3D-printed membrane microvalves and microdecoder

Abstract(#br)A microfluidic system for multichannel switching and multiphase flow control has potential uses in pneumatic soft robotics and biological sampling systems. At present, the membrane microvalves used in microfluidic systems are mostly constructed using a multilayer bonding process so that the device cannot withstand high pressures. In this paper, we demonstrate a design method and the properties of a bondless membrane microvalve fabricated using a commercial 3D printer. We used a multijet (MJP) 3D printer to print a 100-μm-thick and 6-mm-diameter membrane from a relatively hard material (1700 MPa). The membrane’s high toughness ensures that it does not need negative pressure to reopen. The measured operation frequency was less than 2.5 Hz under a pneumatic pressure of 14.5 kPa...

Effect of Enhanced Squeezing Needle Structure on the Jetting Performance of a Piezostack-Driven Dispenser.

Advanced dispensing technology is urgently needed to improve the jetting performance of fluid to meet the requirements of electronic product integration and miniaturization. In this work, an on-off valve piezostack-driven dispenser was used as a study object to investigate the effect of needle structure on jetting performance. Based on fluid dynamics, we investigated nozzle cavity pressure and jet velocity during the dispensing process using theoretical simulation for needles with and without a side cap. The results showed that the needle with a side cap had larger jet velocity and was capable of generating 8.27 MPa of pressure in the nozzle cavity, which was 2.39 times larger than the needle without a side cap. Further research on the influence of the nozzle and needle structural parameters showed that a nozzle conic angle of 85°-105°, needle conic angle of 10°-35°, and side clearance of 0.1-0.3 mm produced a dispenser with a large jet velocity and stable performance, capable of dispensing microscale droplets. Finally, a smaller droplet diameter of 0.42 mm was achieved in experiments using a glycerol/ethanol mixture, with a variation range of ± 4.61%

La(Ca)CrO₃-Filled SiCN Precursor Thin Film Temperature Sensor Capable to Measure up to 1100 °C High Temperature

Thin-film sensors are regarded as advanced technologies for in situ condition monitoring of components operating in harsh environments, such as aerospace engines. Nevertheless, these sensors encounter challenges due to the high-temperature oxidation of materials and intricate manufacturing processes. This paper presents a simple method to fabricate high temperature-resistant oxidized SiCN precursor and La(Ca)CrO3 composite thin film temperature sensors by screen printing and air annealing. The developed sensor demonstrates a broad temperature response ranging from 200 °C to 1100 °C with negative temperature coefficients (NTC). It exhibits exceptional resistance to high-temperature oxidation and maintains performance stability. Notably, the sensor’s resistance changes by 3% after exposure to an 1100 °C air environment for 1 h. This oxidation resistance improvement surpasses the currently reported SiCN precursor thin-film sensors. Additionally, the sensor’s temperature coefficient of resistance (TCR) can reach up to −7900 ppm/°C at 200 °C. This strategy is expected to be used for other high-temperature thin-film sensors such as strain gauges, heat flux sensors, and thermocouples. There is great potential for applications in high-temperature field monitoring

The Impacts of Forest Therapy on the Physical and Mental Health of College Students: A Review

The aim of this review is to investigate the impacts of various forest therapy activities on the physical and mental health of college students. Additionally, it evaluates the research methodologies and existing issues in current studies, providing an important agenda for future research. Research was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The findings suggest significant effects of forest therapy activities on the physiology and psychology of college students, notably improving the cardiovascular system, enhancing the immune system, boosting emotional well-being, alleviating job-related stress, and enhancing academic performance. This study further clarifies forest therapy as an emerging and effective intervention to reduce stress levels among college students, particularly when carried out continuously in easily accessible campus forest environments. Such therapeutic activities could serve as a component of daily stress-relieving programs for college students. This assessment offers valuable information for college students, educational institutions, and policymakers to promote the development of forest therapy on university campuses. However, some of the studies included in this investigation lacked methodological rigor. Future research should employ rigorous study designs to assess the long-term impacts of various forest therapy approaches on the mental and physical health of college students and identify the primary influencing factors. This will aid in determining suitable content, forms, and strategies for forest therapy projects tailored to college students, thereby maximizing the potential benefits of forest therapy on their mental and physical well-being.Forestry, Faculty ofNon UBCForest Resources Management, Department ofReviewedFacultyResearche

The effects and gender-related differences of guided forest therapy program on physiological and psychological health of graduating college students

Forest therapy has been proven to have a quantifiable positive impact on human physiological and psychological health. Given that graduating students at university are easy to stress due to changes in life, pressure from their studies, and independence in finance. The main purpose of this research was to explore the effects of guided forest therapy on graduating college students through a field experiment in Pacific Spirit Regional Park which held significant geographical value. This paper investigated the pressure of graduating college students and their needs for forest therapy, and explored the psychological and physiological changes after guided forest therapy. This study also analyzed gender-related psychological and physiological differences. Thirty-six healthy graduating college students were invited to participate in a 2-hour forest therapy program. Likert scales were used to assess students' pressure and the demand for forest therapy. Most of the students were facing the pressure of graduation and were willing to participate in forest therapy. Systolic and diastolic blood pressure, pulse rate, and heart rate variability (HRV) were used as physiological measurement indices. Our physiological results indicated that blood pressure significantly decreased, the high-frequency component of HRV (HF) was significantly larger, and the low-to-high-frequency component ratio (LF/HF) was smaller after the forest therapy program, and some beneficial changes in females were more significant than that in males. The participants' mean HR decreased throughout the forest therapy, but there were no significant differences. Mental status was assessed before and after forest therapy using the Profile of Mood States (POMS), employment stress scale and State-Trait Anxiety Inventory (STAI) for participants. Overall, the guided forest therapy program effectively reduced participants' employment stress and state anxiety. Our research showed that guided forest therapy had positive physiological and psychological benefits for graduating college students. In addition, females obtained more positive physiological benefits than males, and males obtained more positive psychological benefits than females throughout forest therapy

