3D-printing of a piezocomposite material with high filler content for transducer applications

This work describes the process of synthesizing and printing a novel (0-3) piezocomposite material using solution mixing technique and digital light processing technique. This piezoelectric composite material was developed using a photopolymer, grey resin and lead magnesium niobate and lead titanate (PMN-PT) with particles size 5 µm. The 3D-printing of this thick film was achieved using the piezocomposite material with high filler content upto 60% w/w of PMN-PT. Results showed a satisfactory print resolution, a thick film with high flexibility and exceptionally high d33 coefficient of 49 pm/V during single point scan and an average of 67 pm/V during full surface scan measured using the laser vibrometer technique

Characterization of (0-3) piezocomposite materials for transducer applications

In this study, we have developed and characterized two different (0-3) piezoelectric composite materials with potential to be used in sensing applications. The composite materials were made using Polydimethylsiloxane (PDMS) as the polymer matrix with Barium Titanate (BaTiO3), and Lead Zirconate Titanate (PZT51) as the dielectric fillers. Thin film samples of the (0-3) piezocomposites were prepared using a solution mixing and spin coating method to produce composites with (0-3) connectivity pattern and layer thickness of mathbf{100} mumathbf{m}, The microstructure of the piezocomposites were analyzed using a scanning electron microscope to determine the connectivity structure and homogeneity of the piezocomposites. The mechanical properties of the composites were determined using the method of Oliver and Pharr. FTIR analysis was used to determine the effects of the fillers on the structure of the piezocomposite. The average piezoelectric pmb{d}{mathit{33}} coefficient of the piezocomposites were also measured using the laser vibrometer technique and determined to be 30 pm/V for the piezocomposite consisting of Barium Titanate (BaTiO3) and 32 pm/V for the piezocomposite consisting of Lead Zirconate Titanate (PZT51)

The next step in cicada audition: measuring pico-mechanics in the cicada's ear

Female cicadas use sound when they select a mate from a chorus of singing males. The cicada has a tympanal ear; and the tympanal membrane, and constituent tympanal ridge, act as both acousto-mechanical transducers and frequency filters. The tympanal ridge is physically connected to a large number of mechanoreceptor neurons via a cuticular extension known as the tympanal apodeme. Using microscanning laser Doppler vibrometry, we measured for the first time the in vivo vibrations of the apodeme of female Cicadatra atra in response to the motion of the tympanum driven by sound. These measurements reveal that the nanoscale motion of the tympanal membrane is over a magnitude greater than that of the apodeme. Furthermore, the apodeme acts as an additional mechanical frequency filter, enhancing that of the tympanal ridge, narrowing the frequency band of vibration at the mechanoreceptor neurons to that of the male calling song. This study enhances our understanding of the mechanical link between the external ear of the cicada and its sensory cells

Engineered surfaces that promote capture of latent proteins to facilitate integrin-mediated mechanical activation of growth factors

Conventional osteogenic platforms utilize active growth factors to repair bone defects that are extensive in size, but they can adversely affect patient health. Here, an unconventional osteogenic platform is reported that functions by promoting capture of inactive osteogenic growth factor molecules to the site of cell growth for subsequent integrin-mediated activation, using a recombinant fragment of latent transforming growth factor beta-binding protein-1 (rLTBP1). It is shown that rLTBP1 binds to the growth-factor- and integrin-binding domains of fibronectin on poly(ethyl acrylate) surfaces, which immobilizes rLTBP1 and promotes the binding of latency associated peptide (LAP), within which inactive transforming growth factor beta 1 (TGF-β1) is bound. rLTBP1 facilitates the interaction of LAP with integrin β1 and the subsequent mechanically driven release of TGF-β1 to stimulate canonical TGF-β1 signaling, activating osteogenic marker expression in vitro and complete regeneration of a critical-sized bone defect in vivo

A novel 3D printed hollow microneedle microelectromechanical system for controlled, personalised transdermal drug delivery

