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This paper presents a Discrete Variable Stiffness Actuator (DVSA) based on a Variable Stiffness Parallel Beam (VSPB), where stiffness modulation is achieved through block insertion and cross-sectional reconfiguration. The actuator employs a solenoid-driven planar push-push mechanism to enable rapid and synchronized switching among three discrete stiffness levels. A theoretical stiffness model is established and validated through comparisons among analytical calculations, simulation results, and experimental measurements. The results demonstrate that the proposed model provides high predictive accuracy within practical parameter ranges. A prototype actuator is fabricated, and torque control experiments are conducted under different stiffness configurations. The system achieves a stiffness variation ratio of 78. A PID-based closed-loop controller ensures stable torque tracking performance. By introducing a rollback-assisted strategy, online stiffness switching is realized under closed-loop operation without compromising system stability. Owing to its compact structure, low energy consumption, and reconfigurable stiffness capability, the proposed DVSA is suitable for safety-critical cobots and humanoid robotic systems, providing an effective solution for applications requiring both compliance and high stiffness. 

Although advanced science tools are central to modern research, K–12 students rarely access them due to cost and complexity. Using microfluidic stickers as a design case, this paper explores how such technologies can be repurposed for constructionist "hands-on" science education. By simplifying fabrication, drawing on cultural forms, and enabling hands-on experiments with liquid flow and diffusion, the stickers illustrate pathways to make advanced science tools accessible through everyday making. 

The seismic performance of acceleration-sensitive mechanical equipment is a major area of interest within the field of nonstructural components and systems (NCSs). To save indoor space, conserve energy, or meet functional requirements, such equipment is often installed on building rooftops, where higher acceleration demands during earthquakes make rooftop-mounted units more susceptible to damage. Floor-mounted mechanical equipment is typically supported by vibration and noise isolation devices to reduce the transmission of unwanted motion to the supporting structure. However, limited attention has been given to understanding under what conditions, and to what extent, vibration and acoustical design strategies may enhance, or potentially compromise, the seismic performance of lightweight NCSs. To investigate this issue, five lightweight air-conditioning condenser units, each weighing no more than 1,500 N, including three with a slender aspect ratio of 3.7 and two with a squat aspect ratio of 1.1, were installed on the rooftop of a full-scale, ten-story cold-formed steel (CFS) building tested on a six-degree-of-freedom outdoor shake table. Different base attachment strategies were employed. All three slender units were screwmounted at four manufacturer-provided feet to the CFS studs. Two of the units had a modified base boundary condition, with neoprene pads and spring isolators respectively added under the base feet. Both squat units were screw-mounted using four steel angles connected to the CFS studs, with one additionally supported by neoprene pads placed beneath the equipment. This paper presents the first release of preliminary results from the recently completed experimental program, focusing on rooftop mechanical equipment responses under service-level, design-level, and maximum-considered earthquake motions. Results presented include measured floor acceleration amplification factors, peak component accelerations, and component amplification factors. These findings are compared with code-based provisions to evaluate the adequacy of current design coefficients in capturing the acceleration demands on lightweight components.