This article discusses the use of adhesives in capsule endoscopy. A capsule endoscope is a miniature device that, once swallowed, can capture images of the digestive tract; its shell contains several hundred components—including a lens, an image sensor chip, LEDs, a battery, and an antenna—whose fixation and sealing at every point rely on adhesives, which are also critical to yield and safety.
01 First, take a clear look: where are the 11 adhesive dots located?
Although a capsule is small, it contains all the essential components. From the imaging end to the rear, they are arranged in the following order: an optical window, a lens stack, a CMOS image sensor, a white LED, a PCB/ASIC, a silver oxide battery, a spiral antenna, and a magnetic switch. These components are fixed together and hermetically sealed; virtually every part incorporates adhesive.
Based on their location within the capsule and their intended function, these 11 adhesive application points can be broadly divided into three categories:
- Optical path components: optical windows, lens stacks, CIS mounting, and LED mounting—must be clearly visible.
- Seals: edge sealing, housing joints, and battery securing—all must be properly sealed.
- Functional components: antenna conductivity, encapsulation coating, and magnetic control element fixation—must ensure reliable connectivity and effective protection.
02 Before selecting a model, first pass three stringent thresholds
If you fail to clear these basic requirements, no matter how appealing the other specifications may be, they will be useless.
- Biocompatibility: ISO 10993 series + USP Class VI; tests must include cytotoxicity, sensitization, intradermal irritation, systemic toxicity, implantation, hemolysis, and others. Once the capsule is swallowed and the gel comes into direct or indirect contact with the mucosa of the digestive tract, this stage is the most stringent.
- Sterilization resistance: compatible with gamma radiation, ethylene oxide (ETO), electron beams, and high-pressure steam sterilization. Capsules are generally sterilized before leaving the factory; the gel must not consequently crack, become brittle, yellow discolor, or lose its adhesiveness.
- Solvent-free single-component formulation: no residue after photopolymerization, resulting in a clean process. Intraoperative devices must not contain solvent residues; dispensing must be controllable and capable of automatic detection.
03 When selecting a model, the three variables are what truly matter
Once you have crossed the threshold, proceed with your selection based primarily on three variables.
Light must not penetrate (optical path component) → optical-grade UV adhesive. Since the window, lens, and chip are all located within the imaging optical path, the adhesive must have high light transmittance, low yellowing, low stress, and low shrinkage. Common optical UV adhesives have a refractive index ranging from 1.46 to 1.57; the index should be matched as closely as possible to that of the window material to minimize interfacial reflection. The volumetric shrinkage during curing should also be kept as low as possible—some formulations achieve approximately 0.9%—otherwise, the resulting stress can cause window deformation and imaging distortion.
UV light cannot reach these areas (dark zones) → dual-cure UV adhesive. The joints between the lens module and the main body, as well as deep cavities, are completely out of reach of UV light. If UV curing alone is used, these areas will remain uncured soft zones. A UV humidifying gas or a dual-cure system with direct contact can be employed so that the material can cure into a complete sealing ring even when UV light cannot reach it.
Whether electrical or thermal conductivity is required → conductive adhesive / thermal conductive adhesive. In applications such as antennas, battery terminals, CIS, and LEDs, either electrical continuity or heat dissipation is required, necessitating adhesives with electrical or thermal conductivity.
Next, consider strength and flexibility: for structural strength, chemical resistance, and sterilization resistance, use epoxy; for flexibility, low stress, and a wide temperature range, use silicone; and for rapid, second-level fixation of plastic components, use fast-curing adhesive.
04 The Four Most Common Pitfalls in Assembly
Incomplete curing in the dark zone is the most common issue. UV light cannot reach the edge sealing areas; if dual curing is not selected, the in-factory airtightness test will reveal localized seal leakage. Domestic manufacturers generally perform airtightness testing on each capsule; the consistency of the sealant directly determines the yield rate.
Acid resistance is insufficient. Endoscopic capsules must withstand gastric acid (pH 1–3), which presents more stringent conditions than the intestinal environment. The shell and joint sealants must be resistant to strong acids and high-temperature sterilization. During the development phase, domestic manufacturers noted that achieving acid resistance in the shell itself is inherently a challenging issue.
Magnetic compatibility has been overlooked. The magnetically controlled capsule is manipulated by an external magnetic field through an integrated magnetic sensing unit. The adhesive securing the magnetic module must not contain magnetic conductive fillers, must not interfere with the magnetic field, and must be vibration-resistant and provide precise positioning.
It becomes ineffective after sterilization. Some laminated films appear to have good performance after curing, but once they undergo gamma irradiation or ETO treatment, they become brittle, turn yellow, and lose their tackiness. When selecting a product, comparing its performance before and after sterilization must be included as a mandatory test item.
