Jouni Partanen

• Doctor of Philosophy
• Head of Department at Aalto University

This pilot study develops a process to evaluate in-situ defect detection and self-healing in Ti-6Al-4V fabricated using laser-based powder bed fusion. A tailor-made test specimen was designed and manufactured for the nanofocus tube X-ray computed tomography (XCT) system. In situ optical tomography was used to capture infrared images containing heat...

It is well known that printing parameters strongly affect the mechanical performance of 3D printed parts. This work explores the role of i) extruder temperature, ii) print speed, and iii) layer height on the interlaminar strength of 3D-printed continuous fibre-reinforced composites. The carbon fibre-reinforced thermoset filament is printed concomit...

Particle and gaseous contaminants from industrial scale additive manufacturing (AM) machines were studied in three different work environments. Workplaces utilized powder bed fusion, material extrusion, and binder jetting techniques with metal and polymer powders, polymer filaments, and gypsum powder, respectively. The AM processes were studied fro...

Laser powder bed fusion (LPBF) has become an established method for manufacturing end-use metal components. Exploiting the geometric freedom of additive manufacturing (AM) offers broad possibilities for part optimization and enables performance enhancements across industry sectors. However, part shape and feature size have been found to locally aff...

Purpose: Introducing additive manufacturing (AM) in a multinational corporation with a global spare parts operation requires tools for a dynamic supplier selection, considering both cost and delivery performance. In the switchover to AM from conventional manufacturing, the objective of this study is to find situations and ways to improve the spare...

Vat photopolymerization is the oldest and popular additive manufacturing technique, which can print metal and ceramic parts quickly with high dimensional accuracy. This study successfully produced a metallic alloy from elemental powders by Digital Light Processing (DLP) method. Ni-Ti-Cu powders were blended in a curable resin with a specific ratio....

A major challenge with extensive craniomaxillofacial bone reconstruction is the limited donor‐site availability to reconstruct defects predictably and accurately according to the anatomical shape of the patient. Here, patient‐specific composite bioimplants, consisting of cross‐linked poly(trimethylene carbonate) (PTMC) networks and β‐tricalcium pho...

We developed a 3D-printing process based on thermoset biocomposites termed Delayed Extrusion of Cold Masterbatch (DECMA). DECMA is a processing method, based on controlling the degree of curing, that takes some responsibility of the 3D printing from materials and as such can be used to 3D print otherwise unprintable materials. First, a masterbatch...

The additive manufacturing (AM) methods, selective laser sintering (SLS) and multi jet fusion (MJF), are increasingly used for end-use polymer parts. Chemical reactions caused by ionizing radiation and catalyzed by oxygen, moisture, and heat are known to degrade the polymer structure, result in visual defects, and loss of mechanical properties. How...

Additive manufacturing, or more commonly 3D printing, has been recently established as one of the most advanced technologies for fabricating multi-material parts. In this work, the possibility of manufacturing multimetal parts by material extrusion process was studied for the first time. Three types of samples, named mixed, coupled and graded, resu...

Metals made by additive manufacturing (AM) have intensely augmented over the past decade for customizing complex structured products in the aerospace industry, automotive, and biomedical engineering. However, for AM fabricated steels, the correlation between the microstructure and mechanical properties is yet a challenging task with limited reports...

Direct digital manufacturing (DDM) methods such as additive manufacturing (AM), have been introduced as a production method for some small and complicated parts mostly in aerospace and medical industries (batches of one or a few). However, still it is not viewed as a suitable method for producing numerous parts in small batch sizes. In this study w...

Lignin is introduced as a suitable component for selective laser sintering (SLS) of polyamide (PA12) to reduce costs while maintaining or improving processability and performance. Alkali lignin (sourced as a polydisperse, amorphous powder) was used at a volume concentration of up to 60 vol % for three-dimensional (3D) printing of complex, layered s...

3D food printing is an emerging food technology innovation that enables the personalization and on-demand production of edible products. While its academic and industrial relevance has increased over the past decade, the functional value of the technology remains largely unrealized on a commercial scale. This study aimed at updating the business ou...

