Soft Mold Research Articles

Rapid fabrication of highly integrated and high numerical aperture chalcogenide glass microlens arrays

The fast growing of infrared imaging system for non-contact thermography, night surveillance and night driving assistance demands highly integrated optical lenses with miniaturization feature for performance improvement. Herein, we fabricated refractive type of microlens arrays (MLAs) with high numerical aperture (NA) and high integration on commercial chalcogenide glass (As2Se3) by combining photoresist thermal reflow and soft mold imprinting process. PDMS-type concave MLAs (PDMS-MLAs) soft mold is prepared by transfer printing process on photoresist (PR) MLAs fabricated by standard UV exposure and thermal reflow. The microlens on PDMS-MLAs could be further transferred to the surface of As2Se3 glass through the hot imprinting technique, forming chalcogenide glass-based MLAs (ChG-MLAs). Morphology detection reveals that microlens in the MLAs has an average aperture and sag height of approximately 13.4 and 1.7 μm. Moreover, the optical performance investigation demonstrated that the ChG-MLAs with 700 × 700 array size (10.5 × 10.5 mm) showed good structure uniformity and focusing capability, and through the FDTD simulation, it further evidenced that focal lengths of 6.3–8.1 µm with high numerical aperture of 0.64–0.73 (wavelength range: 3–5 μm) was achieved.

Cut-Off UV Light Filter to Prevent the Negative Slope of the Soft Lithography Hard Mold Walls

Cut-Off UV Light Filter to Prevent the Negative Slope of the Soft Lithography Hard Mold Walls

Laparoscopic Vaginoplasty by Peritoneal Pull through Technique

<h3>Study Objective</h3> Laparoscopic management of MRKH syndrome and use of near ideal vaginal mold made up from locally readily available materials in a rural settings. <h3>Design</h3> Laparoscopic surgery in a diagnosed case of MRKH syndrome and follow up for 1 year and parameter which analysed were 1. Ability to perform sexual intercourse by the couple 2. Pain while using vaginal mold 3. Vaginal length at 6 months and 1 year. <h3>Setting</h3> Semi lithotomy position. <h3>Patients or Participants</h3> A diagnosed case of MRalH syndrome. <h3>Interventions</h3> Laparoscopic surgery and use of special vaginal mold for 6 weeks. <h3>Measurements and Main Results</h3> Vaginal length achieved was 7 to 8 cm, couple found to be performing sexual intercourse satisfactorily, vaginoscopy after 6 weeks showed good epithelization. <h3>Conclusion</h3> 1. Use of soft vaginal mold is associated with lesser pain, and 2. Laparoscopic Peritoneal pull through technique has satisfactory results with apt vaginal length.

Polymeric Microfluidic Devices Fabricated Using Epoxy Resin for Chemically Demanding and Day-Long Experiments.

Polydimethylsiloxane (PDMS) is a widely used material in laboratories for fabricating microfluidic devices with a rapid and reproducible prototypingability, owing to its inherent properties (e.g., flexibility, air permeability, and transparency). However, the PDMS channel is easily deformed under pressures applied to generate flows because of its elasticity, which can affect the robustness of experiments. In addition, air permeability of PDMS causes the pervaporation of water, and its porous structure absorbs oil and even small hydrophobic molecules, rendering it inappropriate for chemically demanding or day-long experiments. In this study, we develop a rapid and reproducible fabrication method for polymer-based rigid microfluidic devices, using epoxy resin that can overcome the limitations of PDMS channels, which are structurally and chemically robust. We first optimize a high-resolution fabrication protocol to achieve convenient and repeatable prototyping of polymeric devices via epoxy casting using PDMS soft molds. In addition, we compare the velocity changes in PDMS microchannels by tracking fluorescent particles in various flows (~133 μL/min) to demonstrate the structural robustness of the polymeric device. Furthermore, by comparing the adsorption of fluorescent hydrophobic chemicals and the pervaporation through channel walls, we demonstrate the excellent chemical resistance of the polymeric device and its suitability for day-long experiments. The rigid polymeric device can facilitate lab-on-chip research and enable various applications, such as high-performance liquid chromatography, anaerobic bacterial culture, and polymerase chain reaction, which require chemically or physically demanding experiments.

