PDMS (Polydimethylsiloxane) Microfluidic Chip Molding for Love Wave Biosensor

Abstract

We present the development of new Polydimethylsiloxane (PDMS) chips, which are coupled with Love acoustic wave sensors to realize a detection cell of bio-organisms in liquid media. Three generations of biocompatible PDMS chips have been developed. Built-in thermistors allow a thermal control (±0.05°C). Unlike the usual assemblies, this chip is maintained by pressure on the sensor and not sticked on its surface. This technique makes it entirely removable and cleanable. Therefore, the surface of the sensor can be functionalized or regenerated. The realization of these chips is quick and inexpensive.We here outline the development of these different cells and present characteristics of the resulting microsensors, depending on the chip configuration. Real-time responses during antibodies immobilization are presented and analyzed. Antibodies at typical concentration of 45μg/ml are successfully fast detected, with response times from 350s for static down to 90s for dynamic detection setup, with similar sensitivity. Discussions on the mechanical fluid behaviour at the near sensor surface allow to better understand these results and to investigate further developments aiming at improving the quality of the fluid stream in order to even increase future sensor characteristics.

Guided acoustic wave sensors for liquid environments

“…In an attempt to design a sensor packaging able to protect the IDTs from the liquid environment and to confine the measurand in the device sensing area, the electroacoustic device can be integrated with different types of microchannels. Typically, the test cell that localizes the liquid to the surface of the device consists of a pre-molded polydimethylsiloxane (PDMS) cell [30], or an SU-8 cell [31] that is mechanically pressed against the surface of the sensor to avoid any contact between the IDTs and the liquid to be tested. The cell can be positioned in three different configurations: (1) in between the IDTs, as shown in figure 5(a), to prevent the presence of liquid on the IDTs; (2) it can occupy the entire device surface if the IDTs are shielded by a proper layer, as shown in figure 5(b), to avoid conduction through the liquid between the electrodes;…”

“…References [27][28][29][30][31][32][33] provide a very useful list of substrate types and crystallographic orientations along which lowattenuated, strongly-coupled PSAW and HVPSAW travel (such as 64°YX LiNbO 3 , 36°YX LiTaO 3 , quartz ST-X, LiNbO 3 with Euler angles (90° 90° 36°), (90° 90° 31°) LiTaO 3 and (0° 45° 90°) Li 2 B 4 O 7 ). For sake of completeness, the same references list other information that is fundamental for the design of the device parameters (operating frequency, IDT's centreto-centre distance, number of IDT finger pairs, IDT's aperture, etc), such as the phase velocity, propagation loss, particle displacement components, electric-to-acoustic energy conversion efficiency, K 2 and power flow angle of the SAW, PSAW and HVPSAW.…”

Inkjet-printed microelectrodes on PDMS as biosensors for functionalized microfluidic systems

“…PDMS-based microfluidic systems have been used extensively in the control and manipulation of different liquids [1][2][3][4][5][6] because of their remarkable biocompatibility and easy fabrication. Electrochemical detection in microfluidics is on the rise, especially in cases where the analyte is present in a sufficiently high concentration to generate a relatively high voltage or current signal, thus allowing a comparatively simple and robust read-out.…”