A conjugate heat transfer (CHT) study of a liquid cooling heat exchanger is carried out using the open source computational fluid dynamics (CFD) library OpenFOAM. The heat exchanger was 3D printed using aluminium and experimentally verified by temperature probing and thermal imaging. The functionality of the heat exchanger in cooling localized heat...

Large critical size bone defects are complicated to treat, and in many cases, autografts become a challenge due to size and availability. In such situations, a synthetic bone implant that can be patient-specifically designed and fabricated with control over parameters such as porosity, rigidity, and osteogenic cues can act as a potential synthetic...

Featured Application The customizable clip system opens new possibilities for occupational health professionals since the basic design can be altered to hold different kinds of samplers and tools. The solution is shared using an open source methodology to allow for distributed manufacturing of the free designs. Abstract Design for additive manufac...

The purpose of this article is to present a design for additive manufacturing assignment focused on creativity rather than functionality and to analyze its results (N = 70) acquired during five years. The assignment teaches the unique advantages of additive manufacturing to engineering students and encourages learning from failure to achieve design...

Free and open-source hardware (FOSH) is rapidly gaining momentum because it provides customized research hardware with over 90% savings compared to the costs of proprietary tools. However, the focused skill sets of researchers who aim to facilitate their own research limit FOSH complexity. The most expensive research equipment normally requires an...

Featured Application Accuracy of additively manufactured implants for clinical surgery. Abstract In craniomaxillofacial surgical procedures, an emerging practice adopts the preoperative virtual planning that uses medical imaging (computed tomography), 3D thresholding (segmentation), 3D modeling (digital design), and additive manufacturing (3D prin...

Increasingly, metal parts made by additive manufacturing are produced using powder bed fusion (PBF). In this paper we report upon the combined effects of PBF parameters, including power and scan speed, in layer-by-layer manufacturing of gas atomized non-modulated (NM) Ni-Mn-Ga alloy. The effects of process parameters upon PBF is studied by applying...

Three-dimensional (3D) printing of biomaterials has the potential to become an ecologically advantageous alternative compared with conventional manufacturing based on oil-derived polymer materials. In this study, a novel 3D printing technology is applied that combines ultraviolet (UV) curing with paste extrusion. This hybrid manufacturing technique...

Large-Eddy Simulation of heat transfer in plate and pin fin heat exchangers is carried out under constant surface temperature assumption while resolving the surface heat flux by a dense mesh of 28 M cells. The heat exchangers are mounted inside a pipe in a highly constrained space. The heat transfer takes place by forced convection at ReD=20000. Th...

The purpose of this article is to demonstrate that additive manufacturing is a viable method for producing counterflow heat exchangers that have a very high power to volume ratio. For this study, a heat exchanger with 144 flow channels in a checkerboard pattern was designed and additively manufactured from AlSi10Mg. The heat exchanger was tested by...

Digital platforms have become an integral part of user-experience innovation in a short period of time. When coupled with innovative production technologies like 3d printing, these platforms facilitate prosumption, i.e., production activities carried-out by the consumers. Prosumption is very much anticipated in the food sector, especially after the...

Purpose Additive manufacturing requires a systemic approach to help industry on technology applicability research. Towards this end, the purpose of this research is to help manufacturing business leaders decide whether digitalised manufacturing based on additive manufacturing are suitable for engineering applications and help them plan technology t...

Companies lack a trained workforce with the ability to justify the utilization of Additive Manufacturing (AM) technologies in manufacturing activities. The problem is that traditional education in engineering design and manufacturing is heavily constrained by the design rules imposed by conventional manufacturing, which are based on subtractive and...

Activities to advance circular economy are accelerating, and ecodesign has been mentioned as a necessary ingredient for their success. These activities might be further accelerated with more shared understanding of the related terminology. Many of these suggested activities take place in companies’ product development where employees should impleme...