Soft Molds with Micro-Machined Internal Skeletons Improve Robustness of Flapping-Wing Robots.

Mobile millimeter and centimeter scale robots often use smart composite manufacturing (SCM) for the construction of body components and mechanisms. The fabrication of SCM mechanisms requires laser machining and laminating flexible, adhesive, and structural materials into small-scale hinges, transmissions, and, ultimately, wings or legs. However, a fundamental limitation of SCM components is the plastic deformation and failure of flexures. In this work, we demonstrate that encasing SCM components in a soft silicone mold dramatically improves the durability of SCM flexure hinges and provides robustness to SCM components. We demonstrate this advance in the design of a flapping-wing robot that uses an underactuated compliant transmission fabricated with an inner SCM skeleton and exterior silicone mold. The transmission design is optimized to achieve desired wingstroke requirements and to allow for independent motion of each wing. We validate these design choices in bench-top tests, measuring transmission compliance, kinematics, and fatigue. We integrate the transmission with laminate wings and two types of actuation, demonstrating elastic energy exchange and limited lift-off capabilities. Lastly, we tested collision mitigation through flapping-wing experiments that obstructed the motion of a wing. These experiments demonstrate that an underactuated compliant transmission can provide resilience and robustness to flapping-wing robots.

Wetting of Superhydrophobic Polylactic Acid Micropillared Patterns.

Superhydrophobic (SH) polylactic acid (PLA) surfaces were previously produced by various methods and used especially in biomedical applications and oil/water separation processes after 2008. However, the wettability of SH-PLA patterns containing micropillars has not been investigated before. In this study, PLA patterns having regular microstructured pillars with 12 different pillar diameters and pillar-to-pillar distances were prepared by hot pressing pre-flattened PLA sheets onto preformed polydimethylsiloxane (PDMS) soft molds having micro-sized pits. PDMS templates were previously prepared by photolithography using SU-8 molds. Apparent, advancing, and receding water contact angle measurements were carried out on the PLA patterns containing micropillars, and the morphology of the patterns was examined by optical and SEM microscopy. The largest contact angle obtained without the surface modification of the pure PLA pattern was 139°. Then, PLA micropatterns were hydrophobized using three types of silanes via chemical vapor deposition method, and SH-PLA patterns were obtained having θs of up to 167°. It was found that the highest θ values could be obtained when PLA pattern samples were coated with a silane containing a fluorine atom in its chemical structure. Washing and service life stability tests were also performed on the coated pattern samples and all of the silane coatings on the PLA patterns were found to be resistant over a 6 month period.

Ultrawide meta-film replication process for the mass production of a flexible microwave absorbing meta-surface.

The manufacturing process for an ultrawide flexible microwave absorbing meta-surface was developed and optimized experimentally. The developed replication process consists of four main steps to demonstrate double-square loop array meta-structures: (1) mechanical machining of a master mold, (2) soft mold replication and patterned film imprinting, (3) conductive ink blade filling, (4) lamination of a base flexible film to meta sheet. Based on experimental optimization of the individual steps, the manufacturing process for a large-area flexible meta-film was established successfully. The feasibility of a developed process has been demonstrated with a 200 mm × 500 mm fabricated meta-film with a focus on microwave absorbing uniformity in the X-band region.

Fabrication and testing of polymer microneedles for transdermal drug delivery.

