# An Accumulation Pretreatment-Free POCT Biochip for Visual and Sensitive ABO/Rh Blood Cell Typing

## TL;DR

A new low-cost biochip allows quick and easy blood typing without sample preparation, making it ideal for emergency or resource-limited settings.

## Contribution

A pretreatment-free, visual biosensing method for ABO/Rh blood typing using a microfluidic chip with improved mixing units.

## Key findings

- The biochip detects blood types using visible RBC cluster accumulation without sample pretreatment.
- The sensor works with as little as 10 μL of blood and provides results in 5 minutes.
- The biochip has a detection limit of 3 × 10⁶ cells/mL and costs about $0.2 per chip.

## Abstract

Rapid blood type detection in point-of-care testing (POCT) scenarios is crucial for various clinical treatments. In this study, we present a sensitive, cost-effective, and straightforward biosensing approach for visual blood typing that notably simplifies the procedure by eliminating any need for blood sample pretreatment. Our technique achieves this by directly trapping and accumulating red blood cell (RBC) clusters within a photolithography-based microfluidic chip, thereby bypassing complex preprocessing. By employing an antigen–antibody assay involving isoagglutinins A, B, and/or D on the RBC surface and their corresponding antibodies, we effectively determine blood types. When antibodies are present, the corresponding RBCs bind to the antibody-conjugated RBC clusters, which are subsequently trapped within the microfluidic accumulation chip, resulting in the formation of a visible bar. The blood group can then be readily identified by observing this visual bar with the naked eye or under microscopy. Notably, we integrate two continuous mixing units (Z and S) at the entrance of the biochip to improve mixing efficiency and accelerate the antigen–antibody interaction. This method demonstrates high selectivity, accuracy, and stability across various clinical blood samples. Moreover, the sensor operates with minimal sample volume (as low as 10 μL) and delivers results within 5 min. The fabrication cost of the PDMS-based biochip is approximately $0.2 per chip, and the limit of detection (LOD) is determined to be 3 × 106 cells/mL, indicating excellent sensitivity and affordability for practical use. Overall, this biochip provides a fast, low-cost, and reliable solution for emergency blood typing, particularly in resource-limited settings.