The purpose of this study is to demonstrate the ability of additive manufacturing, also known as 3D printing, to produce effective drug delivery devices and implants that are both identifiable, as well as traceable. Drug delivery devices can potentially be used for drug release in the direct vicinity of target tissues or the selected medication rou...

The purpose of this research is to develop a computer-driven decision support system (DSS) to select optimal additive manufacturing (AM) machines for metal powder bed fusion (PBF) applications. The tool permits to evaluate productivity factors (i.e., cost and production time) for any given geometry. At the same time, the trade-off between feature r...

Purpose - Innovative startups have begun a trend using laser sintering (LS) technology patents expiration, namely by introducing LS additive manufacturing (AM) machines that can overcome utilization barriers, such as the costliness of machines and productivity limitation. The recent rise of this trend has led us to investigate this new class of mac...

It is necessary to understand the photoinitiated curing process, which occurs in vat photopolymerization resins during exposure, to develop high quality end products. Usually a curable resin contains photosensitizers, crosslinkable monomers and neutral absorbers, which have different roles in the curing process. The photosensitizer initiates the pr...

Tämä raportti on kooste Aalto-yliopiston ja Teknologian tutkimuskeskus VTT:n johtaman ja toteuttaman Digitaaliset varaosat -tutkimusprojektin tuloksista. Projektin päätavoitteena oli luoda digitaalisten varaosien liiketoimintakonsepti ja rakentaa edellytykset toimivalle verkos-tolle, selvittää 3D-tulostusprosesseilla valmistettujen varaosien suorit...

This report is a compilation of the results of the Digital Spare Parts research project, managed and implemented by Aalto University and VTT Technical Research Centre of Finland. The main goal of the project was to create a business concept for digital spare parts and to lay down the foundations for a functional network, analyse the current and fut...

The paper analyses the impact of cheaper metal powder supplies on the comparative competitiveness of additive manufacturing (AM). By utilising two case studies, we compare the economic impact of an innovative titanium extraction method on Selective Laser Melting (SLM) and conventional methods of machining and casting. A switch-over analysis identif...

This study corresponds to the first stage of a project that focuses on optimizing the mechanical properties of titanium dioxide (TiO2) for use in bone implants. The goal of the study is to characterize and compare the stiffness of solid and scaffold TiO2 samples fabricated via three-dimensional material extrusion method. The sample specimens were sint...

Hydrogel nanomaterials, especially those that are of non-human and non-animal origins, have great potential in biomedical and pharmaceutical sciences due to their versatility and inherent soft-tissue like properties. With the ability to simulate native tissue function, hydrogels are potentially well suited for cellular therapy applications. In this...

HepG2 cells seeded on top of NFCA hydrogels and stained with live (green) and red (dead). A) Confocal imaging after 1-week incubation. B) 1-week incubation, HepG2 cells killed with 70% ethanol. C,D) Confocal images after 2-week incubation period showing large hepatic clusters. (TIF)

NFCA coated suture performance on freshly sacrificed mice. Mouse liver (top), spleen (middle) and muscle tissue (bottom) were successfully sutured without NFCA coating peeling off. (TIF)

The objective of this research is to define an optimal innovation policy and funding strategy to improve Additive Manufacturing (AM) capabilities in Finnish companies. To do so, we present an international review of innovation programs in the area of AM. In addition, the study replied upon a survey prepared to evaluate factors for AM implementation...

3D printers are currently widely available and very popular among the general public. However, the use of these devices may pose health risks to users, attributable to air-quality issues arising from gaseous and particulate emissions in particular. We characterized emissions from a low-end 3D printer based on material extrusion, using the most comm...

Circular economy ambitions demand considering lifecycle of products within product development. From the perspective of the circular economy, environmental considerations should, for example, increasingly entail product's use phase not only to increase product's energy-efficiency, but also to prolong the time in use. This paper investigates how the...

This paper presents the current state of additive manufacturing (AM) implementation in complex supply chains, focussing especially on the globalised consumer electronics industry. A literature review sought to identify bottlenecks to technology transfer, while a qualitative study was carried out using interviews with case company personnel. Finally...

