Trench-shaped field-effect transistor integrates electronic particle detection with microfluidics

As more electronic methods for sensing are developed, field-effect transistors (FET) have garnered an increasing use for detecting charged particles. Combining such technology with microfluidic channels shows promise for detecting particles in flow and creating practical biomedical devices. Achieving the necessary sensitivity, however, has remained a challenge.

Park et al. demonstrated a new form of FET for microfluidic applications. By integrating a microfluidic channel, the trench-shaped silicon FET can be used simultaneously for electrical and optical detection of charged fluorescent beads as small as 100 nm when coupled to an epifluorescence microscope.

“Previous attempts have combined FETs with microfluidic modalities, but the semiconductor material properties were unstable in ways that limited detector sensitivity, especially to very small particles,” said author Dong-Wook Park. “Our approach adapted a commercially available silicon semiconductor as a trench structure to achieve stable and high-performance electrical measurements and simultaneous imaging of very small charged objects, such as charged polymeric beads.”

Optical sensors have historically been used for detecting molecules. By contrast, FETs offer the ability to electronically measure potential differences induced by charged analytes.

The team’s design used a polydimethylsiloxane/glass hybrid roof to provide a robust seal while still taking advantage of the thin and flat properties of glass.

The device can conduct simultaneous synchronized time-lapse imaging and electronic detection of bead transport with high transconductance at near-zero gate bias voltage, indicating highly sensitive detection.

The researchers hope to expand on the device’s detection capabilities by optimizing FET geometries and including additional sensing materials.

Source: “Trench field-effect transistors integrated in a microfluidic channel and design considerations for charge detection,” by Dong-Wook Park, Gene Tsvid, Juan P. Hernandez-Ortiz, David C. Schwartz, and Zhenqiang Ma, Applied Physics Letters (2022). The article can be accessed at https://doi.org/10.1063/5.0084758 .