Sacrificial Core Research Articles

Green synthesis of sacrificial UV-sensitive core and biobased shell for obtaining optically hollow nanoparticles

Hollow nanoparticles have been extensively studied in recent years. Obtaining such structures with biobased materials, following greener synthetic routes, is still challenging, especially if accurate particle dimensions are required. This work reports the use of an innovative hybrid silica core (Si@azo) containing UV-sensitive molecule, wrapped in biobased multilayer shell composed of polysaccharides. It is a promising strategy for obtaining optically hollow nanoparticles. Indeed, Si@azo cores have the ability to be partially degraded when irradiated with UV light. Combined with a well-controlled and monodisperse diameter, they provide a good basis for layer-by-layer assembly, leading to a multilayer shell with controlled composition and thickness. Finally, UV irradiation of such a core–shell structure is harmless to the polysaccharide shell, but does impact the hybrid silica core, as revealed by turbidity measurements, among other. Each step, i.e. core synthesis, shell addition, and core–shell irradiation, has been carefully characterized at the macro (Fourier-transform infrared spectroscopy – FTIR, Dynamic Light Scattering – DLS, Zeta-potential measurement, Surface Plasmon Resonance – SPR, turbidity) and microscale (Transmission and Scanning Electron Microscopies). Emphasis is put on how turbidity measurements can be related to the core refractive index (ncore), giving information on the state of core degradation and whether the core–shell particle is optically hollow.

A Dynamic Ultrasound Phantom with Tissue-Mimicking Mechanical and Acoustic Properties.

Tissue-mimicking phantoms are valuable tools that aid in improving the equipment and training available to medical professionals. However, current phantoms possess limited utility due to their inability to precisely simulate multiple physical properties simultaneously, which is crucial for achieving a system understanding of dynamic human tissues. In this work, novel materials design and fabrication processes to produce various tissue-mimicking materials (TMMs) for skin, adipose, muscle, and soft tissue at a human scale are developed. Target properties (Young's modulus, density, speed of sound, and acoustic attenuation) are first definedfor each TMM based on literature. Each TMM recipe is developed, associated mechanical and acoustic properties are characterized, and the TMMs are confirmed to have comparable mechanical and acoustic properties with the corresponding human tissues. Furthermore, a novel sacrificial core to fabricate a hollow, ellipsoid-shaped bladder phantom complete with inlet and outlet tubes, which allow liquids to flow through and expand this phantom, is adopted. This dynamic bladder phantom with realistic mechanical and acoustic properties to human tissues in combination with the developed skin, soft tissue, and subcutaneous adipose tissue TMMs, culminates in a human scale torso tank and electro-mechanical system that can be systematically utilized for characterizing various medical imaging devices.

Integrated Design and Fabrication of Pneumatic Soft Robot Actuators in a Single Casting Step.

Bio-inspired soft robots have already shown the ability to handle uncertainty and adapt to unstructured environments. However, their availability is partially restricted by time-consuming, costly, and highly supervised design-fabrication processes, often based on resource-intensive iterative workflows. Here, we propose an integrated approach targeting the design and fabrication of pneumatic soft actuators in a single casting step. Molds and sacrificial water-soluble hollow cores are printed using fused filament fabrication. A heated water circuit accelerates the dissolution of the core's material and guarantees its complete removal from the actuator walls, while the actuator's mechanical operability is defined through finite element analysis. This enables the fabrication of actuators with non-uniform cross-sections under minimal supervision, thereby reducing the number of iterations necessary during the design and fabrication processes. Three actuators capable of bending and linear motion were designed, fabricated, integrated, and demonstrated as 3 different bio-inspired soft robots, an earthworm-inspired robot, a 4-legged robot, and a robotic gripper. We demonstrate the availability, versatility, and effectiveness of the proposed methods, contributing to accelerating the design and fabrication of soft robots. This study represents a step toward increasing the accessibility of soft robots to people at a lower cost.

Formulation and Biodegradation of Surface-Supported Biopolymer-Based Microgels Formed via Hard Templating onto Vaterite CaCO3 Crystals.