This research presents a comprehensive view of 3D printing technologies and their evolution. Additionally, it provides a Nordic perspective on the topic by summarizing project based research conducted in Finland. Expert interviews and research data extracted from case studies are analysed to cover topical areas on additive manufacturing transferabi...

Direct Digital Manufacturing (DDM), or '3D printing' is often seen to be poised to revolutionize manufacturing and supply chains. The paper presents a research agenda focusing on those aspects of operations management and supply chain management most likely to be affected by growing adoption of DDM. We seek to separate hype surrounding DDM from ec...

Carbon Fiber Reinforced Plastics (CFRP) are getting increasingly used for building light and strong structures. Most CFRP manufacturing of small parts is done manually, exposing laborers to carcinogenic epoxy and also causing inconsistent quality. This problem can be addressed by a compact automated CFRP part manufacturing machine that is capable o...

Additive Manufacturing (AM) or 3D printing (3DP) has received great attention and increased popularity in recent years. The use of desktop printer is becoming commonplace in educational, professional and recreational purposes. Desktop 3D-printers have been shown to generate remarkable amount of ultrafine particles, and have been classified as a str...

Ambitions toward a circular economy will necessitate more pro-activity in the current practices of many organizations in order to reduce environmental impacts. Since a product’s environmental fate is dictated by organization’s product development, it is essential to better understand how environmental issues are taken into account in product develo...

This paper presents the current state of additive manufacturing (AM) implementation in complex supply chains, focusing especially on the globalised consumer electronics industry. A literature review sought to identify bottlenecks to technology transfer, while a qualitative study was carried out using interviews with case company personnel. Finally,...

The paper describes to the machine user community how to improve surface quality and dimensional stability of additively produced parts. A case geometry is designed to compare the subtractive finishing process of FDM parts. Two different machines are used to produce a sample to be postprocessed with a CNC milling machine. Geometrical and dimensiona...

Upon surgery, local inflammatory reactions and postoperative infections cause complications, morbidity, and mortality. Delivery of human adipose mesenchymal stem cells (hASC) into the wounds is an efficient and safe means to reduce inflammation and promote wound healing. However, administration of stem cells by injection often results in low cell r...

Stereolithographic fabrication of graphene-based 3D constructs was demonstrated. The photocrosslinkable resin/graphene oxide mixtures were fabricated to samples that closely followed the structure of the designed 3D model. After 3D printings, the graphene oxide/polymer composites were pyrolyzed to reduce graphene oxide to electrically conductive gr...

Additive manufacturing (AM) is expanding the manufacturing capabilities. However, quality of AM produced parts is dependent on a number of machine, geometry and process parameters. The variability of these parameters affects the manufacturing drastically and therefore standardized processes and harmonized methodologies need to be developed to chara...

Laser additive manufacturing (LAM) is a layer wise fabrication method in which a laser beam melts metallic powder to form solid objects. Although 3D printing has been invented 30 years ago, the industrial use is quite limited whereas the introduction of cheap consumer 3D printers, in recent years, has familiarized the 3D printing. Interest is focus...

The research contributes to the body of knowledge on new product development by considering the potential use of a major emerging production technology in the early phase of final production. Direct digital manufacturing (DDM) methods such as additive manufacturing (AM) have been introduced as a production method for some small and complicated part...

AdManI " project has started by exploring how, in the context of Finnish and Scandinavian industries, AM can be used to innovative product development and manufacturing in order to gain competitiveness with a global perspective. This policy brief is connected to the sub‐projects defined in work packages 2 " Mapping of current AM Practices in Nordic...

In engineering systems, features such as textures or patterns on curved surfaces are common. In addition, such features, in many cases, are required to have shapes that are conformal to the underlying surfaces. To address the fabrication challenge in building such conformal features on curved surfaces, a newly developed additive manufacturing (AM)...

