Engineering Issues for Connectors in Medical Purposes

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The medical gadget business is very regulated the place merchandise are cleared by the FDA earlier than they’ll even be marketed. This course of categorizes these gadgets into totally different lessons (I, II, and III) and, relying upon the danger to the affected person and operator, will both require kind of oversight and management by way of requirements compliance. Together with the medical gadgets and tools, particular varieties of connectors are sometimes subjected to the identical stage of scrutiny. These connectors would require strict compliance with the IEC 60601-1 requirements to forestall hurt to both the affected person or operator. Connectors which can be steadily dealt with by medical personnel, for instance, will typically require polarization of the connector head in addition to the flexibility to visually differentiate between connectors as a way to forestall mismatches and attainable disastrous penalties. 

Whereas this will likely be touched upon on this piece, this text will focus extra on the connectors used inside medical tools (e.g., board-to-board, wire-to-board, and wire-to-wire) in addition to ruggedized implementations of universally used connectors (e.g., USB, HDMI, D-Sub). These connectors usually are not application-specific, nevertheless, they’re nonetheless necessary to the performance of medical tools/gadgets and should typically nonetheless be ruggedized to forestall them from malfunctioning inside and out of doors of their digital enclosure.

Medical gadget developments

Medical expertise has developed with the proliferation of wi-fi networks of every kind (e.g., WAN, LPWAN, broadband, huge machine sort communications, and so forth.). Wi-fi physique space networks (WBANs), for instance, are supposed to gather physiological knowledge from sensors put in on a affected person and wirelessly transmit the data for monitoring and monitoring functions. The expansion of wearable gadgets has led to improvements in sensing, supplies, and wi-fi knowledge/energy switch, shrinking bundle sizes. Many medical purposes will use superior applied sciences to satisfy next-generation healthcare wants. The expansion of AI has additionally unfold into area of interest medical purposes for analysis and even for surgical procedure carried out remotely with robotic arms (i.e., telesurgery). This development requires power-hungry processing duties on the edge the place energy density and processing functionality in more and more small type components is important. For connectors, this interprets to greater pin counts and energy rankings. Nevertheless, these advances should not detract from their security as that is the last word requirement for medical purposes. 

Medical gadget requirements

The ISO 60601-1 commonplace is without doubt one of the primary requirements used for medical tools and specifies technique of affected person safety (MOPP) and technique of operator safety (MOOP) for gadgets touching a affected person or operator. These safety rankings specify creepage and clearance distances that the majority industrial connectors can not meet the place clearance is the shortest distance by way of air between two conductive components resembling pins. Creepage is the shortest distance between two pins alongside the insulating materials between them. These distances are meant to make sure that no arcing can happen between pins inflicting potential hurt to sufferers and handlers. The usual additionally specifies a most leakage present that flows from the probe contact to floor by way of the affected person for 3 classifications: Sort Physique (B), Physique Floating (BF), and Cardiac Floating (CF) as proven in Desk 1. 

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Desk 1: Medical gadgets are classes in line with IEC 60601-1.

A few of the common requirements for the various kinds of connectors and electronics present in medical tools could be seen in Desk 2. 

Desk 2: An outline of varied requirements inside medical purposes. 

As proven above, there may be an excessive amount of regulation round digital medical tools from their high quality assurance and software program, to restrictions in medical gadget {hardware} realization. Designers and producers should adjust to these varied labeling, high quality evaluation, supplies and different necessities as a way to clear their product with the FDA. That is very true when the tools beneath query connects to a affected person. There are, nevertheless, digital gadgets and tools that don’t essentially work together immediately with a affected person. These gadgets nonetheless require a level of ruggedization in opposition to the potential stressors and strains of the healthcare setting. 

Mechanical necessities in medical tools

Medical tools will use various kinds of modalities to check, monitor, or obtain a selected process. Many of those machines will use a mixture of mechanical, hydraulic, pneumatic, digital, optical, and radiological rules for imaging, sensing, actuation, and management. All of those applied sciences could cause mechanical, environmental, and electrical pressure to the connectors. 

A blood analyzer, for instance, will rely and establish blood cells at excessive velocity with accuracy to find out a affected person’s common well being standing and has turn into a routine evaluation for varied technique of detection. The machine itself will take a pattern, typically manually drawn by venipuncture, and can prep the pattern by way of dilution or centrifugation (e.g., spinning blood by way of motor) and use optical or digital sensors for measurement. The pattern could also be damaged down into smaller volumes (aliquoting) as a way to carry out a number of exams on a single pattern. These aliquoted samples are then transported to varied components of the machine and mixed with varied reagents in a mixing chamber to carry out these totally different exams with the usage of hydraulic strains and valves. Samples could be distributed by way of hydraulic dispensers into an analyzer cassette. A primary block diagram of a blood analyzer could be seen in Determine 1.

