The Application of PVDF-Based Piezoelectric Patches in Energy Harvesting from Tire Deformation.

The application of Polyvinylidene Fluoride or Polyvinylidene Difluoride (PVDF) in harvesting energy from tire deformation was investigated in this study. An instrumented tire with different sizes of PVDF-based piezoelectric patches and a tri-axial accelerometer attached to its inner liner was used for this purpose and was tested under different conditions on asphalt and concrete surfaces. The results demonstrated that on both pavement types, the generated voltage was directly proportional to the size of the harvester patches, the longitudinal velocity, and the normal load. Additionally, the generated voltage was inversely proportional to the tire inflation pressure. Moreover, the range of generated voltages was slightly higher on asphalt compared to the same testing conditions on the concrete surface. Based on the results, it was concluded that in addition to the potential role of the PVDF-based piezoelectric film in harvesting energy from tire deformation, they demonstrate great potential to be used as self-powered sensors to estimate the tire-road contact parameters.

Surface Modification of Polymethylmethacrylate (PMMA) by Ultraviolet (UV) Irradiation and IPA Rinsing.

Polymethylmethacrylate (PMMA) is commonly applied to microfluidic devices due to its excellent biocompatibility, high optical transparency, and suitability for mass production. Recently, various surface treatment methods have been reported to improve the wettability of polymers, which is directly related to adhesion. In this research, the effect of a UV irradiation technique and an IPA rinsing technique as surface treatments for PMMA is investigated regarding the water contact angle of the PMMA surface. PMMA sheets that were 1.62 mm thick and commercially available were exposed to UV light with four different exposure times. Significant decreases in the water contact angle were observed after exposure to UV light, and the lowered contact angles due to the UV irradiation increased over time. According to the measurement, the water contact angle is a function of UV exposure dose as well as storage time after UV exposure. We examined the effect of a IPA rinsing process after UV irradiation and observed an increase in the water contact angle.

Connector-Free World-to-Chip Interconnection for Microfluidic Devices.

In the development of functional lab-on-a-chip (LOC), there is a need to produce a reliable and high pressure connection between capillary tubes and microfluidic devices for carrying fluids. The current technologies still have limitations in achieving ideal interconnection since they are bulky, expensive or complicated. In this paper, a novel connector-free technique using an interference fit mechanism is introduced for world-to-chip interconnection. The proposed technique has considerable potential for replacing current interconnection tools for microfluidic devices due to the advantages including no chemical contamination, easy plugging, enough strength to sustain pressure, high density integration, simple and rapid integration.

Hydrothermal Growth of ZnO Nanowires on UV-Nanoimprinted Polymer Structures.

Integration of zinc oxide (ZnO) nanowires on miniaturized polymer structures can broaden its application in multi-functional polymer devices by taking advantages of unique physical properties of ZnO nanowires and recent development of polymer microstructures in analytical systems. In this paper, we demonstrate the hydrothermal growth of ZnO nanowires on polymer microstructures fabricated by UV nanoimprinting lithography (NIL) using a polyurethane acrylate (PUA). Since PUA is a siloxane-urethane-acrylate compound containing the alpha-hydroxyl ketone, UV-cured PUA include carboxyl groups, which inhibit and suppress the nucleation and growth of ZnO nanowires on polymer structures. The presence of carboxyl groups in UV-cured PUA was substantiated by Fourier transform infrared spectroscopy (FTIR), and a Ag thin film was deposited on the nanoimprinted polymer structures to limit their inhibitive influence on the growth of ZnO nanowires. Furthermore, the naturally oxidized Ag layer (Ag2O) reduced crystalline lattice mismatches at the interface between ZnO-Ag during the seed annealing process. The ZnO nanowires grown on the Ag-deposited PUA microstructures were found to have comparable morphological characteristics with ZnO nanowires grown on a Si wafer.

PMMA Solution Assisted Room Temperature Bonding for PMMA⁻PC Hybrid Devices.

Recently, thermoplastic polymers have become popular materials for microfluidic chips due to their easy fabrication and low cost. A polymer based microfluidic device can be formed in various fabrication techniques such as laser machining, injection molding, and hot embossing. A new bonding process presented in this paper uses a 2.5% (w/w) polymethyl methacrylate (PMMA) solution as an adhesive layer to bond dissimilar polymers-PMMA to polycarbonate (PC)-to enclose the PMMA microfluidic channels with PC. This technique has been successfully demonstrated to bond PMMA microchip to PC film. This paper presents bonding strength using a shear strength test and a crack opening method in addition to the fluidic leakage inspection.