Microneedle (MN) patches have considerable potential for medical applications such as transdermal drug delivery, point-of-care diagnostics, and vaccination. These miniature microdevices should successfully pierce the skin tissues while having enough stiffness to withstand the forces imposed by penetration. Developing low-cost and simple manufacturing processes for MNs is of considerable interest. This study reports a simple fabrication process for thermoplastic MNs from cycloolefin polymers (COP) using hot embossing on polydimethylsiloxane (PDMS) soft molds. COP has gained interest due to its high molding performance and low cost. The resin master MN arrays (9 × 9) were fabricated using two-photon polymerization (TPP). A previous gap in the detailed characterization of the embossing process was investigated, showing an average of 4.99 ± 0.35% longitudinal shrinkage and 2.15 ± 0.96% lateral enlargement in the molded MN replicas. The effects of bending, buckling, and tip blunting were then examined using compression tests and also theoretically. MN array insertion performance was studied in vitro on porcine back skin using both a prototype custom-made applicator and a commercial device. An adjustable skin stretcher mechanism was designed and manufactured to address current limitations for mimicking skin in vivo conditions. Finite element analysis (FEA) was developed to simulate single MN insertion into a multilayered skin model and validated experimentally using a commercial Pen Needle as a model for the thermoplastic MNs. Margins of safety for the current MN design demonstrated its potential for transdermal drug delivery and fluid sampling. Experimental results indicated significant penetration improvements using the prototype applicator, which produced array penetration efficiencies as high as >92%, depending on the impact velocity setting.

Design and Manufacture of a Flexible Pneumatic Soft Gripper

The soft robot has many degrees of freedom, strong environmental adaptability, and good human–computer interaction ability. As the end-effector of the soft robot, the soft gripper can grasp objects of different shapes without destructivity. Based on the theoretical analysis of the soft robot, the kinematics model of the flexible gripper and the theoretical model of the bending deformation of the air cavity were established. Accordingly, the relationship between the bending angle of the soft gripper and the air pressure was determined. Through the application of finite element software, the bending degree of the pneumatic network multi-cavity soft gripper was simulated, and the influence of structural parameters of soft actuator on bending deformation was determined. In addition, the 3D technology conducts the printing of soft gripper fixtures and molds, the injection molds the actuator, and the human–computer interaction interface controls the movement of the gripper. This paper proposes the control and monitoring of the soft gripper are realized through the electrical control module, the air circuit control module, and the sensor group module, and the size of the airflow velocity can be controlled by PWM DC speed regulation. The adaptability of the soft gripper in grasping objects was verified. The results shows that the software gripper possesses good flexibility and can better grasp objects of different shapes.

Facile fabrication of stretchable photonic Ag nanostructures by soft-contact patterning of ionic Ag solution coatings

Abstract We describe a rapid and simple method to create Ag nanostructures by using direct mechanical patterning of ionic Ag ink coating under gentle pressure, then thermal annealing to reduce the ionic Ag ink to a metallic Ag layer. The ionic liquid-phase Ag coating is easily obtained by spin-coating ionic Ag ink that has appropriate Ag concentration and can be either printed or imprinted on the desired substrate by using a soft elastomer patterning mold, then reduced to the Ag nanostructure by subsequent thermal annealing. More specifically, we present two methods: transfer printing and soft nanoimprinting. In transfer printing, the ionic Ag ink is first inked onto the elastomer mold which then contacts the target substrate to transfer the Ag nanopattern. In soft nanoimprinting, the elastomer mold conducts soft imprinting to engineer the ionic Ag ink coating to the Ag nanostructure. We systematically investigate the optimal patterning conditions by controlling the initial Ag ink concentration and the coating, printing, imprinting, and annealing conditions, to derive Ag architecture that has tunable photonic functionality. As an example, we demonstrate polarization-sensitive reflective color filters that exploit shape-tunable Ag nanostructures fabricated by soft nanoimprinting using a controllably-stretched elastomer mold.