Determine 1: Primary block diagram of blood analyzer¹.

This machine alone is sort of refined and would require exact timing and fluid controls to course of many samples. The management board throughout the machine will use each header connectors and card edge connectors for sign and energy supply between PCBs. To ensure that these connectors to operate reliably, they’ll require vibration resistance on account of the usage of mechanical strategies resembling centrifugation and hydraulic management programs. 

Connectors in excessive vibration environments resembling with moveable medical tools are prone to fretting corrosion the place the rubbing that happens on the metallic joints of a connection can rub off the plating in addition to the underlying materials inflicting corrosion―a situation that worsens with time. This sort of abrasion additionally happens with frequent mating cycles. A thicker plating will mitigate the danger of that potential failure mode. In different connectors, a excessive retention energy will guarantee any connection isn’t reversed simply. Some examples of excessive retention energy connections are threads, screw-locks, bayonet-style mates, and latches. 

Environmental necessities in medical tools

Medical gadgets have the potential to be subjected to ingress from splashes of chemical compounds, water, and so forth. in addition to mud. A level of moisture and corrosion resistance could also be obligatory as a result of potential splashes from reagents, as an illustration, within the blood analyzer talked about above. For moveable medical tools it’s particularly essential to ruggedize connectors with an ingress safety (IP) ranking. These rankings will classify the extent of mud and water resistance the connector has whereas mated. A connection that may be subjected to immersion in water with an IP67 ranking or above, will most definitely be capable of endure among the splashes that happen in a medical setting.

Electrical necessities in medical tools

One other consideration in medical purposes is the potential for each radiated and performed emissions. One of many main causes of apparatus failing to satisfy emission necessities are connectors and cabling. Cable assemblies can act as an antenna, radiating undesirable noise from medical tools. This noise can, for instance, emanate from the machine’s inner energy provide with excessive velocity switching gadgets. The cable may also conduct noise from different sources that it’s in touch with and produce that to delicate inner circuitry which may trigger tools malfunctions. Connectors that include metallic shells will help mitigate EMI in medical tools in order that it stays inside compliance and doesn’t intervene with neighboring gadgets.

Card edge connectors in medical tools

Card edge connectors enable for PCBs with a collection of pads alongside their edge to be inserted immediately within the connector to interface with one other system. These are sometimes utilized in computer systems as growth playing cards, reminiscence modules, or in knowledge acquisition (DAQ) playing cards to hook up with a excessive velocity interface resembling PCIe. The blood analyzer, for instance, will use DAQ playing cards within the A/D pattern system to gather and course of incoming sensor knowledge. A affected person monitoring system may additionally require card edge connectors to broaden its storage or take a look at capabilities. 

EDAC has an enormous vary of card edge connectors for some of these purposes. Greater gold plating thicknesses on contacts make sure that the extra reactive base metallic used within the pins don’t oxidize and negatively impression conductivity. This thicker plating additionally will increase the connector’s resistance to vibration.

One other danger that comes with vibration, particularly in card edge connectors, is a doubtlessly worsening connection or intermittent connections. Card edge connectors present some elastic assist within the occasion a circuit card is shifting on account of vibrations or transient shock. EDAC’s bellow-style contacts present a superb contact spring pressure to extend vibration resistance. After mating, a excessive integrity connection is fashioned with the copper alloy contacts which have a low resistance of at most 10 mΩ (Determine 2). 

Determine 2: Qualities of EDAC’s card edge connectors that make these connector vibration and corrosion resistant for medical tools resembling blood analyzers. 

For extra vibration resistance, EDAC gives metal-to-metal card edge connectors with a excessive reliability interlock mate. This mate makes use of an progressive hermaphroditic contact design. These equivalent contacts make the most of a fork-like form that slides collectively for a gas-tight mate. On the cross-section, the beveled edges of the contact pins float within the insulator, permitting for motion whereas sustaining a powerful contact regardless of vibration and mechanical shock (Determine 3). This mate removes the rigidity related to conventional card connections, the place stiff leads may yield a shorter life than these interlocked varieties of mates.

Determine 3: EDAC’s card edge connector with a hermaphroditic contact design (prime) and a cross-sectional view of the mate exhibiting a gas-tight connection that may face up to motion on account of vibration and shock.

