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Bioprinting is an emerging technology for manufacturing cell-laden three-dimensional (3D) scaffolds, which are used to fabricate complex 3D constructs and provide specific microenvironments for supporting cell growth and differentiation. The development of bioinks with appropriate printability and specific bioactivities is crucial for bioprinting and tissue engineering applications, including bone tissue regeneration. Therefore, to produce functional bioinks for osteoblast printing and bone tissue formation, we formulated various nanocomposite hydrogel-based bioinks using natural and biocompatible biomaterials (i.e., alginate, tempo-oxidized cellulose nanofibrils (TOCNF), and polydopamine nanoparticles (PDANPs)). Rheological studies and printability tests revealed that bioinks containing 1.5% alginate and 1.5% TOCNF in the presence or absence of PDANP (0.5%) are suitable for 3D printing. Furthermore, in vitro studies of 3D-printed osteoblast-laden scaffolds indicated that the 0.5% PDANP-incorporated bioink induced significant osteogenesis. Overall, the bioink consisting of alginate, TOCNF, and PDANPs exhibited excellent printability and bioactivity (i.e., osteogenesis).

Sodium alginate (SA) is a non-toxic, biocompatible and biodegradable natural polymer. It has good printability, which is why it is often used in inks for three-dimensional (3D) printing in tissue engineering fields. However, pure SA hydrogel has unstable mechanical properties. In this study, we fabricated a structurally stable 3D scaffold by blending SA with poly(vinyl alcohol) (PVA) to enhance the mechanical properties of the scaffold. Moreover, we characterized the surface morphology and various mechanical properties of the scaffolds using scanning electron microscopy, Fourier transform-infrared spectroscopy, thermogravimetric analysis and several mechanical tests. The SA/PVA scaffolds were mechanically more stable than the pure SA scaffold and are good candidate as implantable biodegradable scaffolds for tissue engineering and medical applications.

Cochlear implants (CIs) have become the standard treatment for severe-to-profound sensorineural hearing loss. Conventional CIs have some challenges, such as the use of extracorporeal devices, and high power consumption for frequency analysis. To overcome these, artificial basilar membranes (ABMs) made of piezoelectric materials have been studied. This study aimed to verify the conceptual idea of a totally implantable ABM system. A prototype of the totally implantable system composed of the ABM developed in previous research, an electronic module (EM) for the amplification of electrical output from the ABM, and electrode was developed. We investigated the feasibility of the ABM system and obtained meaningful auditory brainstem responses of deafened guinea pigs by implanting the electrode of the ABM system. Also, an optimal method of coupling the ABM system to the human ossicle for transducing sound waves into electrical signals using the middle ear vibration was studied and the electrical signal output according to the sound stimuli was measured successfully. Although the overall power output from the ABM system is still less than the conventional CIs and further improvements to the ABM system are needed, we found a possibility of the developed ABM system as a totally implantable CIs in the future.

Three-dimensional (3D) bioprinting technology has emerged as a powerful biofabrication platform for tissue engineering because of its ability to engineer living cells and biomaterial-based 3D objects. Over the last few decades, droplet-based, extrusion-based, and laser-assisted bioprinters have been developed to fulfill certain requirements in terms of resolution, cell viability, cell density, etc. Simultaneously, various bio-inks based on natural–synthetic biomaterials have been developed and applied for successful tissue regeneration. To engineer more realistic artificial tissues/organs, mixtures of bio-inks with various recipes have also been developed. Taken together, this review describes the fundamental characteristics of the existing bioprinters and bio-inks that have been currently developed, followed by their advantages and disadvantages. Finally, various tissue engineering applications using 3D bioprinting are briefly introduced.