In recent decades, there has been increased attention to the role of layer-by-layer assembled bio-polymer 3D structures (capsules, beads, and microgels) for biomedical applications. Such free-standing multilayer structures are formed via hard templating onto sacrificial cores such as vaterite CaCO3 crystals. Immobilization of these structures onto solid surfaces (e.g., implants and catheters) opens the way for the formulation of advanced bio-coating with a patterned surface. However, the immobilization step is challenging. Multiple approaches based mainly on covalent binding have been developed to localize these multilayer 3D structures at the surface. This work reports a novel strategy to formulate multilayer surface-supported microgels (ss-MG) directly on the surface via hard templating onto ss-CaCO3 pre-grown onto the surface via the direct mixing of Na2CO3 and CaCl2 precursor solutions. ss-MGs were fabricated using biopolymers: polylysine (PLL) as polycation and three polyanions-hyaluronic acid (HA), heparin sulfate (HS), and alginate (ALG). ss-MG biodegradation was examined by employing the enzyme trypsin. Our studies indicate that the adhesion of the ss-MG to the surface and its formation yield directly correlate with the mobility of biopolymers in the ss-MG, which decreases in the sequence of ALG > HA > HS-based ss-MGs. The adhesion of HS-based ss-MGs is only possible via heating during their formation. Dextran-loading increases ss-MG formation yield while reducing ss-MG shrinking. ss-MGs with higher polymer mobility possess slower biodegradation rates, which is likely due to diffusion limitations for the enzyme in more compact annealed ss-MGs. These findings provide valuable insights into the mechanisms underlying the formation and biodegradation of surface-supported biopolymer structures.

Low-cost prototyping of nitinol wires/frames using polymeric cores and sacrificial fixtures with application in individualized frames anchoring through the atrial septum

Self-expanding frames for minimally invasive implants are typically made from nitinol wires and are heat treated to maintain the desired shapes. In the process of heat treatment, nitinol structures are placed in a high-temperature oven, while they are confined by a fixture. During this process, nitinol exerts a high amount of force. Accordingly, a fixture requires high mechanical strength and temperature resistance; this is why fixtures are typically made from metals. The use of metal fixture also increases the turnaround time and cost. However, accelerating this process is beneficial in many applications, such as rapid development of medical implants that are patient-specific. Inspired by the use of sacrificial layers in microfabrication technology, here we propose a novel method for shape setting nitinol wires using a sacrificial metal fixture. In this process, the nitinol wires are first aligned inside copper hypotubes. Next, the forming process is done using hand-held tools to shape complex geometrical structures, annealing the nitinol reinforced by copper, and then selectively etching copper hypotubes in ammonium persulfate solutions. In this process, other sacrificial cores, which are 3D printed or cast from low-cost polymers, are also used. This combination of polymeric cores and minimal use of metals enables reducing the cost and the turnaround time. As a proof of concept, we showed that this process was capable of fabricating springs with mm or sub-mm diameters. The result showed a change of less than 5% in the intended diameter of the nitinol spring with diameters ranging from ~ 0.7 to 1.9 mm, which confirms copper as a suitable sacrificial fixture to obtain the desired complex geometry for nitinol. A metric, based on the elastic strain stored in copper is suggested to predict the possible variation of the intended dimensions in this process. Finally, to demonstrate the potential of this method, as proof of concept, we fabricated NiTi wire frames designed for anchoring through the atrial septum. These frames demonstrated septal defect occluders that were designed based on a patient’s cardiac image available in the public domain. This low-cost rapid fabrication technique is highly beneficial for a variety of applications in engineering and medicine with specific applications in rapid prototyping of medical implants.

Development of lumen-based perfusable 3D liver in vitro model using single-step bioprinting with composite bioinks.

