Search results

The purpose of this paper is to propose and demonstrate a new additive manufacturing approach that breaks the layer-based point scanning limitations to increase fabrication speed, obtain better surface finish, achieve material flexibility and reduce equipment costs.

The freeform additive manufacturing approach conceptually views a 3D article as an assembly of freeform elements distributed spatially following a flexible 3D assembly structure, which conforms to the surface of the article and physically builds the article by sequentially forming the freeform elements by a vari-directional vari-dimensional capable material deposition mechanism. Vari-directional building along tangential directions of part surface gives surface smoothness. Vari-dimensional deposition maximizes material output to increase build rate wherever allowed and minimizes deposition sizes for resolution whenever needed.

Process steps based on geometric and data processing considerations were described. Dispensing and forming of basic vari-directional and vari-dimensional freeform elements and basic operations of joining them were developed using thermoplastics. Forming of 3D articles at build rates of 2-5 times the fused deposition modeling (FDM) rate was demonstrated and improvement over ten times was shown to be feasible. FDM compatible operations using 0.7 mm wire depositions from a variable exit-dispensing unit were demonstrated. Preliminary tests of a surface finishing process showed a result of 0.8-1.9 um Ra. Initial results of dispensing wax, tin alloy and steel were also shown.

This is the first time that both vari-directional and vari-dimensional material depositions are combined in a new freeform building method, which has potential impact on the FDM and other additive manufacturing methods.

Liquid encapsulation techniques have been used extensively in advanced semiconductor packaging, including applications of underfilling, cavity‐filling, and glob top encapsulation. Because of the advanced encapsulation materials and the automatic liquid dispensing equipment involved, it is very important to understand the encapsulation material characteristics, equipment characteristics, encapsulation process development techniques in order to achieve the encapsulation quality and reliability. In this paper, the authors will examine the various considerations in liquid encapsulation applications and address the concerns on material characterization, automatic liquid dispensing equipment/process characterization and the encapsulation quality and reliability. The discussions will be helpful for future material and process development of semiconductor packages.

Hydrogels with low viscosities tend to be difficult to use in constructing tissue engineering (TE) scaffolds used to replace or restore damaged tissue, due to the length of time it takes for final gelation to take place resulting in the scaffolds collapsing due to their mechanical instability. However, recent advances in rapid prototyping have allowed for a new technology called bioplotting to be developed, which aims to circumvent these inherent problems. This paper aims to present details of the process.

The paper demonstrates how by using the bioplotting technique complex 3D geometrical scaffolds with accurate feature sizes and good pore definition can be fabriated for use as biological matrices. PEG gels containing the cell‐adhesive RGD peptide sequence were patterned using this method to produce layers of directional microchannels which have a functionalised bioactive surface. Seeding these gels with C2C12 myoblasts showed that the cells responded to the topographical features and aligned themselves along the direction of the channels.

This process allows plotting of various materials into a media bath containing material of similar rheological properties which can be used to both support the structure as it is dispensed and also to initiate cross‐linking of the hydrogel. By controlling concentrations, viscosity and the temperature of both the plotting material and the plotting media, the speed of the hydrogel gelation can be enhanced whilst it is cross‐linking in the media bath. TE scaffolds have been produced using a variety of materials including poly(ethylene glycol) (PEG), gelatin, alginic acid and agarose at various concentrations and viscosities.

This paper describes one of the very few examples of accurate construction of 3D biological microporous matrices using hydrogel material fabricated by the bioplotting technique. This demonstrates that this technique can be used to produce 3D scaffolds which promote tissue regeneration.

This paper aims to demonstrate the improved functionality of additive manufacturing technology provided by combining multiple processes for the fabrication of packaged electronics.

This research is focused on the improvement in resolution of conductor deposition methods through experimentation with build parameters. Material dispensing with two different low temperature curing isotropic conductive adhesive materials was characterised for their application in printing each of three different conductor designs, traces, z-axis connections and fine pitch flip chip interconnects. Once optimised, demonstrator size can be minimised within the limitations of the chosen processes and materials.

The proposed method of printing z-axis through layer connections was successful with pillars 2 mm in height and 550 µm in width produced. Dispensing characterisation also resulted in tracks 134 µm in width and 38 µm in height allowing surface mount assembly of 0603 components and thin-shrink small outline packaged integrated circuits. Small 149-µm flip chip interconnects deposited at a 457-µm pitch have also been used for packaging silicon bare die.

This paper presents an improved multifunctional additive manufacturing method to produce fully packaged multilayer electronic systems. It discusses the development of new 3D printed, through layer z-axis connections and the use of a single electrically conductive adhesive material to produce all conductors. This facilitates the surface mount assembly of components directly onto these conductors before stereolithography is used to fully package multiple layers of circuitry in a photopolymer.

