Generation of dynamic chemical signals with microfluidic C-DACs

Abstract

The utilization of microfluidic "lab-on-a-chip" devices in fundamental medical research, drug discovery and clinical diagnostics has rapidly increased in the past decade. Lab-on-a-chip devices process small volumes of analytes and reagents through on-chip microfluidic signal processing circuits. This paper discusses the implementation of a basic microfluidic circuit block, the concentration digital-to-analog converter (or C-DAC) which produces discretized chemical concentrations in a constant stream of solvent. The chemical concentration is controlled by a time-varying digital word; hence C-DACs are suitable for on-chip generation of arbitrary chemical signals. A 4-bit continuous-flow C-DAC was fabricated in two-level PDMS technology and tested. Several chemical waveforms (sawtooth, cosine, and ramp) were generated at flow rates of 2 microL min(-1) and frequencies of 0.6-4 mHz. The frequency cut off of this C-DAC was approximately 500 mHz.

Transport of Dynamic Biochemical Signals in Steady Flow in a Shallow Y-Shaped Microfluidic Channel: Effect of Transverse Diffusion and Longitudinal Dispersion

“…To date, microfiuidics has become a popular and effective experimental platform to study the interactions between cells and their microenvironments [10,11,[13][14][15][16][17][18][19][20][21][22][23]. Many types of microfiuidic devices have been developed to generate biomechanical and biochemical signals for specific cellular biological applications.…”

Teflon-seated one-lambda microvalves for PDMS chips

“…One of its major attractive characteristics is its high density of pneumatic microvalves (~100 valves/mm 2 ) making it suitable for realization of very complex parallel assays [2]. 2L-PDMS technology has been enhanced to include through level vias [3,4] that permit crossing fluidic lines, and various metallization [5] layers. Conventional 2L-PDMS microvalves have minimum size restrictions imposed by the minimum channel height that produces open channels after bonding and the maximum drive pressure that can be practically utilized (~30 PSI).…”

Universal signal generator for dynamic cell stimulation

“…Existing signal generators mainly fall into two categories, (i) they mix a number of input concentrations with equal flow rates to generate a mean concentration 13 or (ii) they mix two input concentrations with varying flow rates to achieve intermediate concentrations. 14–18,12,19–21 Both methods depend on extremely precise control of fluid flow rates, which is a difficult task for PDMS based microfluidic devices due to the compliant nature of the PDMS elastomer and the flexible tubing typically used in such systems.…”