Hepatic sinusoids are uniquely organized structures that help maintain a spectrum of hepatic functions. Although several in vitro liver models have been developed to replicate liver sinusoids, most of these platforms require complex, multi-step fabrication methods making it difficult to achieve truly three-dimensional (3D) channel geometries. In this study, a single-step bioprinting technique was demonstrated to simultaneously print a chip platform and develop a perfusable vascularized liver sinusoid in vitro model. The integrated system uses a co-axial-based bioprinting approach to develop a liver sinusoid-like model that consists of a sacrificial core compartment containing a perfusable pre-vascular structure and an alginate-collagen-based shell compartment containing hepatocytes. The lumen-based perfusable 3D liver sinusoid-on-a-chip (LSOC-P) demonstrated significantly better hepatocyte viability, proliferation, and liver-specific gene and protein expression compared to a 3D hepatocyte-based core/shell model with static media and the standard hepatocyte-based 2D sandwich culture system. A drug toxicity evaluation of hepatotoxins highlighted the comparatively higher sensitivity of the LSOC system with a close estimation of the therapeutic range of safe drug concentrations for humans. In conclusion, the current findings indicate that the combinatorial single-step co-axial bioprinting technique is a promising fabrication approach for the development of a perfusable LSOC platform for drug screening applications.

Structure of swollen hollow polyelectrolyte nanogels with inhomogeneous cross-link distribution

Hypothesis: Recently, it has become possible to synthesize hollow polyelectrolyte nano- and microgels. The shell permeability can be controlled by external stimuli, while the cavity can serve as a storage place for guest molecules. However, there is a lack of a detailed understanding at the molecular level regarding the role of the network topology, inhomogeneities of the distribution of cross-links, and the impact of the electrostatics on the structural response of hollow microgel to external stimuli. To bridge these gaps, molecular dynamics (MD) of computer simulations are used.Experiments: Here, we propose a fresh methodology to create realistic hollow microgel particles in silico. The technique involves a gradual change in the average local length of subchains depending on the distance to the center of mass of the microgel particles resulting in the microgels with a non-uniform distribution of cross-linking species. In particular, a series of microgels with (i) a highly cross-linked inner part of the shell and gradually decreased cross-linker concentration towards the periphery, (ii) microgels with loosely cross-linked inner and outer parts, as well as (iii) microgels with a more-or-less homogeneous structure, have been created and validated. Counterions and salt ions are taken into account explicitly, and electrostatic interactions are described by the Coulomb potential.Findings: Our studies reveal a strong dependence of the microgel swelling response on the network topology. Simple redistribution of cross-links plays a significant role in the structure of the microgels, including cavity size, microgel size, fuzziness, and extension of the inner and outer parts of the microgels. Our results indicate the possibilities of qualitative justification of the structure of the hollow microgels in the experiments by measuring the relative change in the size of the sacrificial core to the size of the cavity and by estimation of a power law function, RH∼csα, of the hydrodynamic radius of the hollow microgels as a function of added salt concentration.

A novel self-activation strategy for designing oxygen vacancies-rich nickel ferrite and cobalt ferrite microspheres with large specific surface area for overall water splitting

Nickel ferrite (NFO) and cobalt ferrite (CFO) have been explored as promising electrocatalysts for overall water splitting in virtue of unique characteristics. However, the poor intrinsic conductivity and the limited active sites of NFO and CFO give rise to sluggish charge transfer dynamics. It is the general approach that the target products implemented as shell are tightly wrapped on the sacrificial core of silicon dioxide (SiO2) to design the hollow/porous electrode materials, while employing SiO2 as sacrificial shell could be a novel method to improve the specific surface area (SSA) of NFO and CFO. Herein, the porous nickel ferrite (P–NFO (VO)) and cobalt ferrite (P-CFO (VO)) microspheres with rich oxygen vacancies and enhanced SSA are reported through the novel self-activation treatment along with reduction process. The simultaneous formation of rich pore channels and oxygen vacancies could expose numerous active sites, optimize electronic configuration, and boost charge transfer. As expected, the elaborately designed P–NFO (VO) and P-CFO (VO) microspheres achieve excellent achievement for HER with low overpotentials (102.9 and 100.7 mV) and relatively small Tafel slopes (45.2 and 60.1 mV/dec), respectively. Beyond that, P–NFO (VO) and P-CFO (VO) microspheres deliver favorable overpotentials of 336.3 and 384.2 mV at 10 mA/cm2 for OER, respectively, which is highly considerable to transition metal oxide-based electrocatalysts. Overall, the versatile strategy could be employed to construct other transition metal oxides with superior electrochemical properties.