This paper aims to present a novel rapid prototyping (RP) fabrication methods and preliminary characterization for chitosan scaffolds.

A desktop rapid prototyping robot dispensing (RPBOD) system has been developed to fabricate scaffolds for tissue engineering (TE) applications. The system is a computer‐controlled four‐axis machine with a multiple‐dispenser head. Neutralization of the acetic acid by the sodium hydroxide results in a precipitate to form a gel‐like chitosan strand. The scaffold properties were characterized by scanning electron microscopy, porosity calculation and compression test. An example of fabrication of a freeform hydrogel scaffold is demonstrated. The required geometric data for the freeform scaffold were obtained from CT‐scan images and the dispensing path control data were converted form its volume model. The applications of the scaffolds are discussed based on its potential for TE.

It is shown that the RPBOD system can be interfaced with imaging techniques and computational modeling to produce scaffolds which can be customized in overall size and shape allowing tissue‐engineered grafts to be tailored to specific applications or even for individual patients.

Important challenges for further research are the incorporation of growth factors, as well as cell seeding into the 3D dispensing plotting materials. Improvements regarding the mechanical properties of the scaffolds are also necessary.

One of the important aspects of TE is the design scaffolds. For customized TE, it is essential to be able to fabricate 3D scaffolds of various geometric shapes, in order to repair tissue defects. RP or solid free‐form fabrication techniques hold great promise for designing 3D customized scaffolds; yet traditional cell‐seeding techniques may not provide enough cell mass for larger constructs. This paper presents a novel attempt to fabricate 3D scaffolds, using hydrogels which in the future can be combined with cells.

The area of microfluidic systems has greatly enhanced the in vitro field of tissue engineering. Microfluidic systems such as microchannelled assays are now widely used for mimicking in vivo cell behaviour and studies into basic biological research. In certain cases engineered tissue cell design use 3D ordered geometrical configurations in vitro (such as microchannel assays) to reproduce native in vivo functions. The most common approach for manufacturing micro‐assays is now rapid prototyping (RP) technology. The choice of assay material is dependent on the proposed cell type and ultimately the tissue application. However, many RP technologies can be unsuitable for cell growth applications because of the construction methods and materials they employ. The purpose of this paper is to describe a comparison between two different RP 3D printing methods of fabrication and investigates the merits of each technology for direct cell culture applications using micro‐assays, while also examining the dispensing accuracy of both techniques.

Using a Thermojet and Spectrum Z510 printer pre‐designed micro‐assays incorporating different size microchannels are dispensed. The base materials of both methods are examined for cytotoxic effects while in solution with primary tendon fibroblasts (PFB) cells. After obtaining favorable results from the toxicology experiments, PFB cells are seeded onto the thermojet structures with a view to investigate cell adherence, encapsulation and how the channel width influences cell alignment.

This research concluded that the thermojet had a higher degree of accuracy when manufacturing structures that incorporate microchannels when compared with the Spectrum Z510. Both techniques show that the accuracy of the build decreases with reduction in channel width. The fact that the Spectrum Z510 structures have to be infiltrated with a hardening glue as a post‐processing technique (since the dispensed material is water‐based and hence soluble) causes a cytotoxic effect compared to the thermojet plastic which is not cytotoxic in solution with PFB cells. Seeding the PBF cells directly onto the thermoplastic structure caused problems due to the hydrophobic nature of the material and this necessitated the technique of soaking the structures in a collagen bath to penetrate the surface and reduce the interactions of hydrophobic species enhancing cell attachment and proliferation. Without this coating the thermojet structures induced strong hydrophobic interactions at the surfaces of the microchannels with the culture media resulting in non‐attachment and poor cell mortality.

This research paper describes a comparison between the base materials and methodology of two 3D printing techniques for applications in basic biological studies. This is achieved by analysing the dispensing accuracy of both technologies and the interaction between cells and surface at the interface.

The purpose of this paper is establishing a general mathematical model and theoretical design rules for 3D printing of biomaterials. Additive manufacturing of biomaterials provides many opportunities for fabrication of complex tissue structures, which are difficult to fabricate by traditional manufacturing methods. Related problems and research tasks are raised by the study on biomaterials’ 3D printing. Most researchers are interested in the materials studies; however, the corresponded additive manufacturing machine is facing some technical problems in printing user-prepared biomaterials. New biomaterials have uncertainty in physical properties, such as viscosity and surface tension coefficient. Therefore, the 3D printing process requires lots of trials to achieve proper printing parameters, such as printing layer thickness, maximum printing line distance and printing nozzle’s feeding speed; otherwise, the desired computer-aided design (CAD) file will not be printed successfully in 3D printing.