3D printed scaffolds composed of gelatin and β-tri-calcium phosphate (β-TCP) as a biomimetic bone material are fabricated, thereby providing an environment appropriate for bone regeneration. The Ca2+ in β-TCP and COO- in gelatin form a stable electrostatic interaction, and the composite scaffold shows suitable rheological properties for bioprinting. The gelatin/β-TCP scaffold is crosslinked with glutaraldehyde vapor and unreacted aldehyde groups which can cause toxicity to cells is removed by a glycine washing. The stable binding of the hydrogel is revealed as a result of FTIR and degradation rate. It is confirmed that the composite scaffold has compressive strength similar to that of cancellous bone and 60 wt% β-TCP groups containing 40 wt% gelatin have good cellular activity with preosteoblasts. Also, in the animal experiments, the gelatin/β-TCP scaffold confirms to induce bone formation without any inflammatory responses. This study suggests that these fabricated scaffolds can serve as a potential bone substitute for bone regeneration.

To adapt biomaterials for solid freeform fabrication (SFF), methoxy polyethylene glycol (MPEG)-(PLLA-co-PCL) (LxCy) block copolymers were prepared using MPEG as the initiator to precisely control the molecular weight of PLLA and PCL. The LxCy block copolymers were designed such that the PLLA and PCL content varied and their molecular weights were within 200–1000 kDa. The cylindrical LxCy scaffolds were prepared by using LxCy block copolymers in SFF. The feasibility of using LxCy block copolymers was examined in terms of flowability from the micronozzle and solidification at room temperature after scaffold printing. The flowability and solidification of LxCy block copolymers mainly depend on the proportions of PLLA and PCL. Fabrication of the cylindrical LxCy scaffolds by using SFF was rapid and showed high reproducibility. In in vivo implantation, the cylindrical LxCy scaffolds exhibited biocompatibility and gradual biodegradation on a 16 week timescale. Immunohistochemical characterization showed that the in vivo LxCy scaffolds elicit only a modest inflammatory response. Taken together, these results show that LxCy block copolymers may serve as suitable biomaterials for the fabrication of well-defined three-dimensional scaffolds by using SFF.

Although three-dimensional (3D) bioprinting technology is rapidly developing, the design strategies for biocompatible 3D-printable bioinks remain a challenge. In this study, we developed a machine learning-based method to design 3D-printable bioink using a model system with naturally derived biomaterials. First, we demonstrated that atelocollagen (AC) has desirable physical properties for printing compared to native collagen (NC). AC gel exhibited weakly elastic and temperature-responsive reversible behavior forming a soft cream-like structure with low yield stress, whereas NC gel showed highly crosslinked and temperature-responsive irreversible behavior resulting in brittleness and high yield stress. Next, we discovered a universal relationship between the mechanical properties of ink and printability that is supported by machine learning: a high elastic modulus improves shape fidelity and extrusion is possible below the critical yield stress; this is supported by machine learning. Based on this relationship, we derived various formulations of naturally derived bioinks that provide high shape fidelity using multiple regression analysis. Finally, we produced a 3D construct of a cell-laden hydrogel with a framework of high shape fidelity bioink, confirming that cells are highly viable and proliferative in the 3D constructs.

Three-dimensional (3D) printing is a novel process used to manufacture bone tissue engineered scaffolds. This process allows for easy control of the architecture at the micro structure. However, the scaffold properties are typically limited in terms of cellular activity at the scaffold surface due to the printed materials properties. In this study, we developed a polycaprolactone (PCL) blended with polyethylene glycol (PEG) 3D printed scaffold using a rapid prototyping system. The manufactured scaffolds were then washed out to form small pores on the surface in order to improve the scaffolds hydrophilicity. We analyzed the resultant material by using Scanning Electron Microscopy (SEM), water absorption, water contact angle, in vitro WST-1, and the Bradford assay. Additionally, cells incubated on the fabricated scaffolds were visualized by Confocal Laser Scanning Microscopy (CLSM). The developed scaffolds exhibited small pores on the strand surface which served to increase hydrophilicity as well as improve cellular proliferation and increase total protein content. Our findings suggest that the presence of small pores on the scaffolds can be used as an effective tool for improving implant cellular interaction. This research indicates that these modified scaffolds can be considered useful for bone tissue engineering applications to improve human health.