In projection stereolithography, the cure depth and thereby the layer thickness in the manufacturing process may be varied by changing the operation wavelength. The change can be made even in the middle of the manufacturing process, which opens up possibilities for additional flexibility and speed-up of the process.In this paper, we investigate how...

A solid imaging apparatus and method employing sub-pixel shifting in multiple exposures of the digitally light projected image of a cross-section of a three-dimensional object on a solidifiable liquid medium. The multiple exposures provide increased resolution, preserving image features in a three-dimensional object and smoothing out rough or uneve...

Purpose: Explore the forms that combinations of digital manufacturing, logistics, and equipment use are likely to take and how these novel combinations may affect the relationship among logistics service providers, users, and manufacturers of equipment. Design/methodology/approach: We apply Brian Arthur’s theory of combinatorial technological evol...

This paper introduces a method of additive manufacturing by injection of light-cured material. A fabrication system to produce three-dimensional parts by extruding multiple layers of photosensitive resin was constructed. The polymerization of the resin is achieved in a curing process that utilizes ultraviolet light-emitting diodes. The device is ab...

Additive manufacturing methods are popularly used in rapid prototyping and rapid manufacturing in the industry and recently they have gained popularity also in hobbyist crowds. Miniaturization of an additive manufacturing device would make it more portable, affordable and thus more accessible for everyone, but it is also important that the manufact...

This DLDM technique has demonstrated some outstanding merits in complex organ manufacturing with two different material systems that are technologically and biologically incapable to produce using the other existing or traditional RP techniques. The potential applications of the assembled elliptic hybrid hierarchical constructs are diverse, such as...

Conclusions: This study demonstrates proof of concept for controlled manufacturing methods that utilize novel tailored biopolymers (3D photocuring technology) or conventional bioresorbable polymers (fused deposition modeling, FDM) for macroscopic and microscopic geometry control. The manufactured scaffolds could be suitable for tissue engineering...

Ultrasonic imaging is an important medical imaging technique. It uses ultrasound over 20K Hz to detect and visualize muscles, tendons, and many internal organs. Previous studies have shown that an improved acoustic performance can be achieved by conformal ultrasound transducer arrays and horns that can wrap conformably around curved surfaces. To ad...

A ∼13% increase in the absorption coefficient is seen by a weak probe beam to build-up exponentially in ∼50 ps and decay in ∼1.4 ns after a ∼30 ps intense pump pulse (∼220 mJ/cm2 ) at 532 nm goes through a bis-benzothiazole/H2SO4 solution. We propose a three-level model to explain the effect and obtain the basic parameters by fitting our data to th...

We use ∼30 ps pulses at 532 nm to measure the complex excited-state molecular polarizability αe in a C60/benzene solution. We determine the imaginary part of αe by measuring the excited-state absorption cross-section in a pump-probe experiment. In a degenerate-four-wave-mixing (DFWM) experiment, we find that in delayed probing of the complex index...

Purpose - The purpose of this paper is to describe and evaluate the potential approaches to introduce rapid manufacturing (RM) in the spare parts supply chain. Design/methodology/approach - Alternative conceptual designs for deploying RM technology in the spare parts supply chain were proposed. The potential benefits are illustrated for the aircraf...

Solid imaging is a technology for fabricating 3D models from computer files. The article describes four commercial laser-based, solid-imaging technologies: stereolithography; laser sintering; laminated object manufacturing; and, laser-engineered net shaping.

Summary form only given. Lasers have been employed to create artificial “laser guide stars” (LGS) by exciting various emissions from the upper atmosphere that are bright enough to correct infrared images. Unfortunately, the atmosphere trembles in such a manner that using adaptive optics techniques to correct distortions in blue starlight requires o...

We determine the band mobility of photoexcited electrons in cubic n-type Bi12SiO20. We measure a room-temperature mobility of 3.4±0.5 cm2/(Vs) that decreases monotonically to 1.7±0.3 cm2/(Vs) as the temperature is increased to 200 °C. We show that electrons in Bi12SiO20 form large polarons. Our results are predicted by strong coupling polaron theor...

