FAQ

The current trend toward miniaturization, simplification, and automation of analysis systems has led to the emergence of the so-called Lab-on-a-Chip (LOC) or Total Analysis MicroSystems (µTAS).

Lab-on-a-Chip (LOC) or Total Analysis MicroSystems (µTAS) are devices that integrate one or several analytical processes (sample pretreatment, mixing, reaction, injection, separation, detection, etc.) performed in a laboratory into a small device (centimeters or millimeters). LOC devices are characterized by providing high analysis speeds, great versatility, high efficiency, low cost, the ability to conduct parallel assays, and reduced sample and reagent consumption and waste generation [+].

Microfluidics (the manipulation of fluids in channels measuring tens of microns) can be considered part of the Lab-on-a-Chip technologies that have been developed in parallel, evolving into a new research field.

A sensor or detector is a device capable of measuring a physical quantity and converting it into a signal that can be read by an observer or an electronic instrument.

Microfluidics falls within an interdisciplinary field that deals with the behavior and control of extremely small volumes of fluids and the design of systems that use these small volumes [+].

Microfluidics, the manipulation of fluids in channels measuring tens of microns, can be considered part of Lab-On-a-Chip (LOC) technology, which has continuously evolved and become a distinct new field.

Electrophoresis on microchips (ME) is an emerging and promising method for rapid analysis of very small quantities of analytes. Electrophoresis microchips can be framed within microfluidic systems and Lab-on-a-Chip.

Electrophoresis microchips have proven to be a powerful tool for developing new analytical systems with multiple applications. They allow for the injection and separation of different components present in a complex sample.

However, these devices require a miniaturizable and sensitive detection system, as well as additional instrumentation to carry out the analysis. Electrochemical detection (ED) has proven to be suitable for this type of device due to characteristics such as ease of miniaturization, sensitivity, low cost, portability, and compatibility with microfabrication techniques. Currently, most electronic components can be easily miniaturized. In contrast, optical components from different detection systems are not easy to miniaturize without losing functionality. In contrast, electrochemical detection systems can be miniaturized without losing sensitivity and even improving the signal-to-noise ratio.

Voltammetry encompasses a series of electrochemical methods based on measuring electric current by applying different potential ramps. Depending on the potential ramps, there are several voltammetric techniques such as:

• Cyclic Voltammetry (CV)
• Linear Sweep Voltammetry (LSV)
• Differential Pulse Voltammetry (DPV)
• Normal Pulse Voltammetry (NPV)
• Square Wave Voltammetry (SWV)
• Alternating Current Voltammetry (ACV)

Voltammetric experiments are conducted with a typical three-electrode system consisting of a  working electrode (WE), a  reference electrode (RE), and a  auxiliary or counter electrode (AE / CE) [+].

Amperometry is an electrochemical technique based on monitoring the electric current generated in a redox process over time. It is a very useful detection method in flow systems (FIA, CE, HPLC) and microfluidics.

There are different amperometric detection methods such as DC amperometry or pulsed amperometry (PAD)[+].

Potentiometry is an electrochemical technique based on measuring the potential of a solution. Typically, the potential is measured between two electrodes: a reference electrode, with a constant potential, and an indicator electrode, whose potential changes with the composition of the solution. Thus, the potential difference between the two electrodes provides insight into the composition of the sample.

Potentiometry generally employs indicator electrodes sensitive to a specific ion, thus they are also known as ion-selective electrodes (ISE). The most common potentiometric electrode is the glass membrane electrode used in a pH meter [+].

A variant of potentiometry is chronopotentiometry, which consists of applying a constant current and measuring the potential as a function of time. In these experiments, a typical three-electrode system is generally used for better control of the current applied in the electrochemical cell without affecting the measured potential.

Electrochemical impedance spectroscopy (EIS) is a non-destructive technique that allows for the characterization of a wide variety of electrochemical systems and determines the contribution of the processes occurring at the electrode and the electrolyte within those systems.

This technique is based on applying a small amplitude alternating signal (5 to 20 mV) to an electrode immersed in an electrolyte. The initial disturbance (applied) and the electrode’s response are compared by measuring the phase change of the current and voltage and by measuring their amplitudes. This analysis can be performed in the time or frequency domain, using a spectrum analyzer or a frequency response analyzer (FRA).

As a result, some of the benefits of EIS are as follows:

• The information provided by EIS is much greater than that from DC techniques or simple frequency measurements.
• EIS can distinguish between two or more electrochemical reactions occurring simultaneously.
• EIS can identify diffusion-limited reactions, such as diffusion through a passive film.
• EIS provides insights into the capacitive behavior of the system.
• EIS can test components within an assembled device using the device’s own electrodes.
• EIS can provide information about the rate of electron transfer reactions.

While interpreting EIS data can be intricate, it serves as a valuable tool in numerous promising applications, including:

• Studying the corrosion of metals.
• Analyzing adsorption and desorption at the electrode surface.
• Investigating the electrochemical synthesis of materials.
• Examining the kinetics of catalytic reactions.
• Developing sensors for electroactive markers.
• Studying ion mobility in energy storage devices such as batteries and supercapacitors.

Photolithography or optical lithography is a process widely used in the microelectronics industry. The process involves transferring a pattern from a photomask to the surface of a wafer. The wafers used as lithographic substrates can be silicon, quartz, glass, polymers, or even metals.

Photolithography (also referred to as “microlithography” or “nanolithography”) operates similarly to traditional lithography used in printing and shares some fundamental principles with photographic processes [+].

This technology is very useful in the production of microfluidic devices as well as thin-film electrodes and microelectrodes (“thin-film”).