Three-dimensional (3D) bioprinting technology is a promising new technology in the field of bioartificial organ generation with regard to overcoming the limitations of organ supply. The cell source for bioprinting is very important. Here, we generated 3D hepatic scaffold with mouse-induced hepatocyte-like cells (miHeps), and investigated whether their function was improved after transplantation in vivo. To generate miHeps, mouse embryonic fibroblasts (MEFs) were transformed with pMX retroviruses individually expressing hepatic transcription factors Hnf4a and Foxa3. After 8-10 days, MEFs formed rapidly growing hepatocyte-like colonies. For 3D bioprinting, miHeps were mixed with a 3% alginate hydrogel and extruded by nozzle pressure. After 7 days, they were transplanted into the omentum of Jo2-treated NOD Scid gamma (NSG) mice as a liver damage model. Real-time polymerase chain reaction and immunofluorescence analyses were conducted to evaluate hepatic function. The 3D bioprinted hepatic scaffold (25 × 25 mm) expressed Albumin, and ASGR1 and HNF4a expression gradually increased for 28 days in vitro. When transplanted in vivo, the cells in the hepatic scaffold grew more and exhibited higher Albumin expression than in vitro scaffold. Therefore, combining 3D bioprinting with direct conversion technology appears to be an effective option for liver therapy.

In this study, we designed scaffolds coated with gold nanoparticles (GNPs) grown on a polydopamine (PDA) coating of a three-dimensional (3D) printed polycaprolactone (PCL) scaffold. Our results demonstrated that the scaffolds developed here may represent an innovative paradigm in bone tissue engineering by inducing osteogenesis as a means of remodeling and healing bone defects.

β-tricalcium phosphate (β-TCP) and polycaprolactone (PCL) composites were manufactured using the lab-made 3D bioprinting system to produce 50TCP50PCL (50% β-TCP with 50% PCL) and 70TCP30PCL (70% β-TCP with 30% PCL) composite scaffolds for bone tissue engineering. The 70TCP30PCL scaffold containing the highest β-TCP content exhibited rougher morphologies and more porous than the other scaffolds ( i.e. , PCL and 50TCP50PCL). In vitro studies revealed that cell proliferation and alkaline phosphate activity were improved on the β-TCP-based composite scaffolds. Our results suggest that our 3-D printed β-TCP-containing PCL scaffolds would benefit new dental applications or regeneration therapies.

Cell-printing techniques that can construct three-dimensional (3D) structures with biocompatible materials and cells are of great interest for various biomedical applications, such as tissue engineering and drug-screening studies. For successful cell-printing with cells, bioinks are critical for both the processability of printing and the viability of printed cells. However, the influence of composition on 3D bio-printing with cells has not been well explored. In this study, we investigated different compositions of alginate bioinks by varying the concentrations of high molecular weight alginate (High Alg) and low molecular weight alginate (Low Alg). Bioinks of 3wt% alginate containing High Alg alone or a 1:2 (Low Alg:High Alg) composite allowed for the construction of 3D scaffolds with good processability and shapes. Cell-printing with fibroblasts and in vitro culture studies revealed good viability and growth of the printed cells after up to 7days of culture. Bioinks prepared with High and Low Alg at a 2:1 ratio exhibited better cell growth compared with those of other compositions. This study progresses the design and applications of alginate-based bioinks for cell-printing platforms in soft tissue engineering.

In this study, we designed a hybrid Ti by heparin modifying the Ti surface followed by Growth/differentiation factor-5 (GDF-5) loading. After that, products were characterized by physicochemical analysis. Quantitative analysis of functionalized groups was also confirmed. The release behavior of GDF-5 grafted samples was confirmed for up to 21days. The surface modification process was found to be successful and to effectively immobilize GDF-5 and provide for its sustained release behavior. As an in vitro test, GDF-5 loaded Ti showed significantly enhanced osteogenic differentiation with increased calcium deposition under nontoxic conditions against periodontal ligament stem cells (PDLSc). Furthermore, an in vivo result showed that GDF-5 loaded Ti had a significant influence on new bone formation in a rabbit model. These results clearly confirmed that our strategy may suggest a useful paradigm by inducing osseo-integration as a means to remodeling and healing of bone defects for restorative procedures in dentistry.

