Biomedical Technologies, Biosensors, and Microfabrication Review

Comprehensive vocabulary flashcards covering introductory biology review, biosensor fundamentals, point-of-care devices, CRISPR considerations, and photolithography microfabrication steps.

Biomarker

A biological molecule found in blood, other body fluids, or tissues that is a sign of a normal or abnormal process, or of a condition or disease; also referred to as a molecular marker or signature molecule.

CD4/CD8

A cell surface protein biomarker expressed on T cells that is utilized for HIV/AIDS management.

CD64/CD11b

A cell surface protein biomarker expressed on cells that is used as an indicator for sepsis and bacterial infections.

Antibody

A Y-shaped protein produced by animals in response to infection or foreign substances, consisting of an antigen-binding fragment ($F_{ab}$) and a constant fragment ($F_c$).

Epitope

A specific location on a protein or antigen that is recognized and bound by an antibody.

Cluster of Differentiation

A standardized protocol used for the identification and investigation of cell surface molecules to provide targets for immunophenotyping.

Immunophenotyping

A laboratory technique used to analyze and study the specific proteins expressed by cells.

DNA Denaturing

The process of converting double-stranded DNA into single-stranded DNA by breaking hydrogen bonds between base pairs using heat or chemical agents.

Uracil

A nitrogenous base present in RNA that replaces thymine and is chemically defined as unmethylated thymine.

Polymerase Chain Reaction

A molecular technique used to exponentially amplify a target DNA segment using primers and DNA polymerase through cyclical stages of denaturation ($94\text{--}96\,^{\circ}\text{C}$), annealing ($68\,^{\circ}\text{C}$), and elongation ($\approx 72\,^{\circ}\text{C}$).

CCR5

A gene encoding a cell surface receptor used by HIV to infect cells, which was targeted for deletion in the 2018 human embryo gene-editing experiment conducted by Dr. He Jiankui.

Point-of-Care Sensor

An automated, handheld, disposable diagnostic device designed to analyze small sample volumes and deliver test results in under $5\text{--}10\,\text{min}$ at or near the site of patient care.

Personalized Medicine

A clinical model that customizes diagnostic and therapeutic decisions for individual patients based on their unique biological response to disease and treatment.

BioMEMS

Biological or Biomedical Micro-Electro-Mechanical Systems that integrate micro-scale components for medical, diagnostic, and biological applications.

Bio-nanotechnology

The biomedical application of nanotechnology tools, principles, and structures engineered at physical scales under $100\,\text{nm}$.

Biosensor

An analytical device that combines a biologically sensitive element with a physical or chemical transducer to selectively and quantitatively detect specific biomolecules in a sample.

Biochip

A microelectronic-inspired device designed for the delivery, processing, analysis, or detection of biological molecules and biological species.

Cleanroom

An environmentally controlled workspace designed to maintain extremely low concentrations of airborne particulates, quantified by particle count per cubic foot of air.

Class 100 Cleanroom

A cleanroom standardization level (equivalent to ISO Class 5) that maintains fewer than 100 particles larger than $0.5\,\mu\text{m}$ per cubic foot of air.

RCA Standard Clean 1

A chemical wet-cleaning step developed by Werner Kern in 1965 at RCA Laboratories using DI water, ammonium hydroxide, and hydrogen peroxide to remove organic contaminants.

RCA Standard Clean 2

A chemical wet-cleaning step using DI water, hydrochloric acid, and hydrogen peroxide designed specifically to remove ionic contamination and metal ions from a wafer.

Piranha Cleaning

A hazardous wet-cleaning procedure utilizing a combination of sulfuric acid and hydrogen peroxide to remove dense organic residues from substrate surfaces.

Wafer Priming

A surface preparation process involving dehydration baking and the application of adhesion promoters to ensure optimal bonding between a wafer substrate and photoresist.

Spin Coating

A process used to deposit uniform thin photoresist films by dispensing liquid resist onto a substrate and spinning it at high angular speeds to spread the material via centrifugal force.

Positive Photoresist

A type of photosensitive coating used in photolithography whose exposed regions undergo chemical change and are selectively removed by a developer solution. unexposed pattern left behind

common materials: PMMA (polymethyl methacrylate): 220 nm sensitivity + requires longer absorption times), DNQ resists (Diazonaphthoquinone): develop rapidly in alkali solutions, solvents → PGMEA, cellosolve

Negative Photoresist

A type of photosensitive coating used in photolithography where exposed areas cross-link and remain, while unexposed regions are dissolved away by a developer solution.

Common example: SU-8 resists

Soft Bake

A thermal heating step ($60\text{--}110\,^{\circ}\text{C}$) applied after spin-coating photoresist to drive off residual solvent, promote adhesion, and harden the resist layer.

Megasonic Cleaning

A gentle wet-cleaning method utilizing high-frequency acoustic waves ($800\text{--}2000\,\text{kHz}$) to dislodge fine particles smaller than $0.5\,\mu\text{m}$ from wafer substrates.

DNA

deoxyrybonucleic acid, carries genetic instructions for the development, functioning, growth, and reproduction

Base pairs: (1) Adenine-Thymine connected by 2 hydrogen bonds (2) guanine-cystosine joined by 3 hydrogen bonds

RNA

ribonucleic acid, gene regulationa nd expression.

Base pairs: (1) Adenine-Uracil→ unmethylated thymine (2) guanine-cystosine

photolithography process order

wafer cleaning → wafer priming → spin coating → soft bake/pre exposure bake → expose photoresist → post exposure bake →develop the wafer → post-bake/descum

wafer wet cleaning techniques (increasing severity)

wafer degreasing, standard clean 1, standard clean 2, piranha cleaning

Over-exposure

radiation scatters sideways into masked regions, features wider at top. sidewalls slope outward

negative resist: remaining pattern has flared/mushroom top

positive resist: developed trenches/holes get wider

Under-exposure

insufficient exposure at edges/bottom of feature, features become narrower + sidewalls taper inwards

negative resist: features taper to a point

positive resist: trenches don’t fully clear at bottom + taper inwards