Concentrated Multi-nozzle Electrospinning

The multi-nozzle electrospinning is under extensive investigations because it is an easy way to enhance the productivity and also feasible to produce special structure fibers such as core-shell fibers and to fabricate composite fibers of those polymers that cannot form blend solution in common solvent. Control over the multi-nozzle electrospinning fibers deposition has attracted increasing attentions. The most common method was to use the auxiliary electrode. However, the concentrated effect of the works of control multi-nozzle electrospinning deposit was inconspicuous. To enhance the controlling of multi-nozzle electrospinning deposition, a set-up based oppositely charged electrospinning was designed. In this set-up the air flow was used to transport neutralized nanofibers. This electrospinning method was named oppositely charged and air auxiliary electrospinning (OCAAES). The capacity of OCAAES in deposition area and pattern controlling were investigated. By the OCAAES, concentrated and several patterned nanofibers deposition were fabricated. Results showed that nanofiber deposition area and pattern of multi-nozzle electrospinning could be controlled actively, and nanofiber deposition could be fabricated in a quick thickening rate

Concentrated Multi-nozzle Electrospinning

The multi-nozzle electrospinning is under extensive investigations because it is an easy way to enhance the productivity and also feasible to produce special structure fibers such as core-shell fibers and to fabricate composite fibers of those polymers that cannot form blend solution in common solvent. Control over the multi-nozzle electrospinning fibers deposition has attracted increasing attentions. The most common method was to use the auxiliary electrode. However, the concentrated effect of the works of control multi-nozzle electrospinning deposit was inconspicuous. To enhance the controlling of multi-nozzle electrospinning deposition, a set-up based oppositely charged electrospinning was designed. In this set-up the air flow was used to transport neutralized nanofibers. This electrospinning method was named oppositely charged and air auxiliary electrospinning (OCAAES). The capacity of OCAAES in deposition area and pattern controlling were investigated. By the OCAAES, concentrated and several patterned nanofibers deposition were fabricated. Results showed that nanofiber deposition area and pattern of multi-nozzle electrospinning could be controlled actively, and nanofiber deposition could be fabricated in a quick thickening rate

The Effects of Dynamic and Static Forest Bathing (Shinrin-yoku) on Physiological and Psychological Health in Males and Females

This study aimed to investigate the effects of dynamic and static forest bathing (Shinrin-yoku) on the physiological and psychological health of males and females. Dynamic pre-test and post-test forest bathing was performed on 11 participants (5 males and 6 females) as a single group in a forest environment. In addition, a randomized controlled trial involving 20 participants (10 males and 10 females) was conducted to evaluate static forest bathing in both forest and urban environments. Various physiological indicators, including systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse, heart rate variability (HRV), and self-assessed psychological indicators such as profile of mood states, were measured. Dynamic forest bathing resulted in a significant increase in the natural logarithmic value of the high frequency (lnHF) of HRV and significantly decreased ratio of the natural logarithmic value of the low frequency (lnLF) to lnHF (lnLF/lnHF) of HRV. Static forest bathing not only had the effects of dynamic forest bathing but also significantly decreased the participants’ SBP, DBP, and pulse. Both dynamic and static forest bathing enhanced human parasympathetic nervous system activity and reduced sympathetic nervous system activity, particularly affecting females. Negative mood state scores (tension, anger, fatigue, depression, and confusion) and total mood disturbance scores significantly decreased after forest bathing. In contrast, positive mood state (vigor) scores significantly increased, indicating an enhancement in positive mood. These improvements in mood were particularly pronounced in male individuals. Short-term exposure to a forest environment has positive effects on both physical and mental health of individuals. The extent of these improvements varied according to factors such as engagement in physical activity and gender.Forestry, Faculty ofNon UBCForest Resources Management, Department ofReviewedFacultyResearche

All-Three-Dimensionally-Printed AgPd Thick-Film Strain Gauge with a Glass–Ceramic Protective Layer for High-Temperature Applications

A high-temperature thin/thick-film strain gauge (TFSG) shows development prospects for in situ strain monitoring of hot-end components due to their small perturbations, no damage, and fast response. Direct ink writing (DIW) 3D printing is an emerging and facile approach for the rapid fabrication of TFSG. However, TFSGs prepared based on 3D printing with both high thermal stability and low temperature coefficient of resistance (TCR) over a wide temperature range remain a great challenge. Here, we report a AgPd TFSG with a glass–ceramic protective layer based on DIW. By encapsulating the AgPd sensitive layer and regulating the Pd content, the AgPd TFSG demonstrated a low TCR (191.6 ppm/°C) from 50 to 800 °C and ultrahigh stability (with a resistance drift rate of 0.14%/h at 800 °C). Meanwhile, the achieved specifications for strain detection included a strain sensing range of ±500 με, fast response time of 153 ms, gauge factor of 0.75 at 800 °C, and high durability of >8000 cyclic loading tests. The AgPd TFSG effectively monitors strain in superalloys and can be directly deposited onto cylindrical surfaces, demonstrating the scalability of the presented approach. This work provides a strategy to develop TFSGs for in situ sensing of complex curved surfaces in harsh environments