Purpose: The major problem in producing artificial livers is that primary hepatocytes cannot be cultured for many days. Recently, 3-dimensional (3D) printing technology draws attention and this technology regarded as a useful tool for current cell biology. By using the 3D bio-printing, these problems can be resolved. Methods: To generate 3D bio-printed structures (25 mm × 25 mm), cells-alginate constructs were fabricated by 3D bio-printing system. Mouse primary hepatocytes were isolated from the livers of 6–8 weeks old mice by a 2-step collagenase method. Samples of 4 × 10 7 hepatocytes with 80%–90% viability were printed with 3% alginate solution, and cultured with well-defined culture medium for primary hepatocytes. To confirm functional ability of hepatocytes cultured on 3D alginate scaffold, we conducted quantitative real-time polymerase chain reaction and immunofluorescence with hepatic marker genes. Results: Isolated primary hepatocytes were printed with alginate. The 3D printed hepatocytes remained alive for 14 days. Gene expression levels of Albumin , HNF-4α and Foxa3 were gradually increased in the 3D structures. Immunofluorescence analysis showed that the primary hepatocytes produced hepatic-specific proteins over the same period of time. Conclusion: Our research indicates that 3D bio-printing technique can be used for long-term culture of primary hepatocytes. It can therefore be used for drug screening and as a potential method of producing artificial livers.

Three-Dimensional (3D) printing technologies have been widely used in the medical sector for the production of medical assistance equipment and surgical guides, particularly 3D bio-printing that combines 3D printing technology with biocompatible materials and cells in field of tissue engineering and regenerative medicine. These additive manufacturing technologies can make patient-made production from medical image data. Thus, the application of 3D bio-printers with biocompatible materials has been increasing. Currently, 3D bio-printing technology is in the early stages of research and development but it has great potential in the fields of tissue and organ regeneration. The present paper discusses the history and types of 3D printers, the classification of 3D bio-printers, and the technology used to manufacture artificial tissues and organs.

Three-dimensional (3D) bioprinting is a free-form fabrication technique enabling fine feature control for tissue engineering applications. Especially, 3D scaffolds capable of supporting cell attachment, proliferation, and osteogenic differentiation are a prerequisite for bone tissue regeneration. Herein, we elaborated this approach to produce a 3D polycaprolactone (PCL) scaffold with long-term osteogenic activity. Specifically, we coated polydopamine (PDA) on 3D PCL scaffolds, subsequently deposited hydroxyapatite (HA) nanoparticles via biomimetic mineralization, and finally immobilized bone morphogenetic protein-2 (BMP-2). Material properties were characterized and compared with various 3D scaffolds, including PCL, PDA-coated PCL (PCL/PDA), and PDA-coated and HA-deposited PCL (PCL/PDA/HA). In vitro cell culture studies with osteoblasts revealed that the PCL/PDA/HA scaffolds immobilized with BMP-2 showed long-term retention of BMP-2 (for up to 21 days) and significantly increased osteoblast proliferation and osteogenic differentiation, as evidenced by metabolic activity, alkaline phosphatase activity, and calcium deposition. We believe that this multifunctional osteogenic 3D scaffold will be useful for bone tissue engineering applications.

This paper demonstrates a simple and cost-effective method to maintain superhydrophilicity of three-dimensional shaped aluminum fins' surface of dehumidifier over long period of time in order to improve water collection and energy efficiency. Wire-metallization, commercially available method in the ...