A Water-Soluble Core for Manufacturing Hollow Injection-Molded Products.

To manufacture a complicated hollow product without any assembly process, for example, the plastic intake manifold, is difficult by the traditional injection molding method. The fusible-core technique, which uses a low-melting-point alloy as a sacrificial core, was developed to solve this problem; however, the limited selection of resin type and the huge capital investment have caused this technique to spread slowly. In this work, a novel method is established that can produce similar products without the limitation of resin type, as well as a lower-energy-consumption process. The concept of the enveloped core defined by a water-soluble core assembled with a shell is proposed herein; it provides both rigidity and toughness to resist the pressure during the injection molding process. The shape of the enveloped core equals the internal contour of the designated product. An insert molding process was introduced to cover the enveloped core with a skin layer. Cut out the end of the enveloped core and immerse it into a water bath. When the water-soluble core inside the shell is dissolved, the product with a special internal contour is accomplished. A tee-joint is presented to demonstrate how the proposed method can be utilized. The optimal ingredient of the core and processing parameters are determined by the Taguchi method. The result shows that the proposed product is molded successfully when the compressive strength of the core is larger than 2 MPa. In addition, the eccentricity measurement of internal contour of the optimal sample exhibits a 56% improvement, and the required time for the core removal is less than 154 s.

Inverted design of oxygen vacancies modulated NiCo2O4 and Co3O4 microspheres with superior specific surface area as competitive bifunctional materials for supercapacitor and hydrogen evolution reaction

NiCo2O4 and Co3O4 have been explored as promising candidates for supercapacitor (SCs) and hydrogen evolution reaction (HER) featured with unique physical and chemical characteristics. However, they suffer from sluggish electrons transfer accompanied by poor active sites. It is the common way that silicon dioxide (SiO2) engaged as a sacrificial core could be tightly wrapped by a shell to prepare the hollow/porous target products with satisfying specific surface area. But to reversely think it, using SiO2 as sacrificial shell could be another way to unlock the bottleneck of NiCo2O4 and Co3O4 in this direction. Herein, a facile encapsulated self-activation strategy coupled with partial reduction method is described to construct order mesoporous NiCo2O4 and Co3O4 microspheres with oxygen vacancies modulation (SA-NiCo2O4 (Ov) and SA-Co3O4 (Ov)), respectively. The specific surface area of SA-NiCo2O4 (Ov) and SA-Co3O4 (Ov) microspheres is significantly increased by a factor of three after introducing encapsulated self-activation strategy, respectively. The superior specific surface area could provide numerous electroactive sites and large electrode/electrolyte interfaces for fast ions diffusion and redox reaction. The oxygen vacancies could offer favorable conductivity and boost ions diffusion. In virtue of intrinsic characteristics and structural advantage, SA-NiCo2O4 (Ov) and SA-Co3O4 (Ov) demonstrate decent specific capacitance (448.2 C/g and 375.3 C/g), and the corresponding asymmetrical devices deliver favorable energy density (31.2 Wh/kg and 29.4 Wh/kg), respectively. Furthermore, SA-NiCo2O4 (Ov) and SA-Co3O4 (Ov) could efficiently catalyze HER with a low overpotential of 141.1 mV and 155.6 mV at 10 mA/cm2 and confirm beneficial dynamics, respectively. This present strategy of using self-activation and oxygen-vacancies to enhance electrochemical properties may open up new opportunities for developing high-performance metal oxide catalysts/electrodes for energy conversion and storage.

Hollow Gold Nanosphere Templated Synthesis of PEGylated Hollow Gold Nanostars and Use for SERS Detection of Amyloid Beta in Solution.