Header connector in multi-board options for medical gadgets

Header connectors are universally utilized in all multi-board options to simply join between boards. Sometimes, versatile cables resembling ribbon cables are used because the cabling whereas headers are the connector heads. These connectors are inevitably present in management boards going into blood analyzers in addition to different medical tools resembling X-rays, CAT scanners, ultrasound tools, diagnostic cardiology tools, MRI machines, heart-lung assist programs, affected person monitoring programs, and extra. They’re the go-to cost-effective resolution for wire-to-board and board-to-board connectors. EDAC gives commonplace field headers in addition to extra specialised E-Socket and E-Pin headers, excessive energy headers, and DIN headers. All of those could also be appropriate for medical purposes.

The E-Socket receptacle and E-Pin male headers mate to supply dependable board-to-board connections. As proven in Determine 4, the fork design of the E-Socket receptacle can sufficiently grasp the E-Pin male connector with a most of 10 mΩ contact resistance. The excessive conductivity copper alloy used within the pin connections gives each a low resistance and a greater contact spring pressure. As much as 50µ” of gold plating can be utilized for a excessive resistance to corrosion and pin injury on account of vibration. Whereas a base materials of UL 94V-0 Thermoplastic Polyester is used for an working temperature vary from -40oC to 105oC, different excessive temperature supplies can be utilized for an prolonged temperature vary. Given the sturdiness of those connections, they’ll face up to a minimal of 200 mating cycles. 

Determine 4: E-Socket and E-Pin headers will mate to type a vibration resistant board-to-board connection. 

For energy connections between circuit boards, excessive energy headers can be used providing as much as 20 amps of rated present with built-in floor aircraft contacts which can be offset from the ability connections. The facility pins themselves have a sizeable pitch of 4 mm to mitigate the danger of arcing between contacts, thereby growing the security of the connection (Determine 5).

Determine 5: Energy header connectors provide as much as 20 amps of present with twin row configuration and a 4mm pitch.  

In-line connectors in medical tools

Inside medical tools such because the blood analyzer use case listed above, the necessity for a wire-to-wire and wire-to-board resolution resembling an in-line connector could also be obligatory the place a card-edge or header connector will not be adequate. In-line connectors are characterised by their comparatively small pin rely. These are perfect for wire harnesses inside medical programs. In lab environments, in-line connectors might face publicity to fluids, doubtlessly inflicting each corrosion and moisture ingress. This could result in an intermittent or failed connection. EDAC gives a variety of IP67 rated in-line connectors making them utterly mud tight and in a position to face up to non permanent immersion in water (Determine 6). EDAC is ready to accomplish a water-proof reference to its E-seal expertise that seals your complete again of the connector fairly than the person pins. This yields an entire seal with a easy end, and ensures no water ingress, as absolutely examined to IP67 requirements

Determine 6: EDAC’s waterproof in-line connectors can face up to immersion in water, making them immune to the splashes in a lab setting. 

D-sub and HDMI connectors in medical tools

D-subminiature connectors are standard interfaces for serial communications resembling RS-232 or RS-485. The connector could be present in purposes spanning from private computer systems for residences to controllers for industrial automation. Medical gadgets and tools will inherently require the usage of sensors and actuators to watch totally different vitals, measurements, and carry out particular duties. Many defibrillators will use a D-sub connector to hook up with a sensor that measures oxygen saturation (Determine 7). 

Determine 7: Philips D-sub-to-pulse-oximeter probe for a defibrillator. Supply: Philips

 A processing unit resembling a DAQ system can then digitize any sensor indicators, e.g., sensory knowledge from blood evaluation, and convert them to stream transmission protocols resembling RS-232 by way of D-sub connectors to be analyzed by a neighborhood laptop. DAQ programs are used for processing in many alternative medical use instances together with imaging resembling magnetic resonance imaging (MRI), positron emission tomography (PET), ultrasound and diagnostics purposes that demand greater knowledge acquisition bandwidths to each enhance imaging decision and permit for faster outcomes processing (Determine 8).

Determine 8: Plexon OmniPlex Neural Knowledge Acquisition System with as much as 512 neural recording channels. Supply: Plexon Inc.

D-sub connectors and HDMI connectors can be used to feed video indicators to computer systems and screens to view pictures. Level-of-care ultrasound (POCUS) , for instance, will use a number of video output choices together with VGA, DVI, and HDMI in addition to extra legacy video outputs resembling S-video or C-video (Determine 9). Each VGA, DVI, and VESA are variants of the D-sub connector optimized for video purposes. EDAC gives all of those variations on the D-sub connector. 