Background/Aims Chronic liver disease is a major widespread cause of death, and whole liver transplantation is the only definitive treatment for patients with end-stage liver diseases. However, many problems, including donor shortage, surgical complications and cost, hinder their usage. Recently, tissue-engineering technology provided a potential breakthrough for solving these problems. Three-dimensional (3D) printing technology has been used to mimic tissues and organs suitable for transplantation, but applications for the liver have been rare. Methods A 3D bioprinting system was used to construct 3D printed hepatic structures using alginate. HepG2 cells were cultured on these 3D structures for 3 weeks and examined by fluorescence microscopy, histology and immunohistochemistry. The expression of liver-specific markers was quantified on days 1, 7, 14, and 21. Results The cells grew well on the alginate scaffold, and liver-specific gene expression increased. The cells grew more extensively in 3D culture than two-dimensional culture and exhibited better structural aspects of the liver, indicating that the 3D bioprinting method recapitulates the liver architecture. Conclusions The 3D bioprinting of hepatic structures appears feasible. This technology may become a major tool and provide a bridge between basic science and the clinical challenges for regenerative medicine of the liver.

Sang Jin Lee1,2, Ha Hyeon Jo1, Seong Keun Kwon3, Jin Ho Lee4, Wan Doo Kim1, Jun Hee Lee1, Il Keun Kwon*2, and Su A Park,*,1 Department of Nature-Inspired Nanoconvergence Systems, Korea Institute of Machinery and Materials, 156 Gajeongbuk-ro, Yuseong-gu, Daejeon 34103, Korea Department of Dental Materials, School of Dentistry, Kyung Hee University, 26 Kyunghee-daero, Dongdaemun-gu, Seoul 02447, Korea Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul 03080, Korea Department of Advanced Materials, Hannam University, 1646 Yuseong-daero, Yuseong-gu, Daejeon 34054, Korea

Biomimetic artificial basilar membrane being a core part of artificial cochlear requires performance evaluationthrough aging test. To evaluate the aging properties of PVDF piezoelectric membrane used for artificial basilar membrane,its mechanical properties such as tensile strength and elastic modulus and piezoelectric property such as piezoelectric con-stant were measured. The aging test conditions and acceleration constants were calculated based on Arrhenius model. Thechanges in tensile strengths and elastic moduli measured were less than 10~20% after aging test equivalent for 10 years.The piezoelectric constants were decreased drastically to 80% of its initial value in the early stage of the aging test andexpected to decrease slowly down to 65% over 10 years. The experimental results show the reliability of totally implantablenovel artificial cochlear and will contribute its commercialization. Keywords: artificial basilar membrane, PVDF film, aging test, piezoelectricity, Arrhenius relationship

In the last decade, stent implantation therapy has been widely performed in the clinic. Although the patient's cardiovascular state depends on their age, gender, and health condition, the development of customized individual stents has been limited. Thus, a patient-specific stent manufacturing system should be devised for more successful stent therapy. In this study, we prepared a 3D printed PLA biodegradable polymeric stent using polydopamine (PDA), polyethyleneimine (PEI) and heparin (Hep) chemistry to prevent restenosis and thrombosis with anticoagulation and good blood compatibility. Physico-chemical characterization indicated that pristine PLA substrates were well modified as the amine abundant surface allowed for coating of a large amount of Hep. From in vitro and ex vivo analysis, heparinized 3D PLA stents showed excellent thromboresistance and hemocompatibility functions as well as modulation of smooth muscle cell (SMC) and endothelial cell (EC) proliferation. In an in vivo study, the heparinized 3D PLA stent showed the widest lumen area with the least neointimal hyperplasia and without atherosclerosis or thrombosis. All of these assessments clearly confirmed that our innovative strategy may suggest a useful paradigm as a preparation method for a patient-customized fully biodegradable individual stent for successful implantation therapy. This would find wide utilization for cardiovascular clinical applications.