The advancement of drug delivery devices is critical for the individualization of patient treatment and the improvement of healthcare. Here, we introduce the 3DMNMEMS, a novel device that combines 3D printing, microneedles (MNs) and Microelectromechanical Systems (MEMS), allowing versatile and controllable by the user transdermal drug delivery. Hollow MNs were designed and 3D printed using Stereolithography, followed by integrating into a MEMS. By employing advanced imaging techniques, we monitored the distribution of liquid delivered by the device within skin tissue in real-time. In vivo testing revealed that the delivery of insulin using the 3DMNMEMS achieved improved glycemic control to diabetic animals compared to subcutaneous injections. These results demonstrated the potential of the 3DMNMEMS as a universal transdermal drug delivery system for personalized care

Time course changes to structural, mechanical and material properties of bone in rats after complete spinal cord injury

Objective: Characterise the spatiotemporal trabecular and cortical bone responses to complete spinal cord injury (SCI) in young rats. Methods: 8-week-old male Wistar rats received T9-transection SCI and were euthanised 2-, 6-, 10-or 16-weeks post-surgery. Outcome measures were assessed using micro-computed tomography, mechanical testing, serum markers and Fourier-transform infrared spectroscopy. Results: The trabecular and cortical bone responses to SCI are site-specific. Metaphyseal trabecular BV/TV was 59% lower, characterised by fewer and thinner trabeculae at 2-weeks post-SCI, while epiphyseal BV/TV was 23% lower with maintained connectivity. At later-time points, metaphyseal BV/TV remained unchanged, while epiphyseal BV/TV increased. The total area of metaphyseal and mid-diaphyseal cortical bone were lower from 2-weeks and between 6-and 10-weeks post-SCI, respectively. This suggested that SCI-induced bone changes observed in the rat model were not solely attributable to bone loss, but also to suppressed bone growth. No tissue mineral density differences were observed at any time-point, suggesting that decreased whole-bone mechanical properties were primarily the result of changes to the spatial distribution of bone. Conclusion: Young SCI rat trabecular bone changes resemble those observed clinically in adult and paediatric SCI, while cortical bone changes resemble paediatric SCI only

Developing and investigating a nanovibration intervention for the prevention/reversal of bone loss following spinal cord injury

Osteoporosis disrupts the fine-tuned balance between bone formation and resorption, leading to reductions in bone quantity and quality and ultimately increasing fracture risk. Prevention and treatment of osteoporotic fractures is essential for reductions in mortality, morbidity and the economic burden, particularly considering the ageing global population. Extreme bone loss that mimics time-accelerated osteoporosis develops in the paralysed limbs following complete spinal cord injury (SCI). In vitro nanoscale vibration (1 kHz, 30- or 90 nm amplitude) has been shown to drive differentiation of mesenchymal stem cells towards osteoblast-like phenotypes, enhancing osteogenesis and inhibiting osteoclastogenesis simultaneously. Here, we develop and characterise a wearable device designed to deliver and monitor continuous nano-amplitude vibration to the hindlimb long bones of rats with complete SCI. We investigate whether a clinically feasible dose of nanovibration (two 2-hours/day, 5-days/week for 6 weeks) is effective at reversing the established SCI-induced osteoporosis. Laser interferometry and finite element analysis confirmed transmission of nanovibration into the bone, and micro-computed tomography and serum bone formation and resorption markers assessed effectiveness. The intervention did not reverse SCI-induced osteoporosis. However, serum analysis indicated an elevated concentration of the bone formation marker procollagen type 1 N-terminal propeptide (P1NP) in rats receiving 40 nm amplitude nanovibration, suggesting increased synthesis of type 1 collagen, the major organic component of bone. Therefore, enhanced doses of nanovibrational stimulus may yet prove beneficial in attenuating/reversing osteoporosis, particularly in less severe forms of osteoporosis