microdrive) to record either a new set of neurons every day or the same set of neurons over time. Ideally, microdrives should be easy to implant, allowing precise and smooth displacement of electrodes. The main caveat of most commercially available microdrives is their relatively short half-life span, in average ranging from weeks to a month. For most experiments, recording days–weeks is sufficient, but when the experiment depends on training animals for several months, it is crucial to develop new approaches. Here, we present a low-cost, reusable, and reimplantable device design as a solution to extend chronic recordings to long-term. This device is composed of a baseplate that is permanently fixed to the rodent’s skull, as well as a reusable and replaceable microdrive that can be attached and detached from the baseplate, allowing its implantation and reimplantation. Reimplanting this microdrive is particularly convenient when no clear neuronal signal is present, or when the signal gradually decays across days. Our microdrive incorporates a mechanism for moving a 16 tungsten-wire bundle within a small (∼15 mm 3 ) lightweight device (∼4 g). We present details of the design, manufacturing, and assembly processes. As a proof of concept, we show that recordings of the nucleus accumbens core (NAcc) in a freely behaving rat are stable over a month. Additionally, during a lever-press task, we found, as expected, that NAc single-unit activity was associated with rewarded lever presses. Furthermore, we also show that NAc shell (NAcSh) responses evoked by freely licking for sucrose, consistent with our previously published results, were conserved from a first implant to a second microdrive reimplant in the same rat, notably showing reimplantation is possible without overtly affecting the functional responses of the area of interest. In sum, here we present a novel microdrive design (low-cost, small size, and light weight) that can be used for long-term chronic recordings and reimplanted in freely behaving rats.

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Additive manufacturing (AM) is the term for a number of processes for joining materials to build physical components from a digital 3D model. AM has multiple advantages over other construction techniques, such as freeform, customization, and waste reduction. However, AM components have been evaluated by destructive and non-destructive testing and have shown mechanical issues, such as reduced resistance, anisotropy and voids. The build direction affects the mechanical properties of the built part, including voids of different characteristics. The aim of this work is an extended analysis of void shape by means of X-ray computed tomography (CT) applied to fused deposition modeling (FDM) samples. Furthermore, a relation between the tensile mechanical properties and digital void measurements is established. The results of this work demonstrate that void characteristics such as quantity, size, sphericity and compactness show no obvious variations between the samples. However, the angle between the main void axis and the mechanical load axis α shows a relation for FDM components: when its mean value μ(α) is around 80 (degrees) the yield strength and Young’s modulus are reduced. These results lead to the formulation of a novel criterion that predicts the mechanical behavior of AM components.

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Traditionally, the use of ferrite as a core of the linear variable differential transformer (LVDT) is suggested in its designs. Nevertheless, problems related to its brittleness and low tensile strength may be considered as important drawbacks for its use as a core material, especially when its geometry is likely to be modified. This work explores other alternatives related to soft magnetic materials, less used in applications of an LVDT core. By means of a decision matrix, from an assortment of different materials, three alternatives were selected. This proposal provides the identification of those materials with higher qualification values to be used as core material. In order to validate the performance of the selected materials, a prototype of LVDT was designed and fabricated. The design was carried out taking into consideration typical performance specifications. Finally, a comparison of the measurements of sensitivity and linearity of the proposed and traditional materials was made.

An analytic approximation for the flow of a linear Phan-Thien–Tanner model fluid through an axisymmetric semi-hyperbolic contraction is presented. Such an approximation allows us to compute velocity and pressure response for the flow through axisymmetric contraction geometries; in particular, we have considered here the semi-hyperbolic contraction, which is a geometry where an almost constant extension-rate is reached at different radial positions. In addition, we present a semi-analytic solution capable of representing the exponential version of the selected viscoelastic model; this solution was compared to the results of commercial software, demonstrating the excellent approximation level of the semi-analytic model proposed. Alternatively, for both approaches (linear and exponential Phan-Thien–Tanner), the flow model equations are solved by considering the Navier boundary condition, which allows these models to represent flows with some degree of slip at the geometry wall.