Isolated primary hepatocytes from the liver are very similar to in vivo native liver hepatocytes, but they have the disadvantage of a limited lifespan in 2D culture. Although a sandwich culture and 3D organoids with mesenchymal stem cells (MSCs) as an attractive assistant cell source to extend lifespan can be used, it cannot fully reproduce the in vivo architecture. Moreover, long-term 3D culture leads to cell death because of hypoxic stress. Therefore, to overcome the drawback of 2D and 3D organoids, we try to use a 3D printing technique using alginate hydrogels with primary hepatocytes and MSCs. The viability of isolated hepatocytes was more than 90%, and the cells remained alive for 7 days without morphological changes in the 3D hepatic architecture with MSCs. Compared to a 2D system, the expression level of functional hepatic genes and proteins was higher for up to 7 days in the 3D hepatic architecture. These results suggest that both the 3D bio-printing technique and paracrine molecules secreted by MSCs supported long-term culture of hepatocytes without morphological changes. Thus, this technique allows for widespread expansion of cells while forming multicellular aggregates, may be applied to drug screening and could be an efficient method for developing an artificial liver.

This paper presents the development of a piezoelectric artificial cochlea (PAC) device capable of analyzing vibratory signal inputs and converting them into electrical signal outputs without an external power source by mimicking the function of human cochlea within an audible frequency range. The PAC consists of an artificial basilar membrane (ABM) part and an implantable packaged part. The packaged part provides a liquid environment through which incoming vibrations are transmitted to the membrane part. The membrane part responds to the transmitted signal, and the local area of the ABM part vibrates differently depending on its local resonant frequency. The membrane was designed to have a logarithmically varying width from 0.97 mm to 8.0 mm along the 28 mm length. By incorporating a micro-actuator in an experimental platform for the package part that mimics the function of a stapes bone in the middle ear, we created a similar experimental environment to cochlea where the human basilar membrane vibrates. The mechanical and electrical responses of fabricated PAC were measured with a laser Doppler vibrometer and a data acquisition system, and were compared with simulation results. Finally, the fabricated PAC in a biocompatible package was developed and its mechanical and electrical characteristics were measured. The experimental results shows successful frequency separation of incoming mechanical signal from micro-actuator into frequency bandwidth within the 0.4 kHz–5 kHz range.

In this study, we prepared a helical, biocompatible, and biodegradable stent by 3D rapid prototyping. The fabricated polycaprolactone (PCL) stent was coated with sirolimus mixed with poly-(lactide-co-glycolide) (PLGA), and polyethylene glycol (PEG), via a spraying method for slow drug release. The engineered, drug-eluting, bio-absorbable vascular stent (BVS) was analyzed and tested in vivo, and proving effective in animal experiments. These findings suggest that our new approach is useful for treating coronary thrombosis, and it may provide a promising scaffold for developing biological stent technology.

Recently, computer-designed three-dimensional (3D) printing techniques have emerged as an active research area with almost unlimited possibilities. In this study, we used a computer-designed 3D scaffold to drive new bone formation in a bone defect. Poly-L-lactide (PLLA) and bioactive β-tricalcium phosphate (TCP) were simply mixed to prepare ink. PLLA + TCP showed good printability from the micronozzle and solidification within few seconds, indicating that it was indeed printable ink for layer-by-layer printing. In the images, TCP on the surface of (and/or inside) PLLA in the printed PLLA + TCP scaffold looked dispersed. MG-63 cells (human osteoblastoma) adhered to and proliferated well on the printed PLLA + TCP scaffold. To assess new bone formation in vivo, the printed PLLA + TCP scaffold was implanted into a full-thickness cranial bone defect in rats. The new bone formation was monitored by microcomputed tomography and histological analysis of the in vivo PLLA + TCP scaffold with or without MG-63 cells. The bone defect was gradually spontaneously replaced with new bone tissues when we used both bioactive TCP and MG-63 cells in the PLLA scaffold. Bone formation driven by the PLLA + TCP30 scaffold with MG-63 cells was significantly greater than that in other experimental groups. Furthermore, the PLLA + TCP scaffold gradually degraded and matched well the extent of the gradual new bone formation on microcomputed tomography. In conclusion, the printed PLLA + TCP scaffold effectively supports new bone formation in a cranial bone defect.