Hollow gold nanospheres (HGNs) have been used as the template for seed-mediated growth of multibranched hollow gold nanostars (HNS). The HGNs were synthesized via anerobic reduction of cobalt chloride to cobalt nanoparticles and then formation of a gold shell via galvanic replacement followed by the oxidation of the cobalt core. We obtained control of the inner core size of the HGNs by increasing the size of the sacrificial cobalt core and by varying the ratio of B(OH)3/BH4 using boric acid rather than 48 h aged borohydride. We synthesized the HNS by reducing Au3+ ions in the presence of Ag+ ions using ascorbic acid, creating a spiky morphology that varied with the Au3+/Ag+ ratio. A broadly tunable localized surface plasmon resonance was achieved through control of both the inner core and the spike length. Amyloid beta (Aβ) was conjugated to the HNS by using a heterobifunctional PEG linker and identified by the vibrational modes associated with the conjugated ring phenylalanine side chain. A bicinchoninic acid assay was used to determine the concentration of Aβ conjugated to HNS as 20 nM, which is below the level of Aβ that negatively affects long-term potentiation. Both the core size and spike length were shown to affect the optical properties of the resulting nanostructures. This HGN templated method introduced a new parameter for enhancing the plasmonic properties of gold nanostars, namely, the addition of a hollow core. Hollow gold nanostars are highly desirable for a wide range of applications, including high sensitivity disease detection and monitoring.

Preparation of Multifunctional Silk-Based Microcapsules loaded with DNA Plasmids Encoding RNA Aptamers and Riboswitches.

We introduce a protocol for the preparation of DNA-laden silk fibroin microcapsules via the Layer-by-Layer (LbL) assembly method on sacrificial spherical cores. Following adsorption of a prime layer and DNA plasmids, the formation of robust microcapsules was facilitated by inducing β-sheets in silk secondary structure during acute dehydration of a single silk layer. Hence, the layering occurred via multiple hydrogen bonding and hydrophobic interactions. Upon adsorption of multilayered shells, the core-shell structures can be further functionalized with gold nanoparticles (AuNPs) and/or antibodies (IgG) to be used for remote sensing and/or targeted delivery. Adjusting several key parameters during sequential deposition of key macromolecules on silica cores such as the presence of a polymer primer, the concentration of DNA and silk protein, as well as a number of adsorbed layers resulted in biocompatible, DNA-laden microcapsules with variable permeability and DNA loadings. Upon dissolution of silica cores, the protocol demonstrated the formation of hollow and robust microcapsules with DNA plasmids immobilized to the inner surface of the capsule membrane. Creating a selectively permeable biocompatible membrane between the DNA plasmids and the external environment preserved the DNA during long-term storage and played an important role in the improved output response from spatially confined plasmids. The activity of DNA templates and their accessibility were tested during in vitro transcription and translation reactions (cell-free systems). DNA plasmids encoding RNA light-up aptamers and riboswitches were successfully activated with corresponding analytes, as was visualized during localization of fluorescently labeled RNA transcripts or GFPa1 protein in the shell membranes.

Designing Tubular Architectures Composed of Hollow N‐Doped Carbon Polyhedrons for Improved Supercapacitance

AbstractDespite great efforts that have been made to develop high performance carbonaceous materials via structure design for charge storage applications, constructing tubular architectures composed of hierarchically nanoscale building units is challenging due to the lack of suitable synthetic method. Herein, using zeolitic imidazolate framework‐8 (ZIF‐8) as the self‐template and electrospun polyacrylonitrile (PAN) nanofibers as the sacrificial core, hierarchically tubular architectures composed of hollow N‐doped carbon polyhedrons (T‐HNCPs) are successfully obtained. Due to its unique structural characteristics and the merit of N‐doping, the as‐prepared T‐HNCPs electrode with much open structure (average pore size of ≈2.38 nm and specific surface area of 1302.5 m2 g−1) exhibits improved specific gravimetric capacitances of 351.2 and 230.4 F g−1 at 1 and 20 A g−1 (corresponding to 65.6% retention), respectively, together with outstanding charge/discharge stability.