05 A Reusable Selection Framework
When encountering a similar assembly involving disposable medical consumables, you can follow this sequence for assessment:
1. First, determine whether the component is part of the optical path: If so, use optical-grade UV adhesive to ensure refractive-index matching, low yellowing, low shrinkage, and a high Tg. 2. Next, determine whether the light can reach the component: If not, employ dual-curing (UV with humidifying gas or contact curing) as a backup solution. 3. Then, determine whether electrical or thermal conductivity is required: If so, use conductive or thermally conductive adhesives. 4. Next, consider strength and flexibility: Use epoxy for structural applications, silicone for flexibility, and fast-drying adhesive for rapid application. 5. Finally, ensure compliance with certification requirements: Include ISO 10993 and USP VI, along with sterilization resistance; none of these requirements may be omitted.
A quick mnemonic: For visible applications, use UV; for invisible applications, use dual-curing; for electrical conductivity, choose conductive or thermally conductive options; for strength, choose epoxy; and for flexibility, choose silicone.
ending
Capsule endoscopes are single-use, high-consumption consumables; the seal is an essential component for each unit and also represents a critical weak point affecting sealing performance and reliability.
The parameters and framework provided here serve as the starting point for product selection, not the final destination. For each specific application site, it is still necessary to create samples, conduct actual testing, and complete sterilization validation before proceeding to mass production. A truly viable solution can only be validated through operation on a real-world production line.
Verified JOME Engineering Grades & Specification Cross-Reference
To qualify an industrial-grade adhesive, potting compound, or thermal interface material for this application, compare verified Shanghai Jome Industrial Co., Ltd. (JOME) formulations below or explore our primary category hubs: UV Curing & Optical Clear Adhesives and Medical-Grade Silicone Gel & Special Elastomers.
| JOME Grade / SKU | Polymer Chemistry & Cure | Key Verified Specification | Primary Industrial Application |
|---|---|---|---|
| GM 3239 / GM 3218 | 1K Optical Clear UV Acrylate Adhesive (LOCA) | >98% light transmittance | 3–10s UV LED cure | Non-yellowing | LiDAR optical windows, display cover glass, PMMA/PC/glass lenses |
| JM 2081 | 1K UV Cationic Epoxy Active-Alignment Adhesive | Low volumetric shrinkage (<1.2%) | High glass/ceramic/metal bond | LiDAR transmission modules, optical transceivers, endoscopic lenses |
| JM 3302 / JM 380 | UV/Moisture Dual-Cure High-Resilience Silicone Sealant | Rapid UV cure + shadow moisture cure | Replaces rubber O-rings | Medical anesthesia masks, disposable catheters, IP68 sensor housings |
| JOMS 5707 | 2K Medical-Grade Biocompatible Addition Silicone Gel | Platinum-cured, ultra-pure, skin-safe & non-cytotoxic | Medical wearables, endoscopic capsules, patient interface cushions |
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Matched JOME Industrial Formulations: For production bonding, potting, and sealing qualification in this application, evaluate UV silicone dual-curing high elasticity sealant can replace rubber sealing rings, UV light-curing rapid fixation structural adhesive, UV-curable epoxy-based adhesive, and High resilience UV glue replaces silicone rubber sealing ring (ISO 9001:2015 and CTI RoHS 2.0 verified; free engineering samples shipped via UPS freight collect).
Frequently Asked Engineering Questions
Q: Which JOME adhesive or potting grades are recommended for requirements and applications of medical-grade adhesives (endosco?
Depending on substrate pair, continuous operating temperature, and curing line constraints, Shanghai Jome Industrial Co., Ltd. (JOME) recommends evaluating GM 3239 / GM 3218, JM 2081, and JM 3302 / JM 380. Review our full specification table on this page or request a customized formulation sample.
Q: Can JOME customize viscosity, cure speed, or thermal conductivity for our automated production line?
Yes. JOME's Shanghai RandD laboratory customizes A/B mix viscosity, thixotropic index, pot life, Shore hardness, and thermal filler loading (0.75 to 25.0 W/m·K) to match your dispensing equipment and environmental test standards.
Industrial Adhesive Categories, Matched Grades and Engineering Guides
Product and Application Categories: Thermal Conductive Bonding Adhesive · Thermal Conductive Grease · Epoxy Potting Compound · UV Potting Compound · Polyurethane (PU) Structural Adhesive · SMP Hybrid Structural Adhesive (MS Adhesive) · Sealant · SMP Hybrid Sealants (Silane Modified Polyether) · UV Curing Sealant · UV Cationic Epoxy Adhesive · Optical Clear UV Adhesive · Pre-coated threadlocker adhesive · Cylindrical retaining adhesive · Silicone · Polyurethane (PU) · Special · Fluorosilicone Sealant · Industry News Guides · Photovoltaic + Energy Storage Integration Guides · Hardware Accessories, Tools, Fasteners Guides · Semiconductor precision packaging Guides
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