For patients who suffer from sensorineural hearing loss by damaged or loss of hair cells in the cochlea, biomimetic artificial cochleas to remedy the dis­advantages of existing implant systems have been intensively studied. Here, a new concept of an inorganic-based piezoelectric acoustic nanosensor (iPANS) for the purpose of a biomimetic artificial hair cell to mimic the functions of the original human hair cells is introduced. A trapezoidal silicone-based membrane (SM) mimics the function of the natural basilar membrane for frequency selectivity, and a flexible iPANS is fabricated on the SM utilizing a laser lift-off technology to overcome the brittle characteristics of inorganic piezoelectric materials. The vibration amplitude vs piezoelectric sensing signals are theoretically examined based on the experimental conditions by finite element analysis. The SM is successful at separating the audible frequency range of incoming sound, vibrating distinctively according to varying locations of different sound frequencies, thus allowing iPANS to convert tiny vibration displacement of ≈15 nm into an electrical sensing output of ≈55 μV, which is close to the simulation results presented. This conceptual iPANS of flexible inorganic piezoelectric materials sheds light on the new fields of nature-inspired biomimetic systems using inherently high piezoelectric charge constants.

In this paper, a simple and low-cost fabrication method is demonstrated to make superhydrophobic and superoleophobic Aluminum (Al) surfaces. The Al surfaces have hierarchical structures mimicking the lotus leaf. The manufacturing process is easily performed via grinding, acid etching, and low surface tension chemical coating, in sequence. The wettability of the fabricated Al surfaces is characterized with several liquids having different surface tension energy such as water, diiodomethane, and hexadecane. The effects of grinding and acid etching on wettability are also investigated to enhance the superhydrophobicity and superoleophobicity of the Al surface. The grinding process makes the surface rough effectively and improves the wetting behavior. Especially, the ground sample prepared with a sandpaper of P1000 grade shows the highest static contact angle and lowest sliding angle among the fabricated samples. Even though the wetting properties are generally improved by increasing the acid etching time, the repellency of the liquids on the surface is saturated at 10min of acid etching time. The morphology difference of Al surfaces is characterized by measurement of field-emission scanning electron microscope (FE-SEM). The hierarchical micro/nanostructures combined with chemical coating enable the Al surface to be superhydrophobic and superoleophobic.

In tissue engineering, fabrication of 3D scaffolds with well-defined, inter-connected pores followed by culture of mammalian cells is a typical approach. In practice, however, hydrophobicity of scaffold surfaces is not suitable for cells to be adhered because of poor wettability. Especially, infiltration followed by adhesion of cells inside hydrophobic scaffolds remains as a challenge. Thus, hydrophilic conversions of the surfaces regardless of surface location are critical for success. Herein, a method to enhance infiltration and adhesion of preosteoblasts inside hydrophobic poly(ϵ-caprolactone) (PCL) scaffolds by a bio-inspired, hydroxyapatite formation is demonstrated. The approach can be a general method for controlling hydrophilicity of inner surfaces of scaffolds.

In this paper, we introduced various 3D printing technology and it`s application on tissue engineering and regenerative medicine. Using the 3D printing technology, Korea Institute of Machinery and Materials (KIMM) has developed 3D bio-printing system. Various 3D tissue engineered scaffolds have been fabricated by the 3D bio-printing system. Cell printing system has been also developed and it is the fundamental technology for organ regeneration in tissue engineering and regenerative medicine.