Micro-accelerometer Based on Vertically Movable Gate Field Effect Transistor.

A vertically movable gate field effect transistor (VMGFET) is proposed and demonstrated for a micro-accelerometer application. The VMGFET using air gap as an insulator layer allows the gate to move on the substrate vertically by external forces. Finite element analysis is used to simulate mechanical behaviors of the designed structure. For the simulation, the ground acceleration spectrum of the 1952 Kern County Earthquake is employed to investigate the structural integrity of the sensor in vibration. Based on the simulation, a prototype VMGFET accelerometer is fabricated from silicon on insulator wafer. According to current-voltage characteristics of the prototype VMGFET, the threshold voltage is measured to be 2.32 V, which determines the effective charge density and the mutual transconductance of 1.545×10-8 C cm-2 and 6.59 mA V-1, respectively. The device sensitivity is 9.36-9.42 mV g-1 in the low frequency, and the first natural frequency is found to be 1230 Hz. The profile smoothness of the sensed signal is in 3 dB range up to 1 kHz.

Thermoplastic fusion bonding using a pressure-assisted boiling point control system.

A novel thermoplastic fusion bonding method using a pressure-assisted boiling point (PABP) control system was developed to apply precise temperatures and pressures during bonding. Hot embossed polymethyl methacrylate (PMMA) components containing microchannels were sealed using the PABP system. Very low aspect ratio structures (AR = 1/100, 10 µm in depth and 1000 µm in width) were successfully sealed without collapse or deformation. The integrity and strength of the bonds on the sealed PMMA devices were evaluated using leakage and rupture tests; no leaks were detected and failure during the rupture tests occurred at pressures greater than 496 kPa. The PABP system was used to seal 3D shaped flexible PMMA devices successfully.

Polarimetric total internal reflection biosensing.

In this paper, a concept of polarimetric total internal reflection (TIR) biosensor based on the method of temporal phase modulation is presented. Measurements of the phase difference between s- and p- polarized light combined with their amplitudes allow simultaneous detection of the bulk refractive index and thickness of the surface biofilms. Obtained experimental sensitivity is better than 10(-5) in terms of refractive index unit and 0.5 nm in biolayer thickness. Relatively simple technological implementation of the TIR sensors on the base of inexpensive and transparent substrates opens a number of novel applications in biosensing and microscopy.

Silicon based total internal reflection bio and chemical sensing with spectral phase detection.

Si-based total internal reflection (TIR) bio/chemical sensor presents an attractive alternative to Surface Plasmon Resonance (SPR) technology due to a relatively simple optical arrangement and technological implementation, as well as a relatively easy bio/chemical immobilization on Si/SiO(2) surface with a number of novel attractive applications. This sensor is based on the control of phase difference between p- and s-polarized components of light reflected from Si/air or Si/water interface in TIR geometry and a high sensitivity of the sensor is granted by a high refractive index of Si (3.56 at 1200 nm). We study properties of TIR sensors in a configuration of spectral phase detection and identify conditions of maximal phase sensitive response. We also experimentally show that the detection limit of Si-based TIR sensor can be lowered down to a level of detection of commercially available SPR devices (10(-6) Refractive Index Units, RIU) under the use of a proper low-noisy method of the phase control. The concept of Si-based TIR opens attractive prospects for the miniaturization of sensor devices, taking advantage of the advanced state of development of Si-based microfabrication technologies, while the proposed spectral phase detection scheme offers much easier packaging and calibration steps.

Designing efficient zero calibration point for phase-sensitive surface plasmon resonance biosensing.

This work is related to the development of phase-sensitive methodologies in Surface Plasmon Resonance (SPR) biosensing. We take advantage of a specific angular dependence of phase of light, reflected under SPR geometry, on parameters of the SPR-supporting metal, and propose a polarimetry-based methodology to easily determine the optimal calibration zero point, corresponding to the maximal phase sensitivity. The proposed methodology can significantly facilitate the calibration of the system in field and multi-channel sensing, broaden the dynamic range, as well as contribute to the development of feedback loops.