The deposition of thin metallic layers is widely used in microfabrication processes. The deposition of these metallic layers on different substrates (silicon, glass, polymers, etc.) can be carried out using various technologies such as physical vapor deposition (PVD) or chemical vapor deposition (CVD).

PVD is characterized by a process in which the material transitions from a condensed phase to a vapor phase and then back to a condensed thin film phase. PVD processes include sputtering, evaporation, pulsed laser deposition, electron beam deposition, etc…. [+].

In CVD, the substrate (wafer) is exposed to one or more volatile precursors, which react or decompose on the substrate surface to produce the desired deposit. Frequently, volatile byproducts are also produced, which are removed by a gas flow passing through the reaction chamber [+].

Thus, the combination of photolithography, metal deposition, and lift-off allows for the production of electrodes and microelectrodes with high precision and resolution that can be used in microfluidic devices and sensors.

The “lift-off” process, within microfabrication technologies, is a method for creating structures (modeling) of a specific material on the surface of a substrate (e.g., wafer) using a sacrificial material (e.g., photoresist). It is an additive technique in contrast to the more traditional subtractive technique, such as etching. The scale of the structures can vary from nanometric scale to centimeters or more, but they are generally in micrometric dimensions [+].

Etching is used in microfabrication to chemically remove layers from the surface of a wafer during the manufacturing process. Etching is a critically important process, and each wafer undergoes many etching steps before it is completed. Different processes such as wet or dry etching can be used to remove specific material layers from the wafers [+].

Wet etching processes use liquid-phase “wet” etching agents. The wafer is immersed in a bath of the etching agent, which must be stirred to achieve good process control. In wet etching, it is essential to properly choose the solution in which the substrate is immersed to obtain the desired characteristics. For example, hydrofluoric acid (HF) is commonly used to etch glass substrates or substrates based on silicon oxide.

Dry etching refers to the removal of material by exposing it to an ion bombardment (usually a plasma of reactive gases such as fluorocarbons, oxygen, chlorine, boron trichloride, sometimes with nitrogen, argon, helium, and other gases), causing parts of the material to detach from the exposed surface [+]. A common type of dry etching is reactive ion etching (RIE) and deep reactive ion etching (DRIE).

Unlike many (but not all) of the chemicals used in wet etching, the dry etching process typically allows for directional or anisotropic etching.

In microfabrication technologies, a bonding process involves sealing different open microstructures to obtain fully closed devices. This process can use various technologies such as thermal bonding, anodic bonding, or adhesive bonding.

Thermal bonding is a process used to join two substrates, typically of the same nature, by applying pressure and a temperature close to the glass transition temperature (Tg) of the material [+].

Anodic bonding is a wafer bonding process used to seal glass to silicon or metal without introducing an intermediate layer. It is commonly used to bond glass to silicon wafers in electronics and microfluidics. This bonding technique, also known as assisted bonding or electrostatic sealing, is primarily used to connect silicon/glass and metal/glass through electric fields [+].

Adhesive bonding (also known as glue bonding) describes a wafer bonding technique that involves applying an intermediate layer to connect substrates of different materials [+].

The product portfolio of MicruX includes:

• Electrochemical sensors and platforms.
• Microfluidic devices and platforms.
• Portable analytical instrumentation.
• Other accessories for electrochemistry and microfluidics.

Users can browse through our online catalog for more information about our products and services.

MicruX has extensive experience in metallic electrodes and microelectrodes manufactured with dimensions of up to 5 microns. Thin-film technologies allow for the fabrication of various designs of (micro)electrodes, including microelectrode arrays (MEA), interdigitated electrodes (IDA/IDE), and interdigitated ring electrode arrays (IDRA).

Additionally, thin-film (micro)electrodes can be easily integrated with microfluidics to create more versatile devices for multiple applications.

Electrochemical sensors are fabricated on a glass substrate. Currently, the electrodes are available in metallic gold or platinum with a thickness of 150 nm. Additionally, a titanium layer (50 nm thick) is used as an adhesion layer between the glass substrate and the functional metal (gold or platinum).

Standard electrodes are equipped with a SU-8 resin isolation layer to passivate the non-functional parts of the sensors, keeping the electrochemical cell and electrical connections open. Electrodes can also be provided without the passivation layer.

MicruX provides microfluidic chips (electrophoresis microchips and thin-film microfluidic sensors) manufactured from hybrid SU-8/Glass material. The microfluidic channel structures are built in SU-8 resin on a glass substrate. The covering of the channels with the inputs/outputs is also made from SU-8 resin.

Other materials can be considered upon request.

Yes. The technologies available at MicruX allow for the development of custom devices to meet the requirements of our clients. In this case, the price will differ from standard devices. However, we can prepare a quote without any obligation.

Customers have several options to acquire products from MicruX:

1. Purchase order sent via email or fax. Customers can contact us directly by email (sales@micruxfluidic.com) or by phone (+34 984151019) to obtain a formal quote for the products they are interested in. The quote will be sent as soon as possible, generally within 24-48 hours. After that, they can send their purchase order (indicating the quote number) via email or fax.
2. MicruX online store. Registered customers can browse our website to add the products they are interested in to their shopping cart. This way, they can directly process the purchase and payment in our secure online store. At the end of the purchasing process, a confirmation email will be sent for the order. This is a quicker and more efficient way to process the purchase of MicruX products.

Registered users (by creating a free account) can check the prices of each product directly on the online store. The prices displayed in the online store are EX-WORKS and do not include taxes, fees, or shipping costs. Shipping costs and taxes will be included at the end of the purchasing process.

In this regard, creating an account on the MicruX website also has other benefits, such as the ability to track the status of their orders and save their shipping and billing addresses for future orders.