Determine 9: VGA, HDMI, and Ethernet ports seen on the Philips CX50 Ultrasound Machine. Supply: Philips

D-sub connector engineering issues

The varied ruggedization strategies for the header and card edge connectors additionally apply to D-sub connectors. These connectors can endure fixed vibration that can deteriorate the standard of the connection over time. Enough gold plating and correct mounting will help mitigate these results. D-sub connectors inside medical purposes must be IP-rated to forestall injury from mud and moisture. EDAC gives D-sub connectors which can be absolutely submersible with an IP67 ranking that use the E-seal expertise described earlier. The connectors could be plated with as much as 30µ” of gold to supply corrosion, vibration and mechanical shock resistance. 

EDAC’s D-sub connectors include metallic shells, when related chassis floor and to the shielding of a cable, this will successfully mitigate EMI (Determine 10).

Determine 10: IP67 rated D-sub cable meeting with a water-proof hood and rubber seal. Metallic hoods can be used the place EMI safety is crucial. 

HDMI connector engineering issues

HDMI connectors are a regular interface for shows, nevertheless, the traditional HDMI connector will seemingly fail or disconnect in a medical setting the place vibration, mechanical shock or moisture ingress might happen. EDAC’s waterproof HDMI connectors use the E-seal expertise for resistance to splashes and doubtlessly corrosive substances. To supply a dependable, vibration resistant connection, the connectors function quarter-turn twist-and-lock over mould (Determine 11). 

Determine 11: IP67 rated HDMI connectors with a quarter-turn twist-and-lock over mould to forestall disconnects within the occasion of vibration and shock.

Spring-loaded pogo connectors in medical tools

Connector options for wearables charging or manufacturing exams would wish a simple blindmate with a excessive sturdiness. Spring loaded or (pogo pin) connectors could be tailored to suit medical purposes resembling listening to aids for a simple clip/unclip charging skill. 

EDAC’s spring loaded connectors are extra handy than commonplace pogo pins by utilizing magnets to each present polarization and enhance the reliability of the connection (Determine 12). These connectors can preserve a connection in environments with vibration with a precision machined end. One issue that maintains a excessive vibration resistance is a spring loaded connector’s stroke distance. The stroke distance is the space from the resting place of the pogo pin to its most compression place when mated. The stroke distance of EDAC’s pogo pins ensures that the connector can preserve a dependable contact throughout vibration and through minor misalignments that might usually break a reference to commonplace contacts. With a sturdiness of as much as 30,000 mating cycles, the EDAC connectors are in a position to face up to the strains of frequent connectors and disconnects. The connectors are assembled right into a high-temperature thermoplastic for a large working temperature vary. 

Determine 12: EDAC’s spring loaded connectors could be tailored for testing/charging purposes for wearables and medical gadget manufacturing. 

Conclusion

Connectors used inside medical tools are sometimes topic to stringent medical requirements. That is notably the case when the connector is immediately related to a affected person or managed by medical personnel. Whereas there are some application-specific connectors (e.g., a connector that mates to ultrasound tools from the probe), the medical business additionally makes use of connectors which can be ubiquitously utilized in most electronics tools. This consists of wire-to-wire (in-line), wire-to-board (in-line, header), board-to-board (header, card edge) connectors, and different typical connectors resembling D-subs or HDMI. These connectors might have to be ruggedized in opposition to vibrations, mechanical shock from dealing with (e.g., drops, crush, and so forth.) and can seemingly have to be each mud and watertight to mitigate the danger of failure from publicity to fluids and chemical compounds. EDAC gives an enormous vary of connectors for medical purposes that meet these necessities. 

References

1. L. Tao, L. Luo and F. Li, “The design and implementation of blood analyzer management system based mostly on the fluid stream aperture gadget,” 2015 IEEE Worldwide Convention on Mechatronics and Automation (ICMA), Beijing, China, 2015, pp. 174-178, doi: 10.1109/ICMA.2015.7237477.
2. Balter ML, Chen AI, Fromholtz A, Gorshkov A, Maguire TJ, Yarmush ML. System Design and Improvement of a Robotic System for Automated Venipuncture and Diagnostic Blood Cell Evaluation. Rep U S. 2016 Oct;2016:514-520. doi: 10.1109/IROS.2016.7759102. Epub 2016 Dec 1. PMID: 28239509; PMCID: PMC5321615.