Abstract
Thanks to advanced semiconductor microfabrication technology, chip-scale integration and miniaturization of lab-on-a-chip components, silicon-based optical biosensors have made significant progress for the purpose of point-of-care diagnosis. In this review, we provide an overview of the state-of-the-art in evanescent field biosensing technologies including interferometer, microcavity, photonic crystal, and Bragg grating waveguide-based sensors. Their sensing mechanisms and sensor performances, as well as real biomarkers for label-free detection, are exhibited and compared. We also review the development of chip-level integration for lab-on-a-chip photonic sensing platforms, which consist of the optical sensing device, flow delivery system, optical input and readout equipment. At last, some advanced system-level complementary metal-oxide semiconductor (CMOS) chip packaging examples are presented, indicating the commercialization potential for the low cost, high yield, portable biosensing platform leveraging CMOS processes.
Highlights
Medical diagnostics have come to play a critical role in healthcare by providing early detection and diagnosis of disease [1], improving timely and appropriate care [2], protecting the safety of medical products such as blood for transfusion [3], and reducing healthcare costs [4]
For an evanescent field label-free biosensor, detection limits (DLs) can be specified in three units: (i) DL in units of refractive index units (RIU) aims to characterize the sensing capability in bulk solution, which offers a rough comparison among different sensors; (ii) DL in units of pg/mm2 aims to characterize the sensing capability at sensor’s surface by using surface mass density; and (iii) DL in units of ng/mL
In 2013, Fard et al fabricated and characterized the strip-waveguide based phase-shifted Bragg grating in the SOI platform, and the Q-factor was measured to be 27,600, which led to a experimental intrinsic detection limit (iDL) of 9.3 × 10−4 RIU [115]
Summary
Medical diagnostics have come to play a critical role in healthcare by providing early detection and diagnosis of disease [1], improving timely and appropriate care [2], protecting the safety of medical products such as blood for transfusion [3], and reducing healthcare costs [4]. The enzyme-linked immunosorbent assay (ELISA), which has been the gold-standard method in biomarker detection and validated for more than 40 years, can obtain an ultra-low detection limit (∼1 pM) [6] This method is based on a label-based approach which delays results, adds to costs due to specialized reagent requirements, and needs complex micro-evaluations using large, automated analyzers. The development of practical biosensors is one of the most promising approaches to satisfy the growing demand for effective medical diagnostic technologies [7]. Examples of some state-of-the-art packaged on-CMOS sensing platforms are reported, showing a promising prospect for the development of fully integrated, portable, lab-on-a-chip biosensing architectures for multiplexed label-free diagnostics
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