Morphological Control: Properties and Applications of Metal Nanostructures

Metal nanomaterials with special physicochemical and plasmatic properties have a wide range of applications in various fields including catalysts, plasmon devices, spectroscopy, fuel cell, and various sensors including chemical, colorimetric, and fluorescence sensors. These applications are made possible by controlling the morphology and properties of nanostructures and increasing their selectivity. Various methods have been developed for the synthesis of metal nanostructures, including the use of prefabricated patterns or hard templates such as anodic aluminum oxide and soft molds such as cetyltrimethylammonium bromide (CTAB).

Fabrication of 1–3 piezoelectric composites via modified soft mold process for 40 MHz ultrasonic medical transducers

High performance 1–3 piezocomposites are important components of high-frequency ultrasound transducers, which are used for the medical imaging of fine structures in human tissues. In this study, a modified soft mold process was developed for the fabrication of lead zirconate titanate (PZT) ceramic 1–3 piezocomposites by compressing soft mold with powder. First, the piezocomposite structures were designed and optimized for high-frequency applications at 40 MHz via finite element analysis (FEA). Then, 1–3 piezocomposites were fabricated through a soft mold process, with PZT pillars as small as 25 μm in diameter. The morphology, phase composition, homogeneity, and microstructure of the obtained 1–3 piezocomposites were investigated using SEM, XRD and Raman spectroscopy analyses. The dielectric, piezoelectric, and acoustic properties of the 1–3 piezocomposites were measured to verify the efficacy of the soft mold technology. The present work introduces an effective and cost-effective strategy for fabricating 1–3 piezocomposites with excellent electromechanical performance for high-frequency transducers, which can be used in the fields of medical imaging and ultrasound biomicroscopy.

Отсекающий УФ-светофильтр для предотвращения отрицательного наклона стенок мастер-штампа мягкой литографии

The general-purpose polymers formation issues are solved using micro- and nanoelectronic technologies of new generation, for example a nanoimprint lithography. One of its subspecies, soft lithography, includes topology formation using soft master die fabricated by hard mold imprint. Therefore, engineering study of possibility of hard molds self-dependent fabrication for the purposes of optoelectronic data bus formation for new generation printed circuit boards using general-purpose polymer materials is a priority. In this work, to rationalize the purchasing cost of an expensive hard mold of soft lithography, an original technological process for a hard mold fabrication based on the SU-8 photoresist has been developed and implemented. During the performing of the proposed technological process, the reason for the negative slope (T-topping) formation of soft lithography hard mold walls made of SU-8 photoresist was determined. A series of cut-off UV filters for optical wavelengths less than 350 nm has been developed and fabricated to eliminate T-topping. Based on the UV radiation intensity experimental measurements data from the i-line mercury lamp of the automated alignment and exposure system EVG620 NT, the UV radiation intensity attenuation dependences on the functional layer thickness of the developed optical UV filter for 365 and 400 nm wavelengths are plotted. The developed UV filters application effectiveness has been proven due to T-topping elimination during the technological process of producing the soft lithography hard mold test topology. The use of soft lithography will make it possible in the future to create a new generation printed circuit boards with a built-in optoelectronic data bus in the form of a polymer planar optical waveguides array and optical input / output elements.

Induction heating ferromagnetic particles embedded PDMS mold for microstructure embossing

Polydimethylsiloxane (PDMS) is an excellent soft mold material with the advantages of precise replication, easy demolding, and low production cost. However, the strength and hardness of PDMS are relatively low, and PDMS cannot be directly inductively heated. In this study, PDMS is embedded with ferromagnetic powders to increase its hardness and make it heatable. Direct induction heating of the PDMS mold can raise its inherent temperature, increase the heating efficiency by 100% compared with pure PDMS, and improve the shortcomings of uneven surface temperature distribution from high thermal resistance. Furthermore, adding the ferromagnetic metal powder to PDMS can improve its conductivity and make the mold a high-low surface temperature gap as low as 1.6 °C. Adding nickel powder to the PDMS mold makes the hardness 2.29 times higher than that of pure PDMS and can withstand a pressure of 7 kg cm−2, which is very conducive to hot embossing. This study used a self-designed five-sided cladding iron block base and a PDMS mold with ferromagnetic metal powder for hot embossing. This heating apparatus can quickly raise the PDMS surface temperature and emboss deep V-groove microstructures on the polycarbonate (PC) film; the replication performance can reach more than 97%.