We have developed a new method of determining in time both the real and the imaginary parts of third-order nonlinear-optical coefficients. In this method the phase-conjugated four-wave-mixing signal beam interferes with one of the transmitted pump beams. By comparing the interference pattern with that of a known reference, we are able to determine...

Summary form only given. Here we measure the band mobility in n-BSO and its temperature dependence by observing the dark diffusion of excited electrons before trapping takes place. In the experiments we excite a sinusoidal distribution of electrons with a 30 ps laser pulse and observe their diffusion in the first few nanoseconds after excitation, d...

Stereolithography is a Rapid Prototyping and Manufacturing (RP&M) technique which can be used to produce 3D plastic parts directly out computer files generated by CAD. Stereolithography systems use ultraviolet lasers to solidify liquid resin into the desired form as defined by the CAD file. Solidified plastic parts are built completely automaticall...

The stereolithography (SL) process has benefited from many advances in the last four to five years. These include new resins with reduced shrinkage and curl distortion, enhanced software, and improved scanning techniques. One can produce highly accurate parts for most dimensions with a few mils of the design value as shown in numerous accuracy and...

form only given. Here we measure the band mobility in n-BSO and its temperature dependence by observing the dark diffusion of excited electrons before trapping takes place. In the experiments we excite a sinusoidal distribution of electrons with a 30 ps laser pulse and observe their diffusion in the first few nanoseconds after excitation, during wh...

Stereolithography is a Rapid Prototyping & Manufacturing (RP&M) technique which is used to produce 3 dimensional plastic parts directly out computer files generated by CAD. Stereolithography systems use ultraviolet lasers to solidify liquid resin into the desired form as defined by the CAD file. In recent years, solid state laser technology has rea...

Stereolithography (SL) is a Rapid Prototyping & Manufacturing (RP&M) technique which can be used to produce 3 dimensional plastic parts directly out computer files generated by CAD. Stereolithography systems use ultraviolet lasers to solidify liquid resin into the desired form as defined by the CAD file. Commercially available photopolymer initiato...

We obtain the correlation pattern between two amplitude-modulated input images of 36 and 280 random black and white pixels, using the standard degenerate four-wave-mixing geometry of 852-nm optical beams in a 1-mm-thick cesium-vapor cell. The total optical input power is 3.2 mW to obtain 0.4 nW of power in the correlation pattern. We verified that...

ATOMIC vapours can exhibit large optical nonlinearities1. When laser light is tuned in resonance with an atomic transition, the absorption cross-section of the atom can become very large, typically seven orders of magnitude larger than the cross-sectional area of its electron cloud2. Because of these strong nonlinearities, different laser beams can...

We measure the magnitude and phase of the degenerate third-order nonlinear optical susceptibility (chi) ⁽³)llll of solutions of various bis-thienyl polyenes (n-BTP) with the number n of the conjugated double bonds ranging from 3 to 9. We study both neutral and bipolaronic (i.e., doubly ionized) forms of n-BTP. We find that, within experimental erro...

We use a pump-probe technique to measure the change in optical transmission through a 1 cm C60/benzene (0.58 g/l) solution caused by a 532 nm 25 ps `pump' pulse having fluence up to approximately 10 mJ/cm2. Temporal dependence indicates that transmission drops within the pump pulse width and stays at the reduced level up to our maximum delay time (...

We present a new phase-sweep method for characterizing laser-induced complex dielectric gratings. This characterization requires four parameters: the amplitudes and the spatial phases of both the refractive-index and the absorption components. We apply this phase-sweep method to study a complex polarizability grating in a nominally undoped cubic ph...

We demonstrate efficient degenerate four‐wave mixing in a 10 μm cell of cesium atomic vapor using resonant light. This thin atomic vapor can be utilized for processing high resolution images in a joint transform optical correlator. A figure of merit is presented showing that thin atomic vapors can perform optical correlation of images using fewer p...