Cu-doped TiO2 hollow nanostructures for the enhanced photocatalysis under visible light conditions

We report a synthetic strategy for fabricating Cu-doped TiO2 hollow nanostructure for visible light responsive photocatalysis. Hollow Cu-doped TiO2 photocatalysts were prepared by sol–gel coating of TiO2 on the surface of SiO2, removal of sacrificial core, Cu2+ ion exchange, and calcination followed by acid leaching. The ion exchanged Cu species allows TiO2 shell to be preferentially crystallized rutile phase, even at low calcination temperature. The acid leaching allows the excess bulk CuO to be dissolved out and Cu-doped TiO2 to expose more reactive TiO2 surface. No measurable CuO composites were observed while uniformly distributed Cu species is detected in acid treated CT–X–HCl samples indicating the Cu2+ ions were homogeneously doped into crystalline TiO2 frameworks. In particular, the CT–650–HCl catalyst that was prepared by calcination at 650°C, followed by HCl leaching, showed beneficial physio-chemical properties, such as narrow bandgap, mixed anatase-rutile crystalline phase, and more reactive TiO2 surface with high surface area, resulting in the best photocatalytic performance towards phenol degradation under visible light conditions.

Nanosac, a Noncationic and Soft Polyphenol Nanocapsule, Enables Systemic Delivery of siRNA to Solid Tumors.

For systemic delivery of small interfering RNA (siRNA) to solid tumors, the carrier must circulate avoiding premature degradation, extravasate and penetrate tumors, enter target cells, traffic to the intracellular destination, and release siRNA for gene silencing. However, existing siRNA carriers, which typically exhibit positive charges, fall short of these requirements by a large margin; thus, systemic delivery of siRNA to tumors remains a significant challenge. To overcome the limitations of existing approaches, we have developed a carrier of siRNA, called "Nanosac", a noncationic soft polyphenol nanocapsule. A siRNA-loaded Nanosac is produced by sequential coating of mesoporous silica nanoparticles (MSNs) with siRNA and polydopamine, followed by removal of the sacrificial MSN core. The Nanosac recruits serum albumin, co-opts caveolae-mediated endocytosis to enter tumor cells, and efficiently silences target genes. The softness of Nanosac improves extravasation and penetration into tumors compared to its hard counterpart. As a carrier of siRNA targeting PD-L1, Nanosac induces a significant attenuation of CT26 tumor growth by immune checkpoint blockade. These results support the utility of Nanosac in the systemic delivery of siRNA for solid tumor therapy.

Preparation and characterization of hollow carbon sphere supported catalysts (M@HCS [M=Pt, Ir, Ni]) for HI decomposition in the iodine–sulfur cycle for hydrogen production

Catalysts for HI decomposition are important in hydrogen production via the iodine–sulfur cycle. The catalysts should have a good activity, excellent thermal stability at 400 °C-500 °C, and corrosion resistance to HI and iodine. In this study, a series of hollow carbon sphere (HCS) supported mono-metallic catalysts M@HCS (M = Pt, Ir, Ni) were fabricated by coating the silica core with dopamine, carbonization, and sacrificial core technique. Active carbon-supported monometallic catalysts (M/C) were also prepared via the impregnation method. Catalytic activities of M@HCS and M/C during HI decomposition at 500 °C were compared. The composition, structure, specific surface area, morphology, and surface chemical states of M@HCS and M/C were characterized via inductively coupled plasma (ICP), X-ray diffraction (XRD), Brunauere-Emmette-Teller (BET) surface area, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. Results showed that the catalytic performance of M@HCS was better than that of M/C probably because of the synergistic effects between the active metals and HCSs.

Diversely Doped Uniform Silicon Nanotube Axial Heterostructures Enabled by "Dopant Reflection".

Here, we propose a novel method for the synthesis of extremely uniform, diversely doped silicon nanotube heterostructures. The method, comprising a simple two-step synthesis, exploits the use of a Ge nanowire sacrificial core upon which a multidoping axial pattern can be easily obtained, that is enclosed in an intrinsic Si shell. The Ge-Si core-shell structure is then heated to 750 °C, allowing the migration of dopant elements from the Ge core directly into the Si shell. Removal of the Ge core, via either wet or dry etch, does not impair the crystallinity of the Si shell nor its electrical characteristics, allowing for the formation of a multidoped axially patterned, conformal, and uniform Si nanotube. The precise dopant patterning allows for the extension of Si nanotube applications, which were unattainable because of the inability to precisely control the parameters and uniformity of the nanotubes while doping the structure simultaneously.