Automated vision-based inspection of mould and part quality in soft tooling injection moulding using imaging and deep learning

Automated real time quality monitoring is one of the key enablers for future high-speed production. In this research, an in-process monitoring procedure based on computer vision inspection and deep learning is proposed to indicate the tool and part quality during soft tooling injection moulding. Multiple types of injection moulding defects can be detected by the proposed method. Geometrical dimensions of the part can be measured simultaneously and the uncertainty can be quantified. Based on the obtained data, automated quality evaluation can be achieved in-process and a decision signal can be sent back to the injection moulding system for process adjustment.

Effect of Soft Mould Pressing on Thermal &amp; Mechanical Anisotropy of the Graphitic Matrix Spheres

Effect of Soft Mould Pressing on Thermal &amp; Mechanical Anisotropy of the Graphitic Matrix Spheres

Fabrication of 1-3 Piezocomposites via Soft Mold Method for High-frequency Ultrasound Transducer

Fabrication of 1-3 Piezocomposites <i>via </i>Soft Mold Method for High-frequency Ultrasound Transducer

Soft Tissue Molding as a Nonsurgical Adjunct in the Treatment of Nasal Deformities

Soft Tissue Molding as a Nonsurgical Adjunct in the Treatment of Nasal Deformities

A MEMS-based electromagnetic membrane actuator utilizing bonded magnets with large displacement

In a previous study, microfabricated bonded magnets have been utilized in MEMS-based electromagnetic membrane actuators (EMMAs) to drive micropumps. However, to maintain the flexibility of the membrane the packing density of the spin-coated bonded magnets needed to be small (6 vol%) and this together with a strong self-demagnetization effect meant that the force generated was weak. As a result, the maximum displacement achieved was only several microns. To overcome this problem, we proposed fabricating bonded magnets using micro compression molding with a soft membrane mold in order to realize both a high packing density and a flexible membrane. The grooves (0.3 mm × 5 mm × t0.3 mm) in the PDMS membrane were filled with a mixture of NdFeB magnetic powder and wax powder. A packing density of 50 vol% for the bonded magnets was realized without undue influence on the flexibility of the membrane. A fine-pitch magnetization pattern was also used to decrease the self-demagnetization effect and thereby improve actuator performance. The experimental results show that the maximum force generated and the maximum displacement achieved using the fabricated EMMAs (12 mm × 12 mm × t1.1 mm) were 2.2 mN and 100 μm, respectively, at the power consumption of 4 W.

Soft Tooling-Friendly Inductive Mold Heating-A Novel Concept.

In order to economize injection molded prototypes, additive manufacturing of, e.g., curable plastics based tools, can be employed, which is known as soft tooling. However, one disadvantage of such tools is that the variothermal process, which is needed to produce polymeric parts with small features, can lead to a shorter lifespan of the tooling due to its thermally impaired material properties. Here, a novel concept is proposed, which allows to locally heat the mold cavity via induction to circumvent the thermal impairment of the tooling material. The developed fabrication process consists of additive manufacturing of the tooling, PVD coating the mold cavity with an adhesion promoting layer and a seed layer, electroplating of a ferromagnetic metal layer, and finally patterning the metal layer via laser ablation to enhance the quality and efficiency of the energy transfer as well as the longevity by geometric measures. This process chain is investigated on 2D test specimens to find suitable fabrication parameters, backed by adhesion tests as well as environmental and induction tests. The results of these investigations serve as proof of concept and form the base for the investigation of such induction layers in actual soft tooling cavities.