A gentle touch: load cells in medical devices

Many medical devices rely on accurately measuring force, enabling adjustments to be made either automatically or manually. What makes accurate measurement so crucial is that many of these devices are now available for patients to use at home, without a doctor or health professional available.

Equally, load cells have been playing a central role in the research and development of touch-sensitive prosthetics and the understanding of how our sense of touch can affect our body posture and accuracy of movement.

Load cells in home medical devices

Diabetes is a familiar condition that can be managed with insulin injections to maintain stable blood glucose levels. For many, that involves pricking their finger, checking the glucose levels and manually injecting the required amount of insulin. New insulin systems can monitor blood sugar levels and automatically deliver the required insulin, with force sensors ensuring just the right dose is given.

 

Load cells in surgery

The way a patient lies on a table during surgery can affect the ability of the surgeon to operate at the optimum angle. Load cells positioned under the table can monitor the patient’s position, and allow the surgical team to make minor adjustments if required. Equally, monitoring the force applied in orthopaedic surgery can help surgeons balance a new joint on fitting, helping patients recover more quickly and walk more naturally.

 

Load cells in prosthetics testing

Modern prosthetics are almost unrecognisable from those produced 20 years ago, thanks to innovative design combining new materials with engineering skill and a healthy dose of robotics too! As detailed in a fascinating article at 3D Print , researchers from the University of Colorado and Rice University designed a fully articulated, ‘powered’ finger prosthesis that contains a gear transmission system. Load cells were integral to the testing of this mould-breaking design:

“Testing was centered around evaluating force and flexion of the fingertips,.. (using a) load cell powered at 24 V for connecting with the fingertip at varying angles… In evaluating force of the prosthetic finger, the researchers position the load cell within contact of the fingertip, while the controller powered the motor—driving the finger to the load cell.”

 

Load cells and touch

Our sense of touch is the result of mechanoreceptors in our skin feeding back signals to our central nervous system. Touch helps us understand objects better in terms of texture and weight and motion, and of course, helps us manipulate them too. A team of Italian researchers investigated how

“Cutaneous signals can also provide cues for proprioception (the sense of position and movement of our limbs and trunk) in perceptual tasks… therefore, touch can inform our brain about body posture and the location of our limbs in space”

The researchers first asked blindfolded participants to slide their finger over a ridged plate in a straight line away from their body. The ridges on the plate were rotated off centre, and the force applied measured by a load cell under the plate. The results showed that it was remarkably difficult to do without visual feedback as well as touch!

 

Helping children with cerebral palsy walk better

Children with cerebral palsy (CP) suffer from stiff joints, spasms and tight muscles that affect how they stand walk and move. Over 90% of children with CP have problems walking. A team from Northwestern University Medical School wanted to see if they could improve the effectiveness of treadmill training for children with CP.

A resistance force was applied to the right leg of CP patients walking on the treadmill. When the force was released, this resulted in in an increased step length and more efficient walking.

“A one degree of freedom tension/compression load cell was attached in series with the ankle cuff and the motorized cable, (and) was used to record the perturbation forces applied. All position signals from 3D position sensors and the load cell were recorded with a sample frequency of 1000 Hz using a data acquisition board.” 

Interestingly, application of gradual force seemed to have the longest-lasting beneficial effect.

 

Custom load cells for your medical research or testing

Whatever you’re researching or testing, we probably have the load cells you need in stock at our online shop. If you don’t see what you need, pick up the phone.

We design, manufacture and deliver our own range of load cells, so we can make whatever you need, to your exact specifications, right here in Reading, Berkshire!

Call us with your requirements – we’re always happy to talk through technical details and specifications so you get the right load cell for the job.