Cooling-Triggered Release from Mesoporous Poly(N-isopropylacrylamide) Microgels at Physiological Conditions.

Poly(N-isopropylacrylamide) (pNIPAM) hydrogels have broad potential applications as drug delivery vehicles because of their thermoresponsive behavior. pNIPAM loading/release performances are directly affected by the gel network structure. Therefore, there is a need with the approaches for accurate design of 3D pNIPAM assemblies with the structure ordered at the nanoscale. This study demonstrates size-selective spontaneous loading of macromolecules (dextrans 10−500 kDa) into pNIPAM microgels by microgel heating from 22 to 35 °C (microgels collapse and trap dextrans) followed by the dextran release upon further cooling down to 22 °C (microgels swell back) . This temperature-mediated behavior is fully reversible. The structure of pNIPAM microgels was tailored via hard templating and cross-linking of the hydrogel using sacrificial mesoporous cores of vaterite CaCO3 microcrystals. In addition, the fabrication of hollow thermoresponsive pNIPAM microshells has been demonstrated, utilizing vaterite microcrystals that had narrower pores. The proposed approach for heating-triggered encapsulation and cooling-triggered release into/from pNIPAM microgels may pave the ways for applications of pNIPAM hydrogels for skin and transdermal cooling-responsive drug delivery in the future.

Negshell casting: 3D-printed structured and sacrificial cores for soft robot fabrication.

Soft robot fabrication by casting liquid elastomer often requires multiple steps of casting or skillful manual labor. We present a novel soft robotic fabrication technique: negshell casting (negative-space eggshell casting), that reduces the steps required for fabrication by introducing 3D-printed thin-walled cores for use in casting that are meant to be left in place instead of being removed later in the fabrication process. Negshell casting consists of two types of cores: sacrificial cores (negshell cores) and structural cores. Negshell cores are designed to be broken into small pieces that have little effect on the mechanical structure of the soft robot, and can be used for creating fluidic channels and bellows for actuation. Structural cores, on the other hand, are not meant to be broken, and are for increasing the stiffness of soft robotic structures, such as endoskeletons. We describe the design and fabrication concepts for both types of cores and report the mechanical characterization of the cores embedded in silicone rubber specimens. We also present an example use-case of negshell casting for a single joint soft robotic finger, along with an experiment to demonstrate how negshell casting concepts can aid in force transmission. Finally, we present real-world usage of negshell casting in a 6 degree-of-freedom three-finger soft robotic gripper, and a demonstration of the gripper in a robotic pick-and-place task. A companion website with further details about fabrication (as well as an introduction to molding and casting for those who are unfamiliar with the terms), engineering file downloads, and experimental data is provided at https://negshell.github.io/.

Preparation and characterization of soy protein microspheres using amorphous calcium carbonate cores

Porous calcium carbonate (CaCO3) vaterite microparticles have been introduced a decade ago as sacrificial cores and becoming nowadays as one of the most popular templates to fabricate microcarriers. Herein we present a fabrication method of soy protein microspheres by templating on porous CaCO3 templates. The CaCO3 templates with a particle size (appx. 3–12 μm) were harvested with a yield of 47%. Soy proteins at varied concentrations from 0.05 to 0.25% (w/v) were applied to fabricate microspheres. Results showed that the highest coating efficiency of 87.9% was achieved at the protein concentration of 0.05%. And the highest protein loading ratio is 55.5 μg/mg. The protein coated CaCO3 microparticles has a spherical shape, however soy protein microspheres formed by dissolving the carbonate templates were wrinkled and partially collapsed. Results further indicated that the secondary structure of microspheres became more ordered with enhanced thermal stability. This study illustrates the feasibility to apply soy protein in the fabrication of microspheres based on calcium carbonate microparticles.