Batch fabrication of polymer microsystems with shape memory microactuators
This paper introduces the technologies of ultrasonic welding and heat-activated bonding for batch integration of micromachined polymer layers and shape memory alloy (SMA) foils or films. A series of ultrasonic welding tests is performed to achieve matter-free bonds on the wafer level with vertical accuracy of 1 mum. Heat-activated bonding is tested for various pressure and temperature conditions using micromachined foils of 60 mum thickness. The technologies are combined in a new process flow for batch fabrication of mechanically active polymer microsystems. The process flow is validated by the fabrication and characterization of SMA-actuated polymer microvalves.
Micro ultrasonic welding: joining of chemically inert polymer microparts for single material fluidic components and systems
This paper presents a novel powerful micro joining process—the ultrasonic welding of real micro polymer parts. It seems to be especially suited for the manufacturing of single material, chemically inert plastic microfluidic components and systems for applications in the field of pharmaceutics, biotechnology and life sciences as well as for high temperature polymer fluidic microdevices. The performance of this ‘micro ultrasonic welding’ process, alone using a pneumatic standard ultrasonic welding machine, is demonstrated by the example of covering and sealing microchannels and assembling a piezo-driven micropump.
Experimental study on bond behavior between high-strength grout and deformed steel bars
Abstract Engineers use high-strength grout to connect precast concrete members for its low shrinkage and good fluidity. This paper designed 87 central pull-out specimens using the control variable method to investigate the influence of factors on the rebar-grout bond property such as compressive strength, steel grade, bar diameter, transverse stirrups, and bond length. The test result showed that improving grout compressive strength (85.8 MPa–122.7 MPa) cannot improve the bond strength, which was different from the previous conclusions of concrete pull-out tests. Simplified formulas were presented for calculating the characteristic values of bond strength, residual strength, peak slip, and relative slip of load-holding platform based on parameter analysis. Then, a constitutive model was proposed to predict the full-range bond stress-slip curve of high-strength grout and steel bar specimens from bearing to failure. Finally, FEA models were established to evaluate the applicability and accuracy of the constitutive model.