Totally implantable middle-ear prosthetic devices, such as the Esteem system (Envoy Medical Corporation), detect vibrational motion of the middle-ear ossicles rather than acoustic stimulation to the eardrum. This eliminates the need for a subcutaneous microphone, which is susceptible to interference by ambient noises. Study of the vibrational characteristics of the human ossicles provides valuable information for determining the site of maximum ossicular motion that would be optimal for attachment of the sensor portion of the prosthesis. In this study, vibrational responses at seven locations on the middle-ear ossicles (i.e., the malleus head, 4 different points on the incus body, middle of the incus long process, tip of the incus long process) in human temporal bones (n = 6) were measured using a laser Doppler vibrometer. The measurements were repeated after separating the incudostapedial joint (ISJ). Measured displacement at each location was normalized with the sound pressure level near the tympanic membrane (TM) for representation in the form of a displacement transfer function (DTF). The normalized squared sum of the DTFs (NSSDTF) was then calculated as a measure of vibration motion through a specific frequency range at the considered sites. The relatively large NSSDTF was observed at the sites on the superior part of the malleus head (MH), on the lateral part of the incus body (IBL), and on the superior part of the incus body near the incudomalleal joint (IBS1) for the frequency ranges of 1-4 kHz and 1-9 kHz, regardless of the condition of the ISJ. This indicates that maximum vibrational motion of the middle-ear is deliverable to the piezoelectric transducer of totally implantable devices through these sites. This article is part of a special issue entitled "MEMRO 2012".

Graphical abstractDisplay Omitted Highlights? Single conducting polymer nanowire is fabricated directly on the device platform. ? Facile method provids the controlled position, width, and length of nanowire. ? Nanowire is electrochemically deposited on the nanopatterned area of electrode. ? Polypyrrole nanowire based field effect transistor is successfully established. In this paper, a facile method by which conducting polymer nanowire can be fabricated directly on the device platform in controlled position, width, and length is proposed. Conducting polymer was electrochemically deposited on the nanopatterned area of a working electrode. The shape and position of the nanowire, in particular the length of the nanowire can be easily controlled by modulation of the nanopatterned area via lithography method. Through the proposed fabrication method, a polypyrrole nanowire based field effect transistor was successfully established. This fabrication design provides an easy way to manufacture the conducting polymer nanowire based devices in controlled manner, and the devices are suitable for application in chemical and biological sensors as well as organic electronics.

Rubber components have been widely used in automotive industry as anti-vibration components for many years. These subjected to fluctuating loads, often fail due to the nucleation and growth of defects or cracks. To prevent such failures, it is necessary to understand the fatigue failure mechanism for rubber materials and to evaluate the fatigue life for rubber components. The objective of this study is to develop the durability analysis process for vulcanized rubber components, which is applicable to predict fatigue life at initial product design step. The determination method of nonlinear material constants for FE analysis was proposed. In order to investigate the applicability of the commonly used damage parameters, fatigue tests and corresponding finite element analyses were carried out and strain energy density was proposed as the fatigue damage parameter for rubber components. The fatigue analysis for automotive rubber components was performed and the durability analysis process was reviewed.

：The fatigue analysis and lifetime evaluation are very important in design procedure to assure the safety andreliability of the rubber components. Recently, the design, analysis and evaluation technology was required to achieve thehigh quality, fidelity, reliability of rubber products. However, rubber manufacturing companies of our country have uesd the method of trial and error and experience in the process of a compound mixing, manufacturing and improvement ofrubber properties. The objectives of this study are to establish the test methods of rubber material and to make the databaseof rubber material properties and to evaluate the performance of rubber components and to construct the prediction systemof fatigue life. Fatigue lifetime prediction methodology of the rubber component was proposed by incorporating the finite element analysis and fatigue damage parameter from fatigue test. Keywords ： automotive rubber component, mechanical property, finite element analysis, fatigue test, database integrateddesign

The basilar membrane (BM), one of organs of cochlea, has the specific positions of the maximum amplitude at each of related frequencies. This phenomenon is due to the geometry of BM. In this study, as the part of the research for the development of fully implantable artificial cochlea which is based on polymer membrane, parametric studies are performed to suggest the desirable artificial basilar membrane model which can detect wider range of frequency separation. The vibro-acoustic characteristics of the artificial basilar membrane are predicted through finite element analysis using commercial software Abaqus. Simulation results are verified by comparing with experimental results. Various geometric shapes of the BM and residual stress effects on the BM are investigated through the parametric study to enable a wider detectable frequency separation range.