A dyne is a small unit of force used in physics, manufacturing, and medicine. It measures the force needed to accelerate one gram of mass by one centimeter per second squared. While most people encounter Newtons as the standard force unit, the dyne remains essential in several fields where tiny forces matter, from testing whether ink will stick to plastic packaging to measuring blood flow resistance in the heart.
The Dyne as a Unit of Force
The dyne belongs to the centimeter-gram-second (CGS) system of measurement, an older framework that predates the modern metric system. One dyne equals 0.00001 Newtons, or put the other way, one Newton equals 100,000 dynes. That makes the dyne useful when you’re dealing with very small forces where expressing things in Newtons would mean writing out awkward decimals.
Physics textbooks and academic papers still use dynes regularly, especially in fields like fluid dynamics, surface chemistry, and electromagnetism where CGS units remain standard. If you’ve seen “dyne/cm” written somewhere, that’s a measurement of surface tension, the force per unit length acting along a liquid’s surface. Pure water, for example, has a surface tension of about 72 dynes/cm at room temperature.
Testing Surface Energy in Manufacturing
The most common real-world use of the dyne is in manufacturing, where “dyne level” determines whether ink, coatings, or adhesives will bond properly to plastic surfaces. Every plastic has a critical surface tension measured in dynes/cm. If a liquid’s surface tension is lower than the plastic’s critical value, it spreads evenly. If it’s higher, the liquid beads up and won’t adhere.
This matters enormously in printing and packaging. Polyethylene, one of the most common packaging plastics, has a critical surface tension of only 31 dynes/cm. Teflon sits even lower at 18 dynes/cm, which is why almost nothing sticks to it. PVC comes in at 39 dynes/cm, and PET (the plastic in drink bottles) at 43 dynes/cm. Nylon reaches 46 dynes/cm, making it one of the easier plastics to print on.
To check whether a surface is ready for printing or laminating, factory workers use dyne pens. These are marker-like tools filled with liquids of known surface tension, available in values from 32 to 56 dynes/cm in steps of 2. You draw a line across the plastic: if the ink stays as a continuous line, the surface energy is high enough for bonding. If the line breaks into droplets, the surface needs further treatment. Most plastics undergo corona treatment (a controlled electrical discharge) to raise their surface energy before printing. Dyne pens let workers verify the treatment worked before running a full production batch, preventing costly waste from poor adhesion.
Measuring Blood Flow Resistance
Cardiologists use dynes to measure how hard the heart has to work to push blood through the body. Systemic vascular resistance (SVR), the total resistance that blood encounters as it flows through arteries and capillaries, is expressed in dyne-seconds per centimeter to the fifth power (dynes·sec/cm⁵). A normal SVR falls roughly between 800 and 1,500 dynes·sec/cm⁵, with an average around 1,060.
Pulmonary vascular resistance, the resistance in the blood vessels of the lungs, uses the same unit but runs much lower, typically between 20 and 120 dynes·sec/cm⁵. These numbers help doctors assess conditions like heart failure, sepsis, and pulmonary hypertension, where abnormal resistance signals that something is wrong with either the blood vessels or the heart’s pumping ability.
Drug Delivery in Muscular Dystrophy
Dyne Therapeutics, a biotech company whose name plays on the physics unit, uses a drug delivery platform built around the concept of force at the molecular level. Their FORCE platform targets a protein called transferrin receptor 1, which sits on the surface of muscle cells and is responsible for pulling iron inside. By attaching therapeutic molecules to an antibody fragment that locks onto this receptor, the platform hitches a ride into muscle tissue, delivering drugs to skeletal, cardiac, and smooth muscle far more effectively than traditional approaches.
The company’s lead programs target two genetic muscle diseases. DYNE-101 is in clinical trials for myotonic dystrophy type 1, a condition where a faulty gene causes prolonged muscle stiffness. The ongoing ACHIEVE trial is tracking whether the drug can correct the abnormal gene activity in muscle tissue. DYNE-251 targets Duchenne muscular dystrophy, a severe condition where muscles progressively weaken due to the absence of a protein called dystrophin. Initial data from the DELIVER trial showed that at 6 months, patients receiving DYNE-251 went from 2.4% dystrophin-positive muscle fibers at baseline to 22.2%, with a favorable safety profile. Those numbers exceeded results from existing approved therapies at the same time point.
Why the Dyne Persists
The international scientific community officially adopted the Newton as its standard force unit decades ago, but the dyne refuses to disappear. In surface chemistry, dyne/cm is so deeply embedded in industrial standards that switching to the metric equivalent (millinewtons per meter, which is numerically identical) would create confusion without any practical benefit. In cardiology, dynes·sec/cm⁵ has been the standard for vascular resistance since the era of early cardiac catheterization, and the reference ranges that doctors rely on are all built around it.
The dyne also has a practical advantage: it operates at a human-friendly scale for the phenomena it measures. Surface tensions of common liquids and plastics fall neatly between 18 and 72 dynes/cm, clean whole numbers that are easy to compare. Vascular resistance values in the hundreds to low thousands are intuitive to work with. Converting to Newtons would shrink these into tiny decimals, making quick mental comparisons harder for the people who use them daily.