Polydimethylsiloxane-integratable micropressure sensor for microfluidic chips

Abstract

A novel microfluidic pressure sensor which can be fully integrated into polydimethylsiloxane ͑PDMS͒ is reported. The sensor produces electrical signals directly. We integrated PDMS-based conductive composites into a 30 m thick membrane and bonded it to the microchannel side wall. The response time of the sensor is approximately 100 ms and can work within a pressure range as wide as 0-100 kPa. The resolution of this micropressure sensor is generally 0.1 kPa but can be increased to 0.01 kPa at high pressures as a result of the quadratic relationship between resistance and pressure. The PDMS-based nature of the sensor ensures its perfect bonding with PDMS chips, and the standard photolithographic process of the sensor allows one-time fabrication of three dimensional structures or even microsensor arrays. The theoretical calculations are in good agreement with experimental observations.

From Cleanroom to Desktop: Emerging Micro-Nanofabrication Technology for Biomedical Applications

“…For example, conductive and elastomeric materials have been long pursued for wearable biosensing and bioelectronics, to which nanocomposite materials offer a simple yet effective solution. In one approach, PDMS pre-polymer has been mixed with conductive nanopowders (e.g., silver particles and carbon nanotubes) to create a conductive elastomeric composite, which can be used in micro-heaters and temperature sensors in polymerase chain reaction (PCR) chip as well as pressure sensors in microfluidics 50,58,139,198. PDMS-based nanocomposites, combined with the aforementioned photopatternability, have proved to be both positively and negatively photo-definable with conductive properties, being useful for bioelectrical sensing and actuation 37.…”

Continuous flowing micro-reactor for aqueous reaction at temperature higher than 100 °C

“…10 Thermoelectrics were also used to realize ice-valving and thermocyling for polymerase chain reaction in an integrated centrifugal microfluidic platform. 11 Conductive PDMS was developed to achieve pressure measurement in microfluidic chip, 12 which could be used for reaction condition monitoring. Besides the above applications with the temperature lower than the boiling point of reagents at the atmosphere condition, reaction at a more elevated temperature, for example, higher than 100 C for an aqueous system, attracts particular interests in the microfluidics community because of its signification in chemical engineering.…”

Measuring the pressures across microfluidic droplets with an optical tweezer

“…A variety of techniques to measure pressure changes or pressure differentials in microfluidic channels have been reported. Examples include membrane-based devices, which electrically [20] or optically [21][22][23][24] characterize the pressure-induced deformation of a thin membrane serving as part of the channel wall, or track the displacement of microparticles due to membrane deformation [25]. However, these methods are in general not appropriate for measuring pressure differentials due to droplets, since deformation of the membrane alters the simple rectangular geometry of the channel cross section, rendering it difficult to interpret and model results for droplets.…”

“…However, these methods are in general not appropriate for measuring pressure differentials due to droplets, since deformation of the membrane alters the simple rectangular geometry of the channel cross section, rendering it difficult to interpret and model results for droplets. Also, membrane-based devices are often associated with tricky or expensive fabrication techniques, such as multilayer soft lithography [20,[22][23][24][25] and reactive ion etching [21]. An alternative scheme for pressure sensing involves connecting microchannels to sealed air chambers and relating pressure to the volume of trapped air [26].…”