Most additive manufacturing machine for user-prepared bio-material use pneumatic valve dispensers or extruder as printing nozzle, because the air pressure activated valve can print many different materials, which have a wide range of viscosity. We studied the structure inside the pneumatic valve dispenser in our 3D heterogeneous printing machine, and established mathematical models for 3D printing CAD structure and fluid behaviors inside the dispenser during printing process.

Based on theoretical modeling, we found that the bio-material’s viscosity, surface tension coefficient and pneumatic valve dispenser’s dispensing step time will affect the final structure directly. We verified our mathematical model by printing of two kinds of self-prepared biomaterials, and the results supported our modeling and theoretical calculation.

For a certain kinds of biomaterials, the mathematical model and design rules will have unique solutions to the functions and equations. Therefore, each biomaterial’s physical data should be collected and input to the model for specified solutions. However, for each user-made 3D printing machine, the core programming code can be modified to adjust the parameters, which follows our mathematical model and the related CAD design rules.

This study will provide a universal mathematical method to set up design rules for new user-prepared biomaterials in 3D printing of a CAD structure.

Points out that emerging designs of modules housing electronic components, such as engine control modules, are putting greater demands on dispensing and robotics equipment. Looks at the key issues of decreased gasket diameters, zero‐knit lines and speed of processing which are facing equipment suppliers.

The purpose of this paper is to present a hybrid manufacturing system that integrates stereolithography (SL) and direct print (DP) technologies to fabricate three‐dimensional (3D) structures with embedded electronic circuits. A detailed process was developed that enables fabrication of monolithic 3D packages with electronics without removal from the hybrid SL/DP machine during the process. Successful devices are demonstrated consisting of simple 555 timer circuits designed and fabricated in 2D (single layer of routing) and 3D (multiple layers of routing and component placement).

A hybrid SL/DP system was designed and developed using a 3D Systems SL 250/50 machine and an nScrypt micro‐dispensing pump integrated within the SL machine through orthogonally‐aligned linear translation stages. A corresponding manufacturing process was also developed using this system to fabricate 2D and 3D monolithic structures with embedded electronic circuits. The process involved part design, process planning, integrated manufacturing (including multiple starts and stops of both SL and DP and multiple intermediate processes), and post‐processing. SL provided substrate/mechanical structure manufacturing while interconnections were achieved using DP of conductive inks. Simple functional demonstrations involving 2D and 3D circuit designs were accomplished.

The 3D micro‐dispensing DP system provided control over conductive trace deposition and combined with the manufacturing flexibility of the SL machine enabled the fabrication of monolithic 3D electronic structures. To fabricate a 3D electronic device within the hybrid SL/DP machine, a process was developed that required multiple starts and stops of the SL process, removal of uncured resin from the SL substrate, insertion of active and passive electronic components, and DP and laser curing of the conductive traces. Using this process, the hybrid SL/DP technology was capable of successfully fabricating, without removal from the machine during fabrication, functional 2D and 3D 555 timer circuits packaged within SL substrates.

Results indicated that fabrication of 3D embedded electronic systems is possible using the hybrid SL/DP machine. A complete manufacturing process was developed to fabricate complex, monolithic 3D structures with electronics in a single set‐up, advancing the capabilities of additive manufacturing (AM) technologies. Although the process does not require removal of the structure from the machine during fabrication, many of the current sub‐processes are manual. As a result, further research and development on automation and optimization of many of the sub‐processes are required to enhance the overall manufacturing process.

A new methodology is presented for manufacturing non‐traditional electronic systems in arbitrary form, while achieving miniaturization and enabling rugged structure. Advanced applications are demonstrated using a semi‐automated approach to SL/DP integration. Opportunities exist to fully automate the hybrid SL/DP machine and optimize the manufacturing process for enhancing the commercial appeal for fabricating complex systems.

This work broadly demonstrates what can be achieved by integrating multiple AM technologies together for fabricating unique devices and more specifically demonstrates a hybrid SL/DP machine that can produce 3D monolithic structures with embedded electronics and printed interconnects.

Light radiation cure adhesives, coatings and encapsulants are being used in the electronics manufacturing industry with increasing frequency because their properties and process advantages are a good fit for the manufacturing requirements which are demanded by current industry drivers, such as miniaturisation, environmental and health & safety demands, manufacturing yield improvement and total product cost. Light curing adhesive systems in the electronics manufacturing industry have found applications in strain relief, wire and parts tacking, coil terminating, tamper‐proofing, structural bonding, temporary masking, potting, encapsulation, glob topping, conformal coating, and surface mount component attachment. This paper describes three case histories where photo cure adhesives were introduced to an electronics manufacturing environment, and discusses their rationale, implementation and their economics. The case histories encompass printed circuit board assembly (including surface mount), electronics packaging and microelectronic encapsulation. Production managers and process engineers are given confidence that practical adhesive application can be clean, fast and economical.